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AFR settings
whitestu - 13/3/09 at 11:32 AM

I tried my JAW for the first time on Wednesday [2.0 Blacktop, MJ & ZX6R carbs].

The mains seem fine at 1.6mm as the AFR on full trottle was between 11-13. It was hard to get a consistent figure without driving dangerously!

when cruising the AFR was 16ish, so a bit too lean.

I've move the needle position to try to counter this, but not driven it yet.

My idle ARF is 11-12 which seems rich, though the car idles fine. I've turned the air screw out 4 turns, though it doesn't seem to make much difference.

Has anyone else got AFR at idle figures I can compare with?

Thanks

Stu

omega0684 - 13/3/09 at 11:46 AM

im running MS and when my car starts from cold the AFR is @ about 12.5, @ running temp idle is about 14. under heavy acceleration its about 12-13. crusing about 15.

whitestu - 13/3/09 at 11:56 AM

Thanks

As mine is on carbs the afr doesn't change much at idle when it warms up.

Anyone know what relationship AFR has to CO and HC figures, if any?

Stu

[Edited on 13/3/09 by whitestu]

theconrodkid - 13/3/09 at 05:52 PM

http://www.perfectpower.com/technical_info/afr.asp



any good?

flak monkey - 13/3/09 at 05:59 PM

quote:
Originally posted by theconrodkid
http://www.perfectpower.com/technical_info/afr.asp



any good?


Thats handy for me too, thanks! I need to tweak the idle mixture on mine to get it in sensible limits.

Project7 - 13/3/09 at 06:42 PM

quote:

when cruising the AFR was 16ish, so a bit too lean.


I think thats dangerously lean, I wouldnt drive it too much like that.

[Edited on 13/3/09 by Project7]

whitestu - 14/3/09 at 08:32 AM

quote:

http://www.perfectpower.com/technical_info/afr.asp



any good?


Thanks, that's really useful.

I think my co needs to be 4.5% / AFR of 12.83 to pass the MOT so won't get through as it is.

The mixture screws on the carbs don't seem to make any difference so I think the float level must be causing the rich mixture.

My carbs aren't mounted at the same angle as they are on the bike, and whilst they work perfectly in every other respect I think getting the float height right so the idle mixture is ok might be a major problem.

I think thats dangerously lean, I wouldnt drive it too much like that.


I haven't gone more that a few miles like that, so should be OK - supposed to be doing a trackday in a week though so I need to check changing the needle height has sorted it.

Stu

[Edited on 14/3/09 by whitestu]

[Edited on 14/3/09 by whitestu]

FASTdan - 14/3/09 at 02:21 PM

quote:
Originally posted by Project7
quote:

when cruising the AFR was 16ish, so a bit too lean.


I think thats dangerously lean, I wouldnt drive it too much like that.

[Edited on 13/3/09 by Project7]


If its only light cruise then it'd probably be ok (as long as it drives + responds ok). If it stays like that when loaded then that is bad - though it'd hold back big style under those conditions anyway.

whitestu - 14/3/09 at 04:38 PM

If I floor it it goes down to 11 ish and then settles atound 12-13.

It was under very light load when it was showing 16.

It drives absolutley fine.

Stu

blitzmk2 - 16/3/09 at 09:51 PM

Slow running adjustment on ZX6R carbs. is a fuel screw, so need to be screwed IN to weaken, NOT out. Prob explains your rich tickover. Baz.