Hi guys

I hope I m not posting on the wrong forum!! but we re all car enthusiasts here...
I own an Audi s3 with the mtm big turbo kit (345hp). the kit comes with an evo 7-8 factory dv. I never really understood why mtm use this dv....but they told me to stick to it! The big advantage of this dv over my old forge one is its size....HUGE in comparison!!
I have some questions though.....
On all the dvs that I had, if you push the piston/diaphragm inward and shut the vacuum with your thumb, the piston will not travel back until you release it. In this dv, the piston will not hold and will travel back. At first I thought that my dv was damaged (fluttering sound, annoying btw) and ordered a new one. Exactly the same + I still have the fluttering sound at part-throttle that I don't get with the forge, with the same turbo setup!! Is it normal or was I unlucky twice??
It may be important to say that the dv on these cars are installed reversed, from factory. (this one too is reversed from the evo setup)

Sorry for my questions , just want to have some answers....the car runs fine and hold boost (1.7-1.8 bar peak, but again it is reversed)....

So my main questions are: is my bov damaged? Why is it reversed? Is the fluttering at part throttle normal or really bad?

Thx a lot!!

 

I don't think it's reversed, those DV's have a pretty high spring rate to them. Mine won't hold open either when you compress it and put your finger over the vacuum nipple. If you want to lower the spring rate to avoid the compressor chatter I'd suggest going to an adjustable spring rate type of valve.

 

Hi

I think that you misunderstood me.... I m saying that all the valves I owned(oem audi and forge) can hold the piston upward after you pushed it. So basically, you push the piston inwards, shut the vacuum, and the piston will hold until you open back the vacuum. It is usually a test to check if the valve is sealed.
I am also sure that the valve is installed in reverse. So my questions are the same....In fact, i would most importantly like to know if the dv is damaged or not( hate them....).
Sorry if I am posting in the forum, but basically I am asking a technical question on an evo part. And from what i ve read this forum has really knowledgeable people.

I attached a pic that will help you see how the dv is installed.
Thx a lot!

 

No, I quite understand what you mean by the "pressure" check, and like I previously said...mine does the same thing. It's the internal spring pressure rate. The spring pressure is greater than the force of the vacuum that you physically put on the valve by holding your finger over the vacuum source, so therefore it tends to spring closed regardless. If you put a vacuum pump on the valve you will see it open up, but it takes a bit to open it substantially.
Also one other thing I noticed in your picture...your diverter valve is positioned backwards. In effect the boost pressure is pushing against the valve while the vacuum is trying to open it, creating your flutter. Reverse the valve (the little triangle on the one port should be the side recirculating back into the intake tract) and it should solve quite a few of your issues.