Story goes,
fitted twin Webers (DCOE 40) and re-jetted.
Have got the mains perfect (according to rolling road, colourtune and
home gas analyser), but the Idle jets have been problem.
suggested jets (as per Triumphtune, Paul teglers website etc) were way
lean (according to rolling road, colourtune and home gas analyser)
registering %CO at << 1%, and causing front firing through the cabrs and
bad performance.
Upped the jet size a few times and am now approaching a reasonable
figure, although probably still a little lean at transition between
idles and mains (2000rpm %CO dips to <1%) but no front firing!
Unfortunately the plugs are beginning to fowl a little so change the
heat of the plugs, and now the front firing is back (only a tiny amount)
but it is obviously a sign of lean running.
I could open up the idle jets further, but they do cost cash and I don't
want to do it for nothing!
Any ideas?
Cheers
tim
Carter Shore wrote:
> Tim,
> What difference(s) in the car's behavior did you
> observe that led to the 'run leaner' conclusion?
>
> The plugs themselves will not affect the leanness or
> richness of the mixture. But they could affect the way
> that the motor runs, in ways that are similar to
> 'lean' or 'rich'.
>
> The heat range of a plug relates to how it is
> constructed, allowing more or less heat from the tip
> to conduct to the outer shell, and thus operate at
> higher or lower temperatures.
>
> Run too cold, the tip will foul, leading to
> misfires;run too hot, the mixture will preignite; run
> just right, and the tip will self clean.
>
> A richer mixture will tend to reduce the combustion
> temperatures, a leaner mixture will tend to raise
> them.
>
> So all else equal, if you make the mixture a bit
> richer, then you might want hotter plugs to compensate
> for the cooler combustion temperatures, to raise the
> tip temperature back up to the optimum operating
> range.
>
> You adjust the plug heat range based on what the car
> is doing with the setup fitted.
>
> Fouling plugs: go hotter
> Preignition: go colder
>
> Of course, if you use Capacitive Discharge ignition,
> then you can run the plugs as cold as you want,
> they'll fire no matter what, and stay clean as well.
>
> Carter Shore
>
> --- "T. .R. Dafforn" <td214@cam.ac.uk> wrote:
> > Was playing around with the spark plugs on the spit
> > the other night and
> > tried out some that were one step hotter than
> > normal.
> > I did this to complement the twin webers I have as
> > they were suggested
> > in the competition manual.
> > Anyhow I'm not sure, but I think it has made the car
> > run leaner. Is this
> > a known effect?
> > Does anyone have any other tips/info on using
> > hotter plugs?
> > Cheers
> > Tim,
> >
> > --
> > Tim Dafforn
> > University of Cambridge
> > Structural Medicine Unit
> > Cambridge Institute for Medical Research
> > Hills Rd, Cambridge CB2 2XY.
> > UK
> > Tel. (01223) 763230
> > Fax. (01223) 336827
> > http://smokeroom.cimr.cam.ac.uk/
> Try FREE Yahoo! Mail - the world's greatest free email!
> http://mail.yahoo.com/
--
Tim Dafforn
University of Cambridge
Structural Medicine Unit
Cambridge Institute for Medical Research
Hills Rd, Cambridge CB2 2XY.
UK
Tel. (01223) 763230
Fax. (01223) 336827
http://smokeroom.cimr.cam.ac.uk/
/// spitfires@autox.team.net mailing list
/// or try http://www.team.net/cgi-bin/majorcool
|