How are intakes supposed to increase power in a turbocharged car?

[keplaffintech]

Upgrading the intakes on the Stinger are done for sound, aesthetics, and performance. Let's focus on performance.

The performance increase supposedly comes from these factors:


More peak power/tq due to colder air

Lowering the temperature of the air reaching the intake manifold will allow you to create more power for the same PSI of boost. Awesome!

But some of these intake systems look like they pull less cold air than the stock system. They have pod filters that are open to the engine bay and sometimes without heat shields. The stock system is well designed to pull in cold air, how do aftermarket intakes do better?

More peak power/tq due to less restriction

This is the part that doesn't make sense to me.

If you want more power in a turbocharged car, you can increase the boost, reduce the intake temps, or advance the timing. Less restriction won't change timing or reduce temps on its own, so the idea is that by less restriction we should get more PSI of boost. However, this is false, as boost is controlled by the ECU operating the wastegate. If you want more boost the only way to get it is to program the ECU to request a higher target. Intakes are not the restriction for boost, the artificial limit set by the ECU is.

You can't trick the ECU with an intake, as the ECU is measuring actual boost pressure and adjusting the wastegate to keep it at target. A piggyback just scales the actual and target measurements so you can't 'trick' the piggyback with an intake either.


Faster turbo spool / better throttle response (due to less restriction).

So this is the last thing that intakes could help with. This wouldn't change dyno peak power numbers. My understanding of turbos is that the intake size or filtering isn't really going to be a restriction here. It's the volume of exhaust gasses that pass through the turbine that is going to limit how fast we spool.



What am I missing?

 

[StingertimeNC]

I think they just sound cool! In my case, running snorkels with the radiator shroud removed and BMS intakes. Honestly have no clue if they produce any power. Not interesting enough to dyno with that vs stock, just to confirm they add 3 HP, etc. Many people just get a high flow filter and snorkels and call it a day.

 

[G70LEbyAdoom]

Upgrading the intakes on the Stinger are done for sound, aesthetics, and performance. Let's focus on performance.

The performance increase supposedly comes from these factors:


More peak power/tq due to colder air

Lowering the temperature of the air reaching the intake manifold will allow you to create more power for the same PSI of boost. Awesome!

But some of these intake systems look like they pull less cold air than the stock system. They have pod filters that are open to the engine bay and sometimes without heat shields. The stock system is well designed to pull in cold air, how do aftermarket intakes do better?

More peak power/tq due to less restriction

This is the part that doesn't make sense to me.

If you want more power in a turbocharged car, you can increase the boost, reduce the intake temps, or advance the timing. Less restriction won't change timing or reduce temps on its own, so the idea is that by less restriction we should get more PSI of boost. However, this is false, as boost is controlled by the ECU operating the wastegate. If you want more boost the only way to get it is to program the ECU to request a higher target. Intakes are not the restriction for boost, the artificial limit set by the ECU is.

You can't trick the ECU with an intake, as the ECU is measuring actual boost pressure and adjusting the wastegate to keep it at target. A piggyback just scales the actual and target measurements so you can't 'trick' the piggyback with an intake either.


Faster turbo spool / better throttle response (due to less restriction).

So this is the last thing that intakes could help with. This wouldn't change dyno peak power numbers. My understanding of turbos is that the intake size or filtering isn't really going to be a restriction here. It's the volume of exhaust gasses that pass through the turbine that is going to limit how fast we spool.



What am I missing?

You've almost got it, what you're missing is the fact that the intakes can take in a larger volume of air than the stock boxes can, when requested. Combine that with the increased amount of air that is required from increasing boost levels, you get the faster spool times. Faster spool times = faster power delivery = increased power in the non peak range of the power band. This can been seen very easily on a tuned car if you where to do a run with the stock boxes and then open air intakes. on a NON tuned car however, they really wont do much besides change the sound, as you stated.

 

[byebyeSTI]

ahhh beavis i think its the theory of more air in more power out ? more cold air in less timing out ?

 

[SuicideSaints]

What about more airflow? I’ve seen graphs showing some intakes get more air in?

Also, what about CAI with snorkels? Not at lower speeds but higher speeds allow for more cold air to reach the engine bay and filters?

Would a better intercooler be the right choice, since it cools the air post compression?

Genuinely asking, I only bought the CAI for the look and sound. I wasn’t banking on getting the 10-20 HP gain claims.

 

[DoctorStiches]

Well layed out post! But i just use intakes (semi enclosed so the engine heat is not just sucked right in) anyway i just use them for the much much better true twin turbo experience. When you put your foot in it a tiny violin starts going ham sammich under the hood louder and louder to please my ears

 

[oddball]

Didn't we just have this discussion?
Look, engines aren't as simple as you seem to assume. For example, check out the engine masters (they fixed the Aus access issue, I hope!) episode where they found that *LESS* boost made *MORE* power!
Improving airflow ability *will* change the charge in the chamber. Regardless of what the turbo is doing.
I'm pretty out of date on OEM ECUs, but it appears that at least this car runs quasi-closed-loop under power, so the ECU will at least somewhat react to the changing conditions based on o2 sensor readings.
AND the ECU is extremely dynamic on ignition timing based on tables AND the knock sensors. It's quite clear that timing has a dramatic impact on performance - look at how it pulls timing during shifts!

