GOOD NEWS -Blower motors are incorrectly dyno tested???!!!
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- เผยแพร่เมื่อ 14 มิ.ย. 2022
- In this, episode 61, DV explains why virtually all positive displacement blower motors are delivering incorrect power output numbers due to an almost universal error made during the process of correcting the figures. Also the misconception that a supercharger increases the engines volumetric efficiency is also challenged.
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My first hands on experience with a dyno was 2007. A brand spanking new DTS, (later bought out by Super Flow). I asked a bunch of questions and the man answered every one, He stated that this dyno spit out 3 power and torque stats, real time as is numbers, corrected numbers and advertised numbers. He also used flywheel diameter and weight and bore and stroke. The first numbers were indeed what the motor made right then and there with the recorded temp, barometric pressure and humidity. The corrected ones with standard pressure temp and humidity added a correction % so if you dynode the motor say in Denver it would read the same, the advertised set of numbers was basically a dialed up percentage that you wanted to add to the real numbers it was total BS. I never saw a corrected reading of more than 1.4% how ever when I could I`d dyno a new customers engines to see what he had before I worked on them and most of the time they were 10% or better over their actual corrected level of the previous shop. That advertised HP correction is a lie to sell more stuff, you can take a 450HP motor and crank up the advertised correction factor to 495HP to 525HP or more no problem. I`m sure you know all this but most people don`t.
David you are a true treasure trove of pertinent information, I used to read your articles in the monthly performance magazines decades ago that formed many of my opinions on engine building today; moreover, I am still learning from your years of engine building and testing. Thank you
Super intro in particular! Thank you so much Dave.
another excellent informative video, thank you
That is quite something David. you know as most blowers listed for sale for LS Ford mod motors and what not are usually in liters. say 2.3 liter blower. I always thought hmm your basically taking let's says a 4.6 ford modular engine and turning it into a 6.9 liter motor which is close to 427 cubes(7.0L)
great video and thanks for sharing
Bless you David!
Interesting info on the Magnuson!
I have been sharing all your great videos. Especially with my friend that has been an engine builder for 35 years. He has a Dyno but can't use it much because he is overloaded with Dealership,racing, antique and restoration engines. Can't find people to hire that he can trust and is knowledgeable these days
Tell him to do "dyno racing" on Saturdays. Grudge matches, reaction times, elimination trees, etc.
@@peterdarr383 I wish but he has to work on putting engines together. An other machine work.
Hi dave, I used to work for Allards, many thanks for the update.
Roger
kart Engine......Uk
Ps. can you cover Ramcharging please.
A few elements of this I found challenging, first the dyno "damping", is this an electronic adjustment from the strain gauge output or a viscous damper smoothing out the torque pulses seen by the strain gauge? Either way an engine with fewer cylinders (and a light flywheel) could presumably produce quite skewed results? As for the supercharged scenario, I appreciate that some of the horsepower is effectively "stolen" from the front of the crankshaft but surely the end user is more concerned with what is available at the flywheel? I am not being deliberately obtuse, I can see that the engine builder or developer wants to know.... you warned us it was esoteric! Thank you for yet another thought provoking video.
Like to have David answer this question
Proper dyno testing is done at steady RPM over a long time period. Doing a sweep isn't the way to go (inertia errors) and a lot of dynos can't hold torque at low RPM, that's why you miss out on the first 3000 rpm. There's a spec J1349?
@@1magnit Power sweeps are generally more accurate, if you have the software for it. (Many sub 2000 systems don´t. Even some sub 2010 systems are challenged on that account) If you want to you can hold it at 1000 rpm. but most of the time we start sweeps around 2000 rpm unless we are looking for something specifific down low. Also, if you want the right picture with steady state measurements youy will have to do a lot of points, like for every 250 rpm or so, or you are likely to miss afr dips or increases as they can come and disappear within 500 rpm. Of course, if you strap a 1000 hp monster on a 800 hp dyno you will be in trouble and it wohnt hold. But if things are matched there should not be any issues with that. Yes, the SAE 1349J have more or less become the industry standard which we all can relate to. Here on the EU mainland most still use DIN or in some cases KW. Both are easily converted if you want the numbers in another format.
