Im glad you didn’t say what everyone else says about turbos… that they don’t require power to operate. Obviously there is work being done by the engine to turn the turbine. As you said, the turbine is a restriction, on purpose! Subscribed!
No free lunch, but you can eat food previously uneaten. The exhaust gas has energy from temperature and velocity, as well as pressure. A properly designed turbine and exhaust system expands exhaust gasses through it, cooling it and slowing it to extract power to turn the compressor. Pressure is kept as low as possible to reduce pumping losses. A turbo system running beyond it's design capabilities will see an increase in pressure between the engine and turbine, with resulting loss of efficiency, and likely longevity. But the turbine can be made to work on exhaust velocity and temperature alone. After WW2, but before jet engines took over, piston airplane engines were developed with turbines connected to the engine crankshaft that greatly increased power and fuel economy. See the DC-7 equipped with power recovery turbines/ turbo compound engines.
@@briancox2721 Thank you for that. There are forces being utilized by a turbocharger system that would otherwise be wasted, and utilizing them does not always equate to a large increase in pumping losses.
@StandRacing for all practical purposes a turbo does, in fact, provide a free lunch. In properly setup race applications, it is always a free lunch. Race turbos REDUCE pumping losses. In other words, the intake pressure will be higher than the exhaust pressure.
You hear a lot about the air piling up against the back of the valve and reflecting back up the tube. This does happen, but it's not the main effect. If you run the numbers for intake resonance under this assumption it looks like the runner should come into resonance every couple of hundred rpm so by that assumption it should never go out of tune. What actually happens is the strong vacuum pulled by the piston on its induction stroke sends a rarefaction wave up the runner. This is then reflected off the open bellmouth _which reverses the sign_ and reflects back as a positive pressure wave. Tuning the runner involves timing the creation of the rarefaction wave (approximately at the point of the piston's fastest movement down the bore) so it reflects back just as the valve is closing on the same induction stroke. That positive pressure wave piles the extra air in, and is a much stronger effect than the reflection of the air off the valve. Have a look at the Speed Talk website for more detail, and people who have actual credentials rather than just some random replying in a youtube comment.
Absolutely right, everybody gets this wrong.. The other thing that grates me is that idea that the wave needs to arrive when the intake valve opens. As you say it needs to arrive just before it closes… (you gotta put the lid on quick after you stuff the last in!)
That also seems more sensible because the gap is smallest just before the valve closes, so it needs all the help it can get to flow through that small opening. The pressure difference should be highest right before the valve opens. With the air already rushing in because of this, that wave coming in at this time would potentially be unnoticeable. Good stuff!
@@MakingforMotorsport Yeah that gets me too. If you pile it in at the start you just get less in through the rest of the induction stroke as it equalises. There might be something to gain by timing it for valve overlap and getting better scavenging, but that's a secondary effect.
@@BiTurbo228 completely agree, I think on most short intakes 1st or 2nd reflection pulses will help for valve overlap, but as there is always more energy on the exhaust side the pulse tuning on the hot side is always the stronger effect…
Dont know if it is mentioned on the website your are talking about but i suppose the window for this harmonic wave would be very smal in rpm range. Unlike a twostroke with its expansion chamber the pulse need aproximatly the same time to travel back and forth to gain more than one atmospher. A fourstroke intakt valve is open lets say 1/4 of all strokes wich leads to 3/4 of closed and therefor to big timeframe difference to gain the same kind of effekt as an twostroke. I may be way of topic but worth mentioning as this has crossed my mind couple of times while i think of this harmonic wave on fourstrokes. Kind regards from Sweden!
A short large runner at low RPM fills the operating cylinder much too fast with low energy/low-velocity air and when the piston reaches bottom dead center, the cylinder pressure equalizes with the short runner pressure and simply pushes everything that entered the cylinder back into the port until the intake valve closes. A longer runner at low RPM, OTOH has more of a restriction, fills the cylinder much slower with higher energy/higher velocity air, and delays the pressure equalization as the piston rounds bottom dead center allowing air to flow into the cylinder until the valve closes potentially trapping more air. With the higher air energy and velocity the air/fuel is also mixed together more efficiently.
When testing custom parts i recommend using gale banks density guage to measure and log manifold Absolute density, this gives flow which ultimately dictates fuel and hp. When you make tweaks to your design rev your motor out and compare logs, if you have rpm against flow you will see where your gains are made 🙂
6:20 also Cam duration and overlap helps. As David Freiburger (Engine Masters/Roadkill) put it, think of a door opening: you open and close it fast, very few people can enter... leave it open for 30 seconds and 100 people can come through. Overlap will help pull in more intake too because of the timing where both Intake and Exhaust valves are open. The exiting exhaust helps draw in more intake due to the displacement (believe that would be positive displacement?), like having two windows open to get better cross flow while in a parked car... another form of Scavenging
Funny thing about aero is, it acts different with different obstacle. Where foil shape has about an inch of noticeable increments, runner acts on fractions of a millimeter. A hair width of material in the wrong place and the horn is out of tune. In the subject of horns, the sound of horn is a pressure wave pulse amplified by the brass via the natural frequency and elasticity of the material. The horn vibrates in sync with the lips and the wet fart gets amplified to a deafening wave of sound. Same concept can be utilized to amplify the valve pulse, but if wrong material is used, the pulse damps into wet fart. Another thing about sound is, it is a pressure wave coming towards you. So if you hear your intake "honk", you know you have lost horse power to vanity. For the positive pressure intake, you could use the secondary curve to fill the box and long runners to fill the combustion chamber. Mind you that the exhaust and cam timing needs to be in tune with the intake for any noticeable result. Again, a hair off and the system is out of tune. Even spark timing has an effect on harmonic flow direction. When your secondary stream fills the box on higher RPM, this compensates the lack of air pressure inside the longer runner leading up to overall power output gain.
Epiphany time: I *love* my 22re (2.4L Toyota) it has an equal bore/stroke, short runners and makes boat loads of torque in the midrange with a (realistically) 4.5k rpm redline and only makes power between 3.2k - 4.2k. Short but very rewarding, especially for tight mountain passes.
