Air/Fuel Question

[jason@scirocco.org (Jason)]

Mind you I am not a mixture expert by any means, but I think that you don't 
have anything to worry about Cory...

I had mixture issues with my Mercedes a few years back, and what you 
describe is normal.  Under constant-speed low-load conditions, the mixture 
should indeed lean out.  I'm not saying it needs to be lean to the point of 
detonation --

But under low load, as long as it's not pinging, you want it to be 
lean.  It helps avoid carbon deposits and promotes better fuel economy and 
emissions.  As long as it richens up under load, it's working just fine.

Verdict:  Ain't nothing wrong, the FI system is doing its job.

Jason



At 09:32 AM 10/17/2002, Dan Bubb wrote:
>As long as your engine runs fine without missing while cruising I
>wouldn't bother trying to richen it up.
>With CIS (i.e. NOT lambda or E) there really isn't any way to change the
>mixture aside from messing with the control pressure and from my
>experience that is a real hairball.
>Changing the idle mixture will have a minor effect on the mixture once
>the throttle is opened even a small amount. eg. if you change the
>mixture 10% at idle then doubling the airflow (say doubling the idle
>speed) reduces the % change to 5%, with 5 times the airflow the % change
>is only 2%. So, the effect of adjusting idle mixture dies out quickly as
>the throttle is opened.
>Personally, I think your a/f readings are interesting but not indicative
>of a problem.
>Dan
>
>Cory Langford wrote:
> >
> > Okay, I have small conundrum I am working on and maybe someone here can
> > throw some info at me to help out :)
> >
> > I installed a cheap autometer air/fuel meter into the '79 with a 1 wire o2
> > sensor.  At start up everything seems normal. I get a rich reading, as I
> > expected due to the cold start injector kicking in.
> >
> > When it is warm and under load it runs just shy or rich.
> >
> > What I have noticed is that when I am simply cruising along a 2,0000-2,500
> > rpm and the engine has no real load, it leans out right to the end of the
> > scale.
> >
> > Step on the gas, back up to stoic just before rich.
> >
> > I can see it getting lean when you take your foot off the gas as engine
> > winds down, but once at a steady rpm I thought it should go back to stoic
> > again.
> >
> > I am going to try and richen the mixture a bit, but I can't seem to think
> > how to get it richer just at the lower rpms (unless I am thinking wrong
> > here) with out richening out the upper rpm range.
> >
> > Any ideas?
> >
> > Thanks
> >
> > Cory Langford
> > '86 turbo project - running, just needs tuning :)
> > '79 daily driver - Restore in progress...
> > '65 Ghia - The next project in the garage
> >
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