Why More Boost Doesn't Always Mean More Power
Motor
Why Do Two Engines With Equal Turbo Boost Make Different Power?
How does elevation affect a car's performance? NA vs Turbo
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If two engines have the same boost, and the same displacement, why does one make more power than the other? The answer is complex, but ultimately it comes down to how much air (specifically oxygen) can you get inside an engine's cylinders. The more air you have, the more oxygen you have, thus you can inject more fuel and produce more power. But manifold pressure is only one measurement that will determine how much oxygen you'll have within your combustion chamber.
Temperature and humidity also play a role on the engine's performance. You need to look at manifold density, instead of simply boost, to really know how much air the engine is getting. Not to mention ignition timing, air/fuel ratios, and the efficiencies of the turbos you are using. This video will break it all down from beginning to end!
Humidity Effects On Performance:
I spoke with a Ford engineer about how humidity affects horsepower. He stated that humidity acts like EGR. For example, combustion with 1% water by mass (not to be confused with relative humidity percentage) is nearly equivalent to using 1.7% EGR. As humidity increases, you increase your mass flow rate, which increases heat capacity, which causes cooler combustion and reduces combustion pressures.
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*Additional comment about humidity!* I spoke with a Ford engineer about how humidity affects horsepower. He stated that humidity acts like EGR. For example, combustion with 1% water by mass (not to be confused with relative humidity percentage) is equivalent to using about 1.7% EGR. As humidity increases, you increase your mass flow rate, which increases heat capacity, which causes cooler combustion and reduces combustion pressures.
Darryl Jones
5 måneder siden
This not the whole story and only a small part of it. It’s more on the efficiency of the turbine not so much the compressor efficiency. If the flow of the exhaust side is increased the effective Volumetric efficiency of the engine / turbine combination is increased. That is the reason more flow with same boost gives more air and more power.
Alan Phillips
6 måneder siden
So let me see if I understand this. Higher humidity equals less power because less oxygen but better heat removal due to the charges increased heat capacity? Can this be used in high performance engines to reduce spark knock at higher rpm by removing excess heat? Could adding moisture to dry air actually increase performance? What does the math say comparing being able to rev higher by decreasing spark knock or would you lose more power due to less oxygen (I’m thinking in high boost engines)? Could the future see computer controlled moisture levels using maybe AC compressor drain water or something that doesn’t need refilling?
Margaux & J-B Roussel
9 måneder siden
Keigyoku NTG Thanks for that. It helps !
Martin Light
9 måneder siden
@Margaux & J-B Roussel That's just it though, since they weigh the same but one has a higher water content and with water weighing more there is a lower percentage of Oxygen in Box 1.
S D
9 måneder siden
So is that bad or good?
how much boost does the mercedes make then?
You mentioned that the throttle is changing the density at 3:24, could you elaborate on that? Isn't the throttle only suppose to change the volume and thereby pressure?
I have a question, so if I have an engine that has a high compression ratio (12 : 1) but restricted and i get a 40% drop in power, the density and pressure drop inside the combustion chamber more or less drop at the same percentage right ? the question is, can we use a turbocharger to get the density and pressure back to normal in order to get the original power output without needing to decrease the compression ratio ?
That seat hugs you better than my ex ever did
At 5:33 i think you ment same volume
Nice video! Please explain the effects of high altittude on turbo and NA cara. Thanks!
40years ago old petrol N/A Engines had intake manifolds which are Heated by circulating hot engine water ,to Vaporizes fuel,,easy burning combustion,water molecules get evaporated,,,for your information 🙂👍
Hardworking Sir...😇👏👏👏👏👏👏💯💯💯👍👍👍💥💥💥💥💥💥
One thing I would like to know about is what the 'safe' limits of tuning is. I mean adding 20 hp may be safe for any engine, but is 50 hp too much?
WOW -- He is actually really wrong on this one!! The compressor efficiency is not the whole story and only a small part of it. It’s more on the efficiency of the turbine or more specifically the flow of the turbine side (A/R ratio and turbine wheel size). If the flow of the exhaust side is increased, the less restrictive the exhaust is. This increases the effective Volumetric efficiency of the engine / turbine combination. That is the reason more flow with same boost gives more air and more power. It is back to Bernoulli equation. Boost just means there is a restriction to flow. If the turbine / engine flows more with the same boost you will have more CFM and more power. - Another engineer.