Recently, Darin Morgan did a episode on Drag Boss Garage. He discussed port length, velocity, VE, etc.. couple hours long, but, there’s some nuggets on this, in there.
You could compine the effect of the "supechargingˇeffect of air speed with a ram air intake. The ram air intake should be positioned at the stagnation point on the body of the car for maximum effect. With this you can get some crazy columetric efficiency with a naturally aspirated engine. You can of course tune your Helmholz resonance in this design as well.
Turbochargers use the expanding heat energy from the exhaust gases in combination with a charge air cooler to generate a higher intake air density than exhaust gas density. If the exhaust was not hot the turbocharger would not be able to generate higher intake air density than the exhaust gas density.
Also resonance tuning is more about optimizing the pressure wave from the back of a closing valve into an opening valve from an opposing cylinder. Not so much back into the same valve.
Around 7min mark I think you are starting to confuse things. The pressure *differential* across the valve combined with the momentum of the air *already flowing through* an open valve gives you the supercharging effect. The velocity of the air flow impacts the strength of the pressure waves, and it’s a balance act between small diameter=high velocity=stronger pressure with larger diameter=greater mass flow potential. The pressure waves drive all of it so the resonance of the duct is critical to making power.
…and at 9:30 or so, restriction of the runner doesn’t depend on length (at least barely at all), and the momentum that builds up is not a function of length the way you describe. It’s the combined effect of pressure differentials across junctions like the valve, runner-to-plenum, combined with how long of time the air has to accelerate. F=ma, p=F/a, etc. The best thing for power is a long drawn out positive pressure pulse over the duration of the intake valve open event, with as long of an open event as possible, while simultaneously having a long negative pressure pulse at the exhaust valve to increase that pressure differential even more. Even with a long skinner intake runner, if the intake valve only opens for 5deg you won’t build up any velocity because there is no time for the pressure/force to accelerate the air.
And at 10:10, you lose power at high rpm with long runner because the pressure pulses start to go out of phase with the valve timing. Yeah, there’s some viscous drag but it’s pretty minimal in a properly sized (diameter) intake runner.
Sorry for the string of replies, but area under the curve does indeed matter, but only in the operating range you use on the track - if your gears are spaced properly, let’s say that worst case (between first and second gear) you keep the engine between 4000-7000rpm, then the average power from 4000-7000rpm is all that matters. And the impact of efforts to make power power at low rpm is pretty small, maybe 10% max, sacrificing a lot of area under the curve of top. You can just downshift and get a much bigger increase in power since your gear steps are always going to be greater than 10%. Remember, power is what gives you acceleration, not torque - let’s say you were going 50mph and could choose between 6000rpm, 200hp, 175ft-lb in 2nd gear or 4000rpm and 150hp/197ft-lb in 3rd gear, you should always choose 2nd gear! F=m*a and P=F*v, so 33% more power in 2nd gear means 33% more longitudinal force (less than 33% more acceleration due to rolling resistance and aero drag). So even though 3rd gear gives 13% more torque it will be much slower!
I'm gonna take all that as homework so I can get a better understanding. I can say though, you're forgetting about mechanical advantage in your 3rd gear 2nd gear scenario. Assuming 2:1 second gear ratio, 1.5:1 third gear ratio, and 4:1 final drive, the car is making 1,400ft/lbs of torque in 2nd at the axle with 175ft/lbs at the crank, and 1182ft/lbs in 3rd at the axle with 197ft/lbs at the crank. That's why 2nd is faster. Vehicle acceleration doesn't take engine RPM into account, only force at the contact patch.
I figure you've thought about this, but why not combine that spiral dual-length manifold from your last video with sliding trumpets? I figure you don't want the added complexity, but taking a page out of Porsche's playbook with their Varioram intakes, you could control intake velocity, optimizing for the helmholtz resonance, and having a short and long intake runner path.
Air speed is going to bev driven by more than runner length. Diameter, cylinder volume, processing time which is the amount of time between valve openings and overlap. Along with density and frequency will dictate charge density.
I didn't think that you didn't know the variables. But the video would leave some people 🙄 thinking that length was the primary thing to tune. Taper to runners can also help achieve a good balance of air speed and frequency. As you stated its not as important but in the condition of cruise we can gain efficiency.
Squeezing the same volume through a smaller space means it has to pass through that space faster. Runner diameter has a greater effect on intake velocity.
The greatest gains are always going to be area just before the valve and to some extent the valve itself. Its generally best to have the greatest velocity across the valve for 65% and the kinda tunes the mass of air bouncing
Nice work, I'm putting an ITB 1.8VVT in my NA when I've finished gathering parts, i'd love to be able to buy a nice proper intake like this to compliment the throttle bodies, cams, and exhaust so it's all nice and free flowing
Just wanted to comment the audio is a little low in comparison to other videos, had to turn my volume up a bit. Awesome video thanks for putting these out!
What you're saying here is the wrong way around. The pressure valve typically comes from opening the valve, sending a negative pressure wave that is reflected at the collector as a positive wave. This wave you want to hit the valve as it is about to close so the pressure in the combustion chamber is higher and you get more air in total into your chamber. (Hope this is gramatically correct, I'm not a native english speaker since I'm german) Greetings.
Btw.... The wave lengh is longer but the wave has less amplitude at low rpm and shorter with a bigger amplitude at high rpm. So aiming for high rpm will give you multiple benefits: Better runner optimization effects due to the bigger amplitude (bigger pressure spike by the wave -> more cylinder pressure) Shorter runner so you have less flow restriction (actually has a less of an effect then you'd think) But due to how the wave behaves over the rpm range, the higher you get the smaller the rpm range in which the runner lengh fits the rpm. Movable stacks give you the best out of all worlds and you can gain a lot of power over the entire rpm range. You can find these for example on the 787B even tho they programmed the system to be controlled by the gas pedal which is not the right way to do it.... Regarding the Helmholz formula... This is rather a guesstimate on where your runner lengh will be since it does not take into account the wave lengh at rpm, origin of the rpm regarding the angle of rotation on your engine (not at tdc or opening event of your valve!!), diameter of the runner etc .... In reality the true runner lengh differs from what the helmholz formula will tell you.
