Lower compression for Turbos?
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- เผยแพร่เมื่อ 5 ต.ค. 2024
- But why?......................... that's it. No more desription.
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Engineering explained the British way, the right way.
💯
Range Rover must not have received the memo.
3;45 " and it's all goina turn to shit" I love the workshop!
love the explination spoken like a true mechanic \
This is a killjoy, I lost my best mate tonight, very good rider. He could make that R6 do anything he wanted. Pastrana on the street, RIP Bradley, my best man to9.
I made him watch your vids, half way, enough, let's go...
His saying was 'put it on the pipe, let er sing"
Thanks mate
"So the crankshaft is going to jerk like a dickhead"
I lost my shit when you said this.
First person to explain it in a way that makes perfect sense to me. Thank you!
This video does a great job explaining why turbos use lower compression than NA engines, and it is fascinating to me how many comments along the lines of "low compression ratios on
turbo's are a thing of the past"... I hear this all the time, even among people that actually claim to know what they are doing. Then of course, they seem so proud to tell me about all the engines they've blown up doing that. But the dream never seems to die. The absolute fact of the matter is that compression ratio mostly only affects the peak cylinder pressure, while boost affects the average pressure, which is way more important for power. Also, it is easier to cure lag by properly sizing the turbo and using one that is efficient enough and or a small shot of nitrous when the throttle is snapped open than it is to fix another blown up engine...
on ethanol you can usally run quite high comp ratios but youll have to back off on the ignition. in diffrent cases it can be preferable with higher comp ratio and later ignition
A machinist friend who did heads for my rally car used to work for Porsche usa as an engine builder/tuner. He had a wicked 996 that made around 900hp, monster boost, huuuuuuge turbo, that car had low compression, something like 7.5:1 or 8:1. It was a dog down low, but i swear when it came on the boost it changed the rotation of the earth, had a power curve like a 2 stroke and was useless on the street ha ha
i really like this video didnt waste time being all PC he was himself and i learned a bit thumbs up from me
I got a good laugh out of that lol
Shit got real when he started explaining the effects of pre-ignition.
i love this video so much. Thank you!
Next time I blow another engine his voice and description of it happening will be running through my head lmao 🤣😆
Great explanation!
Always thought it was counter productive when people would lower compression to "boost" an engine. Thought why do that just run NA with higher compression to make power. Never thought of the fact you push twice as much fuel and air with forced induction which equals more potential energy. Thanks Matt
False
@@elonmust7470 can u explain?
No he can't
Loved this video!
Turbo aolircraft engines can be monitored. By cht and egt. Aircraft have more control over it than bikes with mixture control. Running lean of peak is good .
Is that buddy Jesus from dogma? Something with Kevin Smith..
Yes it is
It’s simple if you have high compression you can’t throw a lot of boost at it if you have low compression you can throw more . It’s really just a balance type thing.
LOL and that's why I do these videos and you don't. It's so 'simple' that you missed the important question - that question is - why.
@@dirtygarageguy so why then? Whats the advantage of low compression higher boost vs high compression low boost/e85 etc? Aren't they gonna be the same thing? That's wats breaking my head r.n. I'm trying to build my bmw n54 engine r.n
Compressing a gases causes that gas to heat up. This is because work is done to the gas. If there's more gas in the same cylinder at bdc then more work and therefore more heat will result from.compressing it.
What about a diesel. sometimes compression is lowered a little to use a turbo. is that because of the same outcome relating to heat that could melt holes. I know its compression ignition but Ive always wondered about it too.
With diesels it's a different story. Yoo high a compression means you're wasting energy in compression. There's a balance to how much is too much etc
And more fuel injected means more cooling of the mixture. That keeps the shite cool to avoid the fuck up.
You're talking about latent heat, and that's something a bit different - one comes after the other and so on.
well i did a lot of research before i supercharged my CLK200 M111 N/A engine with 10.4:1 compression ratio and people told me it was a great risk but i charged it anyway, engine runs on 0.55bar on EATON M62 on stock pulleys, already 7000kms. and nothing bad has happened yet. but thats the sum of having MB engine. Mercedes engines are the strongest european engines for sure, im saying that M104, M111 M112 M113 M119 are just beasts. for a comparison M104 3.0 N/A is almost as strong as 2JZ-GTE block
Everyone in 2019 who knows what they're doing has left the low compression for boost stuff in the past
..
