Ignition advance, was Re: alternative engines, WARPED

[Programmer]

Bob,

I'm sold--you going to post the technical on this setup sometime ??

Lyndon IPTECH
-----Original Message-----
From: rr <RRauscher at nni.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Wednesday, May 19, 1999 7:39 PM
Subject: Re: Ignition advance, was Re: alternative engines, WARPED


>Bruce (or is that Grumpy?) wrote:
>
>>Kinda depends on the WOT pressure drop across the carb., and spring rate
of
>>the vac, advance used.   Even with the same no. degrees per amount of
vac.,
>>by different spring rates/dia. combinations things could vary.  Going from
>>6-10 start to 20 something at 700rpm, 30 something at WOT (@3,000 rpm),
and
>>40ish at cruise with a OD kinda hard to do thata way (mechanical).   Hence
>>the real beauty of ecm's, IMHO.
>>  Grumpy
>
>
>Bruce is speaking huge amounts of wisdom here, nothing can come close
>to how an ecm handles spark control.
>
>I've installed a '747 ecm and spark control system on a carb'd car,
>what a difference. Drivability, power, mileage, have all improved.
>(Yes, I'm still working on the write-up. The cutoff is next week,
>as I'm going back to school, along with working).
>
>Couple of things that mech/vac distrib's aren't/can't do:
>
>  A 210 point table, based on rpm and manifold vac, that defines
>  the main spark advance value. This in itself blows away any
>  centrif/vac-adv distributor.
>
>  Startup spark, additional timing added for a short time after
>  the engine is first started. Keeps engine from stalling (choke).
>
>  Coolant compensation spark, additional timing added/subtracted
>  as a function of engine temp.
>
>  Hi-way spark, after a set period of time, above a set speed,
>  additional timing added for better mileage.
>
>  Knock detect and retard, along with testing of the ESC system.
>
>  PE spark, at WOT, additional fuel is added, and spark is also
>  added to take full advantage.
>
>Well, more than a couple, but I hope I can get the idea across.
>I'm sold on this...
>
>BobR.
>
>>>|      I could be wrong at this, but what I have seen is, ported vacuum
is
>>>dead
>>>| at idle, because it is above the butterfly....and as throttle is
>>>increased,
>>>| vacuum is generated at the "port" and does not go away at full
>>>| throttle,,,,,great for emissions but terrible for performance,,,,,the
same
>>>| for MPG....
>>>| -Carl Summers
>
>>>>|   You sure about that?  I have always understood that a vac advance
can
>>>>|  reads ported vacuum in order to affect a curve that begins as the
>>>>throttle
>>>>|  is opened and increases as more throttle is applied, up to the point
at
>>>>|  which all vacuum (manifold and therefore ported as well) fades under
>>>>heavy
>>>>|  throttle openings, at which point the advance will decline again and
the
>>>>|  engine will see only mechanical advance.  This is apparently to
provide
>>>>|  extra advance for economy at part throttle.  Anybody who can further
>>>>|  illustrate this concept, please do because if I am wrong here I'm
going
>>>>to
>>>>|  have some serious rethinking to do!
>>>>|   Aaron Willis
>
>