The 3.3 doesn't have MAF so really, the ECU doesn't know the oxygen load in the chamber. It makes guesses based on sensors. Changing the intakes will change the oxygen load. Pressure is only one variable in determining the oxygen load.

 

[RM7]

Yes, modern engines are not going to make "more power" just because you have an intake. They have sensors that regulate everything and they are keeping the engines in check. This is even more the case with a turbo engine, because you have so many restrictions to airflow, the turbo, the routing, the intercooler, the manifold, it's foolish to think a little bigger plastic and filter is really doing anything to your engine power.

Now, if you can "fool" the sensor in the airbox, such as some piggy-back tunes do, then you can tell the turbo to spool higher, deliver more air, deliver more fuel, etc. That's what is going to make more power. The "heart" of a turbo engine though is that turbo, that's what sets it all in motion. Increasing the boost is the way to more power, within the limit of what your injectors can support and what doesn't fry out the engine from heat.

Most people "think" they make more power with an intake because it removes the OEM silencing, so you can "hear" the engine more, so they think they are making more power/going faster. They dyno results are those that are within the normal noise for ANY dyno, so saying you picked up 5-20hp is usually just ridiculous. Do 10 runs, alternate intake and no intake on each, then compare the data for statistical significant results. Does anyone really do this? No, because these don't really add power.

Now, with most engines, especially turbo, they'll have some margin in there that is designed in for protection. Turbo engines ram fuel down the throat when under power, to provide cooling, this means the injectors have often have some leeway for tuning and achieving higher boost. This allows you to put more fuel in, and you'll make more power with the tune. You have to be careful, too lean and you'll fry the engine and you might go into limp-mode more often in the desert, but there are ways you can mitigate some of this, bigger intercooler, bigger injectors, etc. Sometimes this gets into chasing your tail.

The biggest thing that is going to help you build more power, besides a tune, is freeing up the downpipe and exhaust (manifolds, turbo-back, etc.), to spin the turbo faster. This requires a tune of course.

Typically, from my WRX/STI days, you had to be running at least a bigger turbo size to get to the point where you needed to increase air tubing size, but again, it's not so much tubing size, since it's pressurized air, so it took some pretty radical mods to get to that point.

 

[Aarvix]

There's a reason turbocharged dragsters don't run filters, and it's not because they want FOD in their turbo.

 

[G70LEbyAdoom]

There's a reason turbocharged dragsters don't run filters, and it's not because they want FOD in their turbo.

Yes, its because dragsters literally run their car a 1/4 mile at a time, and dont drive them on the road.........

 

[keplaffintech]

Didn't we just have this discussion?
Look, engines aren't as simple as you seem to assume.

I want something more concrete than 'engines are complicated, there are many factors'. Did you read my post? I already covered both charge temps and timing as two ways other than boost to increase power.

To dig into your comment a bit:

Changing the intakes will change the oxygen load. Pressure is only one variable in determining the oxygen load.

Can you tell me what component of intake charge adding intakes will actually change? Assuming pressure (boost), and temperature stay constant, how will an intake affect the charge? How do you get more oxygen in the air without changing the temperature or pressure of the air? Because the ECU monitors both of those.

 

[RM7]

I want something more concrete than 'engines are complicated, there are many factors'. Did you read my post? I already covered both charge temps and timing as two ways other than boost to increase power.

To dig into your comment a bit:


Can you tell me what component of intake charge adding intakes will actually change? Assuming pressure (boost), and temperature stay constant, how will an intake affect the charge? How do you get more oxygen in the air without changing the temperature or pressure of the air? Because the ECU monitors both of those.

Yep, and that’s what is downstream of the turbo. I think that’s where people have trouble understanding I think.

 

[th3n4m31zd4n]

I've seen so many posts on all sorts of car forums and youtube videos saying they do and don't increase horsepower that I've just defaulted to the mindset that they don't, to be conservative lol. I just bought mine for the sound and looks (mainly the sound). If performance is the priority, obviously JB4 is the move. I know that's not the purpose of this thread, but most threads I've seen on this topic just go in endless circles lol.

 

[keplaffintech]

most threads I've seen on this topic just go in endless circles lol.

I was expecting to be torn to shreds by die hard believers here but I'm pleasantly surprised at the responses!

Really I wanted to help break the myth that intakes are a 'must have mod' for performance. IMO the 'must have mods' if you are looking for performance are just a tune (piggyback or ECU) + spark plugs.

I think an intercooler will actually give a performance difference when compared to intakes, as an intercooler will actually reduce intake temps.

 

[Aarvix]

Yes, its because dragsters literally run their car a 1/4 mile at a time, and dont drive them on the road.........

I think you misunderstood my comment.
If intakes/filters weren't a restriction, then why do dragsters run without them and risk damaging the turbo?

Intakes probably don't make more power on a stock car, since everything is sized for the inherent restriction in the OEM system. But keep in mind manufacturers have more to consider than max power, like noise and packaging, so compromises are often made.

