Re: Poor Man's ECU Fuel Enrichment

[DeWitt Harrison <de@aztek-eng.com>]

At 07:15 PM 12/30/97 GMT, Phil Payne wrote:
>In message <9712301641.AA11317@aztek-eng.com> DeWitt Harrison writes:
>
>> On Tue, 30 Dec 1997 06:45:29 +0000, Douglas Quebbeman wrote:
>> >[ ... ]
>> >Has anyone considered using the cold-start valve for WOT fuel
>> >enrichment? It seems like it would be pretty simple to do. The
>> >cold start valve delivers fuel at a fixed rate, and it's not metered
>> >by the fuel distributor, of course. [ ... ]
>> 
>> "Not metered" is the key phase.  This sort of full throttle
>> enrichment is, at best, a very crude way to avoid detonation
>> in "poorly" executed turbo designs. With this arrangement,
>> the mixture can only be correct at a single value of air
>> flow or WOT rpm.
>
>You're assuming that it isn't done under ECU control.

Yes, you're right. And it may not be an accurate assumption.
It has been my interpretation of what I've read here that
at WOT, mixture control was accomplished primarily by
the air sensor plate and fuel head with the ECU defaulting
to open loop output settings. It's also my impression that
the mixture frequency valve has a relatively limited
range of control.

If this is incorrect, I would still question whether the ECU
is capable of maintaining mixture control in the face of a large
uncalibrated fuel input or, similarly,  a gross input air leak. What
is your take on WOT cold start enrichment?

DeWitt Harrison    de@aztek-eng.com
Boulder, CO
88 5kcstq