Turbo set up near Scottish Borders
- Thread starter Dci1612
- Start date
PSH
PCGB Member
Hi David
I can't help with advising a place to help but it may be something you can sort for yourself...The few symptoms you list could well be down to a vacuum leak. With the engine running pull one of the vac hoses, the FPR is a good one. Put your thumb over the hose to feel how hard it sucks, it should be pretty good and thus sealing the hose with your thumb as it sucks it in. You should also note a rise in RPM which will show that the FPR is working although you won't know how well without fitting a pressure gauge. If you get no suck or little suck then this is due to a leak or in the worst-case scenario a worn engine that can't produce enough vacuum. Boosting can also be due to a vac leak, if everything is original I'd suspect the cycling valve under the inlet manifold as it will be very brittle and the plastic lugs are prone to break off. I have read that some have managed to replace the valve without removing the inlet manifold, I can't say how easy it is with the manifold in place, mine was done with it removed. The other part is the vac hose to the wastegate, this also gets a lot of abuse due to its position. If the car is modified and new to you it may not have a cycling valve due to the previous owner doing a venturi delete. More info on the car might help diagnose if the above doesn't help.
Pete
I can't help with advising a place to help but it may be something you can sort for yourself...The few symptoms you list could well be down to a vacuum leak. With the engine running pull one of the vac hoses, the FPR is a good one. Put your thumb over the hose to feel how hard it sucks, it should be pretty good and thus sealing the hose with your thumb as it sucks it in. You should also note a rise in RPM which will show that the FPR is working although you won't know how well without fitting a pressure gauge. If you get no suck or little suck then this is due to a leak or in the worst-case scenario a worn engine that can't produce enough vacuum. Boosting can also be due to a vac leak, if everything is original I'd suspect the cycling valve under the inlet manifold as it will be very brittle and the plastic lugs are prone to break off. I have read that some have managed to replace the valve without removing the inlet manifold, I can't say how easy it is with the manifold in place, mine was done with it removed. The other part is the vac hose to the wastegate, this also gets a lot of abuse due to its position. If the car is modified and new to you it may not have a cycling valve due to the previous owner doing a venturi delete. More info on the car might help diagnose if the above doesn't help.
Pete
Brian Millar in Edinburgh knows these cars well. He was Porsche Edinburgh head mech in the 80’s. Did a great job on my 1988 944 Turbo.Dci1612 said:
Dci1612
Member
Thanks for the replies above.
I think I have sorted the vacuum lines as I am now getting 16. My problem is Boost, it does have a Lyndsey racing wastegate so it runs a separate boost line to control it. The car just keeps wanting to boost and won’t go over 3500revs, if I control the boost with the accelerator then I can get higher revs, but not great. If I overtake a car and lose sight of the boost gauge the car with abruptly hesitate and backfire.
Does anyone have any ideas? Thanks
I think I have sorted the vacuum lines as I am now getting 16. My problem is Boost, it does have a Lyndsey racing wastegate so it runs a separate boost line to control it. The car just keeps wanting to boost and won’t go over 3500revs, if I control the boost with the accelerator then I can get higher revs, but not great. If I overtake a car and lose sight of the boost gauge the car with abruptly hesitate and backfire.
Does anyone have any ideas? Thanks
PSH
PCGB Member
Check the BOV valve...the diaphragm may have failed giving an 'overboost' situation. I had this when my car was at a similar state of tune, I fitted a Bailey Motorsport DV30 which cured the issue. A new OEM BOV should do the same thing but perhaps costing more. You should be able to check you BOV by sucking it to see if it has a vacuum.
Pete
Pete
Dci1612 said:
Now getting 16 what? If you’re now getting 16psi and have the original cycling valve hooked up then the KLR is activating its overboost protection and turning the injectors off.
I guess we need a bit more info on your setup: chips, boost control, vac line mods, etc?
scam75
Well-known member
I had the diaphragm fail in my Lindsay WG. Had to order a new one one from them direct, ended up costing about £80 delivered. A failed BOV would also give similar symptoms, I fitted a Forge one ages ago and it's been all good.
I had infinity boost as a result of the failure, noticed 26PSI of boost whilst in 5th gear, thankfully the right foot was disengaged pronto and nothing popped. [&:]
If nothing else it showed having a proper boost gauge fitted is a must in a modded turbo! (as well as an AFR gauge!)
Stuart
I had infinity boost as a result of the failure, noticed 26PSI of boost whilst in 5th gear, thankfully the right foot was disengaged pronto and nothing popped. [&:]
If nothing else it showed having a proper boost gauge fitted is a must in a modded turbo! (as well as an AFR gauge!)
Stuart
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