FW: [V8] 5 speed conversion!

[DasWolfen at aol.com]

In a message dated 12/10/03 10:53:11 PM Eastern Standard Time, 
ekellock at adelphia.net writes:

> Keith, could you expound on "the slow response of the ISV", what its 
> purpose is in the automatic cars and why it work in his favor in this case?  I'm 
> trying to understand the function of the ISV in general and specifically how 
> slower or faster response are more suitable to different conditions.
> 

 I'm not sure why the auto ECU operates slowly under 1500 rpm but my guess is 
it has something to do with compensating for the mass of the autobox torque 
convertor + fluid + rotating internals. I believe the ISV's airflow capability 
is too small to allow the ECU to compensate for this rapidly slowing mass and 
without the slower response stalling could be an issue. 

 Manual tranny cars have less spinning mass to deal with plus they have a 
throttle damper to prevent the throttle blades from slamming closed so they don't 
need a slow ISV.

 With a manual conversion to an automatic car the auto ECU's ISV programming 
prevents the engine from stalling eliminating the need for the throttle 
damper. The only noticable effect is that when the tach drops to about 1500 rpm the 
rate of rpm decrease slows. If you weren't familiar with how both automatic 
and manual cars normally react to a closing throttle you would never notice it.

 I'll be doing a 4.2 swap into a factory 5 speed car soon which may bring up 
another situation. The 4.2 has a staged throttle with a smaller primary bore 
that opens about 1/4 before the larger secondary opens. I want to keep this 
feature for throttle response reasons but keeping it means no throttle damper. 
I'm curious to see how the 5 speed ECU will react to this situation. Which 
reminds me.....

 Didn't someone post something about a stalling problem that was supposedly 
traced to an IA chip in a 4.2 5 spd conversion car in Cali? I wonder what ECU 
they were using and which throttle setup.

KT