Darryl Jones
5 måneder siden
Adding on here. There are two things that change when bolting on a bigger turbo. 1. A lot of the gain of bolting on a bigger turbo is the increased Volumetric Efficiency (VE) of the engine due to the less restrictive turbine housing and more efficient turbine wheel at the same compressor Pressure ratio (psi). This lets the engine flow more at the same psi therefore more cfm and more power. Small turbines and turbine housings choke off the engine's exhaust flow. Try pushing 550 cfm out the tiny exhaust housing and you will get very high exhaust manifold pressure like 100 psi. This will choke off the engine because it can't keep up with the pumping losses to create the pressure. Otherwise we would all be matching up large compressor wheels to really small turbines for quick spool. For every set up there is a linear relationship between the intake manifold pressure and the exhaust manifold pressure. For a small turbo it may be 15 psi (intake) will give you 45 psi exhaust mani pressure. Move to a larger turbo with a large turbine wheel and it may be 15 psi (intake) will give 13 psi of exhaust pressure. This lets the engine flow a lot more air. And more power. This is the trick to big pump gas power. Flow more air at a lower psi. Big power will be made at crossover, which is when the intake pressures exceed the exhaust pressures. The other less important factor is: 2. The charged air is heated less creating more air per volume as you have described. This is not as much of a gain especially if you have an efficient intercooler. This is what he is addressing in the video.
😶😐😲😲😲 NOOOO....pls tell me that the traffic jam at 4:30 wasn;t just about those couple of cones ON THE LINE?!That would be the most aggravating, yet hilarious thing ever!
So why do they call it an air to fuel ratio as opposed to oxygen to fuel ratio?
What is 2.1 litre and psi full form
I’m very curious after seeing this video.... in an speed density based car that has a centrifugal supercharger, is a retune truly required, if a smaller pulley was added to get just 1-2 more PSI through the powerband?
What about the engine heads ability to flow air? In my experience, more boost pressure does not increase engine power if the air flow rate through an engine is already at maximum capacity.
Boost on a gauge is resistance of the air going though an engine
Good video, although you didn’t mention how we can increase compression through tuning to further increase power. That’s another big factor when it comes to performance; a tuned car running the same boost as an untuned one will make make more power.
volumetric efficiency of the engine.... resistance to flow of air will make more boost but flow less O2 that a more volumetric efficient engine with a lower boost level moving more O2
Will the boost not drop when u use an intercooler? cold air will get more compact and the boost wil drop?
will the effect of elevation between an NA of turbo engine not be the same percentagewise ? cheers
So what I'm hearing is that big turbo = more power/less risks 😂
You just in Oregon like that
Why aren't you staying home
I would like to know who was crazy enough to let him use that amazing car while his brain was distracted with the blahh blahhh and while driving down a windy road lol
map/emap ratio it's alto very important, right? Thanks for sharing. Always learn a lot watching your videos
It is surprising to me that nothing was mentioned about how well the heads flow. Poor flowing heads result in higher pressure and less potential power gain.
Damn it jason; are you still confused between turbo lag and treshold ? Just kidding, great content as always ! Thanks for all your work ;)
Why do you always explain almost always about gasoline engines, we want to learn also diesel engine behaviours ... Regards :)
So “boost” is kind of like blowing on your food... when an air molecule speeds up it absorbs energy from your food, so, more molecules means faster cooling, and “blowing” on food increases the number or air molecules colliding with the food/air boundary, and carrying off more heat... which is why we blow on our food... It’s all about air density, since air is a compressible liquid... we might as well take advantage of it.
Need to talk about back pressure since the turbos restrict the exhaust flow and the more you do that the less hp you'll get. For say aircraft engines it is easy to install a large (efficient) turbo since the engine will be running mostly between 60% to 100% of full hp in a relatively tight rpm band (60% at 85% of full hp rpm), car engines will be somewhere between 5% (idle) to 100% and want to get from the low hp end to high hp quickly (no turbo lag) while the pilot can rather leasurely set power and wait for it to build up, The solution for the car guys is the biturbo with a small turbo to get things going followed by a large one to take over when you get serious.
