Background:
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.
Performance Comparison:
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.
Conclusions:
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+.
Will this dv valve fit with the IE inlet elbow and intake?
I don’t have an IE inlet elbow to test fit with. Since it is shorter than the stock DV I imagine it should work with the IE part.
Nice…just saw this had come out as a low-profile version to work with the aftermarket turbo inlets. To me this product really is only a benefit for those with manual transmissions to hold more pressure between shifts vs. the “all or nothing” OE DV that is either open or closed. With the DSG I can’t imagine there is much advantage.
I haven’t seen data from a manual transmission car using one of these to be able to evaluate if it holds boost better between shifts.
That’s really the data that is needed…the DSG basically looses little to no boost on WOT shifts. I’ve never understood using any of the aftermarket DVs unless you were having issues with high-boost tunes etc.
Does the diverter valve not typically actuate between shifts? (On manual transmission) If the car is commanding DV open, the DV will be opening no matter if it’s stock or gfb. If this isn’t the case, that’s a defect is it not? Unless i have a significant misunderstanding of the system, these diverter valves don’t decide when to open themselves and therefore shouldn’t perform substantially differently from one to the other. This is mostly speculation, to be clear
You’re correct.
The difference with the GFB DV+ is that the piston has a spring behind it that is supposed to start closing the piston as boost drops. That way the rate of boost dropping slows versus the fully open stock DV, and then when the ECU closes the DV/DV+, the GFB should have left a higher boost pressure than stock in the system. Building back to full boost should happen quicker with the DV+. At least that’s the concept, in practice the difference between the DV+ and stock appears negligible to me.
Hi Jeff,
How are you liking this DV? I’m debating between this one and OEM. Curious what your impressions are.
I don’t have any complaints about how it operates. I cannot tell a difference in operation from the stock DV, and nothing has stood out on the logs. I do like the lower profile since I am swapping parts quite often and that makes it a bit easier. For me the low profile alone is enough of a benefit to make it worth having.
Is this part still on the car? are you still using it? “long term” use update?
Yes, I am still using the GFB DV. It has been working without any issues. I went with the low profile because I have a temperature probe I use in the Inlet Elbow, and the stock DV presents interference issues. This part eliminates that problem and works as well as the stock part as far as I can tell, both of which I am happy about.