Why More Boost Doesn't Always Mean More Power

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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[@EngineeringExplained]

*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.

[@FXIIBeaver]

So living in humid climates means a higher heat threshold? Thereby performing better?

[@Abdullah..S]

Water is very humid

[@IanF-FPV]

I remember the water injection systems before the throttle for some turbo cars...cooler charge temps.

[@johndeerrm]

Increased heat capacity of the charge air, right? Meaning it’s capable of absorbing more combustion heat due to the higher mass versus dry air. I think egr does similar through inert gasses that don’t contribute to combustion.

[@jackd1582]

Replace ya pointless cold air intakes with a modded watering can 🤦

[@zachwatson2349]

Study for finals? Nah, I’d rather learn this!!

[@stevenmcintyre7960]

lol me rn

[@tompkee9]

Same here

[@Oblithian]

Good luck on your exams!

[@szymon940]

Maybe you've chosen wrong major

[@tompkee9]

@@szymon940 lmao this is my major, ME

[@Code1127]

Engineering explained: “Loraine, I am your density....I mean, your destiny.”

[@ArmchairDeity]

Code1127 I’ve thrown that line out more than once and yanno... it didn’t work much better for me than it did for him at the time. 😂😎😉

[@AtticAZ]

HAHAAAAAA YOU MADE ME SPIT OUT MY BEER, LAUGHING!!!

[@tomg6284]

if someone put handcuffs on him I don't think he can talk.

[@davidsnackbar]

what do you mean

[@snaxgalore5764]

David Snackbar because he uses his hands so much obviously

[@jilledelange620]

@@davidsnackbar Since he always moves his hands when speaking, it can be mistaken for a necessary part of the talking process by someone who is not familiar with the functions of a human body. Tom G uses this as for a joke (that i just butchered)

[@nothingsurprisesmeanymore]

@@muskokamike127 I bet your buddy was expecting something more fun when they tied his hands up 😀

[@BiggMo]

I’m guessing Jason eared his way through school as a mime gesturing for tips

[@monsterram6617]

Didn't you know? The boost gauge is dead. Just ask Gale Banks.

[@EngineeringExplained]

That's a great video! I've actually linked it in the video description as it seemed very relevant here. That dude has a ton of experience/knowledge!

[@ColeSpolaric]

Gale annoys me a bit, but damn does he explain things super well.

[@steveskouson9620]

@@EngineeringExplained, he lost me, when he mentioned the "throttle" on a Diesel. If ANYONE should know about Diesels, it is Gale Banks. Granted, he has been working on cars and trucks, MY whole life, Nixon was VEEP when I was born. steve

[@jimmyguy428]

@@steveskouson9620 He mentioned that diesels are "Fuel" throttled, which they in fact are, so I'm not sure what you mean.

[@jaydunbar7538]

@@steveskouson9620 all engines have a throttle, are you confusing a throttle with a throttle body? Because diesels do not have a throttle body.

[@pnwnative918]

"A friendly reminder that literally no one in Oregon knows how to drive." As a native Oregonian, in the fun area of Hillsboro/Beaverton very close to Portland I can confirm this

[@breisch1986]

I haul up to Hillsboro every week. I too can confirm this...

[@larry71000]

A truer statement has never been written. I live in southwest Washington and travel for work. I have driven in most every state in the union. Oregonians (Portlanders in particular) are the worst.

[@jurgenkeller6225]

Every Saturday you have to clean your white steering wheel

[@BobbyDazzler888]

Jürgen Keller engineers dont get their hands dirty. Labourers do.

[@Jaymac720]

Jürgen Keller if you can afford an AMG GT 4 door, you’re probably not getting your hands dirty

[@emcg5112]

@@BobbyDazzler888 Plenty of engineers get their hands dirty.

[@TheRealMikeWilly]

Why do you think your driver wears white gloves? 👏👏 "Wadsworth! My umbrella! It appears as tho it might began to sprinkle!"