You can have 2 compressor housings and wheels that push the same 20 psi @the same temp into the engine and have 2 completely different power outputs.. the turbine housing and wheel.. one might have a .67a/r and the other 1.34 a/r ... the one with the smaller a/r might have 40psi in the turbine housing and exhaust manifold while the big a/r turbo has only 10psi in the turbine housing and exhaust manifold.. if your turbine housing is too small your engine won't flow no matter what heads, intake, cam, tune you have.. so heat to the intake charge isn't the only thing that can affect horsepower at the same psi with turbos.. there are many factors..
What would happen if you were able to pump in 100% oxygen?
Boost can also be a product of an intake restriction. If your intake tract is restrictive you will build boost easier but the amount of air flowing into the cylinder will actually be less. vice versa if you port &polish the cylinder heads and remove intake restrictions you can see a lower amount of boost with the same amount of air being pushed into the engine.
The Columbia River Highway is a wonderful drive and is a beautiful backdrop for your informative video. Thank you.
I started watching this channel several years ago when his videos were filmed in his dorm room. Glad to see he's kept up with it, love the content.
Love all the veloster n clips.. Wink wink
I used to think no one in Oregon knew how to drive, and then I moved to Washington.
We need Dyson turbos
It took 12 and a half minutes to tell you that hot air is less dense than cold air!
Yeap, you are right about the wheels. Ugly as f....k. But tastes varies...
Finally someone has explained this in a video! Too often tuners talk about CFM being the difference between why big turbos make bigger power. One other thing is also a bigger turbo, or at least a bigger rear wheel/housing lets the engine flow more which is another source of where you make more power.
Sup man I been channel surfing for a while. and I have to say I miss this channel. Thanks merry Christmas and happy New Year!
Buicks 1984 -1985 Grand National & T types were rated 200 hp & 300 ft lbs of Torque. Then in 1986 - 1987 they went to an intercooled design ( yes the piping and location of the turbo was also better ) and HP went up to 245 HP and 355 ft lbs of torque. Both had 12 -14 lbs of boost . Big difference in performance !
I'm hoping to see a 2020 fully animated video from you Jason. Keep editing.
1:27 notice how the bucket seats squeezed in anticipation of the turn!!!
CrimeScene96
9 måneder siden
Damn. WOW
Jupiter Fox!
År siden
Thats cool and creepy.... It's alive! Lol how did you even notice that
that gt2 rs though
I have been thinking of installing a custom turbo setup on my 6.2L superduty for towing purposes. I know it would be easier to just trade for a powerstroke but I'm curious of how the gas engine would perform if boosted. Do you think it would be worth pursuing?
Allen Davis
År siden
@Adrian Nel it's a 2019 F250. I'm just curious of if it would be competitive if it was turbocharged.
Adrian Nel
År siden
don't modify an older engine for more performance,unless you are prepared to spend a LOT of money. Just trade your vehicle. Vehicles are systems. Keep your system integrity,and buy a whole system more appropriate for your needs.
Another bug ugly German car.
It's not about BOOST man, it's abou CFM. Another quote that should be on a shirt and yes I would buy it. ;)
You figure this out when you modify your first turbo car. You put a free-flowing exhaust on and your boost drops a pound or two, but your power increases. The better your engine flows the more air it can evacuate. The less heat it will produce. More power. I actually had an engine detonate because the turbo overpowered what the exhaust could evacuate. Letting exhaust be left in the combustion chamber causing eratic ping/detonation. A 3" turbo back fixed that. And I was laying rubber at highway speeds. Anyone with a turbo reading this. You HAVE to experience e85!!!
Top shelf video as always. Easy to understand and entertaining.
It's not all about air heat. It's a lot abour exhaust restrictions. For exemple in some cases you can make more power with the same boost if you fitt a bigger wastgate. ( like in this case I belive the engien was restricred by the turbo. Then fitting a bigger wastgate or a bigger turbo (set at the same boost) you increase the engine exhaus flow)
I am so disappointed! One of the most important factor, apart from humidity, temp and pressure is volumetric efficiency of engine! engines can have same manifold pressure but due to differences in delivering that pressure to chamber (size of valves, timing, shape) can output very different HP. Volumetric efficiency differs in rpm and. Very rarely exceeds 85-90%
KevinK2
År siden
True, I think he assumed an ideal 100% VE to focus on air density, by way of temperature, humidity, and compressor maps (would have been helpful to show one). VE may be another EE topic. I've had huge power increases on an old NA engine with VE improvements.
