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[alfa] Re: hot restart and throttle comment



At 2:09 PM +0000 6/17/04, alfa-digest wrote:
Date: Thu, 17 Jun 2004 01:11:56 -0400
From: Michael Tiefenback <[email protected]>
Subject: [alfa] Re: hot restart and throttle comment

Date: Wed, 16 Jun 2004 21:18:54 -0600
From: C M Smith <[email protected]>
Subject: [alfa] Hot restarts on V6 engines

Supposedly, opening the throttle on a FI engine has no effect while cranking.
just before gleefully supplying a couple of interesting counter-examples.

I'd suggest a _possible_ mechanism. FI engines monitor air flow and coolant temp and maybe another thing or two to set mixture for running/starting. A fully hot engine makes the ECU lean out the engine. If the false air leaked around the AFM by the idle CO screw dilutes the mix more with only starting RPM
(say, because a sticky AFM door doesn't want to open) then opening the throttle would pull more air through the AFM, opening the door or simply diluting the effect of the idle CO false air. Maybe. Pushing a bit of carb/brake cleaner into the intake of the balky warm engine might show whether it's rich or lean.
Or not. Such a test might indicate what to tweak for improving the warm start behavior if it is a nuisance (say, to a spouse; I've learned that my spouse isn't as handy with or tolerant of funky mechanicals as I usually am).

Michael

Cranking the engine will require more effort on the part of the starter motor when it's sucking air around a closed throttle rather than an open one. If the voltage available to the ECU is already marginal for one reason or another, opening the throttle will make the starter draw slightly less current, and maybe push the ECU voltage over that critical threshold.

-Joe
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