Does an intake decrease stress on turbos?

[VVG]

So if an aftermarket intake increases air flow, does it allow the turbos to create a certain specified pressure with less strain? Is it actually beneficial, from a mechanical reliability standpoint, to have a better flowing intake, performance gains aside?

[DoughBoyFreshLV]

It's always benificial to have more air going to your car, the more air, the more efficient things will run. Just like your body, if you're working out in 100 plus heat would you rather have on a tank top or be wrapped up in a sweatshirt...

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[VVG]

Anyone else care to chime in? Thought this would be a genuine topic that might generate some real discussion

[hubris]

Anyone else care to chime in? Thought this would be a genuine topic that might generate some real discussion

I'm waiting for the engineers to school us

[HeelBuff]

All I know is APR said it measured decreased power after a popular aftermarket intake was installed.

[hubris]

All I know is APR said it measured decreased power after a popular aftermarket intake was installed.

source?

[HeelBuff]

Thought I read it here. May be wrong.

[VVG]

All I know is APR said it measured decreased power after a popular aftermarket intake was installed.

I am curious as to why this would happen. I can see if there was no gain, but a loss????

[hubris]

I am curious as to why this would happen. I can see if there was no gain, but a loss????

Just worse design than OEM. OEM designs everything to work together. They have knowledge of how every other part in the components before and after part A work, and thus part A is designed to those specs. Not to mention, Audi already has a cold air intake type design on these vehicles (vents to front air intake).

[LINDW4LL]

I am curious as to why this would happen. I can see if there was no gain, but a loss????

Heat. The stock unit's sealed box design does a good job of only pulling in cold (ambient temp) air. I can easily see something like the Injen (open element) raising Intake temperatures and hurting performance. That shouldn't be an issue with a sealed unit like the AWE. Stock Audi intakes tend to be very efficient from the factory so it's easy to take a step backward if you do it wrong.

Injen:

[VVG]

Heat. The stock unit's sealed box design does a good job of only pulling in cold (ambient temp) air. I can easily see something like the Injen (open element) raising Intake temperatures and hurting performance. That shouldn't be an issue with a sealed unit like the AWE. Stock Audi intakes tend to be very efficient from the factory so it's easy to take a step backward if you do it wrong.

Injen:

This wasn't what I had in mind when I read "popular aftermarket intake" in post #5 of this thread

[Ensoniq]

I am curious as to why this would happen. I can see if there was no gain, but a loss????

I'll describe my understanding but also stay subscribed in case someone that understands this better chimes in...



It's because the Stoichiometric ratio is lost unless the tune is adjusted to add the extra fuel needed to match the extra air.

there is an optimum ratio of fuel to air (the stoichimetric ratio). when you add air without adding fuel this ratio is lost

The point of boost is to stuff more fuel/air through the powerplant at the optimum ratio,

The above is a basic comment. There are of course strategic adjustments to this ratio (heavy on fuel to avoid detonation for example)

It's more risky to add air without fuel than the other way around - detonation-wise

[Sean@APR]

All I know is APR said it measured decreased power after a popular aftermarket intake was installed.

Yes, we did. A 15 or 20 hp loss if I remember correctly. It was definitely beyond the margin of error of the dyno. We put the stock one back on and the power came right back.

[Sean@APR]

Now, as to the OP.. that's not a simple question. A restrictive intake reduces the absolute pressure of the air entering the turbo. That's simple physics and how throttles work.

Turbochargers operate differently at different pressure ratios (in/out) and at different speeds. There's a litany of factors involved here and a thorough answer would require lots of measurement and plotting on the compressor chart for the particular turbocharger in question. I'm not going to do all of that work. In the hypothetical, higher incoming absolute pressure will require less speed from the compressor to reach the same target output pressure. Since these cars have intelligent boost control and a boost target, the car will "ease off" the turbo once that pressure is reached. A higher inlet pressure will result in the same output pressure with less turbine speed. In theory, this could slightly extend the life of the turbo bearings. In practice, it's like a shortcut that saves 20 feet of driving on a 2000 mile trip, barely worth it.

That's what happens on a stock tune.

