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944 Turbo - suspect dump valve?

Spongebob

Spongebob

New member
I have an intermittent issue on full throttle/max acceleration. Feels like complete loss of boost. Only does it on maximum throttle. Professional opinion is dump valve (original) is failing to hold boost. I've already checked all hoses / vacuum connections and can't see anything wrong or loose.

I can easily go buy a new one (£120) but I would be really grateful if someone could loan me a serviceable valve to prove / disprove the theory before I commit to the spend and find it's not the valve. Obviously very happy to cover costs of post etc and would literally only need for 24 hours
 
Do you have any other Mods? Hitting overboost protection (common in cool temps with a boost enhancer) limits boost for a short period (or if ignition is turned off /on) and that is a sudden complete loss usually at full throttle around 4000 rpm
Dump valves usually fail in one of two ways the diaphragm fails so if you apply suction to the small pipe on top there is no resistance and the valve doesn't open, alternatively they don't seat, if removed you can push open the valve and when released it doesn't spring back to the seat.
Tony

 
I agree with Tony...sounds like 'overboost'...I suffered from this many years ago not long after fitting the DPW...after checking everything we found that the POV (dump valve) had failed...we fitted a bailey motorsport DV30 which fixed the problem

Pete
 
Yes, mild modification in the form of Augment ECU, twin port wastegate and electronic boost control so nothing too radical. It is around 4000rpm and I suppose the weather recently has been cooler. We had it on the rolling road at Augment but could not recreate the fault. One of those really frustrating things!

Should I just bite the bullet and spend the cash?
 
With those mods I'd be tempted to replace the BOV anyway. With an augment ECU I assume you've also got a MAF rather than the AFM. I could possibly loan you my BOV but not for another 2 weeks as I need the car mid next week for a long weekend. I may have the old BOV somewhere, I'll have a look tomorrow but I replaced mine with an Lindsey racing unit....
 
You can easily create a vacuum using any compressor, thin nozzle and a length of rubber hose

Pete
 
PhilKent said:
With those mods I'd be tempted to replace the BOV anyway. With an augment ECU I assume you've also got a MAF rather than the AFM. I could possibly loan you my BOV but not for another 2 weeks as I need the car mid next week for a long weekend. I may have the old BOV somewhere, I'll have a look tomorrow but I replaced mine with an Lindsey racing unit....
Click to expand...
Brilliant. Many thanks and let me know. I have a vacuum brake bleeder so will try just the pump off that and see if it holds.
 
When the membrane in the recirculating valve is broken it should be possible to suck air with the mouth from the nipple...
 
As TTM has said""

When this happened to me I was able to such the top nipple ?? And I could tell that the menbrain was broken as I could basically fill my mouth with fumes and so bought a 911 turbo item I believe? at the time as I was told it was a good upgrade for moded 944 turbos and it's been great ever since.

You should not be able to suck any air from the top, so if you can, you need to replace and go from there.

Ive had the overboost situation also which I needed to chip the car in order to raise the protection limit so that I could go to WOT and this was after the first of my mods the wonderful boost enhancer, but this was the beginning of my mod slippery slope which I'm still sliding down and enjoying ????

atb
daniel
 
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