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The mkiv Supra Owners Club

Boost Leak (well I think)


Chris and Alana

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Hi guys, I think I may have a boost leak but I cant find the bugger anywhere. I boost to about 17psi when on WOT but when Im cruising at 60mph off boost and mash the loud pedal it changes down gear and I get 3psi boost :( If I then let of the throttle and apply again it boosts to 17psi again. It seems that when ever I put a sudden large load (straight into tubbie 2) something gives in, it must happen 50% of the time when I mash the throttle. Iv checked everything I can see and all the hoses are tight, has anyone had/experienced anything like this, what could it be?

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That sounds very like the EGBV not pre-spooling the 2nd tubby and basically the exhaust gases are trying to spool it up instantly while the boost pressure tries to backflow through the IACV causing a bit of gridlock. Letting off gives it a 2nd chance.

Mine was the EGBV vsv.

 

Does it only do it the once then pulls fine through the rest of the gears? Mine only did it after cruising off boost for a while then changed down to say overtake making a sudden demand. It happens due to being off boost after a while No2 winds down again.

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I ended up getting a vsv from Jezzy on here, there 200 odd quid new believe it or not. It should be about 22 - 26ohms on a continuity check and the ports must not be passing. You can also put 12v onto it and check it works.

 

I also excercised the valve with an airline at 10 - 12PS or boost pressure equivalent.

Best way I found was to connect the car into TTC mode then on Ian C's seq plumbing diagram connect your airline into point 10(pressure tank feed).

Pull both hoses off the EGBV vsv and you will hear air coming from one.

Block that with your thumb and both the IACV & EGCV will quickly shut and then the EGBV will start to operate.

When you release your thumb the valves IACV & EGCV will still be closed due to the pressure tank but the EGBV will close again.

 

Hope this helps mate. The above also tests all the hoses for leaks as you may have a cracked hose down on the EGBV actuator and its a pig to get to.

 

Cheers

 

Mike

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