My life is a lie. It all makes sense now. I always wondered how you make more power if your displacement doesnt change. Fricken density.
It's worth saying that in the example you talk about, the engine with the smaller turbo and the lower power output is likely to have the benefit of better low down power and less lag to offset it's reduced top end power, (unless it's just a totally bad design) so there can be good reason to want the smaller turbo option.
100% humidity it’s called rain mofos
Please explain about nissan epower engine system. thanks
Awesome video, i never understood why different turbo's made different power at the same level of boost on the same engine.
if the ads increase, I'll be unsubscribing... one is too many
Great video! You should do an expansion video on this topic and discuss how compression ratio factors in. People talk about boost being related to power, and sometimes fitting a turbo to a naturally aspirated car won’t allow the same psi of boost when compared to a bespoke turbo engine
Come on.... We all wanna see a video about the Bugatti Chiron world record.
Hello sir ! I would like to hear your opinion regarding hydrogen as fuel for cars
Amazing and informative as always!! Love your videos and can’t wait for more 🙌🏼
It sounds like you think that air gets hot in a turbocharger because of it's inefficiency.
Eugene
År siden
@Redtooth 75 Wow! Did you have to take physics in high school? There is such a thing as Boyle's Law. Look it up, I promise you'll find it interesing.
Redtooth 75
År siden
@Eugene read a damn book. A small turbo is more responsive but generates more heat than a large turbo, you are completely wrong
Eugene
År siden
@Redtooth 75 Absolutely incorrect. Heat is not generated by a turbocharger, rather than the act of compression of air itself. This is a law of thermodynamics. Large and efficient turbos heat the air almost exactly the same as small and inefficient ones. Again, the change of pressure heats the air, not the turbo blades.
Redtooth 75
År siden
The heat generated is what makes the turbo inefficient.
The rims on that Mercedes are hideous.
why would you want a car with a white steering wheel?... dirty
Those rims are delightfully ugly.
That was random on the acceleration clip with the fake pop of the exhaust lol.
*20 PSI IS NOT 20 PSI. The question is ...how many O^2 atoms are in there..?*
One doesn't simply drive through the Old Columbia River Highway, ever. There are many hiking spots and waterfalls to stop at and don't even think of driving past Multnomah Falls at more than an infants crawling pace.
Imagine seeing him talk so ambitiously in your rear view mirror while sitting in traffic 😂
So, would another way to explain this be that (1) the purpose of a turbo or the like is to increase the number of O2 molecules per unit of volume (O2 density), because more O2 means you can burn more fuel to produce more release of energy, more horsepower, (2) since PV=nRT, increasing pressure will increase n if T remains constant, but (3) using a turbo or the like to compress the air tends to increase T (unless you cool the compressed air before it goes into the combustion chamber), which depresses n (the density of O2) and somewhat negates the gain from the boost in pressure?
KevinK2
År siden
Mostly true, but don't overplay the effect of temperature on density, unless going for very high boost. 1) temperature in these calculations is in absolute units, like deg_Kelvin . So a ratio based on zero degC, is 3 times higher than the ratio in absolutes. 2) in ratio calculations, the square root of the ratio is used, making the difference in temp from boost have less effect.
air temperature
Anyone ever try to run an engine on pure O2?
Sérgio Alves
11 måneder siden
I'm sure someone has tried it, and basically got a really expensive grenade.
Byron James
År siden
It would take a lot to be able to get enough fuel into it??
As Gale Banks always says (Banks Power on NOlocal) it's all about the pounds of air, psi is a measure of restriction.
Side note, I laughed more than I should when you tried to move around in the seat and you couldn't because of all the bolstering lol
[No stimulants were harmed during the filming of this episode]
nice you have a better camera than back in 2011
Why tho engines can make different power at 20psi of boost? For the same reason two engines can make different power at 0psi of boost.
Can you make a video on water meth injection?
The turbo ford v6 sucks. Just thought I'd say that.
