Background:
The ARM Bicooler is an upgrade path from the ARM Motorsport FMIC that uses the existing stock mount intercooler to increase cooling capacity and reduce pressure drop across the intercooler.
After reading unsubstantiated claims from Equilibrium Tuning personnel about the ARM FMIC performing poorly on any turbocharger larger than an IS38, I installed the FMIC on my GTI with a hybrid turbo and collected evidence proving the claims false.
After testing the ARM FMIC stand-alone, I added the Bicooler hoses and joined the ARM FMIC with the GTI stock intercooler.
This post discusses the results of operating the Mk7 GTI with the ARM Motorsports Bicooler.
Test Process:
The ARM Bicooler supports a Mabotech M520 hybrid turbo operating with a Russell Road & Racing E50 tune. The boost curve for this combination is shown below:
The GTI is operated in 4th gear, and two full-throttle pulls are made from around 2,000 RPM to around 6,500 RPM. There is approximately one minute in between the pulls to reposition the GTI.
Test Results:
The following charts show the performance of the ARM FMIC (blue lines) compared with the ARM/Stock IC Bicooler (orange lines).
The first chart shows the outside air temperature (OAT) during the data logging sessions.
The following chart shows the Intake Air Temperature (IAT) measured at the intake manifold.
This next chart adjusts for the difference in outside air temperature by subtracting the OAT from the IAT, to show how much the IAT is above the OAT during the pulls (DeltaT).
The respective boost curves for each configuration are shown next.
Finally, the turbocharger wastegate duty cycle is compared.
Conclusions:
The ARM FMIC with Stock IC configured as a bicooler was compared with the standalone ARM FMIC using a Mk7 GTI equipped with a Mabotech M520H hybrid turbocharger operating at 32-34 psi and making approximately 500 whp.
The intake air temperature differences between the two intercooler setups were similar.
The bicooler configuration produced a lower turbocharger wastegate duty cycle, an expected result because bicoolers divide the airflow volume between the cores, resulting in a lower flow rate through each core, correlating with a decrease in system pressure drop.
ARM Motorsports advertises the Bicooler hoses as a recommended upgrade when operating with a hybrid turbocharger. The evidence collected using the Mabotech M520H hybrid turbo supports this recommendation.
Previously, I compared the ARM FMIC with the ARM/Stock IC Bicooler using an IS38+ turbocharger. That lower power setup allows for repeat pulls, which shows that the bicooler provides a cooling advantage under repeat full-throttle pulls.