X + Y doesn't equal Y.


If you lower the temp going into the turbo, the output will also be lower

 

but if the air is colder b4 getting compressed wouldnt that be a little bit better?

 

yes

 

exactly

 

So CAI on turbo FTW? Long intake pipe doesnt matter for turbo lag?

 

I would say get a large diametter Intake for cold air and yes as long as the CAI is at least as big if not a little bigger than your intake diamater on your turbo it should be great!

 

Yes if you lower the intake air to the compressor it may lower the boosted air a bit but I guarantee it will not be very much. I mean think abou it.......yeah, you may lower the air temp going into the compressor by 15

 

You have nothing to backup your numbers. You are just making guesses.

Possible surge problems

 

Lower the inlet temperature. The less hard the turbo has to work to compress the air then the lower the temperature the air coming out of the turbo is. This actually hurts the DTlm, but still if it's cooler going in it will be cooler coming out. You can work the turbo less hard by running less boost, by improving the pressure drop between the air filter and the turbo, or by having a more efficient compressor wheel. You can also reduce the pressure drop in the intercooler, which allows you to run the same amount of boost in the intake manifold while having a lower turbo discharge pressure. More on this later. If you can drop the turbo outlet pressure by 2 psi, or raise the turbo inlet pressure by 1 psi, that will drop the turbo discharge temperature about 16 degrees (depending on the compression efficiency and boost level). If the turbo air is going into the intercooler 16 degrees colder then it may come out only 10 degrees colder than before, but that is still better than what it was.

But lets take it a bit further....

Tout = Tin + Tin x [-1+(Pout/Pin)0.263]/ efficiency

This equation shows the outlet temp of a Turbo based on efficency.

the inlet temperature is 100 deg F, the suction pressure is -0.5 psig (a slight vacuum), the discharge pressure is 11 psig, and the efficiency is 75%. What is the discharge temperature?

Tin= 100 deg F + 460 = 560 deg R
Pin= -0.5 psig + 14.7 = 14.2 psia
Pout= 11 psig + 14.7 = 25.7 psia
Pout/Pin = 25.7/14.2 = 1.809 (this is the compression ratio)


So Tout = 560 + (560 x ((-1+1.809)^0.263 ))/0.75 = 685.97 deg R - 460 = 225.97 deg F

Now lower it 30 Deg F.....

So Tout = 530 + (530 x ((-1+1.809)^0.263 ))/0.75 = 649.22 deg R - 460 = 189.22 deg F

That is a 36.74 deg F difference. so lowering the intake temp 30 deg lowers the turbo output by 36.74 deg F. Then this goes through your intercooler. The Delta is a bit different but what you get (and there are MORE equations for intercooler efficency and output temps and sizing but I digress....) is a larger mass of denser air which = More Power.... How much more? a 40 deg drop in air temp is roughly a 7% increase in Air mass.. which on a 500 HP car is roughly 35-40 HP MORE.... just by lowering the intake temp into your turbo.

It is true the closer you get your output temp from your turbo to ambiant tempature the less your intercooler does (The Delta for cooling gets smaller the closer you approach ambiant) but the end result is that the air is 30 deg cooler than you started with... with just a CAI to the turbo.

 

Funny thing is, you can go through your equations all day long but if you don't run a real world test on it, your equations don't mean anything.

I have done testing with a buddy of mine on his Talon that was putting down over 600 whp. We made a cold air intake for it and dyno tested it and in the end of all the headaches and retuning..........He only gained 12 whp and on top of that, started having surge problems.

I used to also work in the aerospace industry for 9 years and there is a reason why you limit the bell mouth's distance to the jet engines intake.