I had a crazy idea here, what if you use a runner with an open cylinder that moves inside it ( pressure+spring / mechanical / solenoid) to changes the length depending on the RPM? The runner (outer part) has a sliding cylinder inside it, in which the outer diameter of the movable cylinder matches the inner diameter of the runner to make a good seal (at least don't let much air escape) thus making the runner short on high RPM and long on low RPM.
8:30 I would say a good explanation is that its like tricking your air into thinking you have a bigger engine. A 2L volume at 1.5 atmosphere of pressure fits 3L of air at 1 atmosphere. One thing Im curious about is how much power draw is a supercharger vs a turbo? I think everyone knows that the turbo is going to cost something as well, But ive had plenty of car people tell me that the costs are negligible. Considering that turbos are put on modern cars partially for fuel efficiency, and that superchargers have no lag + cheaper, there must be some truth to the idea that turbos are more efficient, or else everyone would just use superchargers.
It's largely a matter of preference. Superchargers come on power a lot smoother than turbos, twin-turbo setups can approach this smoothness but with the extra moving parts and tuning complexity it's not always as reliable as supercharged. It's all good fun though.
Turbos take advantage of thermal expansion of the exhaust gases, therefore they are more efficient bcs some of their drive energy comes from an energy source that would otherwise be wasted.
Hey man, realy nice content. When you were talking about combining shot and long runers I would sugest you have a look at the BMW's intake manifolds used on M54 and M52TU engines. They use DISA valve to to direct path of air thru long or short runers depending on RPM however they dont use ITB's since those are normal non M cars engines. Later engines such as N52... use 2 DISA valves.
When i was a litle kid my dad explained it to me in a funny way. He said "lets say there is a game store. And the next cool console is releasing that morning. And the doors of the store is automated to shut periodicaly Then if the store is located out in the open the people will mill around in a big circle around the door. But if the store is located down a long corridor then the people at the back will not even notice the door shutting in the front. And the people at the front is going to be trapped upp against the doors untill they open and they will literaly be pushed into the store by the people behind them"
Don't normally comment on videos but I'm impressed man! Happy I subscribed! I've been fascinated with the B58 intake in the BMWs recently an seen some cool advancements in it. It'd be cool to see you give it a go
What if the runners have a variable length? Maybe variable volume? That way that shockwave is optimized at every rpm range. When the length of the runner changes the volume changes. but the amplitude of the wave stays about the same while it’s frequency increases. What if it was the opposite? The amplitude changes but the frequency remains the same. Idk though I’m not an engineer
so many iconic engine intakes would be interesting to test them, some have a merge style collector with throttle body in the middle others are like yours on one side, lets test the effects on that too? k20 center feed is a great example of this effect
So your second explanation on airspeed is one of the things that led to the poor flowing intake port runners of the '80s and '90s. Since you're really into this one of the things that's really interesting is how some "rebels" of engineering inside GM decided to ignore the airspeed and chase flow. Obviously today we know if you have a massive amount of flow but low air speed you could in theory have the same as an engine that had The ideal high airspeed but had to limit flow... But that wasn't believed at the time. So these rebellious engineers inside GM did not want to see the V8s become overhead cam four valve engines like almost everyone else. They believed that if they applied what they already knew worked out on the track they could prove everyone wrong. And in a way they did. That's how we ended up with the various engine incarnations ending with the whole LS and now LT engine series. These engines use massive intake runners and ports and valves, which lets them achieve excellent cylinder filling at all RPMs... Which is why you can have an engine that is a high torque low horsepower setup, swap out the cam and suddenly it's still breathing and making a ton of horsepower up top. It's not choked off in an attempt to keep air flow up It's opened up and keeping airspeed low but cylinder filling high all the way up to the end.... It completely throws out the theories that you're presenting in the second half of the video, and it works really well when the engine is designed that way. Of course most engines are not designed that way. And you're only working on the intake and not the intake runners on the head. So you're limited to working with what you have. In the end while all this theory is important It does show that sometimes building stuff over and over and seeing what works even if we don't know why it works can give you better results.
A vendor has released an IM with three different length runners. I don't understand why it doesn't lose torque anywhere and has a nice power gain above 5K.
You're doing great stuff. Thanks for making the general concepts and differences understanable and not engine specific. The way you explain stuff makes it easy to apply to other engines. Does the dip in the rev range being earlier help in low speed drivability? I'm guessing a late but consistent curve would be better than and early but bumpy one
The curve I drew was a bit dramatic, it looks more like a turbo car with big low RPM lag. It's hard to talk about driveability without knowing more, but a smooth and mild car is the most fun as a daily in my opinion.
I've wondered the same thing. Each different channel of air should have it's own resonant frequency, so I would expect that trying to discover exactly what's happening inside the manifold would require intricate testing.
I have a long tube intake on my K24A RBB motor and it is a great example of what longer runners can do for torque. It sounds great and feels really good through a 6 speed. I’ve seen some ITB kits online, would a long tube manifold around the ITBs provide even more air speed with velocity stacks?
The same flow rate through a smaller diameter tube = higher velocity. The effect of runner length on velocity is negligible after a few inches. What runner length does do is increase the colomn of mass behind the valve. As the piston slows and the valve starts closing having a larger mass with a higher velocity = greater pressure. A smaller diameter will reduce flow at higher RPMs. The effect of turbulence caused by longer runners also starts to have a more pronounced effect at higher flow rates. Turbulence also has a much more negative effect with fluids of a higher viscosity. Air does not flow like water or oil so that syringe example is somewhat misleading.
im building a inlet manifold for a project of mine and im really space constrained but it is supercharged so would that negate the effects of the short runners i need to use to fit it? they are approximately 40% the length of the factory manifold. fwiw the stock manifold is widely considered one of the best OE manifolds on a 2L turbo production car, and ive just cut iit down and replicated the plenum volume
This might be a stupid question (I don't actually have any experience in this stuff), but could you install a "wastegate" into the long style intake runner? You'd get the good air momentum with the long tube down low and then have it open up at higher rpm or load to get around the restriction a long tube causes? I would think youd have to tune with a map sensor or route the "wastegate" pre maf/afm? Anyway cheers! Love your channel!