10.5:1 isn't high compression these days. 13:1 comes to mind...
Look at the specs table for the GSXR1000
en.wikipedia.org/wiki/Suzuki_GSX-R1000
2001 ~ 2002 = 12:1
2012 ~ 2016 = 12.9:1
You try and run this engine with a turbo and don't lower the compression on 95 octane - detonation will happen...
That puts up the next question: So could that be that the 300 super bike (LMAO) might have one cylinder with an higher compression and got the pre detonation? because the piston was missing chunks... HMMMM?
Fuuny you say that - I have the perfect example - video coming soon.
I got an other idea how that could have caused the pre detonation… the cylinder overheated due to missing oil squirting und the the piston and that could have fucked the super doper slippy sport bike engine. HMMMM?
How low can you go.. How low can you go..
..and what are the negative effects of running too low compression?
Yessssss I love it!
can you do a video on turbo lag and the pro's and con's of turbos on bikes ??? not that i would ever fit one.... or maybe a video on blowers (zx10 h2r) v`s turbos (1980`s gpz 750`s i think ) very interesting subject forced induction i would like to know more if you have the time to do it
cheers
james D
Yes I can
that would be very much appreciated cheers ....... i found it very interesting how kawasaki used the design of a blower off a helicopter they make and applied it to the zx10.... if it wasn't a animal enough holding it on the pin at over 10,000 rpm in the bottom 3 gears normally aspirated lol ......class A drugs in kawasaki japan = lots of fun for us
cheers
james D
Just think, all those dubious ebay engines aren't "worn out" or "knackered" they're turbo ready!
Can you make a video on why exactly, detonation is so bad compared to spark ignition?
Detonation usually occurs in more than 1 location, and is usually an explosion, not a burn
@@dirtygarageguy so the air/fuel mix all reacting at the same time is the issue?
In random pockets. It's the explosion bit that does the damage. Deflagration is a progressive burn. An explosion is a combustion at the speed of sound which creates a shock wave.
thermic engine it's in the name... good video
Top work Matt as usual. What do you think about these Mazda combustion ignition petrol engines ( sky activ X ) with variable compression .
we'll get to them but they're not top of the list being a car thing
Fair point .
This is about the static compression ,the point is the dynamic compression,you forgot the camshafts characteristics and the ignition timing angle ,the decompress plate or pistons was a solution in the past in the time of the poor software , so your video is correct and i agree with the low static compression and turbo because is forgiving mistakes but is not the only way.
Dynamic compression ratios are NOT real.
@@dirtygarageguy is the only real thing ,and the one that really matters.
Do you know what a compression ratio is?
@@dirtygarageguy Are you kidding?Is this a question? I will answer by your way,do you know what dynamic compression is?
A compression ratio is a volume ratio. So the total volume when at BDC compared to TDC.
You think that dynamic compression ratios are something you actually know, when infact what you mean is cylinder density. This can be effected by the following;
Air density
Valve timing
Inertial filling
Engine temperature
Fuel ratio
Valve bounce
Intake resonance
Exhaust scavenging efficiency
Here's a good example for you, let's say your static compression is 10:1 and you think your dynamic compression is 8.2:1. At what rpm? What air density? Because if you change these variables your power output will change.
And one last one. So your dynamic comp is 8.6:1, what are you gonna do with that number? That number that is changing all the time? (Because that's what dynamic means...)
I’m still waiting for turbo your bike 4 or 5 ... still haven’t gone over exhaust design turbo pre or post expansion chamber, Matt it’s been over a year I’ve been watching, where’s the cheap Chinese motor and duplicate turbo design, I know you’ve done things to further this!!! Come on man!!! My boat, rotax 587cc turbo is waiting waiting for your video lol
The lower compression, the sweeter the boost...
Um no... the lower the compression, the more boost you need to make the same power as a higher comp engine.
