Background:
Modifying the Mk7 GTI air intake can be a relatively low-cost alternative to the purchase of an aftermarket intake. A question that might be asked about this option is how well the modified stock intake performs compared to aftermarket intakes, such as the Blaze Performance ATOM Race V2, which is marketed as:
Blaze AToM v2 consistently outperforms competitor intake systems when paired with turbochargers requiring additional airflow.
Equilibrium Tuning Inc. advertising
For this comparison the Mk7 GTI stock intake system has been modified with several “no-cost” changes, and three component swaps to aftermarket options.
You may have read that the modified stock intake is “good for 500 WHP“, in this post I discuss what I learned when operating it at 500 WHP.
Test Setup:
The GTI is equipped with a Mabotech M520 turbocharger making 34 psi and tapering to 32 psi. The engine runs a custom E50 tune from Russell Road & Racing. This hardware and software combination produces roughly 500 WHP and 500 WTQ.
The stock air duct has been opened on the front driver’s side to allow air in directly in front of the air box opening. The rear passenger side is covered to block warmer engine compartment air from being drawn into the duct. The snow guard in the lower half of the airbox is removed, and a hole is made in the lower airbox to allow more air in.
The stock panel filter is replaced with a BMC aftermarket panel filter, the stock accordion hose is replaced with a smooth MST turbo inlet hose, and the stock turbo inlet pipe (TIP), which has a 49 mm outlet to the turbocharger, is replaced by a DBV2 TIP which has a 55.3 mm outlet to the turbocharger.
The Blaze Performance ATOM Race V2 intake is matched with the Blaze 56 mm turbo flange.
Note: The Mabotech M520 has a 60 mm compressor inlet. The similar dimensions of the DBV2 TIP (55.3 mm) and Blaze hybrid flange (56 mm) help focus the comparison on the intakes by reducing the difference in airflow caused by the component (TIP/flange) connecting the intake to the turbocharger.
Test Process:
Generating the data for comparison will be done by operating the GTI on the street and recording engine variables using the SimosTools logger. The car will be accelerated at full-throttle in fourth (4th) gear beginning around 2,000 RPM and concluding around 6,500 RPM.
The variable of interest is the turbocharger wastegate duty cycle (WGDC). If there is a difference in WGDC, this will indirectly indicate there is a difference in resistance caused by the air intake systems.
Because WGDC is not a measure of air resistance, if the WGDC values differ, it won’t be possible to determine how much difference there is in the intake-caused resistance, only that there is some difference.
Test Results:
The outside air temperature is a significant factor affecting the turbocharger WGDC. Controlling this variable while recording the engine performance is vital for a valid comparison.
Mabotech M520 Cool Weather Pulls
The outside air temperature was similar between the data collection sessions, with only a 1.4-degree Fahrenheit difference.
The intake manifold intake air temperature (IAT) was also very similar, with a difference of 1-2 degrees Fahrenheit.
The Boost pressure curves were also very similar, with slight differences no greater than 0.2 psi, a magnitude likely attributable to random variation.
The variable of interest, the waste-gate duty cycle, is also very similar. Again, each intake setup shows some random variation, which produces momentary differences, but there is no consistent difference in the WGDC values between the intake setups.
Conclusions:
A modified stock GTI air intake system was installed on a Mk7 GTI with a hybrid turbocharger operating at 32 to 34 psi and producing around 500 WHP. Engine variables related to turbocharger work level were recorded and compared to the exact vehicle using an aftermarket Blaze Performance ATOM Race V2 intake system.
No significant difference in performance was measured between the modified stock GTI intake system and the Blaze Performance ATOM Race V2 intake system.
These results support claims that the modified stock GTI intake system is “good for 500 WHP” and suggest that it can satisfactorily support more than 500 WHP.
These results do not support the claim that the Blaze Performance intake system “consistently outperforms competitor intake systems.”
On the contrary, because the GTI stock intake system can be easily modified to match the performance of the Blaze Performance intake using a hybrid turbocharger, it is unlikely that the Blaze intake consistently outperforms competitor intake systems.
Irony:
Meanwhile, at the same time, over in the echo chamber:
Reader Concerns:
After posting the test results above, I received feedback from a reader who suggested that my modification, applying duct tape to the back of the stock air duct, might be too difficult for others to replicate.
I want to assure readers that this modification is not very difficult to perform. It is easier with the duct removed from the car, but the tape can also be applied when the duct is installed.
Additionally, for others like Barren who are concerned with the appearance of the inside of their engine compartment, an OEM solution in the form of a block-off plate is available. Two parts vendors who offer this product are UroTuning and ECS Tuning.
Finally, don’t feel compelled to modify your car in the manner I have mine. Because I perform a significant amount of testing with my GTI, I make choices that facilitate testing but might not be suitable for people who aren’t performing tests with theirs.
What was the cost for all the pieces to modify your stock intake for this test? How would this compare at higher power levels?
The MST inlet hose was donated along with their elbow for the TIP testing I conducted in 2019. The DBV2 elbow I purchased used; I don’t recall what I paid for it as it was a couple years ago. The BMC filter was about $75. The Blaze ATOM was purchased on sale and was $550 with tax and shipping.
As for a higher power comparison, clearly this test does not address the condition you are asking about. Depending on what you have in mind as being “higher power”, the further that condition gets from this test case the less likely a speculative answer will end up being correct. In any case, it would just be a guess.
Great data. Above all else for me, this seems to validate all of your previous flow bench testing for air intake pieces.
Thanks!
There has never been a question in my mind of the correlation of flow test data to pressure drop on the car. Unfortunately, people like Ed Susman from EQT put profit above ethics and have misled people about flow testing.