Navi
Autocross Champion
- Location
- BK/NYC/Hamptons
That does make sense about heat from the engine components throwing off air temp readings.
Also, I took another look at the data from APR, since it is the only "real" data I have seen.... They did 6 consecutive runs, with 30 second intervals.
Their data shows that IAT temps with their intercooler barely change. From beginning of the first run to the end of the 6th run, temp increases by 7 degrees (C)
The crazy part is that this temp increase over the 6 pulls does not happen during the run. It happens in the 30 sec interval between the pulls!
With the stock IC, temps jump significantly during the pull...which is what we would expect.
I'm including a simple spreadsheet...One detail that stuck out to me is that the stock IC cools down 22 degrees (C) in the 30 second interval between runs. But the first run gained 28 degrees. If a longer interval was used, the results would be more favorable for the stock intercooler.
So based on this data, "heat soak" is only a thing if you are doing full pulls every 30 seconds or less. That is quite a lovely piece of data, isn't it?
In this data, "heat soak" accounted for 17 degrees (C) temp increase on the 6th run. But there was another 25 degree temp increase due to compressing the intake air. So 40% is heat soak, and 60% is compressing the air. Again, with a longer interval, that heat soak contribution would be essentially zero.
Now, for some math! First run. Assuming PSI numbers that are easy to work with...
43 degree (C) air @ 14psi (absolute) = 1.06363 kg/m^3
71 degree air @ 28psi = 1.9542
Intake Air density at 28psi is 1.83x
41 degrees @14psi = 1.0704
41 degrees @28psi = 2.1408
Intake air density at 28 psi is 2.00x
On the first run, the stock IC lost 17% air density compared to the APR (at the same PSI...). That is losing something like ~14% HP.
On the final run, the APR IC has 11% higher air density than the stock IC.
And their data shows a 9% gain in HP on the last run, which is surprisingly close to the 11% difference in air density I casually/haphazardly calculated..
And...another topic for discussion...it looks to me like the APR Stage 2 dyno charts are only possible with their intercooler. (I wanted to ask, but never did...) They do not say anywhere that the IC is required to reach the 304hp peak power number. And the tuner I went to didn't think the IC was a big deal, saying he would rather ad turbo noises than do the IC...
But if their IC data I'm playing with is correct, showing a peak of 298hp after a 3% loss in air density (due to 9 degree temp increase)...that means the advertised 304hp is only possible with their IC...That means I'm not getting anywhere close to 300hp...more like 260!
Grrrrr..... I love the new clutch I just got, but with the DP and tune it doesn't really feel like a lot more power than I had before....I guess now I know why it doesn't feel like 304hp!
that's what I was going to say