I'd say drag racing is the most important time to have a high average HP/broad powerband. You want to get the most out of each gear. If you have a narrow powerband you're not gonna be able to stay in the power without shifting often Maybe in rally racing or drifting with a close ratio gearbox you could keep the engine speed within a few hundred RPM and make use of a peaky engine.
Yeah the compressor has a efficiency curve though.. smaller blowers hit harder down low but fall off, big big blowers you might never hit their peak efficiency. Twin screw and roots blowers can have a lot of rotating mass to get moving
Would forced induction change the restriction effect since its already under pressure? Like if you took that syringe and attached a compressor itll shoot the plunger out.
@StandRacing hey I just took apart a Cadillac dts with the all aluminum v8 and it uses kinda the same design for the intake runners that you are designing. Also might be good to look into the Taurus sho for intake ideas. Super jealous wish I could be doing this kinda stuff.
The benefit of variable lift technology is superior the the benefit of an over-engineered intake manifold. It doesn't make manifold development completely obsolete but it is the more effective way to put the power where you want it on the HP curve.
@StandRacing I was running my n52 with an open trumpet intake and gave up the math cuz I couldn't figure how to incorporate that variable in the design.
Sweet stuff mate. I understand the runner needs to be bent to a "U" shape to increase the intake length, but do you know if it actually increases or decreases the flow through the runner? I'm trying to design a 3d printed itb plenumn with my brother. keep up to the good work dude
@@StandRacing yep, that's what I was asking. There's no real way of getting around it though ay. Benefits of a longer runner will probably outweigh the effects of the bend of the runner. Thanks for the reply, Cheers 🤙
I did an fluid FEA on a "U" vs straight intake when I designed an ITB intake for my Miata, and a relatively tight 90° bend had pretty poor flow characteristics. The airflow will basically "apex" the cross section of the intake when there's a significant bend, where the bulk of the airflow takes what looks like the racing line through the bend and the other areas have very slow, turbulent, or even separated flow at higher speeds. That's basically the same effect as decreasing the diameter of the intake in those areas... I can't imagine any other reasonable intake designs having much worse flow. You should make sure that any bend in your intake isn't tight enough that the inside of the curve is significantly shorter than the outside, a rule of thumb is to not curve it tighter than the stock intake. The one shown in these videos goes for what looks like the widest bend possible, but unless you're going to do a very detailed analysis and commit to a plenum setup, a straighter intake is the much simpler, easier, and likely better option. I ended up with an intake that's curved maybe 30° total. The only reason I curved the intake was to get clearances near the frame, and I ended up just maximizing the available space to get the longest intake length I could fit.
@@agerrgerra1361 Wow that awesome. Thanks for the reply. Ivs got itbs on NB mx5. So basically, straight is best, and if it needs to be, less angle of bend the better. Cheers 🤙
@@StandRacing Are you going to cover intake manifold optimization for turbos in a future video? And does runner length matter when supercharged (both kinds) or does all forced induction kinda defeat the purpose of runner length since they're compressing more volume into the plenum, anyway? ((The only one I can see it still mattering for is centrifugally charged, since those do basically nothing until about half the rev range, anyway.))
That would be a good topic of study. I would expect the manifold design having a measurable effect on the "turbo-lag" section of the curve before the turbo makes much boost. But I'll take it as homework.
The throttle bodies themselves? I don't know if I would trust plastic to maintain the level of tolerance required to keep throttle position constant in their closed positions. Maybe start with PA-CF and use brass inserts for the throttle shaft. Be cautious, and let me know how it goes!
It seems to me that if you want good tuning for 3 or 4 different engine speeds, you'd just bolt on 3 or 4 separate throttle valves and use the computer to switch which one is open depending on engine speed. It's a bit Neanderthal compared to the "perfect" engineered intake, but you can be really lazy with simulations and just build essentially a trumpet. EDIT: If you're looking to build a bolt-on aftermarket component, then the above definitely doesn't work. In any case nice work.
If you could make a Chevrolet 6.0 gas save fuel at low load, the world would be a better place. Brand new trucks, and they're tuned like a Corvette. There has to be a way to get a generic fuel tuner. There's demand.
Im glad you didn’t say what everyone else says about turbos… that they don’t require power to operate. Obviously there is work being done by the engine to turn the turbine. As you said, the turbine is a restriction, on purpose! Subscribed!
No free lunch! Thanks for the support
No free lunch, but you can eat food previously uneaten. The exhaust gas has energy from temperature and velocity, as well as pressure. A properly designed turbine and exhaust system expands exhaust gasses through it, cooling it and slowing it to extract power to turn the compressor. Pressure is kept as low as possible to reduce pumping losses. A turbo system running beyond it's design capabilities will see an increase in pressure between the engine and turbine, with resulting loss of efficiency, and likely longevity. But the turbine can be made to work on exhaust velocity and temperature alone. After WW2, but before jet engines took over, piston airplane engines were developed with turbines connected to the engine crankshaft that greatly increased power and fuel economy. See the DC-7 equipped with power recovery turbines/ turbo compound engines.
@@briancox2721 Thank you for that. There are forces being utilized by a turbocharger system that would otherwise be wasted, and utilizing them does not always equate to a large increase in pumping losses.
@StandRacing for all practical purposes a turbo does, in fact, provide a free lunch. In properly setup race applications, it is always a free lunch.
Race turbos REDUCE pumping losses. In other words, the intake pressure will be higher than the exhaust pressure.
You hear a lot about the air piling up against the back of the valve and reflecting back up the tube. This does happen, but it's not the main effect. If you run the numbers for intake resonance under this assumption it looks like the runner should come into resonance every couple of hundred rpm so by that assumption it should never go out of tune.
What actually happens is the strong vacuum pulled by the piston on its induction stroke sends a rarefaction wave up the runner. This is then reflected off the open bellmouth _which reverses the sign_ and reflects back as a positive pressure wave. Tuning the runner involves timing the creation of the rarefaction wave (approximately at the point of the piston's fastest movement down the bore) so it reflects back just as the valve is closing on the same induction stroke. That positive pressure wave piles the extra air in, and is a much stronger effect than the reflection of the air off the valve.
