ox sensor on sequential efi,high overlap cam....

[Gary Derian]

I also concur.  The reason that the old mechanically mapped alpha-n systems
were so sensitive to mechanical condition is that in those days, for the US
market, they were set on the ragged edge of lean surge.  Any small change in
VE will push them over the limit.  A not so close to the limit system and/or
better electronic mapping should make an alpha-n system more forgiving.

Gary Derian <gderian at cybergate.net>

<snip>
>>Actually, might be worth the effort to forget the sequential efi (unless
you
>>want to impress everyone in the staging area with your flawless idle
>>quality) and just batch it (I just found out about this and it has changed
>>my whole outlook on efi!).   You have that much cam, you're not idling
>>anyway!
>>
>>rick
>>
>Amen, And this is why efi setups for REALLY hot cams use a tps input
>(rather than MAF or MAP) along with rpm as the second coordinate of the
>air/fuel map in the ecu--TPS is simply a far more accurate indicator of
>what is going on in the engine at low throttle openings and low engine
>speeds than either of the other sensors under these kind of cam conditions.
>Some which are set up this way even switch from TPS input back to MAP at
>higher engine speeds and loads--the exact area where those funny looking
>cams really DO work!!
>
>Drag racers have always been pretty damn good at figuring out what
>WORKS--and not always so good at explaining why!!
>
>Even a fairly tame engine can be made to run very well indeed with a
>TPS/RPM based fuel map--witness the SPICA (mechanical) injected 1750 Alfas
>of the late sixties/early seventies. It is just not as easy to do as it is
>with MAP or MAF, and it is WAY more sensitive to changes in mechanical
>engine conditions. For instance: setting the valve lash on one of the above
>mentioned Alfas .002" tighter than factory spec would create a flat spot
>every time!!
>
>Regards, Greg
>