[Diy_efi] Typical boosted ignition timings

[mrbeau0]

So it has stock CR with twin plug--the ignition timing may not be as
retarded as I initally thought.  EGT's may prove to be interesting though.
I want to say the early intercooled 911's (without the boost retard
distributor) ran about 26 degrees of timing.  It'd be interesting to see
what sort of lamda values the factory CIS runs at.

I plan on EFIing a twin plug 2.8L of mine, but it's NA and 10.5:1 so not a
good comparison...

Matt.

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
Behalf Of Marc Reviel
Sent: March 31, 2003 11:15 PM
To: List for general do-it-yourself EFI talk
Subject: Re: [Diy_efi] Typical boosted ignition timings



----- Original Message -----
From: "mrbeau0" <mrbeau0 at yahoo.com>
To: "List for general do-it-yourself EFI talk" <diy_efi at diy-efi.org>
Cc: <marc at powerlogix.com>
Sent: Monday, March 31, 2003 10:03 PM
Subject: RE: [Diy_efi] Typical boosted ignition timings


> A bit late to the thread, but what sort of EGT did you measure (if you
were
> measuring that is)?  12 degrees at 1.25 bar with only 0.85 Lamda sounds
like
> exhaust valve melt-down territory...  And with an air cooled engine, the
> heat build-up can lead to pre-ignition a bit more easily than water
pumpers.
> What sort of CR?
>
> This is all by-the-cuff though as I haven't had the pleasure of playing
with
> a turbo 911 (yet).  I'm going the high CR/RPM route myself with my '73.
>
> Matt.

CR is 7.5:1 - Mahle piston/cyclinders.  No EGT at the moment - I am planning
on getting EGT sensors asap before going any further.  (Btw, anyone know of
inexpensive sources for these (and the signal conditioning circuitry)? )
Since I have it twin-plugged, this seems to be critical for getting the
maximum burn rate for this late of timing,  The EGT's will confirm.  Sure
wish I had more timing data from others out there to compare to (similar
type engines).

Marc J. Reviel
Director of Engineering
PowerLogix
http://www.powerlogix.com


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