@@elonmust7470 bro i say sweeter coz the temps in the engine run a bit cooler than the high compression alternative.. but u can make more boost though
@@TalkSteer I haven't built a boosted engine under 10.5:1 in the last 5 years....
They all scream...
@@elonmust7470 bro whats your most powerful build to date?
10.5:1 isn't high compression these days. 13:1 comes to mind...
Look at the specs table for the GSXR1000
en.wikipedia.org/wiki/Suzuki_GSX-R1000
2001 ~ 2002 = 12:1
2012 ~ 2016 = 12.9:1
You try and run this engine with a turbo and don't lower the compression on 95 octane - detonation will happen...
3:03 70:1 COMPRESSION HOLY SHIT!
The H2 runs 8.5:1
The H2 sx se is 11.2:1
The H2 sx is 11.5:1
Great you can copy and paste - was this meant to be some sort of revelation? Seen as though you love to copy and paste - match these up with the boost pressures.
@@dirtygarageguy after running the numbers.
The H2 makes an insane amount of boost
Want to avoid all this, with serious boost, one word, Diesel.
i was told f1 drivers can reglate boost while driving is that true? if so how is it done. electronically,mechanically,ect?
I don't know, F1 is for twats
What if using E85?
In relation to what?
So you could have a diesel engine with extremely low compression. Say 10.1 but you could use an electric turbo to produce the needed compression.
"electric turbo" - no.
Don't listen to this guy, he's wrong..
Prove it.
@@dirtygarageguy one guy did & it looks like his posts're gone..
I have a question, if an engine have a high compression ratio (12 :1) but very bad volumetric efficiency (restricted to about 60% VE) can we use a turbocharger to bring that VE up towards the unrestricted VE (@ about 90%) without lowering the compression ratio. Does VE have something to do with temperature inside combustion chamber ? (we use 98 octane pump gas)
Yes. Heat is generated during compress because of the act of compressing. The issue you have is that Ve changes over the rev range
Sooo anyone up for doing the math? How much compression could you have if you were feeding the piston cryo fuels like liquid oxygen and liquid hydrogen? Ignore the ability to cool the cylinder with the fuels!
Just answered a question very similar to this -
"So, let's say i've got a boosted engine (1.5 bar of boost pressure), with a compression ratio of 10:1. To minimize the chance of detonation i lower the compression ratio. Now i've got an aftercooling system for the engine, is it possible to lower the initial air temperature as far as to the point at wich i can use the original the original compression ratio of 10:1? I probably would need some kind of heat pump for this massive heatflow."
My answer -
Yes. Heat is energy - its as simple as that. So based on this fuel requires 'x' amount out of energy to combust. Compression adds energy to the charge. The more you compress the harder the engine has to work - we call this load. But this compression in finite. In other words the engine can only compress so much before TDC is reached.
To make this easier to understand you think about this in Kelvin. Where 0 Kelvin is no energy. So 0dgeC = 273K (but we'll round to 270) So just say your fuel auto ignites in air at 200deg C - that's 470K. This is all we care about.
If 10:1 compression with 1.5bar boost increases the energy to say 500K then we've passed that limit of the fuels ignition point.
So our air is say 20degC or 300K. Compression increases that by 200K to equal the 500K. If you drop the air 'energy' to 250K then thats -
250K air intake + 200K due to compression = 450K and our fuel auto ignites at 470K - we're all good. Now we can convert back to degC (or F if you live in the 1940's) This would mean your intake would have to be -20degC (or more precisely -23degC).
This is the problem. If you have a 1 litre engine @ 10,000 rpm that's 5000 litres per minute or 83 litres per second. This is the volume of air you have to chill down to -20degC from say +20degC. That's a delta of 40degC.
In other words, that's fucking hard to do. Or you can just lower the compression ratio. This is why this is done. Great comment. Will be a video soon.
Ahh the 1940's what a wonderful time
Sooooo cryo fuels are a go then!
Ya know the beauty of injecting liquid O and H into an engine is the lack of intake! You could have 4 OHV but all of them exhaust, cool the cylinders with incoming fuel (like rockets do) SOUNDS LIKE A GREAT PROJECT FOR A PLACE CALLED THE WORKSHOP!