@@torbenalstrup3902 There's no such thing as an 800HP dyno nor a 1000HP dyno, they don't measure power, they measure torque and RPM and calculate power from there.
@@nicknick2350 A brake
"How's that for a revelation" = Prof. Vizard mic drop.
MIND BLOWN 🤯 🤯🤯
Mind Supercharged !
I've been into the automotive field for years. I've always said it's how the dyno is adjusted and all dynos are not created equal. I like to dyno an engine for max power but I would much rather track tune my car to lower and lower the ET it's more of a challenge and fun to make it faster. For me street and strip racing is just a fun hobby!
Mile an hour seems to be more accurate for me
David.......Back in the day we referred to that devise under the console as the "California Knob" jokingly.......
So sorry for your loss mr vizard
Thanks!
Great video, FYI, 18,000 is 1/2 Atmosphere pressure, Question, @ 18,000 feet on STD day my experimental turbocharged Lycoming IO-360 can still hold 29.92 inches of Manifold pressure @ 2500 rpm. At sea level the Crankshaft is getting power from the chamber explosion pushing down on the piston acting Against standard atmospheric pressure of 29.92 inches will be on the other side of the piston. @ 18,000 feet altitude the Same Cylinder explosion is acting against half of the pressure On the other side of the piston Significantly increasing the power To the crank shaft.
My question is how much am I overboosting the rated horsepower, due to the 18000' half an atmosphere and having sea level pressure in the Turbo charged intercooled intake to engine ?
Mr Vizard, I am ignorant of the "frictional" corrections applied to engine dynos. I would like to learn more. On a dynojet 248, we measure what makes it to the tires. Even with an manual transmission, we sometimes see enormous losses from overcorrected engine dyno numbers.
Dave - you are mostly correct - most of the effect of supercharging IS caused by raising the density of the air-fuel mixture supplied to the engine. But if you have a large volume such a water cooler bottle - you may see that merely by the feeble 1/2 psi most peoples lungs can pressurize such a volume to - and then releasing the pressure - that even a closed vessel may be used as a sort of pump. If you can get a slight suction (a pipe elbow turned facing backwards in a slipstream for instance) and a slight pressure to alternate then large amounts of mixture can be moved this way (crankcase scavenged 2-cycles prefer 1.5 to 1 crankcase compression ratio for this reason)(no lower, and no higher),
Harry Ricardo in 1926 tests arrived at the conclusion that "given unlimited supercharging for any given fuel octane rating maximum INDICATED horsepower will occur at mechanical compression ratios between 6.5 and 7 to 1."(neglecting blower parasitic losses)
And sure enough the racing aircraft piston engines I work on bear this out. That range is where the amount of energy thrown away out the exhaust by even lower compression ratios becomes balanced by the beneficial effect of the VE increase I mentioned PLUS the greater BMEP obtained by longer working cycle (shorter valve timing) and the comparatively large combustion chamber providing comparatively more cylinder pressure farther down the power stroke until exhaust open event.
Patrick, I am only using the boost/displacement numbers here for the sake of easing an explanation.
I get the impression from your statements here you are well versed in boosted engine tech. Got all that from a learned response. Thanks for meeting a hi-standard here. look forward to your future comments.
DV
@@marvingvx1 I just want guys to know the benefits as well as drawbacks of "low" compression ratio engines for maximum BHP.
The drawbacks are many starting with lousy NA power, fuel economy and greatly increased exhaust gas temperatures.
Richard Holdener for example refuses to even consider running less than 8 - 1 CR engines.
But setups that would have been considered unthinkably complex for an automobile in my youth are now appearing as original equipment. A 7-1 CR engine with a now common bypass equipped Roots could make somebody an affordable hotrod with the bonus of veeeery wide and responsive powerband.
(I call myself a toolmaker) Just like combining many different methods of removing stuck bolts has the vice of complexity it also has the virtue of not having to "push" only one method to a point of diminishing returns or failure.
