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Stock BOV adjustment? Where am I loosing boost?

benl1981

By benl1981,
in Engines & Forced Induction

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benl1981 Grand Master

benl1981

Posted
Posted

My car (Skyline R33 RB25DET, manual trans) doesn’t reach full boost in 1st gear and I seem to have lost about 1-1.5psi peak boost over the last month or 2. I’m thinking it could be a leaky BOV (I only have the stock one)…or the wastegate actuator has deteriorated slightly so it is slightly open all the time or opens up too early.

I have run with and without solenoid so the solenoid isn’t the problem. The intercooler hoses are on tight. No leaks there. My friends R33 reaches the full boost in 1st easlily. He has better tyres, maybe the fact mine is wheel spinning a little is limiting boost build up in 1st. Not sure.

So I’m thinking

1. Check BOV

2. Check actuator

3. Anything else? Air filter…I doubt it..

You can adjust the preload on the wwastegate right? If I screw it in so it is tighter it won't oppen quite as easily right? But I odon't want to fiddle with this as it shouldnt have come out of asjusment.

Also does the BOV have asjustment. Boost is being measure at the plenum...where the stock BOV usually takes its reading.

Is it bad to run the car with the BOV disconnected and a plate over the hole for a while to test!???

predator Grand Master

predator

Posted
Posted

I would try blocking the BOV temporarily just to test.. The odds of permanent damage just to test for a little while aren't massive. Often a failure to reach full boost (or reach rapidly) from what I've find can depend on ambient air temperature, amount of cool air getting to your filter (compared to hot air of engine bay), exhaust too small/restrictive, slight miss, or leaking or blocked hoses. Its basically a restriction on the turbo doing what it is set to be doing. Also the tune can matter as well.

I found that in my old r33, that running low boost (say 11 instead of 12-13) and getting an agressive tune resulted in more consistent boost in different temperatures and conditions. It may have been that there was some component letting the system down (quite likely), but in the end that was the best solution.

What's your clutch like? Are you dropping revs also, or just boost?

p.s. i have a stock r33 bov for sale.. if u do find its the bov :thumbsup:

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