HYDE161
Go Kart Champion
Disclaimer: I am only providing my feedback to help people decide if they feel they would benefit from what I have installed and tested in my own car.
Diverter Valve Progression:
My basic diverter valve experience comprised of swapping my diaphragm design “G” version diverter valve to the piston design “D” version diverter valve as soon as I tuned the car. From there I wanted to explore some advertised benefits around a diverter valve relocation kit and possibly running a stronger mechanical diverter valve to hold boost.
Diverter Valve Relocation Explanation:
The advertised benefits of a diverter valve relocation setup include removing the diverter valve from the heat of the exhaust manifold (could improve durability), while improving functionality and responsiveness. The majority of the time when the diverter valve is open, it is recirculating hot air from the turbo back into the intake. By relocating the diverter valve to just before the throttle body, it now recirculates cool air that has already passed through the intercooler or which has been “treated” by optional water methanol injections systems. It also depressurizes the closed system at the point of obstruction (the throttle body). The advertised benefits of a diverter valve relocation setup include cooler intake temperatures, faster diverter valve response, less turbo spool down on shifts and off throttle and diverter valve durability.
Synapse Synchronic Diverter Valve & ModshackTTuned DV Relocation:
I recently tested and reviewed the Synapse Synchronic Diverter Valve & ModshackTTuned DV Relocation. This was my first attempt at seeing how the car would react with a diverter valve relocation and perform with a mechanical diverter valve (stiffer spring with vacuum actuated diverter valve vs. the OEM light resistance spring with electronic actuated diverter valve. While running a K04 turbo, my boost numbers always looked strong but I wanted to see if I could log actual vs. requested boost and get them closer in terms of the already minimal variance. From what I could gather from the data it looked to provide good results but the loss of electronic controls for safety was a concern to me so I switched back to the OEM electronic piston design “D” version diverter valve and kept the ModshackTTuned DV Relocation.
Unitronic 2.0 TSI Diverter Valve Relocation Kit:
Modshack helped source the very first custom diverter valve relocation kit for the FSI / TSI owners with great success. Most recently, Unitronic released their 2.0 TSI Diverter Valve Relocation Kit, and while I haven’t provided a stand-alone review on this setup, I will include a few notes and photos in this review. Without a doubt, the kit is much nicer as a complete kit than sourcing individual parts for the ModshackTTuned DV Relocation. The differences include a much nicer fluted DV adapter which uses a throttle body silicone T-coupler vs. using the Golf R inspired BSH throttle body pipe bung. The Unitronic 2.0 TSI Diverter Valve Relocation Kit also comes with a molded hose, decent silicone clamps and routes the cooler re-circulated air to Unitronic’s proprietary turbo inlet coupler found in their recent Unitronic 2.0 TSI Cold Air Intake System. To read more, please read HYDE16 Reviews - Unitronic 2.0 TSI Cold Air Intake System. Moving to the Unitronic 2.0 TSI Diverter Valve Relocation Kit allowed me to swap the BSH throttle body pipe to the Neuspeed HI FLO Air Charge Pipe wrapped in DEI gold foil as the BSH throttle body pipe bung was no longer needed. The Unitronic 2.0 TSI Diverter Valve Relocation Kit (specifically the Unitronic OEM DV Block-Off Plate) is compatible with the stock K03/IHI turbo and the AWE/CTS Turbo K04 (with compressor mounted diverter valve) turbos. The Unitronic OEM DV Block-Off Plate does not currently work with the APR K04 turbo but Unitronic will be revising their block-off plates to fit all applications in the near future.
OEM Diverter Valve Examination:
After I finalized my diverter valve relocation choice, I ruled out the option for a full mechanical diverter valve for K04 power levels and stuck with the OEM electronic piston design “D” version diverter. There is a theory among tuners that the OEM diverter valves are built with a spring and a plastic shroud which are designed to hold OEM level boost pressure and prevent the bleeding of boost under full throttle. Once tuned, the increase in requested/actual boost may force the OEM diverter valves open under boost pressure above OEM levels thus bleeding boost at full throttle. Currently, there are 4 revisions of the factory diverter valve that we've come across so far, and just to make it confusing there are two different versions of the revision "C" diverter valve (one which has a diaphragm design and the other which has a piston design).
