My Forge recirc DV has a blue spring, and juddered horribly even on fairly smooth lift off after the FMIC went on. Since the OEM DV was so much smoother I was all for selling it, and I am getting a yellow and a red spring to try from Forge to try and remedy the problem. Order of strength is as title (red is strongest). Forge reckon that the yellow spring is the one to use, but others tell me the red will sort the problem. When the juddering was happening you could hear the DV venting on and off with the juddering. Any further input appreciated. The OEM one drives nice but at 1.5 bar it may leak a bit even if you can't hear it I gather.

[Edited by john banks - 9/18/2002 3:20:43 PM]

 

John

You should get a measurement of the actual strength of the spring as opposed to just the colour it has been prepared in

Perhaps Forge will be able to supply you with a range on strengths in original uncoloured form so you can experiment, and establish what best suits your current configuration

 

try this one. on my wrx01 works beautifully. you can buy it together with a wastegate. the model works on pre my01 with an adaptor.

http://www.bonalume.com/upload/pdf_press/09.pdf

C.

 

John

Is it the car juddering or the dump valve juddering that you are talking about ?

 

Both judder together. Really does not feel healthy. Totally fine with the OEM DV.

 

Could it be the compressor going past the surge line ? Or the mixture running weak as the air expands back through the recirc route ? (this is not seen as airflow by the MAF but flow still exists into the engine)

 

For the compressor to surge it would require considerable flow through the exhaust housing of the turbo? Low compressor flow, high pressure ratio, high turbine speed could result then leading to surge?

Re the MAF I will log it when I fiddle with different springs and see.

 

Just the inertia left in the rotating assembly can be enough to push past the surge line when the throttle is closed in.
The compressor RPM is still high but the flow is very low until the dump valve opens. Suggest you want a lower pressure spring but that brings you back to standard dump valve pressure during gear shifts. Retention of some charge pressure I presume was the reason for initially fitting it ?

 

Yes and not leaking at high boost. Maybe the yellow spring will do the job then.

 

Would a dual dump not solve this too ?
I could let you have the APS one for a try when it arrives John ?

 

It would if it was MAF misreads, not if compressor surge?

 

Would've thought that when it dumps to atmosphere during higher pressures, it'll cure the re-circ problems.

Offer stands though, you've helped me out enough times !

 

John any news on this?

 

I think JB's on holiday in Greece for a week but may still post from Wrexy's garage

 

Sorted with yellow spring.

 

John,

people pay good money and a lot of time to get their BOVs to 'chatter' not 'judder'. Mine does - although it does not seem to upset the car at all.

Tries to maintain charge just that fraction longer for gear shifts and sounds the nadgers

Trout

 

nice one JB !

Trout IIRC you have a link ? I think it is the JECS MAF meter being confused regarding airflow (in, out or roundabout) that causes the 'judders'. Me.... I just love it it's like a like a big bad dog straining to get off the lead

 

Hi Andy.

John Banks certainly is here in Greece with me and he will post from my garage.

Cheers,

Wrexy.

 

John, glad you got it sorted.