On a performance tune things are different. Winter air is more dense than summer air. The car, in stock form, doesn't really capitalize on that. It hits the target and opens the gates . That's why your car performs similarly in summer and winter while stock (up to the limits of physics). They set the targets low enough to be usually achievable at sea level and 70F. We tune our cars to achieve target at about 1000ft elevation and 100F (typical conditions in Alabama). We also give a more room beyond that so you can benefit from cold winter air if it's available.

Remember when it first got cold and a couple people had overboost issues with our tune that we released in the summer? Bingo.. this is precisely why. We expanded those boundaries a bit more to further compensate for winter conditions. It's all modeled in the ECU, but sometimes even the best engineers (a combination of Bosch, Audi, APR and the turbo manufacturer in this case) can't always nail the prediction math 100%. (Obviously, Audi didn't come to us to work on this. But, Audi, Bosch and the turbo manufacturer did the measurements and constructed the model from them.)

Back to your question: A tuned car will use up some of that "room" to take in more air from a less restrictive intake (if you actually have one that is less restrictive.. we haven't seen one yet for these cars) and give you more performance. The turbo will spin about the same speed it did with your stock airbox, but you'll get a few more HP out of it.

[hubris]

We also give a more room beyond that so you can benefit from cold winter air if it's available.

...

Back to your question: A tuned car will use up some of that "room" to take in more air from a less restrictive intake (if you actually have one that is less restrictive.. we haven't seen one yet for these cars) and give you more performance. The turbo will spin about the same speed it did with your stock airbox, but you'll get a few more HP out of it.

Fascinating write-up, Sean. Thanks! In regards to the benefit from colder air... it hit below 30 here the other day, I hammered on the throttle (after waiting a half hour for the car to warm up ) and checked my P3 OBDII boost gauge afterwards to see how much boost the car made on APR tune: 19.1!!! Usually it tops out around 13-14. I haven't seen it boost that high since. It worried me a bit as that is quite a bit of pressure. However, winter air is more dense as Sean mentioned, so I know that plays a role. No CEL or codes, I didn't use VCDS to check for soft codes.

[VVG]

Now, as to the OP.. that's not a simple question. A restrictive intake reduces the absolute pressure of the air entering the turbo. That's simple physics and how throttles work.

Turbochargers operate differently at different pressure ratios (in/out) and at different speeds. There's a litany of factors involved here and a thorough answer would require lots of measurement and plotting on the compressor chart for the particular turbocharger in question. I'm not going to do all of that work. In the hypothetical, higher incoming absolute pressure will require less speed from the compressor to reach the same target output pressure. Since these cars have intelligent boost control and a boost target, the car will "ease off" the turbo once that pressure is reached. A higher inlet pressure will result in the same output pressure with less turbine speed. In theory, this could slightly extend the life of the turbo bearings. In practice, it's like a shortcut that saves 20 feet of driving on a 2000 mile trip, barely worth it.

That's what happens on a stock tune.

On a performance tune things are different. Winter air is more dense than summer air. The car, in stock form, doesn't really capitalize on that. It hits the target and opens the gates . That's why your car performs similarly in summer and winter while stock (up to the limits of physics). They set the targets low enough to be usually achievable at sea level and 70F. We tune our cars to achieve target at about 1000ft elevation and 100F (typical conditions in Alabama). We also give a more room beyond that so you can benefit from cold winter air if it's available.

Remember when it first got cold and a couple people had overboost issues with our tune that we released in the summer? Bingo.. this is precisely why. We expanded those boundaries a bit more to further compensate for winter conditions. It's all modeled in the ECU, but sometimes even the best engineers (a combination of Bosch, Audi, APR and the turbo manufacturer in this case) can't always nail the prediction math 100%. (Obviously, Audi didn't come to us to work on this. But, Audi, Bosch and the turbo manufacturer did the measurements and constructed the model from them.)

Back to your question: A tuned car will use up some of that "room" to take in more air from a less restrictive intake (if you actually have one that is less restrictive.. we haven't seen one yet for these cars) and give you more performance. The turbo will spin about the same speed it did with your stock airbox, but you'll get a few more HP out of it.

Thanks Sean!! Exactly the info I was looking for !!