Hi guys


My boost level drops in high rpm does anybody know what leeds to this problem . I'm running a Turbonetics t3/t4 t04e .63ar tial wastegate with a 7psi spring. We were tuning the car yesterday and realized that round the 6000-7500 rpm boost level drops back to 4 psi we have checked everything vacuum line etc cant find anything. The tuner says theoretically it should be the turbo itself cause the rest is all good .
What do you guys think about this situation all advice welcome
Thanks.

 

What is your boost set at?

 

boost set at 7psi round 6psi it starts to drop back to 4 psi

 

Boost leak

 

thats gonna be hard to find i'm gonna start with changing all vacuum lines
and proceed from there headache hahahaha

 

Do yourself a favor and head to your local hardware store and get a plumbing coupler cap the same size as the compressor inlet of the turbo. Pop a hole in it the size of an air compressor nozzle and pressurize the charge pipes to 10psi or so (boost gauge) and check/listen for leaks. Plenty of how-to's on this as well

 

Will probably be a fairly large leak. Split silicone coupler etc...

 

It's more than likely a boost leak. The other thing it could be is a turbocharger problem.

If there's a bearing, seal, or oil supply problem the turbocharger won't behave properly. Check it for shaft play and any signs of an oil leak. Verify your feed line isn't clogged or kinked.

 

bearing/seals/oil feed line are all good

 

Have you physically checked for excess shaft play? And did you actually look it over in detail or just glance at it?

Most oil leaks aren't observable from the exterior. You'd need to pull the charge pipe off and look and at least look at where the turbine housing and CHRA meet and the gasket between the turbine outlet and downpipe. Next step after that would be pulling the downpipe off.

 

Also the easiest way to check for a boost/vacuum leak if you don't have a tester is to start the car and spray brake cleaner on every coupler and every place that has a gasket. Charge piping, throttle body, cylinder head/intake manifold flange, etc.

It's also possible that there's a small puncture somewhere on the intercooler core. Even though they are typically small it doesn't take much to cause a drop in pressure so spray it too.

If that yields nothing then you'll need to make a DIY leak checker out of PVC with a schrader valve so you can pressurize the system. It just needs to be the same diameter as the coupler on the compressor housing outlet, there are plans for these online. Then you pressurize the system to 20-30psi and spray soapy water on every coupler, the intercooler, and any place with a gasket.

 

I took off the turbo today to take a better look and a there was a little bit oil on one bolt for the turbine housing backplate was not tighten good enough. Did a check on the other bolts everything is tighten well for the rest i can not really see any other faults that leeds to boost leak. Did a test run a still boost leak

 

First things first, boost leak test. Then leakdown test. I would inspect the wastegate and make sure it's functioning properly, and inspect the turbo for anything strange. Unless you were seeing big fat clouds of oil smoke from your exhaust, it should still build more boost than that.

 

wastegate was inspected its all good leakdown test was done also