[@hectorandem2944]

@@BobbyDazzler888 Engineers who get their hands dirty: _"Am I a joke to you?!"_

[@danielchin8073]

🤣"As we sit here and admire this traffic jam..."

[@TheRealMikeWilly]

Daniel Chin that's Oregonians for ya. Except that guy in front of him had a Washington plate 😂😂

[@DeXel55]

Every minute in LA...

[@danieljensen329]

That's what you get for driving the Columbia River Senic Highway... 90% of the drivers are tourists. Should have picked SR-14 on the Washington side; it's also more fun as a driving road (although perhaps a bit dangerous if you want to record a video while driving).

[@nickc5220]

You should make a video on why more timing doesn’t always mean more power

[@alexbra282]

it's because the combustion will partially occur during the exhaust stroke meaning that all the explosion power won't serve you to put the piston down. But it does some pretty bang bang and flames which is cool

[@splewy]

Enough timing can equal less pistons though!

[@joshuabarkey4554]

I think that would be a great video! Something to show my friends that think you should just advance timing until you hear detonation no matter what rather than doing the math

[@mantis_toboggan_md]

69 degrees of timing LoL

[@1EVILZ06]

Spark knock....

[@Hatchmade]

That drive looks like the columbia river drive, one of my favorite drives ever. I really miss living there.

[@tdawg719]

Short version: turbo efficiency in regards to heat.

[@656hookemhorns]

You forgot the most important factor, cylinder head flow. Boost is just a measurement of restriction, 20psi with restrictive heads will not perform like 20psi with good flowing heads. CFM of the heads is the MOST important factor.

[@Ebonyqwe]

Yeah massive omission in that he didn’t mention that Pressure Doesn’t Equal Flow.

[@THEREAL_GZUS]

Touch of Gray also forgot compression rAtio has a major role in this

[@TJDukit1]

Love to see another video addressing boost vs M.A.D. Gale Banks the M.A.D. scientist has been killing it with his diesel monster truck series lately completely ignoring boost pressure.

[@andrewf8486]

Pressure is a function of the resistance. You can have 20 lbs on a poor flowing head and 20 lbs on a high flowing head and produce much different hp.

[@TheEsseboy]

Yes, but it is less inportant on 4V/Cyl engines as they have such large intake area. On 2V it is critical because they breathe through a tiny straw.

[@Kyrazlan]

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.

[@JPMotorhead1993]

Nicely explained Jason. One other thing that goes along with different turbo sizes at the same boost is exhaust drive pressure. A smaller turbo will require more exhaust drive pressure to make 20psi than a larger turbo. Lower exhaust pressure means better scavenging and more power👍🏻

[@EngineeringExplained]

Yep, it all matters! If you have a super restrictive turbo on the exhaust side, that means less power overall.

[@AlanTheBeast100]

A proper turbo implementation can keep "sea level" + boost pressure up to the limit of the turbo's ability to "pump" (critical pressure). (Why some piston powered aircraft use turbo's is not more power, per se, but for maintaining power as they climb. This works to maintain a flat power level up to the turbo's critical pressure altitude after which pressure (and power) fall as a function of increasing altitude.) For cars this is best implemented when the car uses an electrically actuated wastegate and ambient pressure sensors. It's also important to use higher octane fuels at altitude when using turbo to prevent detonation.

[@D2O2]

I was a turbocharger application engineer for 8 years and i have no idea what you are talking about when you say "critical pressure"?

[@AlanTheBeast100]

​@@D2O2​ When you get to the altitude where, with wide open throttle and closed wastegate, you cannot maintain maximum MP, you are at the critical pressure (or altitude). Higher than that and power decreases. Below that altitude the pilot has to open the wastegate enough to not pass maximum MP for the RPM (Most aircraft engines have a maximum MP for a given RPM - lower the RPM (via propeller pitch) and you have to reduce MP to not over stress the cylinders [you actually decrease MP before reducing RPM and v-v]). In many recent (last 20 years or so) aircraft this is all automated in varying degrees.