Diaphragm Diverter Valves:
06F 145 710 C
06F 145 710 G
Piston Diverter Valves:
06H 145 710 D - has the conical "shroud or basket" surrounding the piston
06H 145 710 C - found on late Mk6 and Mk7 GTI, this one has exactly the same piston as rev D, but without the "basket" surrounding it
GFB T9351 DV+ Diverter Valve Kit:
After reading the GFB DV+ Diverter Valve Kit - anyone tested this? thread and speaking with GFB for several days, I wanted to explore their latest GFB T9351 DV+ Diverter Valve Kit. This review will focus on the combination of the GFB T9351 DV+ Diverter Valve Kit installed on the 06H 145 710 C OEM diverter valve with the Unitronic 2.0 TSI Diverter Valve Relocation Kit. As per GFB, the T9351 DV+ works with all 4 revisions of the factory diverter valve, despite the difference in appearance after disassembling the face of the solenoid valve and will improve performance and reliability regardless of stock or modified hardware/software. My current setup includes OEM K03/IHI turbo, OEM Volkswagen software (~10psi boost max), 3” TBE, APR intercooler, Neuspeed TOP and TBP and the Unitronic 2.0 TSI Cold Air Intake System. I plan to circle back to this review after I test the same hardware with Stage 2 software and finally with my APR K04 kit in Spring.
GFB Explains Benefits of the T9351 DV+ Diverter Valve Kit:
GFB expands the DV+ range with a direct-fit solution for the weak factory diverter valve used on many European vehicles. The solenoid coil itself from the factory-fitted valve is great (the ECU opens it faster than any pneumatic valve so why replace it?), but the weak point however is the valve mechanism itself. So GFB’s DV+ solves this problem by replacing just the valve parts with an anodized billet aluminum housing fitted with a brass piston machined to exacting tolerances. The end result is sharper throttle response, lightning-fast valve actuation, and it will hold as much boost as you can throw at it. Read all about the DV+ story on the next page. Other manufacturers’ products involve replacing the entire system with a traditional pneumatic valve, requiring long vacuum hose runs, additional parts for tapping into the intake manifold vacuum, plus either a different solenoid valve to actuate the pneumatic valve or a ballast resistor to plug into the OE wiring loom. All these additional items result in a product that is slower, less responsive, more expensive and takes much longer to install. GFB’s DV+ solution on the other hand is more responsive, less expensive, easier to install, and doesn’t cause compressor surge/turbo flutter. Oh, and it doesn’t require different springs or frequent re-builds.
-Retains the factory solenoid coil for seamless integration
-Replaces plastic valve parts with metal for reliability and strength on chipped engines
-Direct-fit replacement with GFB’s TMS benefits
-Exclusive “pilot-actuated” valve mechanism for rapid response at high boost
GFB Explains Turbo Lag and the TMSR Valve - How to Reduce Turbo Lag
Turbo lag should not be confused with boost threshold, which for simplicity’s sake we’ll say is the engine RPM above which the turbo is capable of producing a “significant portion” of its maximum boost pressure. For example, stamping the throttle open at 1500RPM and having to wait until 3000RPM for boost is not so much lag as it is a function of the engine and turbo system’s boost threshold. Once the engine is operating above the boost threshold however, then the delay when the throttle is opened can be assumed to be turbo lag.
“TMSR (Turbo Management Solution) Valve” is a term used by GFB to describe a valve designed to enhance or supplement the basic factory DV functionality through the ability to adjust aspects of the valve’s operation critical to its performance. It may be either atmosphere or recirc venting, being differentiated from a typical DV by the fact that its operation is designed to maximise throttle response and boost for improved performance outcomes.
By designing and adjusting a TMS valve to specifically suit the application, GFB has made it possible to reduce turbo lag during gearshifts or when modulating the throttle by holding some pressure in the intercooler and piping. By venting only enough air to prevent compressor surge, pressure in the intercooler can be maintained for as long as the turbo’s inertia will allow.
During a high RPM/full throttle gearshift for example, boost pressure in the intercooler with a factory valve will typically drop to zero (atmospheric) before the throttle is re-opened. With a GFB TMS however, the rate at which the boost pressure drops can be reduced, so that it is possible to have positive pressure in the intercooler when the throttle re-opens. This gives more power immediately as pressure is higher, and also reduces the time taken to reach maximum boost.
