Background:
With the air temperature dipping below 50F, I took the GTI out to make a couple of pulls and see what differences may result from the last pulls made in October when the air temperature was 85F.
The intake setup continues to consist of the APR PEX intake, MST inlet hose, and MST V2 turbo inlet elbow.
I still use the Russell Road & Racing E50 tune discussed in the October post.
Results:
As mentioned, the outside temperature was significantly lower than the last time I logged the car.
This translated to a drop in Intake Air Temperature (IAT).
With denser air being drawn into the compressor, the turbine does not need to supply as much work to the compressor as with the higher outside air temperature.
Depending on the engine speed, the wastegate duty cycle decreases by 10-20%.
Boost pressure is similar for each air temperature. Notably, the M520 is hitting 30 psi around 2900 RPM in 4th gear at this cooler air temperature.
The wheel horsepower and torque peak estimates using Virtual Dyno are 505 WHP and 498 WTQ.
I have seen a comment that the stock airbox is “good to 500 hp,” but like many bits of information I come across, I haven’t seen this substantiated.
With the power level around 500 whp, I had the idea to swap intakes from the APR PEX to the stock airbox later in the day.
A previous comparison of the stock GTI airbox with modifications and a Mann panel air filter was made against the Blaze Performance ATOM Race intake when boost pressure was around 29 psi.
In that comparison, the modified stock airbox increased WGDC after 6,000 RPM, maxing out at 6% greater WGDC around 6700 RPM.
This outing, boost pressure is increased to ~34 psi through the midrange and tapering to ~32 psi at 6500 RPM.
Most significantly, the stock airbox will be outfitted with an aftermarket panel air filter from BMC.
Stock airbox results:
By afternoon, the air temperature had risen 15F to 63F. This was not ideal for comparing with the morning session, but it was still an opportunity to see what would happen.
The IAT increased with the rise of the outside air temperature
Interestingly, given the higher air temperatures and change from the aftermarket intake to stock intake, the WGDC did not increase much.
Boost pressure continued to be consistent, around 34 psi before tapering.
The two warmer air pulls varied more in the Virtual Dyno estimates, averaging around 500 WHP and 490 WTQ.
Conclusions:
The GTI was logged during cool weather with air temperatures between 48 and 63 degrees F and compared with results logged with the same setup when the air temperature was 85 degrees F.
The power and torque results are summarized below (Intake/OAT):
- 505 WHP and 498 WTQ (APR PEX / 48F)
- 500 WHP and 490 WTQ (Mod. Stock / 63F)
- 496 WHP and 472 WTQ (APR PEX / 85F)
The cooler air temperature correlates with an increase in peak wheel horsepower.
Assuming the linear relationship between the APR intake data points is accurate (a weak assumption), the change from the APR PEX intake to the stock GTI airbox produced a negligible effect (~1 whp decrease) on the peak wheel horsepower for the limited data collected.
Note: Using only one or two data points is insufficient to conclude confidently the observed outcomes.
Next steps:
The Blaze Performance ATOM Race V2 intake will be installed for the next comparison.