[@D2O2]

@@AlanTheBeast100 I understand critical altitude, just never heard it referred to as "critical pressure" and the term didn't and doesn't make sense to me in this context.

[@AlanTheBeast100]

@@D2O2 You're surely right about the terms. Just stuck in my head as critical pressure.

[@derrickbonsell]

And now everyone knows why turbochargers were invented for piston-driven airplanes.

[@spencermurray4378]

I thought they were technically turbo equalizers

[@JOHN_WICK_IS_SICK]

Dude I cant tell if you're 25 or 45 even after multiple years of watching your videos.

[@03chrisv]

I think he's in his 50s. Looks good for his age.

[@rgbii2]

Googled it. 29.

[@03chrisv]

@@rgbii2 I stand corrected. I'm older than him and I can still pass off as someone in their mid 20s if I shave my beard off. He looks like he's 45....

[@cec4]

205

[@GRosa250]

rgbii only until December 13th, then he’s 30.

[@Mr.Killjoy95]

I've actually experienced a significant increase in power at 100% humidity when the temperature is in the 40s and 50s. My theory is that the water vapor helps with heat transfer on the intercooler and the water vapor helps absorb more heat after the air is compressed in the turbo like a natural water injection system. I have been skeptical but every winter since I tuned my car, I feel a significant increase in acceleration when it's cool, rained within half a day, and humidity is at 100%. I once recorded a rough increase of 30whp based on vehicle weight and acceleration via gps. I get that an increase in water vapor means less oxygen but it would be cool to look at the difference between the rates of density change by unit of temperature and humidity.

[@va_innovations]

PLEASE do a video on cleetus mcfarland’s corvette leeroy. Talk about everything about it, its turbos and engine displacement, why it makes so much power, tires, weight, and especially its lack of AERO. This video would go viral IMO

[@joshuabarkey4554]

Used to be a big fan of Cleetus until he purposely blew up that 5.3. I understand that to him the engine was nothing since he's huge now with sponsors and tons of viewers, but that waste for nothing left a really bad taste in my mouth.

[@Trendyflute]

It's so true, nobody in Oregon knows how to drive >< I find that also extends to Washington state. Great explanation Jason, thanks!

[@larry71000]

All the Washingtonians that can't drive are either from Seattle or moved to Washington from Oregon...

[@755hp]

Boost pressure also reveals how much air did *not* enter the engine; assuming other parameter magnitudes are known (IAT, humidity, ambient pressure, etc).

[@pyric]

boost is a measurement of restriction 2 engines of equal size the more efficient engine itself (heads, cams, etc) will require less boost to make the same hp as the less efficient engine

[@panzerfaust375]

Yes. I noticed this with my supercharged V8 I opened up the exhaust with extractors and all I got was less boost. It made the same power. The only thing it allowed me to do was to give me more head room to run more boost (by a small amount).

[@nesmio7378]

Take a look at the Banks Power KZbin channel, they do amazing things related to this, why boost doesn't really mean anything in itself and why density is a lot more important, and sorry Jason but they did / do a lot better job at explaining this. I honestly really recommend it, it is an amazing channel for car / engine geeks.

[@EngineeringExplained]

It’s a great channel haha, that’s why I linked one of their videos in my video description.

[@vikary5747]

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.

[@macro820]

Someone's been watching Banks Engineering :)

[@D2O2]

Engineers don't need to watch Banks Engineering.

[@MaxS2000]

I wish you would’ve talked about compression and boost

[@lag_profil]

Gale Banks has made some good videos about intake air density vs power. Chilled boost air contains more oxygen than hot boost air etc...

[@pjay3028]

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.

[@danpop1714]

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.

[@Conservator.]

I’m a Beemer kind of guy but that Merc is fantastic.

[@kaelanburke2097]

Agreed

[@3991melkoun]

Can you and Gale Banks make a collaboration? He was just talking about this on his most recent video. I'd love to see you two talk about the engineering behind power

[@TATER_24]

Banks would destroy him..

[@al_capad]

Gale Banks' Manifold Air Density system explains it perfectly (and measures it)

[@johnnyboyssite]

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 !

