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The mkiv Supra Owners Club

Strange boosting???


Dash Rendar

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My run of bad luck doesn't seem to have ended yet.

 

I put my foot down today, and the first turbo didn't seem to want to reach full boost. It reached about 0.5, and then started dropping. Then, #2 comes on and boosts all the way up to 1.4 bar!! How can it boost to 1.4 bar when it's got a 1.2 bar restrictor ring? This behaviour seems to be slightly intermittent, but it's worrying me.

 

The car definitely seems more laggy.

 

Help!!

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Is it possible for the restrictor ring to fall out? I was previously only boosting to 1.2 bar, so I can only assume that it was fitted as requested.

 

Is it obvious to tell if it's there or not? I've had a look under the car and all I can see is the joins between exhaust components.

 

No boost controller.

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As James already said, check for split hoses.

 

It doesn't sound like a restrictor ring problem, your 1st turbo boost would not be affected by that going missing.

 

If the first turbo is underboosting, then when 2nd comes online its overboosting it may well be a problem with one of the valves that controls boost to the 1st turbo (1st turbo is highly restricted making 2nd turbo overboost). Maybe the wastegate valve or Exhaust bypass valve...

 

Hopefully someone with more knowledge of the turbo system will be along shortly.

 

Edited to add - Jeez, you're not having much luck mate :(

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Thanks Ian. I know roughly where the turbos are buried, so presumably getting to this feed is a bit tricky for a rank amateur like myself?

 

The problem seems intermittent as it was boosting normally again today. I'll put this on my list of stuff to sort out!

 

Until I get it sorted, will an occasional blast at 1.4 bar do any damage to my car? I'm currently running stage 1 hybrids.

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If you are running standard injectors and fuel pump with stock regulator at 1.4bar i would think you are lean which can be a problem.

 

You should be able to see the restrictor ring by looking at the join between the cat bypass and downpipe or rear section, they are about 4mm thick and would look like a thick gasket.

 

I would say you have a hose issue :)

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It was rather cold, but not quite arctic. :) I guess that would account for a slight overboost, but to go from around 1.2 to 1.4 (actually, closer to 1.1 to 1.4 with my silencer in) and to see #1 underboosting is just all too much.

 

I'm fairly convinced it's a hose or valve problem now... Not that I know anything!!

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