My point is that a positive displacement blower wouldn't have to be unhappily trying to make high pressure ratio, heat and lousy efficiency/high parasitic - if one would then simply add on a single turbo with a "loose" scroll A/R and let all the wasted exhaust heat+volume handle the (now) less critical task of spooling up for the highly boosted and aftercooled phase of acceleration.
Coming from an aviation engine background I think it's normal to keep the original engine redline, stroke and cam specs - while lowering compression, trying to keep or gain some combustion chamber turbulence in the process, avoiding mis-matches like highly over-crankshaft-speed-driven centrifugal blowers (ProChargers etc) when trying to get an engine to increase rpm rapidly - and just bite the bullet in terms of complexity and fit the thing with a Roots + Turbo+Aftercooler ("Dual Charged" or "Multi Charged") setup.
Paraphrasing Smokey Yunick "It's important to NOT do what DOESN'T make you go faster!"
I would like to see articles on easy ways to add piston cooling oil jets, vastly increase oil capacity, make affordable sodium cooled valve setups - and not so many on how to get another 1/8" of stroke, or super light valves and super strength rockers and pushrods, and loose torque converters to make up for the deficient power bands that result from traditional misguided power boosting approaches.
Thanks for letting me rant, Dave - you're a Class Act.
What is the SuperFlow sample rate at the torque sensor ? ,,, something else that adds some attention, is that a large percentage of general aviation limits boost to only bring an engine back to sea level power . Not talking experimental or racing or " war " power .
Always learn something profound.
Off topic comment. What is the material and method you used to insulate the bottom of the intake manifold in your how to build HP book?
Mr. Vizard, at 15:38 you mentioned the Magnuson supercharger as "the best one to get." Where can I get one that fits a (very common) SBF Windsor and uses a carb?
What are the average "friction correction" percentages/factors of a 302sbc vs a 454 at 6000rpm. How about the 302sbc at 8000rpm. Are these corrections added to the actual measured output of the engine?
Thank you for helping the kids we love it!!
Could you take the same engine and run it with a blower at say 15 psi and see what it makes and then install a turbo at the same boost level and measure it's power and wouldn't that tell you the friction losses of the blower for the most part? I know it's not an exact direct comparison but should be close
David, you keep busy, you still work, and you have more knowledge about engines than most people ever will. I had to chuckle when you mentioned brain damage. Your willingness to share your knowledge and the fact that you do is commendable. We met and talked many years ago and you are still the same person I remember and still incredibly knowledgeable. Yes we are far older than we were years ago, but we have aged well. As well as can be expected I guess, lol. The topic of testing blower motors has been brought up by others, and I have never heard it explained they way you do by anybody else. Some just said it was wrong, without much of an explanation. Others did not have the understanding to explain why in detail. One of those people that questioned it, was you. Imagine that. That is what we talked about all those years ago. Wishing you all the best.
Gold mine of information
I have only used standard electric or water brake dynos. I was always suspicious of dynos that measure during acceleration. I doubt they could possibly get accurate data, not easily anyway. Not with what I see they are using, they are giving rough estimates not data.
Mr. Vizard have you ever considered joining the cast of the Harry Potter franchise? You'd be a perfect all knowing Wizard....Vizard the Wizard!
I prefer to just go with actual measured steady state horsepower numbers, I believe these to be the most useful for me. What an engine makes in another enviroment really does not matter as what it makes where I am is all I have available to use. Also at steady state it shows a continuous generated power. Running sweep rates wind up showing accelerational power. Now for a drag racing type situation the acceleration is important but in a full load pulling situation the power it can sustainably produce is what is important. I prefer to think of dynos as a comparative tool more so than a be all end all say on power production.
Bcbloc02 all that is well and good until you need to quote power figures for an airframe designer who needs an absolute figure for comparison of one brand of engine to another!
DC
David please get back to me on my question of what cam should I run in my 383 Chevy with a 671 roots blower 8.5 to 1 195 blue print heads forged bottom end 1.52 rockers
He gets PAID to dispense such advice, my son.
My I ask. When using your 128 formula, do we use this info for positive displacement superchargers into our cubic inch numbers to get a proper LSA? Or is there something else?