[@swagstein9322]

From my experience, it's an engine head design. For example, if we use a Garret GT35 20psi @8500rpm on Honda k20 and and Mitsubishi evo 4b11t (BOTH 2.0L ENGINES), the k20 will make more power, but 4b11t will spool faster and be more mpg efficient in cruising. 4b11has narrower ports, smaller cams, smaller valves, and it all causes more restriction at higher power, but has better air and exhaust velocity at lower load than a k20. 4b11 head flow is that of a 1.5L N/A engine, because it needs to stay efficient, but to maintain good horsepower at that efficiency, it needs more psi. That's why many manufacturers are turbocharging their cars: More power than N/A but same eficiency due to an addition of a turbo and a redesigned cylinder head.

[@JESUS_IS_GOD]

This car is a BEAST & has the Nurburgring Record for a 4 seater sedan!! 630HP & 661 Ft Lb Torque!! 0-60 2.8 seconds in the real world!! 😎🌴❤👍

[@ADRIAAN1007]

Banks power on youtube has an excellent series explaining why boost is useless as a measurement of power is all about MAD (Mass Air Density)

[@busterscrugs]

The GT Four Door is beautiful! Love those monoblock style wheels too.

[@SusedatLubo]

To my understanding another big factor in engine performance is Head Flow Rate. Say you have 2 identical engines with identical turbo setups, but one of them has a modified head(porting, polishing, bigger valves, bigger cams, etc.). So it's only logical that the better flowing head will allow more air to enter the cylinder and thus making more power, even though the boost pressure is 20 psi for both engines.

[@kurtmundt2736]

The Columbia River Highway is a wonderful drive and is a beautiful backdrop for your informative video. Thank you.

[@nasaa2884]

😶😐😲😲😲 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!

[@35057]

Air density is what makes efficiency from a compressor system. Boost air density and manifold air density. Boost psi is just a reference we all use.

[@FlatPlaneCranky]

Jason, you and Gale Banks have the same mind! M.A.D. Is his entire forte....he doesn’t focus on boost....

[@paulwood6729]

See if you can find Guy Martin's TV programme where he built his own bike, put a massive turbo on it and raced it up Pikes Peak. The turbo was so big he couldn't get the bike to work during practice, so the race was his first real attempt!

[@joecool509]

Banks has a great video on this as well. Charge air density is the term he uses. Thanks for sharing.

[@DeltaSierra426]

The most obvious and practical answer is that different engines are tuned differently. With or without turbos, same displacement engines don't yield the same power outputs as differences may include timing and lift, intake and exhaust characteristics, throttle body size, A/F tuning, compression ratio, head design, fuel injector max flow, and more. Additionally, an engine may he tuned to peak or optimum performance, then detuned to offer more products in the market for lower price points. This is especially common with diesel tractors and boat motors.

[@CarsLife]

I have a 5.2L engine that makes 150 hp less NA than the NA gt350 5.2L. Boosted the difference would be 300 hp. A much bigger deal than a negligible temperature difference imo. I think a better way to pose the problem is to assume same power levels at zero boost and all else equal (compression ratio, displacement, intercooler rating, tune, etc.). This video considers only a small subset of a broader problem.

[@HachiMiura]

You're always coming over to Oregon driving through the Gorge. There are other good roads around there besides the old highway you know.

[@syntropy3020]

Exhaust pressure also makes a big difference, which is why larger turbine AR will provide more power at the expense of lag.

[@kevink2315]

True for A/R, but also with smaller turbo with same A/R. Oem low lag turbo's can have turbine back pressure equal to boost at peak power, restricting exhaust flow from the cylinder.

