# WAI/CAI and turbos.



## PatScottAKA99XE (Apr 30, 2002)

Ok, no I have not see a lot of turbo cars, but most if not all of the ones I have seen are running a WAI. What is the reason for this, packaging? road water?. I think that a turbo would benifit from a CAI because it would help keep air temps down. Is this untrue becasue the temp difference is little and the IC would(does) take care of it? I dunno, maybe I just answered my own question.


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## Guest (Aug 3, 2002)

On my car, I have a cone filter down in the front driver's side corner way down underneath the bumper right near the front of the car. From there, there's some mandrel bent piping that goes straight into the turbo... so it's really not a WAI at all.


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## Murph (Aug 8, 2002)

last time I checked air get kinda warm going through a very hot turbo, but i suppose a cia would help a little. Nothing concrete, just what I figure.


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## SuckiT (Jun 13, 2002)

This debate has been all over I-club. The general concensus was that the intercooler cools the air. Also the air can only be as cool as the air passing through the intercooler, if using an air/air.


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## Guest (Aug 12, 2002)

Yeah... but that's after it goes through the turbo. I think the question is really about whether the air temp difference between a WAI and a CAI makes a difference when it goes into the compressor side of the turbo. Obviously the cooler the better, but if the difference is, say 15 degrees... does that make any difference considering it gets heated up so much from being compressed?

Obviously the lower the air temp exiting the compressor side, the cooler the intercooler will be able to get it... obviously only down to ambient temps but depending on how efficient your IC is you may not be getting the air all the way down to ambient when you're running the car hard.

So does the initial air temp before it goes into the compressor matter at all? Or is any conceivable temp difference between WAI and CAI simply eaten up by the compressor? I'm sort of tempted to believe it doesn't make a difference... even with just a WAI, even if it's pretty hot air going in... it gets quite a bit hotter than that in the compressor.


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## bahearn (Jul 15, 2002)

Son of Schmilsson wrote:


> I think the question is really about whether the air temp difference between a WAI and a CAI makes a difference when it goes into the compressor side of the turbo.


Of course it makes a difference. Same as on an N/A car. Cooler air is denser, you get more of it in a given volume (namely, the intake plumbing up to the compressor inlet).

As for the intercooler, air density must increase as temperature falls per the ideal gas law but that just regains most of the density lost due to compression heating; its primary purpose is to cool intake charge for detonation resistance.


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## Guest (Aug 15, 2002)

Think about this, if you compress air, it will get quite hot, right? So having a cai wouldn't really make much of a difference at all. If you have air going into the compressor from a cai 15 degrees cooler than if it was through a wai, it's probably not going to come out 15 degrees cooler, they will probably be right around the same temp. 
Also, why waste the performance value on a cai? All that a cai is going to do is slow the air velocity to the compressor down. This is true on all intakes though, turbo or N/A. This is why they make heat shields for intake filters, so that you can have a high velocity of air while still keeping it relatively cool, though still not as cool as a cai. It's a compromise really.


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## Murph (Aug 8, 2002)

makes sense that the cold air entering the turbine would be warmed up for its short stay within the turbine. It would heat up and expand and would be compressed while STILL in the scoops of the turbine.

So its somewhat of 2 compression sources. The fact that the turbine is forcing the air and the air prssure within the turbine scoop is release as soon as it hits the "outlet" (?)


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## Guest (Aug 28, 2002)

that outlet is called the exducer, it looked like you were wondering.


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## Murph (Aug 8, 2002)

as opposed to the 'inducer' on the intake side of the compressor?


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## Nismo Skyline (May 2, 2002)

since none of you has taken the time to test your theorys, I'll tell you what I found with an actual test.

I did this on my 85 300ZXT with an intercooler. I put a thermocouple in the intake manifold right behind the throttle body to measure the intake air temp. My car had a WAI K&N sitting in the engine bay just above the radiator. I drove the car around watching the temps under various conditions. Then I constructed an air box out of cardboard and duct tape to see if there was any difference. Just driving around, it dropped the intake temp about 30 degrees F. Under load it was more in the 10-15 degree range. 

Did it make a difference? YES! Will it be the same on all cars? Maybe. Every 10 degrees is about 1% horsepower gain. So if you cool it only 10 degrees on a 250 hp engine, thats 2.5 hp gain. But the gains are only apparent at low MPH. At high MPH, you have a lot of air moving around under the hood, so the air isn't as hot as it is at low speed and stopped. Under stopped conditions, I saw differences of almost 50 degrees. I think that since most street drag races are from a stop to 60 mph, it would help alot, but on a freeway race, it would help a bit less.


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