IIRC Detroit Diesel rate their Roots blower pumping losses at .7PSI as ~ 100hp! Consider this low pressure and that automotive Detroit Diesel two strokes typically are governed to only 2100RPM. That gives one an idea of the pumping losses involved, which all have to be paid for in fuel BTW.
Roots blowers on turbocharged Detroit Diesel two strokes also have a bypass valve. This is for a couple of reasons, firstly an aftercooler is incorporated under the blower therefore the charge cooling is after the blower. Any adiabatic heating of the intake air could heat the blower lobes causing them to expand, touch then scuff and as a side benefit it saves ~ 30HP in blower pumping losses.
They retain the blower on Detroits because of starting, idling and low RPM responsiveness. A hybrid centrifugal blower/turbocharger with overrun clutch similar to EMD Uniflow Diesels was proposed but dropped due cost.
👍👍👍
What are your thoughts on figuring out whp from acceleration? Should be foolproof, given traction is sufficient?
I've done it, is giving me about 60 to 70% the engine "advertised" power. I'm correcting for wind and drag resistance or the difference would be bigger. Great way to compare before and after installing a mod tho. Doing it in 2nd gear to avoid spinning wheels and also to avoid going too fast to the point wind resistance is huge.
I have a question regarding the 0 hp loss exhaust system. When using a supercharged engine, does the volume required for the termination chamber change based on the max volume output of the blower?
John, I have never tested for that but I don't think it's a big issue.
@@DavidVizard Thanks for the reply, I've one more question. On your seminar web site all the dates are old, are you planning for any seminars in the near future?
I knew those dynos were scamming
Eaton makes 90% of the world's superchargers. Magnuson makes the world's bestselling "aftermarket" supercharger. I think that's what DV meant. Nice to know it rivals the efficiency of a turbo.
DV, for many years, I've heard that 15 lbs of boost effectively doubles the displacement of the engine. So your 500 ci engine, under 15 psi of boost, will act like an NA 1000 ci engine, is that correct?
Yes - but by the time inefficacy's are added in means the realities are somewhat different.
Your thoughts on centrifugal superchargers???
Belt driven Supercharger. Boost is linear with RPM, the more rpm you make the more boost it makes.
So it makes less low speed power than a positive displacement supercharger. But you make more top end power than a typical roots blower at high rpm, assuming cylinder head flow and cam timing can support higher engine speeds.
For some reason I had no sound when he was speaking but had sound for the adds
I am not sure why as a community we get hung up on a number on a piece of paper. I think of a Dyno as a tool. You show up with 700 hp and leave with 750 after you tweak it. The Dyno helps you get the most out of your combo. That's it.
The real key is how it actually performs.
My stock 4500 lb 2016 Hellcat Challenger went 10.84 @ 126mph.
I know she was making more than the advertised 707 hp that day.
My street car averages out to around 10.90 in 1/4 and actual time slip of 7.07 at 96 mph in 1/8 best ET with 87 octane with a high rear gear 3.31 no power adder yet and around 3800 pounds with me in car. I need to lighten my car some time. You know how things are always a lot of things you can do to make them go faster. Lighter is less breakage, better gas mileage and easier on parts when lighter and of course faster! Your doing good at 4500 pounds. Each 1000 pounds removed is almost .80 off in the 1/4 mile. I have heard 1000 pounds is 1.00 but the other figure is more conservative. Could spray your intercooler with nitrous for cooling. Just don't get nitrous into engine and try to start it. Doing this good chance of engine fire and explosion. I've seen it over the years. I wonder what the first gear ratio in the Hellcat automatic is? It must be low and strong to get 4500 pounds moving. I don't know how long these automatic transmissions with soft tires are lasting but they built a pretty tough transmission a whole lot better than most things out there so far. I'm sure you probably know there's all kinds of upgrades you can do to your car, bigger blower with Teflon rotor strips, under driven pulleys, nitrous, rear end gears and so many more. Is 4500 lb with driver in the car at scale? Does your hellcat have a trans brake in your car? I plan to get a trans brake sometime. I'm a Chevrolet man but I have two Cummins Dodge trucks they're the best,, strongest and most dependable in the business.
@@tomtee4442 it is an 8HP 90 so first gear is 4.71.
