PURPOSE
The purpose of this evaluation is to compare the airflow, boost pressures, and intake air temperatures between a popular design of a 3” intake and a popular design of a 3.5” intake for the B8.5 Audi S4. The intakes tested were a modified Injen intake and the CTS Turbo intake which is identical in design to the Roc Euro intake (identical with respect to pipe diameter, filter diameter, heat shield area).
THE INTAKES
CTS TURBO:
http://img.photobucket.com/albums/v714/bhvrdr/IMG_20151012_123107-s_zps8qofl7be.jpg
MODIFIED INJEN
http://img.photobucket.com/albums/v714/bhvrdr/IMG_20151012_120809-s_zps5tft55kp.jpg
PROCEDURE
All efforts were made in order to eliminate confounding variables. As such the following procedures were performed.
- All testing was performed on the same open stretch of closed course pavement the same direction of travel during the same ambient conditions (82 degrees F, 54% humidity, 29.95in pressure). The entirety of the testing was completed on the same day within 30 minutes from start of testing until end of testing.
- Prior to the beginning of testing the vehicle was driven for 3 baseline runs and then parked for 5 minutes in order to allow heat soaking. This was in order to make all beginning runs of both intake groups the same beginning conditions (each run group initiated after 3 successive runs).
- The first intake tested was the 3.5” Injen intake that was run with no heat shield and no portion of the OEM airbox in place.
- Each intake was run for three successive third gear runs from approximately 2000rpm to 6200rpm. Each run group was completed after the vehicle idled for approximately 5 minutes. Runs 2 and 3 were performed immediately after Run 1 as the vehicle came down to a 2000rpm speed in third gear from the prior runs.
- The intake was swapped out from the Injen intake to the CTS intake in the same 5 minute idle time that was given prior to testing the Injen intake in the beginning of the test.
RESULTS
http://img.photobucket.com/albums/v714/bhvrdr/Air%20mass%201s_zps1wjbjspf.jpg
http://img.photobucket.com/albums/v714/bhvrdr/Air%20mass%203s_zpsl0h4cawi.jpg
http://img.photobucket.com/albums/v714/bhvrdr/boost%201_zpsbkojgyre.jpg
http://img.photobucket.com/albums/v714/bhvrdr/boost%203_zpszz6gebpg.jpg
http://img.photobucket.com/albums/v714/bhvrdr/IAT%201_zpscmwavxoh.jpg
http://img.photobucket.com/albums/v714/bhvrdr/IAT%203_zpsf4yhppws.jpg
SUMMARY
NOTE: Both intake air mass and boost settings will appear universally low for both intakes. This is due to the use of a piggy back that attenuates the ECU signal to see lower boost and consequently air mass (which is calculated form boost). This should not impact the test results in any manner as the attenuation is equal for both test sessions and both intakes.
Interestingly the 3.5” non heat shielded Injen intake appeared to slightly surpass the performance of the 3” heat shielded intake in the categories of air mass and boost, although the difference was negligible. Intake air temperature results indicated a more significant difference between the two.
One may have expected that the 3.5” Injen intake would have been at a disadvantage due to the total lack of heat shielding. At the very least during the first run after the car had heat soaked from idling one may have surmised the non heat shielded intake would have produced higher IATs and less air mass. This is not what the data reflected.
The larger diameter of the 3.5” Injen versus the 3” CTS did appear to offer advantages. This was reported by Injen designers/engineers who originally developed a 3” design and later terminated that project in favor of a 3.5” design after they reported seeing an 8hp increasing using the larger diameter intake.
Perhaps what was also helpful with respect to the Injen was the design of the tube that places the intake filter directly in the path of the incoming air. Refer to the above picture to note the intake air path in reference to each, the Injen and CTS filter.
LIMITATIONS:
The limitations of this evaluation was the omission of testing the Injen intake in its original configuration using the bottom of the stock airbox with their own airbox lid. In retrospect, it also would have been helpful to log actual timing for each intake. It had not been expected that there would be a significant difference in intake temps, and particularly the Injen being the intake with the lower intake temps. Had these intake temp differences been better anticipated, timing could have been logged to see if the reduction in intake temps produced increased timing utilized.