But intakes definitely make a difference on a tuned car because you're asking the system to flow more air than it was designed for.

This article explains it pretty well:

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[keplaffintech]

But intakes definitely make a difference on a tuned car because you're asking the system to flow more air than it was designed for.

This article explains it pretty well:

Thanks for this, finally an answer with some real science! The only flaw I have with that explanation is that it's all theoretical: how do we know the pressure drop caused by OEM airbox is actually significant and not negligible? The OEM box design or filters aren't particularly restrictive.

Maybe the best way is to do a real world dyno test on a tuned car. E.g. run map 2 with stock filters, then with aftermarket intakes. I haven't really seen a good independent dyno run of these, only runs provided by the intake manufacturers (which you can't really trust).

 

[G70LEbyAdoom]

Thanks for this, finally an answer with some real science! The only flaw I have with that explanation is that it's all theoretical: how do we know the pressure drop caused by OEM airbox is actually significant and not negligible? The OEM box design or filters aren't particularly restrictive.

Maybe the best way is to do a real world dyno test on a tuned car. E.g. run map 2 with stock filters, then with aftermarket intakes. I haven't really seen a good independent dyno run of these, only runs provided by the intake manufacturers (which you can't really trust).

I mean, if you want to cover the 150 USD it will cost me for some dyno runs, I will happily get you the data you want. I am 99% certain that it will tell us what we already know, but my offer is there.

With me getting a brand new engine, the stock intakes are going to be on the car, so I will happily put on my JB4 only, do a dyno pull on map2, swap the intakes to my K&N ones, let the car cool, then have another pull done with those being the only variable.

 

[oddball]

Thanks for this, finally an answer with some real science! The only flaw I have with that explanation is that it's all theoretical: how do we know the pressure drop caused by OEM airbox is actually significant and not negligible? The OEM box design or filters aren't particularly restrictive.

Maybe the best way is to do a real world dyno test on a tuned car. E.g. run map 2 with stock filters, then with aftermarket intakes. I haven't really seen a good independent dyno run of these, only runs provided by the intake manufacturers (which you can't really trust).

In the case of the Stinger, the intake restriction is the silencer on the front of the core support. Taken off your bumper and looked at that thing? It literally makes several bends, then has a small opening to pull in air from a very small gap (<1/2") between the silencer and the flat plate of the bumper. I swapped to big mouth intakes and there is a significant and noticeable intake pull even when just revving in park. As in this thing pulls more air than my 500 hp v8.

I know the ECU makes its decisions based on a VE table since it only has MAP sensors. I know VE tables are built to represent the total engine dynamics. Change anything and the VE of the engine changes. I'm willing to admit that I do not know all the details of effects on volumetric efficiency. For example, pressure and temp are not the only variables that determine chamber charge. Those variables to not take into account the velocity of the airflow or any pressure waves within the intake track.

If the only way to convince you is independent dyno testing, then put up the cash!

 

[G70LEbyAdoom]

In the case of the Stinger, the intake restriction is the silencer on the front of the core support. Taken off your bumper and looked at that thing? It literally makes several bends, then has a small opening to pull in air from a very small gap (<1/2") between the silencer and the flat plate of the bumper. I swapped to big mouth intakes and there is a significant and noticeable intake pull even when just revving in park. As in this thing pulls more air than my 500 hp v8.

I know the ECU makes its decisions based on a VE table since it only has MAP sensors. I know VE tables are built to represent the total engine dynamics. Change anything and the VE of the engine changes. I'm willing to admit that I do not know all the details of effects on volumetric efficiency. For example, pressure and temp are not the only variables that determine chamber charge. Those variables to not take into account the velocity of the airflow or any pressure waves within the intake track.

If the only way to convince you is independent dyno testing, then put up the cash!

Ive already put the offer up to do it with my car with a brand new engine, so the offer is out there for @keplaffintech to take up

 

[SuicideSaints]

I mean, if you want to cover the 150 USD it will cost me for some dyno runs, I will happily get you the data you want. I am 99% certain that it will tell us what we already know, but my offer is there.

With me getting a brand new engine, the stock intakes are going to be on the car, so I will happily put on my JB4 only, do a dyno pull on map2, swap the intakes to my K&N ones, let the car cool, then have another pull done with those being the only variable.

Thanks for this, finally an answer with some real science! The only flaw I have with that explanation is that it's all theoretical: how do we know the pressure drop caused by OEM airbox is actually significant and not negligible? The OEM box design or filters aren't particularly restrictive.

Maybe the best way is to do a real world dyno test on a tuned car. E.g. run map 2 with stock filters, then with aftermarket intakes. I haven't really seen a good independent dyno run of these, only runs provided by the intake manufacturers (which you can't really trust).

I think this has already been done right? Burger has posted numerous dynos showing stock maps and then BMS intake maps. In the N54 thread I think this has been done too. I won’t be reading the entire 100+ pages but even Terry has posted stock, map 2/3 and then added intakes only and reposted. I know it’s not independent but others have posted.

I tend to think under stock conditions intakes alone do nearly nothing. Under tuned conditions intakes can supply more airflow.