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The mkiv Supra Owners Club

Boost problem?


JamieP
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Ive had a boost problem with the car for a few weeks now, it will not boost above 1.2bar (will only just hit 1 bar in the first 3 gears) and is about 1000rpm more laggy than it was. i was hitting full boost average 3500rpm depending on gear and now its about 4500rpm.

 

Changed the boost solenoid for a new one and fitted a boost controler instead of running of the AEM and no change.

 

Checked all the boost pipes and cant find any leaks... striped down the wastegate today and there was a small split in the diaphram, i thought great we found the problem.... replaced the diaphram and its still the same:search:

 

What to try next???

 

I was thinking of taking the IC of on saturday to pressure test it.

Also possible problem could it be a leaking inlet manifold? Cant hear any leaks, and cant see a small leak making that much difference to spool and boost?

 

The car ticks over fine and runs loverly, any suggestion of what to try would be great .

 

Regards Jamie:)

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it will not boost above 1.2bar (will only just hit 1 bar in the first 3 gears)

 

What boost controller are you using? Some of the better ones allow you to map the boost settings against speed, which means you can maximise boost whichever gear you are in ie. you should be able to hit 1.2bar (or desired max) in every gear.

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Ash im up Turbofit now and we just tried doing that test you linked, wow what a brilliant way of testing, ive got a couple of big leaks on the inlet manifold, thanks,

Greg said give him a ring because he has a thank you for you:)

 

That's what it all about mate, sharing and careing. :)

 

Glad you got sorted and let Greg now i be down one day for coffee. ;)

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Turned out to be a few things.

 

The rubber ring that seals the cold side on the turbo was leaking like mad, appeared to be be ok but would not seal, put one off a T70 on and it sealed great.

 

One of the 90 degree bendes on the cold side was leaking, had a small split in it where i did up the jublie to tight.

 

The Greddy inlet had a leak where it joins on the runners.

Hopefully all sorted now, the boys are just putting the Tb back on now.:)

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Arrrrgggg, the saga continues.

 

All boost leaks now fixed and it holds pressure but its boosting very strange.

1st/2nd gear im getting 1 bar

3rd/4th 1.2/1.3 bar

5th 1.5bar

 

My afr's are out now aswell, full wot im in the 12.1/12.3 range when before it was mid 11's so im not booting it now till Dan has checked it.

 

Only thing i think it can be now is a wastegate issue so we are gonna swap it with another on saturday. what else could it be????

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Glad to hear you are getting it sorted.

 

I thought your boost control via the AEM was the AEM ECU not a seperate Tru-Boost controller.

 

EDIT: I split a 90deg at the weekend, should be fitting replacement tomorrow :)

 

Hi Wez,

 

I was running boost via the ecu but i thought id try a tru-boost BC just to eliminate if there was a problem with the settings.

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Have you tried disconnecting boost controller and work of waste-gate. What ever your spring rate is that what it should boost at.

 

Yea tried that mate, its a 0.8bar spring and works fine but still has the extra 1000rpm lag over what it was, wind the wastegate in a bit to raise boost and it does raise it but ony in the higher gears, basicly the same as the BC is doing.

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Yea tried that mate, its a 0.8bar spring and works fine but still has the extra 1000rpm lag over what it was, wind the wastegate in a bit to raise boost and it does raise it but ony in the higher gears, basicly the same as the BC is doing.

 

sounds like waste gate leaking mate have you checked the manifold for any cracks around the take off for it ?

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