Author Topic: Timing / Air/fuel  (Read 1538 times)

Offline jimmyb1982

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Timing / Air/fuel
« on: September 28, 2010, 08:17:57 pm »
Hey guys, the G40 is back. However I'm having trouble with the timing set up and fuel at high revs. If I set the timing correctly the car runs great about town but then leans out to Stoich at high revs where as if I retard the timing from the correctly timed position then it misses when driving slowly but keeps the air/fuel the right side of rich when on boost.

I spoke to Darren at G werks and he said get a fuel pressure gauge as it could be the fuel pump which I replaced in 2004 or the map I have but the map was fine with my old dizzy.

P.S. the dizzy was replaced in 2007 just before it came off the road. Cars been back on the road 6 weeks now.

Any ideas. I thought about getting a rolling road set up but the guy asked if theres a fuel mixture adjustment?

- Jimmy B

Offline PeteG40

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Re: Timing / Air/fuel
« Reply #1 on: September 28, 2010, 08:22:23 pm »
what chip do you have fitted?

and how do you know its lean? i.e. do you have a wideband fitted?

Offline Andy

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Re: Timing / Air/fuel
« Reply #2 on: September 28, 2010, 08:47:55 pm »
You saying it leans out to stoich on full throttle at high revs, or partial throttle?

If you haven't got a wideband you can't really tell what the fuelling's doing. And it's unusual for minor timing tweaks to make such a difference to the AFR - unless you're really swinging the dizzy around massively.

Are you setting the base ignition timing correctly? Is the dizzy the right part?

Offline jimmyb1982

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Re: Timing / Air/fuel
« Reply #3 on: September 28, 2010, 09:46:59 pm »
The chip is an SNS Green injectors PSD chip. No I'm not using a wideband, just a narrow band. I tried to time it on the top pulley because my toothed pulley has no notch or anything so I just tried with the top one but I'm not sure if thats right or not?

I've been told its a G40 part yes. What should the car idle at when warm? Is it about 950rpm?

- Jimmy

Offline jimmyb1982

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Re: Timing / Air/fuel
« Reply #4 on: September 28, 2010, 09:49:08 pm »
Sorry it leans out into stoich on full boost.

Offline PeteG40

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Re: Timing / Air/fuel
« Reply #5 on: September 28, 2010, 10:00:10 pm »
should be 5+/- 1 degree advance on the top pulley.

what pullies are you using they should have a notch

Offline jimmyb1982

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Re: Timing / Air/fuel
« Reply #6 on: September 28, 2010, 10:15:25 pm »
I'm using the PSD toothies

Offline jimmyb1982

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Re: Timing / Air/fuel
« Reply #7 on: September 28, 2010, 10:16:27 pm »
how do I know if its 5+/-1 on the top pulley?

Offline PeteG40

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Re: Timing / Air/fuel
« Reply #8 on: September 28, 2010, 10:30:41 pm »
you get a timing gauge where you can dial in advance.

If you are timing by the top pulley (not ideal in any case) with a static gun you'll be on tdc.

Offline hayesey

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Re: Timing / Air/fuel
« Reply #9 on: September 29, 2010, 09:29:06 am »
Quote
No I'm not using a wideband, just a narrow band.

then you really have no idea what the fuelling is doing, a narrowband just isn't accurate, at all. Mine seems to show around 14:1 at high rpm/high boost but when remapping and we had the wideband connected it was really around 12:1 and 11:1.

Offline jimmyb1982

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Re: Timing / Air/fuel
« Reply #10 on: September 29, 2010, 07:31:11 pm »
should I get a rolling road set up do you think?

Offline Andy

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Re: Timing / Air/fuel
« Reply #11 on: September 29, 2010, 09:26:08 pm »
Get the ignition timing set properly to start with, then if it still runs badly take it to a rolling road that'll do you a power run with AFR plot. Speaking of which, John Sleath would do that for you at the G40 RR day in a few weeks...