DIY_EFI Digest V5 #454

[Rodney_L_Wiggins at keybank.com]

>>Hi List,
>>            Under what condition is 'decceleration fuel cut' used?  Is fuel
>>totally stopped to the engine?  How can you tell (via MAP, TPS, RPM
>>whatever) if the engine is stealing torque(braking - absorbing power)
versus
>>producing torque for either constant speed or acceleration?  Is cutting
fuel
>>always appropriate during engine decelleration? (I'm guessing no, as you
>>could be decelleration while going up a hill decelerating slower than
>>gravity would accelerate you in the reverse direction so theres alway a
load
>>on the engine!)
>>


>If you (or anyone else) are contemplating this on a race car - DONT! - its
>lethel, and just asking for the rear end to step out when you aren't
>expecting it.

>I have the dents to prove it.


This can get VERY hairy at moments. Especially in a turbo car.  But we should
all know better than to
completely close the throttle in the middle of a turn.  However, I've added a
small switch in my 944 turbo
near my shifter that when opened disconnects the  closed-throttle switch from
the cpu. I use it for track and autocross.
The engine then idles at  1900 to 2200 (Idle stabilizer valve is held fully
open) which also helps limit compressor stall
 between shifts.  It also helps me keep the drivetrain loaded and makes throttle
transitions smoother and less likely
to upset the car in an at-the-limit turn. But on later motronics isn't there a
fuel cut simply on reductions in throttle angle?
Even when you don't let the throttle close completely it acts as though fuel is
being reduced dramatically.
I'd love to be able to eliminate this fuel cut altogether.

Rod


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