Tuning continued...

[Gary Derian]

Very lean mixtures burn slowly and ignite the intake when the intake valve
opens.  I have only had exhaust popping when there was misfire and
accumulated fuel explodes.  I suppose this could also be caused by a lean
mixture.

Gary Derian <gderian at oh.verio.com>

>
> ALSO found out that a lean condition can result in popping out the
> exhaust as well!!
>
> Any technical expertise as to why this occurs?
>
> You'd THINK that if the a/f ratio was lean, REALLY lean, that
> predetonation would occur, however, it seems that the opposite is
> true...
>
> And the popping actually occurs out the exhaust!!
>
> Maybe the mixture was SO lean that the spark couldn't ingite the mixture
> whilst it was in the chamber but COULD once it was in a lower pressure
> environment outside the chamber in the exhaust system???
>
> Just a thought...
>
> Great discussion on troubleshootin/tunin...
>
> Keep it up!
>
> Learnin a lot... as always....
>
> LATER!
>
> Todd....
>
> http://www.c-com.net/~atc347/toddlnk.htm
>
> christer.medin at lennoxintl.com wrote:
> >
> > Yeah, we were wondering if maybe the advance was too much, but it's
fairly conservative - 36 degrees at 3000RPM.  Good info about the wires, if
the plugs are ok, I guess we can just swap the stock wires back in and see
if it makes a difference. Thanks.
> >
> > Christer
> >
> > ----------
> > From:   MIME :n5xmt at bellsouth.net
> > Sent:   Wednesday, June 16, 1999 12:39 PM
> > To:     gmecm at efi332.eng.ohio-state.edu
> > Subject:        Re: Tuning continued...
> >
> > It could be the advance you have dialed in is too much for the engine at
> > that particular RPM/load... What works on a dyno doesn't necessarily
> > corrrelate to what works in the vehicle... varying load in the car from
> > Trans, road conditions etc.
> > Another point is the plug wires... Don't know how many times I had weird
> > stumbling/miss problems on my Buick GN, change plugs, no change, check
> > wires, all measure great (remember, the DMM uses between 1 and 9 volts
for
> > Ohms... Ignition blasts 20K plus depending on the type of ignition) and
> > finally changed the wires just because... Stumble/miss disappeared.
> >
> > Later,
> > DAve