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The mkiv Supra Owners Club

Declining Boost


Samurai 20V

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Guys,

 

I have been noticing in gear 4 and 5.. car is boosting on the first turbo to about 0.7bar, then the usual dip and boost hits 0.7 bar and then declines to 0.6bar..

 

Car is still running with both cats.. (rattling like crazy though)...

 

Is there anything to worry about? The temp was pretty high today, but took it for a spin at night and seems to be doing the same..

 

Thks..

Edited by Samurai 20V (see edit history)
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could be a number of things.

someone will correct me im sure but some of the valves can stick in the boost pipework. there are a number of them.

Im prety sure it happened in mine the other day. first turbo was fine then 2nd turbo boost dropped right off to zero. then all of a sudden it all worked fine.

 

or the exhaust is just too restrictive with the cats in it? 0.7 is stock boost isnt it?

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could be a number of things.

someone will correct me im sure but some of the valves can stick in the boost pipework. there are a number of them.

Im prety sure it happened in mine the other day. first turbo was fine then 2nd turbo boost dropped right off to zero. then all of a sudden it all worked fine.

 

or the exhaust is just too restrictive with the cats in it? 0.7 is stock boost isnt it?

 

Will have to give these the once over..

 

My car is at stock boost at the moment.

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If the cats themselves are rattling it *may* be one has collapsed inside and is restricting exhaust flow. Do you have an EGT gauge fitted?

 

Or the rattling could be just the heat shield and have nothing to do with the boost issue.

 

This is what I was going to say, would explain the high temp too.

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SO used the car to work today...

 

1st gear and 2nd gear,was only seeing 0.5bar boost, other gears were as I described above.

 

Then booted it a bit more, 3rd was 0.6bar, 4th was 0.7bar and 5th gear was seeing 0.8bar.. All were holding steady, no declining.

 

I think it may be a VSV or a vacuum hose, need to do some trouble shooting..

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