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The mkiv Supra Owners Club

My car is boosting perfect again


jevansio
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Not that I thought something was wrong before, but since I got that exhaust valve thing in and the quiet backbox my car would never hold boost to the redline.

 

I just put up with it, had a little play in the boost my myself & gave the wastegate extra duty at high RPM which helped a little.

 

Any yesterday I got the vavlve removed & the original HKS Ti box put back on. Straight away it was overboosting so I took it easy until I could have another look at the map.

 

Today I dropped 10% off the entire duty map, brilliant, it wasn't overboosting, but it was still a bit high, dropped another 10% off and got this run, it holds 22 PSI spot on in 5th, need to do some more tweaking but I think I can have it running 1.6 BAR perfectly to 7k :D

 

Here's the graph, gears are 3rd, 4th & 5th, graphs are RPM, Boost, Duty

 

attachment.php?attachmentid=91040&stc=1&d=1240055199

Boost.jpg

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3" DP/MP with 4" full exhaust, I've got a 4" DP/MP combo to go on though

 

I'm having trouble living with a 4" system. Peak noise is not too bad but the motorway drone is too much.

 

Was thinking of ways to silence it, but there is no room in the front half of the exhaust......

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So this was basically all down to have an exhaust that was too restrictive?

Partially true. I only swapped the rear muffler (both were 4" but one was longer). My main exhaust was the same before and after (3" DP/MP & 4" cat back exhaust). The thing I think made the biggest difference was removing the 4" butterfly valve I had in to control noise.

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