[@jeffbeasley8235]

Turbo compressor efficiency is a relatively small factor and can be totally compensated for with a more effective intercooler. Much more important (in my experience) is cylinder head / camshaft design and turbine efficiency. Naturally aspirated engines of the same displacement can also have huge differences in power. But they are operating with the same manifold pressure (unless something upstream is significantly restricting the flow). It's the same story with boosted engines. Manifold pressure is just the starting point: you still need port diameter, valve area, and valve lift to actually get the air into the cylinder. The turbine comes into play no matter what kind of cooling system you have or what ambient temperature you have, because it causes higher pressure at the exhaust manifold, which dramatically increases pumping losses at high mass flow (high power). A bigger turbine can help this by extracting more work without needing a higher delta pressure across the turbine at the higher massflow.

[@joshlemons3662]

Gale Banks recently posted a great video about the same topic, with test data. Manifold air density is king.

[@EngineeringExplained]

Linked in video description! (Or it might be an old one).

[@XFolf]

What does an engine want? A loving, emotionally stable owner who values routine services... OOOOH, you mean.....

[@drnono8605]

Nicely explained - can you please make a video on why torque matters, how or where it is measured and what it has to do with the gearbox?

[@Kepe]

He has many videos on that subject already. Search for torque on his channel.

[@jaydunbar7538]

As Gale Banks always says (Banks Power on KZbin) it's all about the pounds of air, psi is a measure of restriction.

[@ignasanchezl]

I'm pretty sure valves and piston count/ bore-stroke differences matter way more than people give them credit. Also, one simple detal, pumping losses. The pressure on the exhaust manifold. With a small turbine, you will probably require much higher exhaust pressures to generate the same amount of boost on the compressor side, meaning that the engine will loose more power on the exhaust cycle.

[@GrahamWood]

Would be great to see you do a collaboration with Gale Banks.

[@inertiaMS]

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.

[@ArmchairDeity]

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.

[@steventenney8797]

It's the same thing when recovering refrigerant and using a subcooler. Less pressure more pumping . A high efficiency air conditioning unit uses the concept of more pumping less resistance . More suction pressure less discharge and more gas volume pumped

[@80KG_Costco_Chicken]

The RPM that the turbo can hold the pressure is absolutely the key factory. A 48mm turbo can probably hold 28 psi until 5000 RMP. But a 70 mm turbo can hold 28 psi until 9000 RPM. That’s where the difference is made. And really, pressure is from restriction, not from the turbo. Even two same engine with the same turbo, the engine with better air flow will make more power with the same pressure.

[@Sir.VicsMasher]

You oughta hook up with Gale Banks Engineering and test his new Manifold Air Density gauge, he's been saying "The boost gauge is dead to me" due to this MAD gauge.

[@kevink2315]

A density gauge is another tool, that corrects for temperature. Boost gauge reading needs to be corrected for mass flow, as Jason showed.

[@MagnumMuscle1000]

A large garden hose at 5 psi flows more water than a small garden hose at 5 psi. The same with a large turbo and intake ports. More air=more power. (assuming the engine is also optimized to take advantage of the increase in air with proper fueling, proper porting and valve sizes, sufficient cam lift and duration, properly sized exhaust, etc).

[@armandolios4561]

Nice video man, as always. How about the relationship between bigger tyres on torque and MPG.

[@RzVids]

Dale Alexander Wrong dumbass, bigger wheels covers more ground than smaller tires just like a bicycle hence you go faster.

[@flopponator]

@@RzVids he doesn't mean bigger in the way of more diameter but wider tyres

[@aneejit9079]

Larger tires cover more ground per rotation. By running larger tires your effectively increasing the final drive ratio. So if you do lots of motorway driving you could see more MPG from running larger tires, as the engine would be doing slightly less RPM than before for the same road speed. But it would require more energy to get the vehicle moving, so acceleration would be worse and you would be using more fuel at the same time. So for lots of city driving a smaller tire would reduce the final drive ratio, making it easier for the vehicle to accelerate and it would use less fuel accelerating. But the vehicle would be using more fuel on the motorway because the engine is now running at a higher RPM for the same road speed.

[@TATER_24]

What about turbine wheels vs compressor wheels.. which one should be larger on your turbo?

