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The mkiv Supra Owners Club

Was this fuel cut?


SMW

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Been trying to get to grips with MANU mode recently as many have said that you get better acceleration from a standing start.

Whilst I wouldn't disagree with that a strange thing happened on my way back to work at lunchtime.

I seemed to hit fuel cut (judder,loss of power and several lights on the dash)

Wasn't paying that much attention to speed but doubt if I exceeded 110-115.

DSBC peak read 1.28 (warning is set to 1.40)

I have seen 1.30 and didn't get fuel cut so I was wondering if MANU mode made any difference in this instance??

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Originally posted by SMW

I have seen 1.30 and didn't get fuel cut so I was wondering if MANU mode made any difference in this instance??

 

Fuel cut isn't just dependant on boost level. The length of time that the vehicle stays at that boost level is also taken into account. We're not talking big differences in time, but it may just be enough to explain why it didn't cut at 1.3.

 

Your only real option is to carry out a test in both MANU and regular modes.

 

BTW, I wouldn't run stock turbos beyond 1.2 anyway. Just my 2p.

 

Cheers,

 

Nathan

TDI PLC

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I seemed to hit fuel cut (judder,loss of power and several lights on the dash)

 

I agree with Nathan that fuel cut is also time dependant.

 

But another thought for later is that you may get juddering if your spark plugs are not of a sufficiently cold grade.

 

You may need to replace the spark plugs with a colder grade set.

Some people say they experience fuel cut at 110-120mph but in my experience the warning lights did NOT illuminate and the actual culprit was the ignition breaking down.

 

Now I know you had the warning lights which seems to suggest that it is fuel cut. But something to remember.

 

Pete

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Originally posted by TRL Performance

I agree with Nathan that fuel cut is also time dependant.

 

But another thought for later is that you may get juddering if your spark plugs are not of a sufficiently cold grade.

Pete

 

Agreed. It appears that the Mk4 ignition isn't as bullet proof as we at first thought.

 

One of our big twin customers bought an HKS Twin Power ignition amplifier off us purely because he was having ignition problems when injecting NOS on full boost (he was already using brand new HKS S45i's). The Twin Power cured it, but surprisingly he also mentioned that the driveability off-gas was noticeably improved. Full boost runs felt much stronger and the mid-range far more 'crisp'.

 

I must admit that there is more to a spark than just whether it fires or not. A lot of folks think everything is fine if there are no misfires but it seems that you can indeed improve even a non-missfire situation.

 

Like Pete says, it does sound like your problem is with fuel cut but at least make sure you have decent plugs in the car. And, FWIW, I've yet to see a 3 quid plug perform as good as a 15 quid HKS or Blitz iridium jobbie.

 

Cheers,

 

Nathan

TDI PLC

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Nathan, Pete

 

Thanks for your input on this.

I have the colder HKS plugs so I'm hoping that isn't what caused the problem, although I'll certainly get them checked out if it happens again.

I've hit fuel cut once before (after removing baffle from nur back box) and what occurred yesterday was pretty much the same.

Had me wondering whether or not it could be attributed to MANU mode in any way but I guess not.

Maybe just a glitch and I won't worry too much about it unless it happens again.

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