Have a look at the Speed Talk website for more detail, and people who have actual credentials rather than just some random replying in a youtube comment.
Absolutely right, everybody gets this wrong..
The other thing that grates me is that idea that the wave needs to arrive when the intake valve opens. As you say it needs to arrive just before it closes… (you gotta put the lid on quick after you stuff the last in!)
That also seems more sensible because the gap is smallest just before the valve closes, so it needs all the help it can get to flow through that small opening.
The pressure difference should be highest right before the valve opens. With the air already rushing in because of this, that wave coming in at this time would potentially be unnoticeable. Good stuff!
@@MakingforMotorsport Yeah that gets me too. If you pile it in at the start you just get less in through the rest of the induction stroke as it equalises.
There might be something to gain by timing it for valve overlap and getting better scavenging, but that's a secondary effect.
@@BiTurbo228 completely agree, I think on most short intakes 1st or 2nd reflection pulses will help for valve overlap, but as there is always more energy on the exhaust side the pulse tuning on the hot side is always the stronger effect…
Dont know if it is mentioned on the website your are talking about but i suppose the window for this harmonic wave would be very smal in rpm range. Unlike a twostroke with its expansion chamber the pulse need aproximatly the same time to travel back and forth to gain more than one atmospher. A fourstroke intakt valve is open lets say 1/4 of all strokes wich leads to 3/4 of closed and therefor to big timeframe difference to gain the same kind of effekt as an twostroke.
I may be way of topic but worth mentioning as this has crossed my mind couple of times while i think of this harmonic wave on fourstrokes.
Kind regards from Sweden!
A short large runner at low RPM fills the operating cylinder much too fast with low energy/low-velocity air and when the piston reaches bottom dead center, the cylinder pressure equalizes with the short runner pressure and simply pushes everything that entered the cylinder back into the port until the intake valve closes. A longer runner at low RPM, OTOH has more of a restriction, fills the cylinder much slower with higher energy/higher velocity air, and delays the pressure equalization as the piston rounds bottom dead center allowing air to flow into the cylinder until the valve closes potentially trapping more air. With the higher air energy and velocity the air/fuel is also mixed together more efficiently.
When testing custom parts i recommend using gale banks density guage to measure and log manifold Absolute density, this gives flow which ultimately dictates fuel and hp.
When you make tweaks to your design rev your motor out and compare logs, if you have rpm against flow you will see where your gains are made 🙂
You're doing cool stuff here. Excited to see the intake on the dyno!
Thanks, me too!
The youtube algorithm worked for once. Immediate subscribe, I love DIY focused car channels.
6:20 also Cam duration and overlap helps. As David Freiburger (Engine Masters/Roadkill) put it, think of a door opening: you open and close it fast, very few people can enter... leave it open for 30 seconds and 100 people can come through. Overlap will help pull in more intake too because of the timing where both Intake and Exhaust valves are open. The exiting exhaust helps draw in more intake due to the displacement (believe that would be positive displacement?), like having two windows open to get better cross flow while in a parked car... another form of Scavenging
Funny thing about aero is, it acts different with different obstacle. Where foil shape has about an inch of noticeable increments, runner acts on fractions of a millimeter. A hair width of material in the wrong place and the horn is out of tune. In the subject of horns, the sound of horn is a pressure wave pulse amplified by the brass via the natural frequency and elasticity of the material. The horn vibrates in sync with the lips and the wet fart gets amplified to a deafening wave of sound. Same concept can be utilized to amplify the valve pulse, but if wrong material is used, the pulse damps into wet fart. Another thing about sound is, it is a pressure wave coming towards you. So if you hear your intake "honk", you know you have lost horse power to vanity. For the positive pressure intake, you could use the secondary curve to fill the box and long runners to fill the combustion chamber. Mind you that the exhaust and cam timing needs to be in tune with the intake for any noticeable result. Again, a hair off and the system is out of tune. Even spark timing has an effect on harmonic flow direction. When your secondary stream fills the box on higher RPM, this compensates the lack of air pressure inside the longer runner leading up to overall power output gain.
Happy to be subscribed for a while now, this is some of the coolest new stuff coming out. And the best part is I can understand it!
Epiphany time: I *love* my 22re (2.4L Toyota) it has an equal bore/stroke, short runners and makes boat loads of torque in the midrange with a (realistically) 4.5k rpm redline and only makes power between 3.2k - 4.2k.
Short but very rewarding, especially for tight mountain passes.
Nice to see someone reference Scott Hatch, he specs my cams amongst many other things, never been wrong !
Edit: misspell
Recently, Darin Morgan did a episode on Drag Boss Garage. He discussed port length, velocity, VE, etc.. couple hours long, but, there’s some nuggets on this, in there.
You could compine the effect of the "supechargingˇeffect of air speed with a ram air intake. The ram air intake should be positioned at the stagnation point on the body of the car for maximum effect. With this you can get some crazy columetric efficiency with a naturally aspirated engine.
You can of course tune your Helmholz resonance in this design as well.
What you are doing is really cool and super useful.
I want to see the results, I hove it shows exceptional results.
Turbochargers use the expanding heat energy from the exhaust gases in combination with a charge air cooler to generate a higher intake air density than exhaust gas density. If the exhaust was not hot the turbocharger would not be able to generate higher intake air density than the exhaust gas density.
Also resonance tuning is more about optimizing the pressure wave from the back of a closing valve into an opening valve from an opposing cylinder. Not so much back into the same valve.
A well designed factory intake can change between two different length runners.
Lexus 3UZ-FE
Around 7min mark I think you are starting to confuse things. The pressure *differential* across the valve combined with the momentum of the air *already flowing through* an open valve gives you the supercharging effect. The velocity of the air flow impacts the strength of the pressure waves, and it’s a balance act between small diameter=high velocity=stronger pressure with larger diameter=greater mass flow potential. The pressure waves drive all of it so the resonance of the duct is critical to making power.
