I decided the first performance upgrade for the Fiat 124 Spider would be a new diverter valve. The diverter valve’s job is to release excess turbo boost back into the intake when you lift off the throttle. This allows the turbo to keep spinning and be at least partially ready for when you are back on the throttle. A diverter valve is not the same as a blow off valve which simply releases the excess pressure to the atmosphere with the unmistakable pssshhhhh noise! There are blow off.diverter combinations but because this is my wife’s car and she is not big on drawing too much attention to herself I chose the GFB (Go Fast Bits) DV+
The solenoid coil itself from the factory-fitted valve is great (the ECU opens it faster than any pneumatic valve so why replace it?)
According to Go Fast Bits, 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 anodised billet aluminium 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.
Fitting the GFB DV+
The instructions that come with the kit are fairly clear and fitting it was very straightforward so there is no point repeating them all here. It is simply a matter of undoing three bolts and removing the original unit, replacing the parts supplied in the beautifully packaged GFB kit and bolting it back into place. One potential challenge is removing the original piston sleeve from the diverter body. The instructions say to do this CAREFULLY in capital letters, as it is very fragile. Fragile is an understatement and personally I found it impossible to remove without damaging the sleeve, it’s made of some sort of especially fragile material, possibly even the material from butterfly wings.
This isn’t a massive issue, as you are replacing the sleeve and just keeping the diverter body although, as stated in the instructions, you will not be able to re-use the factory piston if you do damage the sleeve. So that’s me not reusing the factory piston then! When you look at the factory piston compared to the GFB DV+ piston I think you’ll agree that you wouldn’t want to put it back! So save yourself some time and just get the thing out of there.
The DV+ can be configured in two different ways, depending on your desired outcome. Fitting the DV+ with the main spring installed means the DV+ can open and close progressively in response to how much boost pressure is present, unlike the factory diverter which just opens fully regardless of whether there is boost to vent or not. Because this operation method is different from the factory diverter, it is not unusual or detrimental to hear a different sound from the intake when lifting off the throttle at low RPM, especially if you have an aftermarket intake or a larger turbo installed. Using this spring can also cause the ECU to think something is up and throw an error, so you can fit without the main spring and just have the DV+ act like your regular diverter, only stronger and no leaks. I fitted the spring and have no fault codes.
So, does it make any difference?
Well, in reality, you are just replacing one part with another than functions in much the same way. The GFB DV+ is much more substantial and much higher quality than the part it replaces and allegedly on releases boost it needs to, rather than all of it, but if your original part was functioning properly, which it should do if relatively new, you will not notice any difference, despite all over the net of “much improved throttle response, less turbo lag” ete etc. GFB do claim that the plastic piston-type (Which the Fiat original is) leaks far more than most people realise (by design, not from wear), and doesn’t always close after a high-boost gear shift. I can’t say I’m able to notice any difference but I am reassured to know there is a better quality part doing quite an important job and I don’t get any fault codes with the spring fitted.