RBob,

I have read some of your comments before that you like to set TF Gain% so as to get MAX IAC steps at ~ 100% TPS. I have my MAX IACs set at 175 and a TF% Gain at 70%. So I decided to datalog this and see what IACs were at TPS =
99+%. IACs hardly moved at somewhere around 23 steps. I am obviously misunderstanding how you are going about this. Would you clarify further?

 

It is likely something in the code, I'm not running $D0. If there is a max TF steps parameter be sure it too is set high.

RBob.

 

Check this table @ L87D9 (or @ L87DC, 3 byte offset?):

Throttle Follower vs MPH * 2

That may be a maximum allowed TF versus MPH.

RBob.

 

Exactly RBob. When I read your first post, I thought of that table and saw that the max TF at the MPH was that #. I need to get above 92mph to get to the 175 IAC counts. I did notice that dropping the gain % did make the accelerator more responsive. Right now I have it set at 70%. Not sure I want it more sensitive but there's only one way to find out

 

Too much gain makes TF sensitive to throttle input. I reduce the gain to make it more linear.

TF also affects HC emissions on a lift. More so on a wet flow system such as TBI.

RBob.

 

RBob,

Interesting because the stock calibration uses a 99% TFGain. I would agree w you that my setting at 70% has the pedal feel much more linear to the desired output based on the input.

 

But the amount of TF steps is limited at low speeds. 30 steps at 0 MPH (prevent stalling when taking off). Then 5 steps from 8 - 48 MPH. Then 25 steps from there to 88 MPH. At which time the maximum steps really goes up (125 - 175).

Yep-er', as the engine performance goes up, it is more responsive to throttle. Taming down the IAC TF helps in this regard.

Another one that can drive you batty is stall saver (TBI only, does not apply to $D0, $8D, $32 or $6E). I had the trip point too high at one time. So nearly every time I let out the clutch the RPMs would dip, hit the stall saver, and the ECM yanked the IAC open to prevent it from stalling.

The issue was that once the RPM recovered the stall saver steps were decayed out and the car stopped accelerating. I then had to depress the go-pedal further to continue on.

RBob.

 

RBob,

In fact, not only did I lower the TF Gain % but I also dropped the Max IAC v MPH
COUNTS until higher speeds. As for the Stall Saver, I took your advice and dropped the disable down to 0 and now it doesn't stall when free-wheeling in neutral down to a stop.
Even though its SPFI and not TBI, you still want as much air velocity going through the throttle body as possible and not bypassing thru the IAC.

 

The stall saver in the $D0, $8D, $32 or $6E masks is a bit different. No IAC action, they just assert the EST/BYPASS line to force the ICM to base timing. It may work for stock engines, but it sure doesn't work on modified engines...

RBob.

 

"But the amount of TF steps is limited at low speeds. 30 steps at 0 MPH (prevent stalling when taking off). Then 5 steps from 8 - 48 MPH. Then 25 steps from there to 88 MPH. At which time the maximum steps really goes up (125 - 175)."


RBob,

So 88mph is when things really begin to happen? Sometimes the LT-5 feels as if it has a
Flux Capacitor! . LOL!

 

To me, it would seem that GM wants the car to be drive-able, without driving into the rear end of the car in front of them. My Firebird is still somewhat in that category. I always pause before taking off.

RBob.