would take far more sophisticated equipment, and sampling at locations that we did not have access to.

Here's my theory on TC and IAT. When the TC occurs the throttle plate went to about 40%. I expect that the DV opens to recirculate the charge air back into the intake side. So you've got pressurized air at ~110F being routed into atmospheric pressure air at ~80F. Higher temperature air mixing with lower temperature air should raise the intake air temperature. But, that compressed air is also expanding and dropping in pressure, which means it is also cooling from the expansion process. How much does air cool when dropping from 15 psi gauge to 0 psi gauge? Probably a good bit, considering that when it was compressed to that 15 psi it rose a good 200 or so degrees, (remember the intercooler takes a lot of that heat away).

That air is then going back through the turbocharger, but the turbo now should be making much less boost, let's say 5 psi, so the outlet temperature is much less, on the order of 100F lower than at 15 psi.

So the air that returns to make it to the IAT sensor when TC occurs ought to be a fair bit lower than what gets there under full boost.

So in our tests, from this aspect the IPP IC's had the advantage of potentially lower intake air temps versus the stock IC's.

Regarding your second question about the boost levels being different. With an intercooler operating at 70% efficiency, the difference in 15 psi and 17 psi of boost is only going to be about 5F out of the IC. The compressor efficiency is not really a factor at those levels on the K04's which is what Michael has. The TC that happened with the IPP IC's meant that full boost was not being made for the higher rpm portion of the FATS, where the high IAT's typically show up.

It would have been extremely difficult to hold boost pressure to the same level on all tests. By doing multiple runs and averaging the results we tried to minimize the affect of varying boost levels.

You bring up some valid points for consideration. I'd be very surprised though if they affected the results we got.

National Motorists Association