…and at 9:30 or so, restriction of the runner doesn’t depend on length (at least barely at all), and the momentum that builds up is not a function of length the way you describe. It’s the combined effect of pressure differentials across junctions like the valve, runner-to-plenum, combined with how long of time the air has to accelerate. F=ma, p=F/a, etc. The best thing for power is a long drawn out positive pressure pulse over the duration of the intake valve open event, with as long of an open event as possible, while simultaneously having a long negative pressure pulse at the exhaust valve to increase that pressure differential even more. Even with a long skinner intake runner, if the intake valve only opens for 5deg you won’t build up any velocity because there is no time for the pressure/force to accelerate the air.
And at 10:10, you lose power at high rpm with long runner because the pressure pulses start to go out of phase with the valve timing. Yeah, there’s some viscous drag but it’s pretty minimal in a properly sized (diameter) intake runner.
Sorry for the string of replies, but area under the curve does indeed matter, but only in the operating range you use on the track - if your gears are spaced properly, let’s say that worst case (between first and second gear) you keep the engine between 4000-7000rpm, then the average power from 4000-7000rpm is all that matters. And the impact of efforts to make power power at low rpm is pretty small, maybe 10% max, sacrificing a lot of area under the curve of top. You can just downshift and get a much bigger increase in power since your gear steps are always going to be greater than 10%.
Remember, power is what gives you acceleration, not torque - let’s say you were going 50mph and could choose between 6000rpm, 200hp, 175ft-lb in 2nd gear or 4000rpm and 150hp/197ft-lb in 3rd gear, you should always choose 2nd gear! F=m*a and P=F*v, so 33% more power in 2nd gear means 33% more longitudinal force (less than 33% more acceleration due to rolling resistance and aero drag). So even though 3rd gear gives 13% more torque it will be much slower!
I'm gonna take all that as homework so I can get a better understanding.
I can say though, you're forgetting about mechanical advantage in your 3rd gear 2nd gear scenario. Assuming 2:1 second gear ratio, 1.5:1 third gear ratio, and 4:1 final drive, the car is making 1,400ft/lbs of torque in 2nd at the axle with 175ft/lbs at the crank, and 1182ft/lbs in 3rd at the axle with 197ft/lbs at the crank. That's why 2nd is faster. Vehicle acceleration doesn't take engine RPM into account, only force at the contact patch.
If the tire has a 12" radius 1,400ft/lbs becomes 1,400lbs of force at the contact patch.
I figure you've thought about this, but why not combine that spiral dual-length manifold from your last video with sliding trumpets? I figure you don't want the added complexity, but taking a page out of Porsche's playbook with their Varioram intakes, you could control intake velocity, optimizing for the helmholtz resonance, and having a short and long intake runner path.
I’ve been looking into designing an intake for my 91 Miata and your videos have been seriously invaluable i thank you sir🫡
Air speed is going to bev driven by more than runner length. Diameter, cylinder volume, processing time which is the amount of time between valve openings and overlap. Along with density and frequency will dictate charge density.
Yes. I wasn't meaning to answer, "what affects airspeed?" I only meat to answer "why does runner length affect airspeed?"
I didn't think that you didn't know the variables. But the video would leave some people 🙄 thinking that length was the primary thing to tune. Taper to runners can also help achieve a good balance of air speed and frequency. As you stated its not as important but in the condition of cruise we can gain efficiency.
Squeezing the same volume through a smaller space means it has to pass through that space faster. Runner diameter has a greater effect on intake velocity.
The greatest gains are always going to be area just before the valve and to some extent the valve itself. Its generally best to have the greatest velocity across the valve for 65% and the kinda tunes the mass of air bouncing
Nice work, I'm putting an ITB 1.8VVT in my NA when I've finished gathering parts, i'd love to be able to buy a nice proper intake like this to compliment the throttle bodies, cams, and exhaust so it's all nice and free flowing
Just wanted to comment the audio is a little low in comparison to other videos, had to turn my volume up a bit. Awesome video thanks for putting these out!
What you're saying here is the wrong way around. The pressure valve typically comes from opening the valve, sending a negative pressure wave that is reflected at the collector as a positive wave. This wave you want to hit the valve as it is about to close so the pressure in the combustion chamber is higher and you get more air in total into your chamber. (Hope this is gramatically correct, I'm not a native english speaker since I'm german)
Greetings.
You got it!
Btw.... The wave lengh is longer but the wave has less amplitude at low rpm and shorter with a bigger amplitude at high rpm.
So aiming for high rpm will give you multiple benefits:
Better runner optimization effects due to the bigger amplitude (bigger pressure spike by the wave -> more cylinder pressure)
Shorter runner so you have less flow restriction (actually has a less of an effect then you'd think)
But due to how the wave behaves over the rpm range, the higher you get the smaller the rpm range in which the runner lengh fits the rpm.
Movable stacks give you the best out of all worlds and you can gain a lot of power over the entire rpm range. You can find these for example on the 787B even tho they programmed the system to be controlled by the gas pedal which is not the right way to do it....
Regarding the Helmholz formula... This is rather a guesstimate on where your runner lengh will be since it does not take into account the wave lengh at rpm, origin of the rpm regarding the angle of rotation on your engine (not at tdc or opening event of your valve!!), diameter of the runner etc ....
In reality the true runner lengh differs from what the helmholz formula will tell you.
@@maximilianstobinski2469 all excellent advice here!
I had a crazy idea here, what if you use a runner with an open cylinder that moves inside it ( pressure+spring / mechanical / solenoid) to changes the length depending on the RPM? The runner (outer part) has a sliding cylinder inside it, in which the outer diameter of the movable cylinder matches the inner diameter of the runner to make a good seal (at least don't let much air escape) thus making the runner short on high RPM and long on low RPM.
8:30 I would say a good explanation is that its like tricking your air into thinking you have a bigger engine. A 2L volume at 1.5 atmosphere of pressure fits 3L of air at 1 atmosphere.
One thing Im curious about is how much power draw is a supercharger vs a turbo? I think everyone knows that the turbo is going to cost something as well, But ive had plenty of car people tell me that the costs are negligible.