When driving, a factory diverter valve will typically create a slight hesitation immediately upon re-opening the throttle, followed by a noticeable turbo lag. Fitting a GFB TMS will sharpen the response by eliminating the hesitation and then reducing time to peak boost. During a quarter mile race (where 3-4 gearshifts can occur) the time saving is quite significant, and on the circuit the power delivery upon corner exit is sharper and more responsive to the throttle opening.
A GFB TMS valve can help maintain boost pressure in the intercooler and pipes whenever the throttle is closed with the following benefits:
-Higher boost available upon re-opening the throttle for instant response
-More boost throughout the spool-up process (up to 40%)
-Shorter lag time (reduced by up to 30%)
-No compressor surge
GFB T9351 DV+ Diverter Valve Kit Unboxing:
There is no doubt that this GFB T9351 DV+ Diverter Valve Kit is a high quality kit. The machining and finish is flawless for such tiny pieces. The box comes with the parts shown below, longer screws (see separate explanation below), a good set of assembly instructions and a warranty.
GFB T9351 DV+ Diverter Valve Kit Assembly:
Installation is very straight forward and disassembling the OEM diverter valve is a breeze with the included assembly instructions. Follow this video and instructions below for trouble free assembly.
http://blog.moddedeuros.com/wp-content/uploads/2013/09/go-fast-bits-t9351-instructions.pdf
GFB T9351 DV+ Diverter Valve Kit and Unitronic 2.0 TSI Diverter Valve Relocation Kit Installed:
Concern Over Length of Included Bolts:
I want to sum up the concern around the need to source 1 longer bolt for the APR K04 DV housing.
OEM K03/IHI turbo = use the 3 included (longer) GFB T9351 DV+ bolts, no need for longer bolts
AWE K04 = use the 3 included (longer) GFB T9351 DV+ bolts, no need for longer bolts
CTS Turbo K04 (DV Relocation) = use the 3 included (longer) GFB T9351 DV+ bolts, no need for longer bolts
Unitronic DV Relocation) = use the 3 included (longer) GFB T9351 DV+ bolts, no need for longer bolts
APR K04 = use the 2 included (longer) GFB T9351 DV+ bolts, then source 1 longer (Metric 316 Stainless Steel Socket Head Cap Bolt (M6 Thread, 45mm Length, 1mm Pitch)). Since the single APR K04 longer bolt has a shank length of 35mm and the GFB T9351 DV+ adds 11mm, that means the new longer bolt needs a shank 45-46mm.
GFB Technical Bulletin: GFB T9351 DV+ Initial Leak Issue:
After their initial batch of GFB T9351 DV+ units, GFB has recently made changes to both the spring and the plunger to ensure that there is no boost bleeding under boost and that it continues to open reliably when the solenoid is actuated electronically by the ECU. The changes to the GFB T9351 DV+ are detailed below. For this review I have the revised spring and plunger installed.
-We have manufactured a spring that holds the plunger down with more than twice the force of the original factory spring.
-To ensure the solenoid is able to reliably retract this harder spring, the plunger has been made slightly longer to shorten the stroke. This means the electromagnetic retraction force of the coil on the plunger is significantly increased.
-The diameter of the silicone o-ring on the front of the plunger has been reduced so the area exposed to the boost pressure is smaller, which further increases its ability to resist being pushed open (smaller area means for a given pressure there is less force being applied).
GFB T9351 DV+ Configuration / Tech Tip:
The GFB T9351 DV+ can be configured in two different ways depending on your own personal preference and what you want to achieve. During assembly, you can choose to install the main piston spring (indicated below by the arrow) or not. The configurations for the GFB T9351 DV+ are detailed below. For this review I have the main piston spring installed.
Using the spring is recommended because it results in the best possible throttle response and minimum lag on gearshift, particularly on manual cars. This can sometimes result in a slightly different sound from the intake at low RPM, which is no cause for alarm – it’s simply the different way in which the valve works. If however the noise is objectionable, removing the spring will make the DV+ operate the same way as the factory valve, albeit at the expense of throttle response.
