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The mkiv Supra Owners Club

Brexit celebrations tonight but i am having "boost" celebration !


herbiemercman

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Hi Dudes, Yes i am having a "Boost" celebration as i have been struggling with mega power loss for weeks thinking it was my new cylinder head gasket thicker and more robust, but reducing my CR from 10to1 to 9to1.

Estimates from the club were circa an estimated loss of 50BHP? also some said it would be much less, very little?

Today after looking at all my boost pipe connections which looked ok, i decided in rage to just remove all the system, and low and behold i found a large tear in the pipe which connects to the air intake manifold. The tear was between the underside of the pipe and the top of the trubo fan scroll, impossible to be seen, even if you carried out the blanking test to see if the engine stopped, you would still find it difficult to locate this leak.

Anyway my performance is fantastic, just like the original NAT build, and i have a head gasket which should last longer. My boost gauge is still only measuring negative readings so i think this needs changing, this made my investigation hard work, i do not think it ever gave + positive readings.

Many thanks to all who tried to help, i have also learned a great deal from this problem, all the twists and turns, was it the boost? or was it the CR down? was it the ignition timing, was it the wastegate stuck open, was it the MAP pressure readings connection?, yes it was a frustrating time, but i great feeling at the end. Herbie.

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Hi Swampy, Yes i know that, but,be honest, who would look under the pipe where it was tight up against the top of the turbo.

However i have learned a lot and it is hard not to check all the things you are being advised by experienced people. Also i had reasons at the time for thinking i had lost a lot my power due to the CR reduction from the head gasket, the timing, boost controller connections etc. Herbie

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Hi Swampy, I learned from the situation in that i now realize that just looking at the boost pipes and pulling them is not enough to find a boost leak. The leak that was causing my problem was hidden underneath the turbo housing, so this tells me you have to remove the pipe connections and examine the silicone rubber connectors, They are designed to withstand 185 deg.C.and what caused a 75mm tear is beyond me? Herbie.

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  • 2 weeks later...
Hi Swampy, I learned from the situation in that i now realize that just looking at the boost pipes and pulling them is not enough to find a boost leak. The leak that was causing my problem was hidden underneath the turbo housing, so this tells me you have to remove the pipe connections and examine the silicone rubber connectors, They are designed to withstand 185 deg.C.and what caused a 75mm tear is beyond me? Herbie.

 

This is probably the elbow outlet from the compressor housing near the exhaust manifold.

 

People weld an elbow often. This is a hot zone. If I'm guessing correctly anyway. No other reason to have silicone underneath turbo housing.

 

185c isnt much of a deterrent when the exhaust manifold takes much higher temperature.

 

I was always blowing silicone joiners on that location.

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