Considering that turbos are put on modern cars partially for fuel efficiency, and that superchargers have no lag + cheaper, there must be some truth to the idea that turbos are more efficient, or else everyone would just use superchargers.
It's largely a matter of preference. Superchargers come on power a lot smoother than turbos, twin-turbo setups can approach this smoothness but with the extra moving parts and tuning complexity it's not always as reliable as supercharged. It's all good fun though.
Turbos take advantage of thermal expansion of the exhaust gases, therefore they are more efficient bcs some of their drive energy comes from an energy source that would otherwise be wasted.
Hey man, realy nice content. When you were talking about combining shot and long runers I would sugest you have a look at the BMW's intake manifolds used on M54 and M52TU engines. They use DISA valve to to direct path of air thru long or short runers depending on RPM however they dont use ITB's since those are normal non M cars engines. Later engines such as N52... use 2 DISA valves.
When i was a litle kid my dad explained it to me in a funny way.
He said "lets say there is a game store. And the next cool console is releasing that morning.
And the doors of the store is automated to shut periodicaly
Then if the store is located out in the open the people will mill around in a big circle around the door.
But if the store is located down a long corridor then the people at the back will not even notice the door shutting in the front. And the people at the front is going to be trapped upp against the doors untill they open and they will literaly be pushed into the store by the people behind them"
1:00 port velocity
Don't normally comment on videos but I'm impressed man! Happy I subscribed! I've been fascinated with the B58 intake in the BMWs recently an seen some cool advancements in it. It'd be cool to see you give it a go
Thank you so much! I'd love to have team going one day where we can explore all sorts of different avenues of tuning.
What if the runners have a variable length? Maybe variable volume? That way that shockwave is optimized at every rpm range. When the length of the runner changes the volume changes. but the amplitude of the wave stays about the same while it’s frequency increases. What if it was the opposite? The amplitude changes but the frequency remains the same. Idk though I’m not an engineer
so many iconic engine intakes would be interesting to test them, some have a merge style collector with throttle body in the middle others are like yours on one side, lets test the effects on that too?
k20 center feed is a great example of this effect
I think that's a good idea
So your second explanation on airspeed is one of the things that led to the poor flowing intake port runners of the '80s and '90s.
Since you're really into this one of the things that's really interesting is how some "rebels" of engineering inside GM decided to ignore the airspeed and chase flow. Obviously today we know if you have a massive amount of flow but low air speed you could in theory have the same as an engine that had The ideal high airspeed but had to limit flow... But that wasn't believed at the time.
So these rebellious engineers inside GM did not want to see the V8s become overhead cam four valve engines like almost everyone else. They believed that if they applied what they already knew worked out on the track they could prove everyone wrong.
And in a way they did. That's how we ended up with the various engine incarnations ending with the whole LS and now LT engine series. These engines use massive intake runners and ports and valves, which lets them achieve excellent cylinder filling at all RPMs... Which is why you can have an engine that is a high torque low horsepower setup, swap out the cam and suddenly it's still breathing and making a ton of horsepower up top. It's not choked off in an attempt to keep air flow up It's opened up and keeping airspeed low but cylinder filling high all the way up to the end....
It completely throws out the theories that you're presenting in the second half of the video, and it works really well when the engine is designed that way.
Of course most engines are not designed that way. And you're only working on the intake and not the intake runners on the head. So you're limited to working with what you have.
In the end while all this theory is important It does show that sometimes building stuff over and over and seeing what works even if we don't know why it works can give you better results.
This guy is going to be huge
Thanks for your support man 👍
Time to give those crawford power blocks a spin on the BRZ!
A vendor has released an IM with three different length runners. I don't understand why it doesn't lose torque anywhere and has a nice power gain above 5K.
This one?
www.fuelairspark.com/lsxr-high-hp-intake-manifold-runner-set.html
This is not a good idea without corresponding individual cylinder fuel maps…
You're doing great stuff. Thanks for making the general concepts and differences understanable and not engine specific. The way you explain stuff makes it easy to apply to other engines.
Does the dip in the rev range being earlier help in low speed drivability?
I'm guessing a late but consistent curve would be better than and early but bumpy one
The curve I drew was a bit dramatic, it looks more like a turbo car with big low RPM lag. It's hard to talk about driveability without knowing more, but a smooth and mild car is the most fun as a daily in my opinion.
Great video! I wonder if you can even use helmholtz for your hybrid intake or the effect would be distorted by the complex geometry
I've wondered the same thing. Each different channel of air should have it's own resonant frequency, so I would expect that trying to discover exactly what's happening inside the manifold would require intricate testing.
I only can assume that there is a direct relation shape to your intake runner length and the camshaft selection.
I have a long tube intake on my K24A RBB motor and it is a great example of what longer runners can do for torque. It sounds great and feels really good through a 6 speed. I’ve seen some ITB kits online, would a long tube manifold around the ITBs provide even more air speed with velocity stacks?
10:41 has anyone tried making a trumpeting (variable length) sliding runner?
Yes this is the way some sport bikes do it.
K20a2 engine has a similar intake concept.
Great shtuff!!
The same flow rate through a smaller diameter tube = higher velocity. The effect of runner length on velocity is negligible after a few inches. What runner length does do is increase the colomn of mass behind the valve. As the piston slows and the valve starts closing having a larger mass with a higher velocity = greater pressure. A smaller diameter will reduce flow at higher RPMs. The effect of turbulence caused by longer runners also starts to have a more pronounced effect at higher flow rates. Turbulence also has a much more negative effect with fluids of a higher viscosity. Air does not flow like water or oil so that syringe example is somewhat misleading.
good on you to take the first steps. have you seen 4age garage? he does a bunch of videos with dynos and has tried a lot of things . start there
Oh definitely. I watched a lot of those before I started this project.
im building a inlet manifold for a project of mine and im really space constrained but it is supercharged so would that negate the effects of the short runners i need to use to fit it? they are approximately 40% the length of the factory manifold. fwiw the stock manifold is widely considered one of the best OE manifolds on a 2L turbo production car, and ive just cut iit down and replicated the plenum volume
This might be a stupid question (I don't actually have any experience in this stuff), but could you install a "wastegate" into the long style intake runner? You'd get the good air momentum with the long tube down low and then have it open up at higher rpm or load to get around the restriction a long tube causes? I would think youd have to tune with a map sensor or route the "wastegate" pre maf/afm? Anyway cheers! Love your channel!
