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The mkiv Supra Owners Club

Overboosting..


robin
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Fitted an aem tru boost with the intention of basicly using it as a boost gauge and maybe upping the boost to 1 bar if needed. The car gets to about 0.75 bar on turbo 1 but when the 2nd comes in all hell lets loose. within half a second and on half throttle it reaches 1.3 bar... no boost cut or anything. Needless to say im driving it off boost at the moment.

 

Shouldnt the stock computer be hitting boost cut at this level?

 

Adjusting settings on the controller doesnt seem to change anything. The solenoid will buzz away as soon as there is positive boost. Any ideas?

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It wont hit fuel (or boost as you reference it) cut if it has a fuel cut defencer fitted. This stops this happening when you reach the pre-determined boost of 16 psi I think it is........

 

I take your de-catted without a restrictor ring, thats why your over boosting........that'll be the J-spec ceramic blades...

 

£20 ring from the man Chris Wilson, stuff it in your pipe...;)

 

That will hold you to 1.2bar, then use your boost controller to up the boost......

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A few questions Robin:

 

1. What boost is the car making without the boost controller turned on ie. the base boost level?

 

2. Do you have a fuel cut defender (FCD) and stock ECU fitted (any aftermarket ECU fitted)? Stock fuel cut is 1bar, if you are boosting higher than this then I would check the ECU to see if there is anything wired into the harness.

 

3. Have you removed both cats?

 

I notice yours is a UK spec, so you shouldn't need a restrictor ring, with the boost controller turned off you should only be seeing stock boost ie. circa 0.8bar. If you are seeing more than this, I'd suspect that you have a leak, probably where the boost controller has installed.

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Solved the problem. It was only plumbed in to turbo one. May also have been a leak. Now its in to both turbos the boost is alot more reasonable and when it hits 1bar for a couple of seconds I get the fuel cut. No warning light, just a sudden loss of power.

 

I currently have both cats in. I am surprised by how much quicker the boost raises, especially with only light throttle. I really dont have to try very hard and it is up to 1 bar in moments.

 

With the controller off I get 0.75 on turbo 1 and a little bit more about 0.82 on turbo 2.

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