TT 1UZ Monaro help needed

**hillbilly** · 12-11-2006, 02:39 PM

Because it takes me forever to type i have just done a copy and paste of my post on Lextreme forums, hope someone can help me please

Hey guys, finally got my monaro up and running and its bloody awesome.
Car has had a basic road tune and will be heading back to get final Dyno tune done this week.
Cant believe the power these motor's make while keeping thier smooth driveabillity.
Anyway have got one issue with the turbo's. They are Garret GT28R turbo's (The unit formerly known as "the GT28R" (part number 466541-1) is now in the GT25R family. More specifically, it is now a GT2560R model).

I start by removing the air intake filters, i then get someone to hold thier hands close to the turbo intakes while increasing the engine rpm to around 3000, you can feel the turbo's suck you hands in then they blow back then suck in then so on. I have been told that they are pulsating rather like it would do if you had miss matched turbo's. Any one have any idea what this is caused by or how i can fix it.
I have a turbosmart blow off valve fitted
Is running 7lb's of boost
Front mount intercooler
Brand new matching turbo's
3inch dual exhaust

**SL666** · 12-11-2006, 03:49 PM

so basicly it happens when you have the engine free reving, sounds like compressor surge? your BOV operates correctly yes? (on some setups it would be venting if the turbo's are pushing air and there's some vac in the manifold)

i'd suggest that the exhaust sides might be a little too small.. but i wouldn't let it worry you, if you are concerned just loosen off your BOV (if its a model that can) and let it vent.. it won't do it under power.. there's a place for the air to go..

**[email protected]** · 13-11-2006, 01:03 AM

do you cop a lot of shit from people for not putting a v8 holden or chev in a monaro

**SL666** · 13-11-2006, 06:53 AM

Anyone who gives anyone shit for putting a TTV8 in anything, should be removed from the car community.

**Grega** · 13-11-2006, 07:06 AM

where have you mounted your blow off valve(s)?
i'm wondering if when you rev and decel the surge is caused by pressure build up against the throttle butterfly?

**hillbilly** · 13-11-2006, 09:27 AM

Also happens when driving along at about 2500 or so RPM.
BOV seems to be working ok as can hear it vent on gear changes etc.

Most ppl that see the engine are a back dumb struck at first, i'm sure the flannel shirt brigade will hang some shit when it makes an appearance at motovation in January.
But i think it is expected as i put a RB20DET in my son's HQ.

BOV is mounted on intake pipe about halfway between intercooler and throttle body.

**Norbie** · 13-11-2006, 10:07 AM

Definitely compressor surge, which typically happens when you have a big turbo trying to push lots of air at low-ish RPM. It falls off the compressor map and can no longer compress the air, resulting in a brief reversal of flow. I believe this can cause serious damage to the turbo if allowed to continue.

There are several ways to eliminate compressor surge but the best method is to get a correctly matched turbo!

EDIT: this has nothing whatsoever to do with the BOV.