Small point of order, most factory turbocharged cars will lose horsepower at altitude at the same rate normally aspirated cars will. That's because stated max boost pressure is measured at sea level, just as the stated max horsepower is. Factory turbocharged engines are usually tuned to maintain max boost pressure as a multiple of the ambient air pressure. So a turbo that produces 1 bar of boost at sea level will only produce around 0.7 bar of boost at 10,000 feet because of the 30% drop in ambient air pressure. They're tuned like this precisely because of the volumentric inefficiencies you discuss starting at about 7:47, otherwise the turbo designed to produce 1 bar of boost at sea level would lose efficiency trying to produce 1 bar of pressure at 10,000 feet. The perceived difference in power loss between normally aspirated and turbocharged cars at altitude is just that, perceived; probably because the torque is available across a wider RPM range in a turbocharged car so it still "feels" strong. Of course this is also true at sea level.
KevinK2
År siden
10,000 ft is an extreme case. Power loss will not be at the same rate as a NA engine, at typical altitudes. Air density at 4000 ft in Denver is ~15% less than at sea level. There is often enough room on the compressor map to lose efficiency by only 5% in providing a full 1 bar of boost. So the absolute pressure ratio is higher with a pressure regulated turbo, vs the NA that sees the full 15% power loss. The turbo will supply full gauge pressure, but ambient is still lower, so you still lose some power with the turbo in this case.
This car is obsolete. An engineering nightmare. lease it, never buy it. The simplicity of EV's will drive the prices of these monsters into the ground. Buy this or a Tesla? That is a no brainer. In 5 years ICE cars won't have much value other than classics, supercars, and oddities.
Why not specify mol O2 (or mol/L O2) instead of PSI? I assume it's because of the variability that occurs during driving; the PSI is a factor that is potentially a lot more measurably consistent. Any other ideas?
Waaaaaay to many AMG logos on that vehicle.
Why not just get big oxygen tanks and put the outlet in the intake of the car? Will that make it chooch faster?
That steering wheel looks like it has two Chevy logos on it
People in Oregon don't know how to drive...lol. Come up to the Seattle area! Morons here make me LOVE driving in Oregon!
Can you talk about unequal drive/half shafts and if it has any effect on handling? i.e. Subaru/Audi's integrated transfer case in the transmission housing resulting in "symmetrical" and equal front wheel shafts, vs other AWD systems where the shafts are unequal? As well as any other applications to which this may apply? Not sure if I used the correct terms, but I hope you understand what I mean. Thanks!
Hi Jason, Your comparaison with 20 psi at a inefficient point and an efficient point is right air intake temperature wise but in a turbocharged engine a lot start at the hot exhaust side and it's where a lot is gained and/or loose. keeping your exemple of small inefficient turbo and bigger more efficient turbo: To produce those 20 PSI the small restrictive one will produce a lot of back pressure and thus all that intake boost will be there only to fight that big back pressure , let's say 10 psi so only 10psi of the 20 are effective to cram fresh intake mixture into the engine. On the other hand the bigger more efficient turbo with it's bigger hot side flow will produce a 5psi back pressure so on the 20psi intake boost pressure, 15psi are effectively putting fresh air mixture into the engine to be burned. That's why a good boosted engine is firstly a well breathing engine likes ... good N/A engines just tweked to deal with higher back pressure due to turbine, lower CR due to fuel octane number and beefier internals to handle higher combustion pressure. The less boost you need to reach your power target , the better the boosted engine is.
KevinK2
År siden
Right, small turbo give fast response but high turbine back pressure at high power. But it's not a 1:1 boost loss. I have measured backpressure on a stock 2L turbo, and it was about equal to the boost level, but the car was still very fast and NOT running with no boost effect. Yes, it would make more power with less back pressure.
So what you're saying is. I don't need a bigger turbo, i need a bigger intercooler. :D
Not a single compressor map. I am dissapoint.
That's a very long way of saying: Compressing air makes it heat up & some turbo's are worse than others. Cold air is more dense and makes more power, so use a decent turbo and use an intercooler that's right for the job.
KevinK2
År siden
True, his on the road lectures have less tech content, and limited scope. I suspect Mercedes is a better customer than the white board maker.
You need to team up with GALE BANKS .
So the bolsters are like a hug from mom?
Someone's been watching Banks Power videos... 😂
you follow modern editing principals to a tee, about 10-15 sec between shots, thats exactly how to keep attention spans of youtubers.... all rnd well done, your knowledge has been great to boot.
Happy 30's anniversary Jason!
Looks like Multnomah Falls?