Just had my car mapped by Andy F at the weekend but I seem to be having a few issues now. I fitted a FMIC and a forge reicirculating DV and at around 4500 if I back off slightly and hold the revs the dump valve can be heard venting air unit till I open the throttle fully or back off altogether, is this correct?

Also seems to surge at low speeds. I'm guessing its nothing to do with mapping as AF is highly skilled in this area so i'm thinking it's something else just not sure what. I have tried the standard DV but it still surges and generally runs rough at low speeds.

 

Car judders at 4500 revs if i back off by about 250rpm, been told DV is not opening and blowing boost back over maf so ecu is adding more fuel making car judder, any fix's anyone?

 

Try it with the OEM dump valve

 

Swopped from OE to forge but still have surge / rough running at low speeds, not sure about high revs issue will swop and see what happens.

Cheers

 

I have this problem when overtaking on the motorway and backing off to get back into the original lane. The whole car shakes and judders, It's not just mine that does this though and has done it since mapping.

Vented air from the DV does not pass the MAF again as it's a closed system.

Low speed surging on light throttle also happens but again this has been covered on SN before.

What does Andy F say ?

Shaun

 

Andy says: If the dump valve is not releasing the boost then it blows back through the maf sensor when you partially lift off, this causes the ecu to add fuel when it is not needed, hence the shudder.

 

Therfore try the OEM vlave which may have a softer spring.

 

softer spring required .. I think I tried 3 before I was happy on my forge recirc.... settled on the green one I think

 

I had to go the other way!!

Settled on the RED spring on a Forge Re-circ. Car now has No violent 'jerk' on going from slight boost (say 0.5bar) to 0

 

Cheers guys i will have to dig a little deeper and swop a few bits around.