The Workshop That cool intake (-23°) could cause problems for the fuel to be atomized and cause a bad mixture of fuel with air?
Yes it does - another reason why it's not done.
Heat the fuel cool the intake could definitely run a rankine cycle heat pump to solve those problems
Hey my engine has a 6.28:1 I lowered it too much? I also got a turbo I planned to run on high boost
can i put 2, 3 ,4 or more head gaskets to reduce the compression ratio? will this easy cause a leakage? i really need to know, thanks guys
Not a head gasket - a base gasket yes
i may tell you the full story of my case, i have a nissan figaro, i am about to change the cylinder head, and i bought a nissan micra cylinder head from ebay, because it look the same, but unfortunately i found that it is actually different, Nissan figaro cylinder head has a step inside as figaro has turbo but micra doesn’t have turbo, so the figaro cylinder head designed with a step to reduce the compression ratio, but now i bought a Micra cylinder head which without a step so if i install it, my figaro is gonna have much higher compression ratio and will hurt the pistons i believe, so now i am thinking to get 3 - 4 more head gasket to increase the gap in order to lower the compression ratio, but in the market there is no any super thick head gasket, so i am thinking to put more head gasket together, do u think it will works? thanks
No. You can't just fuck around like that. You have to check the valve clearance and everything else
Got real angry there for a second. Sounds like you’ve blown a few motors lately. To sum it up... if I’m trying to lower my compression ratio to add a turbo... I get bigger injectors and pump more fuel in?
So I shouldn’t turbo my 13.5-1 or could I do it on low boost like 5 psi
I need a new regulator rectifier for my yamaha where do you get your parts from
You won't get engine damage with high compression and boost if you use direct injection, because there's no fuel in the cylinder before TDC (the spray starts just before, at, or just after TDC depending on the RPM/mapping strategy). This is why most new cars are turbocharged and direct injected, and you can generally get better thermal efficiency with direct injection.
At least the combustion can only start around TDC and not halfway up the compression stroke, so the piston is already on its way down by the time a decent amount of combustion pressure is produced.
Mazda's Skyactiv X engine basically runs like a diesel engine when it's up to operating temperature where the ~18:1 compression ratio ignites the lean mixture with compression alone.
Fucking love it
Would changing the octane of the fuel stop the pre-ignition? Say, for example, you turbo your engine without changing the compression ratio, and you get pre-ignition with regular old 91 octane, if you increase the octane, to say 98, would that work?
Yes - but this is complicated and not easy to work out. A lot of testing is usually done, with a lot of parts suffering detonation to find out what works.
The Workshop I dont see how that is true. Race gas and E85 has been tested on high compression big boost aplications for many years. Professional drag cars run high compression and massive superchargers/turbos with 30+psi. I myself run a Vortech V7 YSI with 26psi and 11.1cp with e85. My car is just fine.
Higher octane, forged internals, proper intercooling and professional tuning is the key to sucess.
The Workshop Also to note, a higher compression motor is way more fuel efficient. A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency. Just dont go crazy on ingition timing because it takes less boost to make power a power target.
8.1 CP with 40psi to make 700whp?
Or
12.1 CP with 20psi to make the same power and have a better powerband?
Its a no brainer.
@@bluestreamde6114 This guy is stuck in the 90s is all..
10.5:1 isn't high compression these days. 13:1 comes to mind...
Look at the specs table for the GSXR1000
en.wikipedia.org/wiki/Suzuki_GSX-R1000
2001 ~ 2002 = 12:1
2012 ~ 2016 = 12.9:1
You try and run this engine with a turbo and don't lower the compression on 95 octane - detonation will happen...
"This guy is stuck in the 90s is all.."
- And you don't know what the fuck you are talking about...
😂 I love it!
No No No...
The pressure before compressing does NOT have a significant influence of the final temperature...
