[Diy_efi] Ignition Timing

Adam Wade espresso_doppio
Tue Jul 26 20:57:48 UTC 2005


--- "Becker, Damon (Damon)" <damonb at avaya.com> wrote:

> Since I'm knock-limited, I won't hit MBT timing
> before I hit knock, right?

AFAIK, that's what "knock-limited" means.

> I have read many books that advocate reading the
> plugs as a great way to set the ignition timing.  I
> have read other places that using a stethoscope
> against the block and listening for knock under
> heavy loads while doing the dyno runs is the best
> way.  I have yet others say it's best to use the
> stock knock sensor (unmodified internals, stock
knock
> sensor still valid) to listen for knock.  

With a turbo application, I'd think it would be far
easier to make an MBT ignition map and let the stock
knock sensor back off the timing as needed.  There are
a lot of variables in the operation of a turbocharged
motor, and I would expect it to be fairly
time-consuming and difficult to map ignition timing
specifically for every combination of intake temp,
engine speed, throttle position, engine temp, and
boost level.

You may well want to data-log the resulting ignition
timing in operation, as you may be getting so much
retard that you wish to take other steps to move the
spark back closer to MBT (intercooling, piston crown
oil squirters, richer mixture, less boost).

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