Totally! What you described is a secondary set of butterflies. This setup comes standard in the factory Miata manifold.
@@StandRacing Dang! Here I was thinking I had an original thought 😅 thanks for the info!
I think it's also in the 991.2 Porsche gt3
Odd idea... but variable length intake runners. Like a trombone maybe?
The final design will be variable length.
It has been done before.
Drag racing is where peak power wins I’m sure.
I'd say drag racing is the most important time to have a high average HP/broad powerband. You want to get the most out of each gear. If you have a narrow powerband you're not gonna be able to stay in the power without shifting often
Maybe in rally racing or drifting with a close ratio gearbox you could keep the engine speed within a few hundred RPM and make use of a peaky engine.
No such thing as too big supercharger. Just as long as the boost isn't excessive
Yeah the compressor has a efficiency curve though.. smaller blowers hit harder down low but fall off, big big blowers you might never hit their peak efficiency. Twin screw and roots blowers can have a lot of rotating mass to get moving
Would forced induction change the restriction effect since its already under pressure? Like if you took that syringe and attached a compressor itll shoot the plunger out.
Yes, I'm fairly sure that even a modest amount of boost will actually generate a very small amount of torque on the intake stroke.
@StandRacing hey I just took apart a Cadillac dts with the all aluminum v8 and it uses kinda the same design for the intake runners that you are designing. Also might be good to look into the Taurus sho for intake ideas. Super jealous wish I could be doing this kinda stuff.
1.6? Please 😅
What kind of wrench does bmw valvetronic throw into this? Variable intake lift should have an effect on charge air velocity?
The benefit of variable lift technology is superior the the benefit of an over-engineered intake manifold. It doesn't make manifold development completely obsolete but it is the more effective way to put the power where you want it on the HP curve.
@StandRacing I was running my n52 with an open trumpet intake and gave up the math cuz I couldn't figure how to incorporate that variable in the design.
very informative!
Thanks!
Very cool!
Sweet stuff mate. I understand the runner needs to be bent to a "U" shape to increase the intake length, but do you know if it actually increases or decreases the flow through the runner? I'm trying to design a 3d printed itb plenumn with my brother. keep up to the good work dude
Thank you! The bend itself will be less efficient than a straight section if that's what you're asking.
@@StandRacing yep, that's what I was asking. There's no real way of getting around it though ay. Benefits of a longer runner will probably outweigh the effects of the bend of the runner. Thanks for the reply, Cheers 🤙
I did an fluid FEA on a "U" vs straight intake when I designed an ITB intake for my Miata, and a relatively tight 90° bend had pretty poor flow characteristics. The airflow will basically "apex" the cross section of the intake when there's a significant bend, where the bulk of the airflow takes what looks like the racing line through the bend and the other areas have very slow, turbulent, or even separated flow at higher speeds. That's basically the same effect as decreasing the diameter of the intake in those areas... I can't imagine any other reasonable intake designs having much worse flow. You should make sure that any bend in your intake isn't tight enough that the inside of the curve is significantly shorter than the outside, a rule of thumb is to not curve it tighter than the stock intake. The one shown in these videos goes for what looks like the widest bend possible, but unless you're going to do a very detailed analysis and commit to a plenum setup, a straighter intake is the much simpler, easier, and likely better option. I ended up with an intake that's curved maybe 30° total. The only reason I curved the intake was to get clearances near the frame, and I ended up just maximizing the available space to get the longest intake length I could fit.
@@agerrgerra1361 Wow that awesome. Thanks for the reply. Ivs got itbs on NB mx5. So basically, straight is best, and if it needs to be, less angle of bend the better. Cheers 🤙
"No such thing as free lunch"...
Nitrous has entered the chat.
😂 I think the fact that it's temporary is a pretty expensive lunch. Automated nitrous systems though? 👌
What would be your price of a intake manifold like the black one you had in your hands
Hmm, too early to know. There are more pieces needed to make it complete that haven't been printed yet.
Does runner length matter for forced induction(particularly turbo)?
There are things you can design into the intake manifold to improve turbo performance, but for the most part no.
@@StandRacing Are you going to cover intake manifold optimization for turbos in a future video? And does runner length matter when supercharged (both kinds) or does all forced induction kinda defeat the purpose of runner length since they're compressing more volume into the plenum, anyway? ((The only one I can see it still mattering for is centrifugally charged, since those do basically nothing until about half the rev range, anyway.))
That would be a good topic of study. I would expect the manifold design having a measurable effect on the "turbo-lag" section of the curve before the turbo makes much boost. But I'll take it as homework.
Hey, I’m planning on making my own itbs. What material do you suggest to survive the heat?
The throttle bodies themselves? I don't know if I would trust plastic to maintain the level of tolerance required to keep throttle position constant in their closed positions. Maybe start with PA-CF and use brass inserts for the throttle shaft. Be cautious, and let me know how it goes!
@@StandRacing I meant the velocity stacks mb
@@Jimbob-2 You might be okay with just ABS/ASA its good to ~200F
love
It seems to me that if you want good tuning for 3 or 4 different engine speeds, you'd just bolt on 3 or 4 separate throttle valves and use the computer to switch which one is open depending on engine speed. It's a bit Neanderthal compared to the "perfect" engineered intake, but you can be really lazy with simulations and just build essentially a trumpet.
EDIT: If you're looking to build a bolt-on aftermarket component, then the above definitely doesn't work. In any case nice work.
Morrrrrrrrrrrre!!!!!!!!!
are your arms ok?
Yeah. My immune system thinks my skin isn't supposed to be there and tries to reject it. Psoriasis.
@@StandRacing That is not good, I hope you heal from it, or find some remedy to lessen it.
If you could make a Chevrolet 6.0 gas save fuel at low load, the world would be a better place. Brand new trucks, and they're tuned like a Corvette. There has to be a way to get a generic fuel tuner. There's demand.
Try a turbine intake.