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The mkiv Supra Owners Club

High boost death - SBC-iD


GetawayDriver

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I've just had a boost controller fitted to my UK TT 6 along with an FCD.

I've been playing with the settings and trying different levels of boost/gain etc. i've got everything set so maximum boost is about 1.2 bar depending on the ambient air temp and boost response is reasonable.

 

Here's my settings

 

CH1 to 20mph 80 gain 26

CH2 to 40mph 75 gain 26

CH3 to 60mph 65 gain 26

CH4 60mph + 62 gain 26

 

I've based my settings on JB's figures, with little tweaks to get similar max boost on CH1 and CH2. see JB's settings here --> http://www.mkivsupra.net/vbb/showthread.php?t=4547

 

But i have a problem, under hard acceleration in a high gear, 4th, 5th, even 6th as the boost builds there is suddenly a huge bang, mostly from the drivetrain, as fuel/boost is cut, total loss of power violently. Engine light comes on and stays on for about 5 secs.

Obviously it really upsets the cars stability too when it happens, It happened lastnight almost flat out in 5th in the rain, needless to say i almost shat myself.

 

My questions:

 

Is this fuel cut? i'm pretty sure it is, but it never seemed so violent in other members posts i read. it's different when it happens to you... sob :cry:

 

What damage can this do? aside from the savage trauma the transmission and my underwear.

 

I'm guessing it's caused by a boost spike, what causes boost spikes likes this?

 

How much extra boost does the FCD let you have before invoking fuel cut?

 

I know the overall solution is to turn the boost down... but it feels so good! and i'm running the same figures as JB who also has a UK spec and who doesn't get fuel cut. why? I still have one Cat, i'm guessing JB has none, could that cause it?

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Sounds defo like the FCD may need a little adjustment, my fuel cut was exactly like that, racing an EVO6 just slipped into top gear, boost just coming on song, pulling ahead nicely then BANG!! lights on the dash loss of power etc, then back to life again after slowing down and pooping oneself.

I take it it's a genuine HKS FCD????

What have you got it set to?

Think when i used to have my FCD, after decatted with restrictor ring boost was peaking approx 1.1-1.2bar and FCD was set to channel 9, dunno if you can just adjust it a little more to compensate for boost spikes from having the boost controller (thought boost controllers were meant to smooth out boost spikes??)

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Think most of them are adjustable, but not summink you should just keep fanny about with if the boost cut comes in, sensible option is to turn boost down.

HKS ones have a tamper sticker which is usually stuck over the adjustment potentiometer once set up, not familiar with the TRL, as you said Matt's the man!!

:nana:

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when i fitted my TRL FCD and boost controller on my uk i still hit fuel cut at around the 1.2bar mark. pete at thor advised to adjust the internal pots to a higher setting. cant remember what they were now though. i can run 1.3bar with no bother at all now

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Internal pot leetts refering to is the "Potentiometer" an adjustable screw, like whats behind the knob of a stereo volume control.

 

exactly. there is two of them labelled ob(overboost) and gain IIRC. a>f and 0>9. they just need tweaking around a notch or two. pete will advise on the exact settings im sure. hes a very helpful bloke

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The FCD will be mounted very near/under the ECU. Lift the carpet and unbolt the black plastic ECU cover and I'm sure you'll locate it easily enough.

 

Open up the FCD, inside you'll find two small pots, (dials). The one labelled OB or Overboost, should be set to position B as standard, increase this to C, and it should stop your problems.

 

Feel free to phone if you're not sure about anything.

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I have, I think ;-) not looked at it properly, a HKS FCD. I had my Blitz SD blabla running at 55% gain - 12. It has been boosting fine up around 1.2 1.3. However this morning I had the FCD kick in, as you say, loss in power etc etc. I think it was close to 1.4 this morning going by my gauges.. But until that happened the HKS has been letting me do good boost. J-SPEC.

 

Would not be Rev limited or speed?

 

By the way, any idea which I should belive, as my Defi guage and my Blitz boost controller say different peaks and slightly different readings, which should I belive the most?

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Jay,

 

maybe I'm missing something - so this is only a suggestion ....

If youre getting hard accelleration in lower gears without problems, this wouldn't be fuel cut - it sounds more like the prob I had with a loose connection in the wiring of my delimiter.

My problem was the result of removing the upper dash a few times and eventally causing one of the wires to the ECU on the back of the odometer to become loose.

 

I could be way off, and I'm in no way suggesting anyone else's comments are wrong ( or dissing workman-ship ) - it's just that the symptoms are exactly like mine were.

 

Steve.

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It could be either of the things you both suggested.

 

I think there may have been a loose connection before i had the boost controller and fcd fitted. I also have a blitz turbo timer which sometimes records a peak speed of 399kph - i assume this could be caused by a faulty connection. Could this same fault affect the boost controllers speed detection cause undesired fuel cut? i haven't seen any weird max speed recorded on it, just some outrageous hp figures - seems to happen when the car looses traction.

 

Having said that, fuel cut has always occured at the red line in 4th and 5th, not 3rd - given that experience, i'm in no hurry to try the red line in 6th.

 

I shall do some investigations today - thanks for all your comments/ideas, i'll let you know how i get on.

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