[@Harddeckmyass]

Some turbo manufacturers used to produce maps showing where the turbo was most efficient (efficiency island etc). Very helpful for proper sizing.

[@hearthawaii23]

Pressure across the engine is also a factor with a turbo that is to small

[@SkunZielonyJakMech]

You can explain it simply by Clapeyron equation: pV = nRT To calculate amount of oxygen molecules (n in the equation) you have to determine its pressure (=boost), its volume (=displacement) but also temperature.

[@erail1213]

Tomasz Kudłacz what a troll

[@LaurentVanderdonck]

Damn it jason; are you still confused between turbo lag and treshold ? Just kidding, great content as always ! Thanks for all your work ;)

[@KeepOnJeepinOn]

I love how you made a video talking about mass flow rates through a turbine right after I took my Thermo 1 final

[@fatboy19831]

Most of this one went over my head. I understand the sizing of a turbo with the same boost makes a difference in power.

[@BigUriel]

How much air actually goes into the engine depends not just on pressure, but also temperature (mainly). Turbos have efficiency maps, just like the engines they go into. The more efficient the turbo the cooler the air that comes out of it, at a given pressure, therefore the denser the air, and the more of it goes into the engine. So it's important to pick the right turbo for the job. Generally speaking a small turbo being asked to produce a very high flow rate or a large turbo being asked to produce a very low flow rate is inefficient.

[@RB-xv4si]

I was a little confused from his talk, honestly. What I think he’s trying to say (I may be wrong) is that smaller turbos running at higher boost levels generate a lot of heat that ends up dissipating into the intake air (on top of the heat that’s already being generated just by compressing the air).

[@adamc8409]

Simply put the intake temp impacts power big time. To make big power you want to keep the air charge cooled.

[@garnetcampbell4389]

Gale Banks of Banks Power doesn't use a boost gauge. He uses a Manifold Air Density gauge. He figured it out decades ago.

[@zuilok]

Air temp is definitely a big part of it but lets not forget compression, cam angles, intake and exhaust restrictions, valve size/cylinder fill efficiency, air fuel ratio etc.

[@realvanman1]

Increased elevation does not necessarily reduce the output of a turbocharged engine, until a certain maximum elevation is reached. Indeed, one of the main reasons turbos are used in aircraft are to compensate for altitude.

[@TriviaNight]

Great explanation on turbo boost and power.

[@kevink2315]

The assumption was 100% VE to start with, which is a theoretical target for max power. Jason just spoke about the larger turbo operating on a higher efficiency "island" of the compressor map. In reality, the VE is closer to 85% w/o turbo, and maximizing the VE would be another step in increasing mass flow rate for the same boost and displacement, increasing power. Includes porting, chamber shape, exhaust & intake systems, etc. If you have 1 psi pressure drop in a restrictive intake system (some stock systems), your effective ambient pressure in this EE case would be 13.7 psi, not 14.7 psi, for a 7% power loss for NA engine. ! A turbo would partially compensate this loss, by spinning faster.

[@dj_paultuk7052]

Also a lot of it has to do with heat. So a Saab B234 with a Garrett T25 tuned to 1.4 bar will make 275bhp. A Saab B234 with a Mitsubishi TD04-15T tuned to 1.4 bar will make 308bhp. Not only due to the much larger air-flow capability, but also due to the temps of the air coming out. The little T25 is being far overspun at 1.4bar so its just producing superheated air, which as we know will badly effect power output. Us Saab enthusiasts have done lots of testing in this area, given our cars having been using Turbos since 1974.

[@Runkization]

Talking about positive displacement superchargers it's not only about pressure but how much air you shove in the engine, too.

[@morrari690]

My Man! somebody give this man a cookie!

[@shortbusshorty1879]

Could you make a video on solid state batteries plz 🙏

[@joes.7536]

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!!!