Look at this:
Before compression #1
T_gas = 0,00 °C
p_gas = 1,0000 Bar
v_gas = 0,78376 m^3/kg
h_gas = 501,93 kJ/kg
s_gas = 3856,33 J/(kg K)
After compression #1
T_gas = 399,25 °C
p_gas = 24,8644 Bar
v_gas = 0,07838 m^3/kg
h_gas = 913,84 kJ/kg
s_gas = 3856,33 J/(kg K)
------------------------------------------
Before compression #2
T_gas = 0,00 °C
p_gas = 2,0000 Bar
v_gas = 0,39162 m^3/kg
h_gas = 501,66 kJ/kg
s_gas = 3656,48 J/(kg K)
After compression #2
T_gas = 403,04 °C
p_gas = 50,5430 Bar
v_gas = 0,03916 m^3/kg
h_gas = 918,32 kJ/kg
s_gas = 3656,48 J/(kg K)
(pressures are absolute, and the gas is air R729, N2/O2/A (76/23/1))
You can see that I the compression ratio is exactly one and that the compression is isentropic (which is quite close to what happens in an engine)
Look, the difference in final temperature is less than 4 kelvin after "giving the engine 1 bar of boost"
Where the fuck did you get this from?
The Workshop
From a refrigeration software package..
Btw. Auto ignition does not depend on temperature alone. Time is also a factor. I read some research about injecting different chemicals (fuel) into a gas turbine.. Pressures where 20ish bar and 500ish degrees C and they measured the ignition delay (several milliseconds)
Why is your gas constant number 729? Why is the density 0,07838 m^3/kg? The density of air @ 0deg = 1.2922 kg/m3
"Auto ignition does not depend on temperature alone."
Ignition delay in this respect it to do with mixing. Seen as though a cylinder based combustion event is quite evenly mixed then it does. Delay has nothing to do with, is there going to be ignition. I can't see why you've mixed them up.
"From a refrigeration software package"
- Well this makes sense. Wiki to the rescue -
"Air is so frequently used as a coolant that air cooling is seldom mentioned in a refrigeration context. Due to the low boiling point of its constituents and low heat-carrying capacity, air is infrequently used as a refrigerant.
Air has been used for residential, automobile, and turbine-powered aircraftair-conditioning and/or cooling. The reason why air is not more widely used as a general-purpose refrigerant is because there is no change of phase, and is therefore too inefficient to be practical in most applications.
Now it makes more sense. And why your calculations don't make sense. Phase change.
So, let's say i've got a boosted engine (1.5 bar of boost pressure), with a compression ratio of 10:1. To minimize the chance of detonation i lower the compression ratio. Now i've got an aftercooling system for the engine, is it possible to lower the initial air temperature as far as to the point at wich i can use the original compression ratio of 10:1? I probably would need some kind of heat pump for this massive heatflow.
Yes. Heat is energy - its as simple as that. So based on this fuel requires 'x' amount out of energy to combust. Compression adds energy to the charge. The more you compress the harder the engine has to work - we call this load. But this compression in finite. In other words the engine can only compress so much before TDC is reached.
To make this easier to understand you think about this in Kelvin. Where 0 Kelvin is no energy. So 0dgeC = 273K (but we'll round to 270) So just say your fuel auto ignites in air at 200deg C - that's 470K. This is all we care about.
If 10:1 compression with 1.5bar boost increases the energy to say 500K then we've passed that limit of the fuels ignition point.
So our air is say 20degC or 300K. Compression increases that by 200K to equal the 500K. If you drop the air 'energy' to 250K then thats -
250K air intake + 200K due to compression = 450K and our fuel auto ignites at 470K - we're all good. Now we can convert back to degC (or F if you live in the 1940's) This would mean your intake would have to be -20degC (or more precisely -23degC).
This is the problem. If you have a 1 litre engine @ 10,000 rpm that's 5000 litres per minute or 83 litres per second. This is the volume of air you have to chill down to -20degC from say +20degC. That's a delta of 40degC.
In other words, that's fucking hard to do. Or you can just lower the compression ratio. This is why this is done. Great comment. Will be a video soon.
Or use higher grades of fuel that resist detonation better. High octane race blends of petrol, ethanol, methanol, nitro....
I am just going to say, Dodge Demon has refrigerated intake :p Don’t know about other cars, but that’s one of the things what they did in that stock 5l v8 (turbo) to achieve 840hp. Now, you can say: ,,blahblah, 840 is shit, I’ve seen smaller enines getting 1500hp”. Allright, but did you see their exhaust? They inject 2x the fuel to air needed just to evaporate it, so the thing does not to blow.