The 2016 used a 2.62 rear end.
My 2020 I special ordered a 3.09.
Back to the useful tool part. Most of the hellcat engines have an extremely flat power curve. So when you hit the next gear horsepower is nearly identical
As an example... With the mustangs I have seen the power curve is very peaky. So when the shift they nose over and then come on hard, then nose over again.
I have an in car video of me running 11.2 and it looks like I am out for a Sunday drive. The car just pulls away and shifts smoothly, never nosing over
@@tomtee4442 to add to that. I think a Dyno is useful to figure things like shift points and gear ratios the obsession with having a big number on paper to me means nothing. Its like they are trying to win the racing from there keyboard
Imagine the hellcat engine transmission and rear end in a 70 cuda. I would say without a driver would probably be around 3,400 through 3,600 lb because I imagine the hellcat engine is aluminum head with a steel block?
@@tomtee4442 I am not sure but I think it is all cast iron
That’s why at higher altitude to get power from the same engine,you supercharge it.
It’s called air pressure and the air you pack into it.
Boost equals power if you can contain it.
Turbo is the most efficient.
air density is the secret not boost pressure
More boost can make more heat many people don’t know that sometimes less boost is more power due to heat
Boost is only a measure of restriction in the engine, volumetric efficiency is where it's at
@@jerradstilson7285 you still need to get the air density at your volume to make power when boosted.
Wow
For those among us who don't have access to dyno......you just shed some light and corrected a misconception, they we didn't know existed. does magnuson make a supercharger for SBC today?
Sure do!!!
@@DavidVizard Thanks for the reply it's greatly appreciated. I have been a fan since I saw a DV article where you hopped up a yellow Monza, back in 77,78. I've been looking for a Magnson Part# for SBC, but can't pin one down. Thanks again.
I realize this is the wrong video for this comment but, in regard to the hollow rod journal, is it safe to say that a hollow rod journal is stronger than a solid journal the way a driveshaft is hollow to resist twisting as a solid driveshaft would.
Not quite.
64 years for free. DV I was hoping for 65. 64 that's it just joking nice job
how we sponsor ?
When I Dyno I don't want Corrections .I'm there to tune .Not tickle ego's.
So sorry David, where is the thanks button?
Can money be sent directly to you under “Grief Relief” fund?
It should be toward the right of the screen just below the bottom of the pic.
Every dynosheet I have says - Smoothing: 50%.
Okay, maybe I missed the point. An Otto cycle is 4 cycles, 5 if you include the overlap periods. I think I don't understand how a supercharger can displace "500" ci in 2 cycles. My guess is the calculated displacement of said supercharger. Should one induce 500 ci of air, during 2 rotations, given the gear set up, then wouldn't you only receive 500ci of air? The intake valve is only open for a stated amount of time. I don't know, maybe I'm putting too much math into it. Either way, please David, continue to teach, if no one else, me. I'm open to your gracious efforts of shared knowledge. I will sleep on this and consume copious amounts of caffeine to get it into this thick skull. I've projects to build, and you provide keys to power for these endeavours.
Think of the air in quantity of "mass flow" instead of raw flow and the superchargers theoretical displacement will make more sense......example if you take 500-cu/in of air at standard atmospheric conditions and compress it into 1/2 the space the pressure ratio will now be 2:1 but, the weight of that box of air will weigh the same amount as the atmospheric air no matter how much it is compressed.....so if your engine is 500-cubic inch V8 it take 720-degrees of crankshaft rotation for ALL 8-cylinders to go through a complete cycle, and if the blower is 500-cubic inches per revolution, then the engine will be requiring only 250-cubic inches of air per rev. @ 100% volumetric efficiency (VE), yet the blower is displacing 500-cubic inches of air @ 100% volumetric efficiency (VE), therefore the MASS of air as well as PRESSURE-RATIO of air in the intake manifold will both be 2:1 if there were no losses and everything was 100% efficient.....in the real world the engine can be X>100% VE and the supercharger will be X
@@ericschumacher5189, thank you. That sums it up perfectly for me. I understand the MASS portion of the air, just forgot to think of it in that way. I understand now. Thanks again.