[@toddpettyjohn2454]

I suspect there are 3 main factors of near equal importance: 1. You would need a difference of ~ +60 degC intake manifold temperature to explain the 18% power increase (325 vs 275 HP in your example). I think that's an unlikely observation, especially for modern intercooled applications. The two unmentioned ones: 2. Relative exhaust manifold pressure difference due to turbo size selection. Compressor efficiency directly influences how much power the turbine needs to provide. A small turbine will provide more power to the compressor at a lower flow, but require a large fraction of the flow to bypass through the wastegate at high flow. This reduces the apparent turbine efficiency, so the end result is excessive pressure in the exhaust manifold ("pumping work") thereby reducing the brake power output. Exactly how this pans out gets a little muddier if you consider VGT instead of Wastegate, but the relationship still holds. The impact on brake power can be upwards of 10%. 3. Rated speed. For the same displacement and boost level, clearly an engine spinning faster will ingest more air.

[@Maroco918]

At guy meets there's always that one guy " oh turbo? How much boost you running?" Then proceeds to tell you how much power you are pushing before knowing the size of the turbo....

[@craigkincaid9064]

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.

[@ElSikario100]

The interwebs needed this one Jason, thank you!

[@ichheissedamian]

Damn that GT63s is gorgeous, how did you get your hands on one?

[@ristekostadinov2820]

He is pretty big automotive youtuber, the rest you figure out

[@1theheightofparadise]

He probably got it from a dealership and will bring it back once he finishes the video. I doubt he bought it

[@EngineeringExplained]

It was one of the cars at a media event I attended (Automotive Video Association).

[@marcdegasperi6762]

Totally disagree, i find the spec he got is one of the worst.

[@bigwahoo8686]

@@marcdegasperi6762 who?

[@fascistpedant758]

You skipped over the question of back pressure. All else being equal, it's usually the most important difference between turbos affecting power/boost.

[@Pwnsweet]

That seat hugs you better than my ex ever did

[@bmwm30072007]

Air density is important but there are more things to consider. Such as valve size, piston speed, valve timing, valve angle, size of intake and etc. In other word easier cylinder gets fill up with air which also determines higher CMF of air.

[@oscarbaez2098]

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!

[@1300l]

Jason, does big down size affect the turbo too? I mean, there is only so much exhaust gases a 1.0 engine can make on Low RPM to spool, right? Where a equal boost and even HP 1.4 engine would spool better i assume

[@omnipresentvideo7686]

Look at old F1 turbo cars, 1.4l making 1600 hp.

[@m.h.3679]

omnipresent video he said low rpm, those things revved to 13000rpm

[@straight_intro]

@@omnipresentvideo7686 they have a great flow at those high RPM, probably around 10-14 thousand. At lower RPMs the manifold pressure is negative. You could use a smaller turbo, but it won't provide enough airflow at higher RPM.

[@1300l]

Yea but these old F1 had no low torque and would actually be a pain to drive on the roads. Also, i'm positive that at the high end, the downsize make it up with tech, but i'm talking about the engine load that ppl use (or want to) now days on the road, that is 2k RPM or even less.

[@Monkey_on_Call]

Wait a second... I know that road! You're headed west on HWY 30, close to Multnomah Falls!

[@caboosez250]

Gale banks has been schooling this in his recent videos. Manifold Air Density is king. Boost pressure means nothing.

[@acts2211]

Another Factor worth mentioning is the compression of the motor prior to boost will have a huge impact on power generation

[@cray1801]

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.

[@adamc8409]

Volumetric efficiency is what it comes down to, more air in and out means more power. That's why cars running cooler gas like methanol or nos make more power is the air fuel charge is cooled.

[@jonnoMoto]

Gales bank is the person to listen about. Manifold air density is what matters

[@henryostman5740]

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.

[@rustyshaklferd1897]

Let’s put the saying of no replacement for displacement to bed once and for all. A half displacement engine with 14.7psi is a direct replacement for displacement. Other engineering magic adds to this fact.

[@BPMoments]

It's called dynamic seating. It's an awesome AMG option. Been around for decades.

[@schifoso]

PV=nRT, so n=PV/RT. Volume and R are constant, so n=P/T. So either increase pressure or decrease temperature to get more molecules of O2.