To explain further, minimum lag on gearshift on any petrol turbo engine is achieved when the diverter or blow-off valve vents only just enough air to prevent compressor surge. Venting more air than necessary increases lag on gearshift because the intercooler is completely relieved of pressure, meaning it takes longer to return to peak boost when the throttle is re-opened. This is the basis behind GFB’s TMS principle (as explained in this article here), and is also the principle that all GFB valves operate on.
The DV+ is no exception, because unlike the factory diverter, the DV+ opens and closes in response to both the ECU command AND the amount of boost pressure in the intercooler. So when the ECU triggers the solenoid, the DV+ piston will only open as far as the boost pressure in the intercooler can push it against the spring. The factory diverter on the other hand will simply open regardless of the boost pressure.
The different sound you may hear on throttle lift-off at low RPM is simply because of this different operation method, and it does not adversely affect the turbo or engine. Removing the spring means the DV+ piston will simply open and close when directed by the ECU, just as the factory diverter does.
Rest assured that even with the spring removed, the DV+ will still continue to hold boost normally, however you will forfeit the benefit of the TMS principle and throttle response will be the same as with the factory diverter.
Customer Service Response to GFB T9351 DV+ Configuration / Tech Tip:
After reading this Tech Tip, I reached out to GFB’s excellent customer service for a little more clarification. Their customer service response is listed below. For this review I have the main piston spring installed.
We recommend using the main spring unless there is a reason not to, so that throttle response is optimized, since that’s one of the key reasons to replace the factory valve (as well as longevity and boost-holding). As the tech article explains, the turbo will make a different sound under certain conditions at low RPM (only noticeable with an aftermarket intake), which is not compressor surge and is not harmful to the turbo or engine, but nonetheless some people may not like it. In that case, removing the spring will make the DV+ behave like the factory valve, so the different noise will be gone.
The boost pressure and turbo are fairly irrelevant as far as the main spring go. You could potentially say as a blanket rule to the guys with a DSG gearbox that they can install the DV+ without the spring, because throttle response on gearshift is much less important than it is to the manual guys. Personally however, I’d always take the opportunity to improve throttle response by installing the spring and taking it out if necessary, rather than not installing it and never knowing potentially what I’m missing. That’s really the whole point of modifying something. There’s absolutely no harm in trying it – the worst that will happen is you don’t like the noise in which case you take it out.
Overall Results and Recommendations:
After an easy bolt-in installation I pulled my VagCom cable out, reset the fuel trims and went off for a drive around town to measure the response feedback. In lower gears or stop and go traffic I was hard pressed to notice a difference in performance or noise due to the low requested/actual boost levels. Since I was already used to the quiet operation of the Unitronic 2.0 TSI Diverter Valve Relocation Kit, the addition of the GFB T9351 DV+ Diverter Valve Kit yielded no additional noise increase or decrease. The next day I had a long highway commute where I could stretch out the OEM turbo and reach peak OEM boost levels (~10psi). This is where I was really able to measure the response feedback. Without a doubt, the GFB T9351 DV+ Diverter Valve Kit made NOTICEABLE difference in how the car reacts under high boost or full throttle. Originally, with the Unitronic 2.0 TSI Diverter Valve Relocation Kit, OEM K03/IHI turbo and OEM Volkswagen software, boost would peak to ~10psi but would scale back slightly in the high end of the rpm range. With the GFB T9351 DV+ Diverter Valve Kit boost was pinned at the max through every full throttle pull and the boost delivery also felt a tad more linear. At peak OEM boost levels (~10psi) I did realize a very small increase in additional noise but this was more of a sharper boost ventilation when off throttle. Some people have said that the pigeon fluttering noise (wastegate, not compressor surge) is still apparent with the GFB T9351 DV+ Diverter Valve Kit installed. I do not currently have this noise but it could be a factor of Stage 1 / Stage 2 software / K04 / Intake combinations. Next up was actually running VagCom logs where I saw a tighter grouping of requested vs. actual boost when compared with multiple data logs I ran with the 06H 145 710 C OEM diverter valve and Unitronic 2.0 TSI Diverter Valve Relocation Kit before installing the GFB T9351 DV+ Diverter Valve Kit. Improving OEM boost levels (~10psi) is great and all but I really look forward to providing response and noise feedback when I test the same hardware with Stage 2 software and finally with my APR K04 kit in Spring. At the end of the day, it’s completely a matter of preference or data for each individual application.
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