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Logs from my rebuilt STi engine and FP Green install (no gain over my VF-39)

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#1 ·
A couple of months ago my stock 2004 STi that I have owned for 10 years now decided to burn up a bearing at 130,000 miles. Instead of rebuilding the old short block, I just opted to purchase a new short block and install the old heads and the rest of the parts from the old engine.

I also picked up an HTA FP Green, APS 65mm cold air intake, and APS 725 FMIC , water injection and a what looks like a 4 inch down pipe and 3 inch exhaust from a local kid who totaled his STi.

I tuned the car with Rom Raider and logged with ECU Explorer. I also used an Android application called Force that uses the GPS and acceleration sensor to estimate torque and power along with measuring vehicle's acceleration and speed to make comparing logs much more objective (no more butt-dyno).

A couple things worth noting.... APS says the 65mm cold intake will "maintain stock Air Flow Sensor operation and to work in harmony with the stock engine management". Nope. It took hours of mindless driving to re-calibrate the MAF sensor.

The new hotness.


Installed and almost ready.


I decided to log the car with the stock VF-39 with the stock tune and then with a tune that was aggressive as I felt was safe. Then I swapped in the FP Green the next day and logged again with essentially the same aggressive tune I used with the VF-39. Same road, same temperature (80 degrees). I could only get 22psi or so out of the VF-39 and FP Green with the duty cycle at 100%. I live at about 6,000ft in elevation, so ambient air pressure is only about 12psi (versus 14.7 at sea level). A stock STi in Denver

The Summary Results:

Stock Tune:
Peak Torque: 247 ft/lb
Peak Power: 211 whp
50-80mph: 5.46 seconds

If the numbers seem low, it is because of the altitude. A dyno from a stock STi in Denver makes about the same power. The SAE corrected for 1.21, so you have to divide those numbers by 1.21 to get the raw numbers, which are almost exactly what I measured.

VF-39 Full Tune:
Peak Torque: 321 ft/lb
Peak Power: 300 whp
50-80mph: 3.824 seconds

A gain of 74 ft/lb and 89 whp! Almost 2 seconds faster from 50-80mph. Can't complain about that.

FP Green Full Tune:
Peak Torque: 297 ft/lb
Peak Power: 322 whp
50-80mph: 3.808 seconds

Still excellent gains over stock, but I really just shifted the power band up with the FP Green over the VF-39. I cannot get the FP Green to boost over 21psi and I can get 23psi from the VF-39. However, the where the VF-39 tapers a lot, the FP Green holds the boost better and flows more up top. At any rate, the duty cycle is at 100%, I have even tried extra springs on the waste gate of the FP Green and I still can't get more boost out of it. Very frustrating. Very little (if any) performance gain over the VF-39. I might go back to the VF-39.

Logs for those that care:

You can see that the FP Green is just shifting the power band up compared to the VF-39.


You can see that the VF-39 is making more peak boost, but the FP Green is making more boost up top.


And the resulting airflow is what you would expect. The FP Green is slacking right at peak engine load...


I could have a slightly more aggressive timing map with the VF-39, too.


And finally, what the acceleration ended up looking like. The FP Green was technically just a tiny bit faster, but meh.
 
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