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The mkiv Supra Owners Club

problem raising boost


philsmith1a
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I have just fitted a double decat to my j spec tt, after fitting with a 52mm dia. RR it ran .9bar, I filed it out to 54mm and it is still .9bar. iv got a walbro pump but not yet fitted. The exhaust is a 3” blitz nur spec r.

I doubt the boost isn’t rising due to the lack of a decent fuel pump, can anyone suggest what the issue could be?

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i wish my boost would be that low.

 

 

tbh mate, your better keeping it like that, then having a boost controller to increase the rest.

 

 

i have the Blitz nur & double decat also, boost goes 1.4bar :rolleyes:

 

so its not you have a restrictive exhaust. either increase the Restricotr ring or get a EBC :)

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I would do the following, remove the restrictor ring, do a test drive and see if it'll boost higher than 0.9bar - be careful with your right foot not to boost too high. If it will boost higher then the RR is adding too much of a restriction at the moment and needs the hole increasing further.

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Right, first off I misread the boost gauge, it wasn’t .9bar it was 9psi!

I’ve taken the rr out, took her for a run out and did a few high speed pulls and it did hit fuel cut once(at about 6500rpm)-boost gauge reading was 14psi. So I recon I must have a boost leak as the exhaust is 3” straight through or if there was a leak would the boost have stayed the same if it had a rr in or not??

 

Any ideas?

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I have a the same sort of thing , i have a double decat ,nur spec , fuel pump ,front mount , bov valve , boost controller , induction kit , fuel cut defender ,

 

The car was all done when i got the car and the boost controller was already set up ,

In 3rd and 4th gear hard pulls it makes spikes at 1.15 bar and holds 1.03 bar in 3rd and 1.05 bar in 4th in 5th and 6th im only holding just under 1 bar. the boost controller is on max .

 

i know the car can make more as i have a pipe come off the boost controller one day and the car fit 1.8 bar , i let straight off as i know there was something wrong plus i had fuel cut ,

 

So why will the car not make and hold 1.2 bar , its been driving me mad for months .

 

The car is a j spec tt 6 manual there is a rr ring fitted but im not sure what size , i have brought a 1.2 bar ring to put in a try .

 

Rich.

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Sounds like one or both turbos are on the way out. This could be very costly I am afraid. I am finding the majority of used front turbos I get to send for re conditioning have bad cracks in the turbine housing wastegate seat. These can be welded but often crack again. I recommend new ones from Toyota for true peace of mind, but I am unsure if anywhere still has stock as they have discontinued them.

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Bad news! All I wanted was a reliable 400bhp.

I’m thinking I might be better off buying some second hand turbos, I have found some on ebay with 3 months warranty ,I can’t justify going single as it’s an auto and I have been advised against hybrids.

 

What to do??

 

Also should I stop driving it? If the seals went completely would I wreck the engine?

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  • 2 weeks later...

I’ve sourced some very low mileage turbos, during fitting 3 cracked pipes were found so that was the boost leak sorted.

 

In hindsight maybe I should have kept the old turbos as they only puffed the smoke the once and that was with no RR. I’m guessing most turbos with no back pressure in the exhaust would allow a drop of oil into the exhaust after a hard drive and long idle.

 

Thanks for everyones help on this.

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  • 3 weeks later...

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