The consistency of the dyno is more important than the accuracy of the dyno.
If you have accuracy you automatically have consistency but if you have consistency you do NOT automatically have accuracy. To me the accuracy is paramount because you can't get much science from a better/worse,more/less situation. You need to know detailed data on all the parameters in order to know where the engine needs work and where it is a waste of time to work.
@@billshiff2060 My point was when comparing parts to see which one makes the most power, consistency is paramount. As far as what power the engine actually makes, I don't think any two dyno's would come up with the same number. Ask 10 engine builders the same question, you'll get 10 different answers. People who build dyno's are no different.
Imagine a world where an engine builder doesn't try to put down another one, only in your imagination. It will never happen. I wonder how many engine builders there are in the US. They all think their better than the next one. Let the builders that win races cast the first stone. Steve Morris, pro line, Brad Anderson, Allen Johnson etc.
The biggest mistake is "corrected" HP for atmospheric conditions, it's folly to say this engine makes X power at such and such atmospheric conditions and will make X + or - at such and such atmospheric conditions, that simply isn't correct
@@carstennobody7047 not all engines are turboed, and engines that run constant displacement super chargers have to be spun faster with pulleys, or they won't make the same power at high altitudes, I've raced blown engines since the mid 70s. Worked for 3 shops that had Dynos, and normally aspirated engines don't change much because of atmospheric barometer reading, they only see changes with humidity reductions
Neal Williams is the inventor of the super flow dyno He grew up in Inola, Oklahoma, I've known him since the early 70s
@@carstennobody7047 normally aspirated engines lose significant power at higher elevations, but Dyno testing and corrected to atmospheric conditions doesn't guarantee the engine will actually make corrected power at the corrected statistics, the only engines who can maintain power to 10,000' are turbocharged engines, because the lighter air the inlet turbine spins faster. Engines with fixed speed superchargers can if the manifold pressure is high enough, roots and screw type compressors are fixed displacement, they will only give a certain amount of boost, the Drive ratio determines how fast or slow it makes the pressure, my Blown Alcohol Hydroplane was powered by a 567" Chrysler, with a standard Helix 14, 71 blower, running a 14mm drive, I spun that blower as fast as possible, at 1.71 x crank speed, I didn't see the reason to apply boost slower, when acceleration was the game.....we were quite successful, I retired in 83', after 7 years, my Driver was killed in 86'
@@carstennobody7047 depends on the engines and turbo, or mechanically driven super charger....
A stroke is 180 degree or half a revolution.4strokes engines have a intake stroke ever 4th stroke
intended for or likely to be understood by only a small number of people with a specialized knowledge or interest
Haha! of course you're on one of the pioneers of engine buildings channel!! No disrespect but he's actually explaining that for the laymen and that's why I watch him because I'm one of those guys.
Well,, fake Dynos have problems;;-)
Systems and Programs makes differense.
Dyno sessions in internet are 4to5 sec , some those engines can't take More ;-)
Estimatet loses are BS. Engine produce torque, that have to measure right, and engine inertia and dyno inertia can measure. When engine is taking RPMs fast it will genereit less power, and if it is pulled down fast it is making More power, engine inertia does that.
Steadystate measuring is absolut right.
Sveap or estimating somethig is BS.
Too fast raising RPM also affects cylinder filling neg, rpm is rising in also intakestroke time,(portveloxity).
ThankYou
Please... invest in a 2 channel mic... I'm tired of hearing David speak into my left ear (headphone user here)...
Saint Jude ya do it give likes they do wonders for kids please help thanks
Peace.....
Blower motor myth#1.. You have to use 6-1 pistons,not sure where this started,but it's wrong. I have 11-1 slugs under my 14-71 blower and I've never had a problem
Where is this myth... you're making a strawman argument. Not everyone uses race fuel, and not every supercharged car is drag only.
@@superkillr I drive my car on the street,and yes I use Cam2
Compression- timing-boost , pick which one you want , you can use any one but you .must sacrifice the other !!💥
Thirty years ago this guy was spewing the same BS
DV; Thank you. v/r wh
Thanks!
Thanks!
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Thanks!