Because of Pascal's law.
Sugs from Madness has really let himself go...;)
Everyone knows that fitting a turbo to your baggy trousers makes them super slippy...!
What was the best Japanese turbo bike? I vote for the CX650, despite pushrods, lateral top heavy overhang and excessively complex engine. It was a Honda FFS.
Mans your van run 10:1 easy amn my twin turbo mustang is 10:1 lol and I’m find I run e85 and I have a run gas then with water meth
Sayonara, see ya fuckin' later
Lmaooo I love this 😭😭😭😭😭😭😭
I have a question on engines that is high compression but puts a supercharger does that actually take away from the compression ratio in a sense and makes it to where you don't have to reduce the compression ratio on a naturally-aspirated engine that's a fuel injected what's your opinions on that?
Don't really understand your question but yes you still need to lower CR for supercharger. It applies to any type forced induction.
Oh okay then how exactly did it say it was able to with stand 10 lb of boost
fitting a super charger to a NA engine is the same as a turbo it's just driven differently. So everything Mat said will still apply. On the builds I've seen in magazines back in the day , tuners usually use two metal head gaskets to lower the compression ratio.
Do you know where I can find a thicker head gasket for my 1990 Kawasaki zx6d1?
The number related to boost means nothing in this respect without knowing the static and dynamic compression and the fuel used.
As Chris says above, just because an engine might have had 11:1 compression when stock doesn't mean it has 11:1 compression now the engine is fitted with a supercharger.
As ratgreen said. Turbos are actually called 'turbo superchargers" whilst roots blowers and alike are just called 'superchargers' - the turbo bit just informs you that its a turbine driven system. All of these systems are called forcedinduction as ratgreen said. If you force air into a cylinder to increase the charge density then it's forced induction.
Hence why 2 stroke motorcycle engines are NOT forced induction or 'supercharged' This is a fuction of the system, and not an addition to that system. 2 Stroke use this system to fill the cylinder - and not to pressurise it.
4:36
First love it
HAHA you love second
Sorry but this is all false. The biggest part being that you completely failed to factor in the added cylinder pressure before TDC under boost. More compression at X boost value will always yeild more power... The days of having to run low compression for boost are friggin LONG GONE.....
I've been running between 10.8:1 & 11:1 on the last 4 forced engines I've built, no detonation at all...
"More compression at X boost value will always yeild more power... "
- Wrong, but nice try.
"The days of having to run low compression for boost are friggin LONG GONE.....
I've been running between 10.8:1 & 11:1 on the last 4 forced engines I've built, no detonation at all..."
- And what you 'failed to factor in' is higher octane rating of fuel. And you think 11:1 is high compression? My bike outside runs 13:1 - sorry dude but you're already out of date - try and catch up with the current state of things.
Oh look
en.wikipedia.org/wiki/Yamaha_YZF-R1
Yamaha R1 2015 ~ 2019
Compression ratio = 13:1...
@@dirtygarageguy You never proved anything with all of your white boarding, why do I need to? I know damn well 10.5:1 isn't considersd high compression, before messing with turbos it was high comp NA stuff with 116. I also know that I'm not detonating on 93 octane..........
& yes more cylinder pressure with all of the variables at a constant, will yeild more power.
Look nobody builds 8:1 turbo engines any more.......
"You never proved anything with all of your white boarding, why do I need to?"
- Because you're the one making stupid claims.
"I know damn well 10.5:1 isn't considersd high compression"
- Well then this makes your original comment dumb -
"The days of having to run low compression for boost are friggin LONG GONE.....
I've been running between 10.8:1 & 11:1 on the last 4 forced engines I've built, no detonation at all..."
- But 10:1 IS low compression compared to 13:1...
"& yes more cylinder pressure with all of the variables at a constant, will yeild more power."
- please explain. I'd love to here this one in as much detail as you can make up.
"Look nobody builds 8:1 turbo engines any more..."
- Yeah thye do dickhead. There are loads of guys building Bandit turbos etc and they run about 8:1. Where in this video did I say 'this is the latest technology?' - that's correct fuckface - I didn't.