DeTomaso Mailing List: April 2000, Message #280

I'm no expert in this particular area, but I wouldn't expect it to be as
simple as linear.  Air flow thru the engine is greatly influenced by
reflecting intake and exhaust pressure waves who's sequential timing to cam
events (tuning) changes with RPM.  This is especially evident in individual
runner systems, which I recall you have, maybe.  You could also get fuel
supply pressure reduction as the fuel flow rate increases.  This can drive
the PWM duty rate up non-linearly.

----- Original Message -----
From: Kirby Schrader <schrader@ev1.net>
To: Multiple recipients of list <detomaso@realbig.com>
Sent: Sunday, April 09, 2000 12:46 PM
Subject: EFI experts: Question!


>
> I'm still messing with my Haltech system after more than two months,
> but as of this afternoon, I think I'm as close as I can get without
> getting back on the track again or, better yet, on a dyno. I'm
> working on getting to a dyno and my son has a connection that I hope
> will get me in one day soon... Ever tried to get on a dyno in the
> spring? It's racin' season, dudes! Everybody's dyno is booked solid
> for weeks! Or at least that's the case here in Houston.
>
> I spent a good half hour accelerating up and down a deserted street
> here this afternoon. From about 1500rpm up to 7000rpm in 2nd gear
> while taking quick glances at the O2 sensor. The few folks that did
> drive by thought I was obviously nuts...
> I'd seen 'fat' place and lean places previously, so I was using this
> session to fill in the lean places at wide open throttle. I was
> amazed at how much I had to increase the injector time from around
> 4000 to 6000rpm... And then it sort of levelled out.
>
> Anyway, the question...
>
> I had just figured that the response of the engine should be linear.
> i.e., for a given rpm range, the amount of time the injectors spend
> open should increase linearly. Methinks I'm simplifying it too
> much... Or full of shit... or whatever.
>
> Just based on the fuel/air meter, 'seat of the pants' and the SWAG
> factor, I find that it's not linear at all. Or else the O2 sensor
> can't handle the higher rpms? Or something I'm not considering like
> the cam response and all that good stuff.
>
> What do all you EFI experts have to say on the subject?
>
> What kind of curve would you expect when you plot rpm vs. injector
> milliseconds at wide open throttle?
>
> Thanks,
>
> Kirby
>
>
> --
>
>
> /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
> Kirby Schrader                   schrader@ev1.net
>
> '71 Pantera #1661
> '78 Longchamp GTS #3001  (It's for sale! Contact me if interested)
> '96 Mustang GT  The wife's
> http://users.ev1.net/~schrader/
>