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BPU Supra - Boost Issues - Solved


Samurai 20V

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Hi Chaps.

 

I have recently had some boost issues with my BPU TT6.

To resolve them I have changed the ffg:

 

- IACV VSV

- EGCV VSV

- EGBV VSV

- Wastegate VSV

- Black Intake Link pipes

 

These resulted in the boost issues being resolved, car was very quick after this, best its ever been.. Used to make 1.2bar from 2nd gear.

 

Yesterday, I did some maintainence on the A/C system (new expansion valve & dryer).

Car was boosting normally, after the work, but today it only made 0.89 bar..

 

I found a loose vac pipe on the power steering pump, fitted that back on, made 1.05 bar..

 

To troubleshoot, I pulled a hose off the IACV, there was no whoosh, no pressure released from the system.

I drove home, adjusted the gain on the EBC, raised it by 17%, made 1.09 - 1.15 bar, still a bit short..

At home, pulled the same hose, again, no pressure.

 

Is my diagnosis of failed pressure tank correct? As far as I know its never been changed.

I don't think its another hose/pipe, as it should not have raised the boost with the adjustment in gain?

The work on the A/C system did not have anything to do with Vac system, I guess it was coincidence..

 

Looking for some confirmation here, thanks in advance.

Edited by Samurai 20V (see edit history)
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Can't help as I'm not that experienced with all the boost pipe work, however I wanted to say I'm interested in the outcome if you find out and/or others chip in as long term I can see these trouble shooting threads being valuable and I know that posting threads with no follow on comments can lead you to think it's a waste of time.

 

Hopefully someone knowledgable will be along to confirm or refute your suspicion.

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Guys,

 

This is what I have done to try to resolve my cars issues, with marginal success.

 

- Change Pressure Tank with brand new unit, found the vac pipes leading to them have been changed to silicon versions, one had loose cable ties as well.

Renewed the pipes with OEM new.

 

Drove the car, still had max 1.05 bar.

 

- Pulled feed to IACV, slow whoosh but better than before.

- Discovered the feed hose to the IACV had a pinhole, swapped that for OEM new pipe.

 

Drove the car, achieved 1.2bar, but not consistently. With an eye on the boost gauge, with 2nd turbo boost was fluctuating erratically bet 1.05 and 1.2.

Suspected the IACV VSV was acting up.

 

- Pulled feed to IACV hose, again a slow whoosh

- Tested IACV according to manual, checked out fine.

 

So, my feeling is the two vac pipes on the turbo side for the pressure tank may be at fault.

 

Can anyone concur my thinking? Becoming frustrating now..

 

Thanks.

Edited by Samurai 20V (see edit history)
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  • 2 weeks later...

Gents,

 

Much happened in the last 2 days.

 

Replaced the 2 hoses behind the turbos, one had a pin hole, but not convinced it was through and through.

Some of the Charcoal hoses on the turbo side were dodgy, replaced those as well.

Changed the actual IACV with a low mileage item. (10000kms)

 

Test drive, at first no luck, only 1bar. Then got 1.3bar out of nowhere and then back to 1.0bar.

 

Rechecked the ECGV lines as these where changed with used OEM items, found 1 pinhole and 2 large tears. Replaced with new OEM hose.

Drove again, still 1.0bar, but noticed there was no throttle opening percentage on my EBC.

 

Opened up the ECU side, found throttle wire of EBC was loose, secured that and EBC now reads throttle opening. I think it got distrubed when I took the evaporator out.

 

I have not driven the car, but I think with 0% throttle the EBC could not raise the boost, it could not activate the map within it.

I will drive it tomorrow as its late now.

 

My question is, why in the world have I got so many vac leaks all of a sudden? Its crazy that I found 3 pipes with issues, yet the car was perfect before working on the A/C.

 

Sorry for the long post..

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Just depends on the life expectancy of the vac pipes mate , if they last around 10 years you could expect to change them around 10 years , its just a coincidence.

I have only just seen this but was going to say a preasure leak does not mean preasure tank

 

Thanks mate..

 

I figured out that the tank is fine, testing it out of the car.. But I had a new one so its not a train smash.

 

Lets hope its sorted, will drive the car today..

 

The vac hoses are a pain..

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Solved..

 

It was the throttle input for the EBC...

 

Car is a madman now, I had to back the gain off to maitain the 1.2bar. The IACV change did definitely help..

 

Changing the vac hoses was not a wasted exercise as I found so many with issues...

 

I am on the lookout for a good EGCV to complete the set..

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