Lately, I’ve been using the Go Fast Bits T9351 Diverter Valve in my GTI, but is the recently available T9381 a good alternative? Time to find out.
Recording measurements on my GTI can sometimes present challenges to finding locations that are convenient and useful where I can install sensors.
Recording the air temperature just prior to entering the turbocharger is useful for evaluating a number of intake-related modifications and the turbo inlet elbow is a good location to take measurements at.
Fitting a temperature probe presents some challenges with the space that the stock Mk7 Diverter Valve occupies, which has led me to swap in a Forge BOV when I want to record the temperature at this location.
In search of a solution that has the benefits of the GFB T9351 DV+ as well as economic use of space that allows me to install a temperature probe at the inlet elbow has been on my mind.
Go Fast Bits T9381 DV+
The GFB T9381 DV+ presents a solution for using the air temperature probe with a recirculation-type diverter valve that should be more reliable in the long term compared to the stock Mk7 Diverter Valve.
I picked up a T9381 model DV+ and set about installing it on my Mk7 GTI.
The T9381 electrical connector can rotate which is a bonus for me when trying to fit the diverter valve next to the air temperature probe.
The T9381 retains the metal piston design of the T9351 and incorporates an electronic actuator.
The T9381 DV+ is a lower profile than the Pierburg diverter valve I have used, and much more so than the Pierburg with T9351 DV+ model (shown at the top of the page).
Installation was straightforward, although initially the electrical connector was pointed toward the coolant hard pipe and had me puzzled for a minute until I remembered that it rotates.
The T9381 has good clearance with the turbo inlet elbow as well as the temperature probe.
Installation of the T9381 DV+ went smoothly.
Given the similarity of the piston designs it was not surprising to find that the T9381 performs similarly to the T9351.
Two measures I recorded using the DV+ are the rate at which boost pressure decreases after the throttle plate begins to close, which corresponds with the recirculation valve opening, and the rate that boost pressure builds once the accelerator is depressed to 100%.
The rate of boost pressure decay is shown in the chart below. No surprise, it is the same for both of these products.
Measuring the time for boost pressure to build after getting on the accelerator is trickier.
This procedure begins by letting off the accelerator so that boost pressure begins to drop, and then as the pressure is dropping the accelerator is fully depressed. The time for boost pressure to reach 20 psi is calculated.
Repeatability of this process is difficult, so a scatter plot of the time for boost pressure to increase, versus the boost pressure when full throttle is applied, is created.
The scatter plot allows for trend analysis. Based on 6 data points using the T9381, this newer product appears to perform similarly to the T9351.
The GFB T9381 DV+ was installed on my GTI to allow me to use a recirculating type of diverter valve along with an air temperature probe at the turbo inlet elbow.
The T9381 should be more reliable than the stock GTI diverter valve.
Initial measures using the GFB T9381 DV+ show similar performance to the GFB T9351 DV+.