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Losing Boost After 4500 Rpm.

Simmo1985

By Simmo1985,
in Engines & Forced Induction

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Simmo1985 Community Regular

Simmo1985

Posted
Posted

I've got my turbotech boost controller set to 10psi, and it worked great for about a week. Now when accelerating past 4,500rpm boost drops noticeably to about 5psi (although the gauge shows 5psi it doesn't even feel like it's making that much boost). It's a really noticeable drop off in power.

I took it to the mechanics the other week and wouldn't you know it, the car worked fine when I was there.. but the problem is back now. Any suggestions of where to look? Will it just be a leak in the vacuum line?

Problems driving me nuts.. boost seems to work and pull fine prior to hitting those higher revs, like the additional pressure is causing a leak???

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https://www.sau.com.au/forums/topic/188252-losing-boost-after-4500-rpm/
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Cubes Grand Master

Cubes

Posted
Posted

When I removed my plenum to inlet manifold gasket I noticed it had been leaking.

When refitting inlet manifold/plenum/throttle body gaskets I gave them a spray with Hylomar just incase.

Using Hylomar also helps should you have to pull it apart again; it prevents gaskets ripping etc so you can save a few $$ and reuse. :(

tezflow Rising Star

tezflow

Posted
Posted
When I removed my plenum to inlet manifold gasket I noticed it had been leaking.

When refitting inlet manifold/plenum/throttle body gaskets I gave them a spray with Hylomar just incase.

Using Hylomar also helps should you have to pull it apart again; it prevents gaskets ripping etc so you can save a few $$ and reuse. :(

could you haer a sucking sound coming from the plenum when it was leaking.

Simmo1985 Community Regular

Simmo1985

Posted
  • Author
Posted (edited)
could you haer a sucking sound coming from the plenum when it was leaking.

I can hear a sucking or hissing type sound coming from my plenum at the moment. Didn't know what it was though, just thought it may have been normal. Guess my plenum is leaking then?

Edited by Simmo1985
Simmo1985 Community Regular

Simmo1985

Posted
  • Author
Posted (edited)

Would a leaking plenum cause any other problems? Just trying to figure out if that is in fact the problem, because the car drives perfectly normal otherwise.

Edited by Simmo1985
Cubes Grand Master

Cubes

Posted
Posted
could you haer a sucking sound coming from the plenum when it was leaking.

No strange sucking noises apart from the usual idle sssshhh noise :)

I think mine was only leaking on boost as it didn't cause any strange idle issues or afm readings.

EVL-R33 Proficient

EVL-R33

Posted
Posted

i got this same problem, i hear a loud hissing like noise come from the plenum at high boost and notice my PSI drop from 20 to 15.. I still haven't got around to pulling the plenum apart and changing the gasket, but i'm pretty sure thats the problem..

  • 3 months later...
benl1981 Grand Master

benl1981

Posted
Posted (edited)

I think I have a similar problem. Had it tuned running 18psi no worries but after a week of driving it doesn't seem to hold boost. After 6000rpm the boost drops from 18psi to about 5psi. I can't hear any strange noises though..

I dont think its the inlet sucking closed as I placed a metal pipe in part of it. It looks a little weepy round the plenum gasket. Hopefully thats it..

ANYone got the part no. for R33gtst?

Edited by benl1981
benl1981 Grand Master

benl1981

Posted
Posted (edited)

The mechanic reckons I should just change the gasket without even running it on the dyno. They reckon theyve seen a lot of this on the rb25s. It isn't always that easy to hear apparently - and under load there is so much air floating around there with the fan going etc..

Will have a bit more of a check myself..

Nissan want $85 for one! There was a little oil residue around the join. We cleaned this off but there isn't really much coming back. Might run it up onto boost a few times and check again. I did a few 0-100km/h runs the other day which may have blown it apart..

Edited by benl1981

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