Off Throttle Dropping Through Idle

[SOMhaveit]

I've searched and haven't seen a difinitive answer to this so here goes.

I have changed my setup from a 347 to a 383 and changed cams from a 220/220 .620 114 to a 228/232 .612/.600 111.

I have done the RAFIG and my VE table is close running SD.

Idle is fine, and if I am running at speed and thow it in neutral and let the clutch pedal out, the RPMs drop to idle and are stable. On the other hand, if I push the clutch pedal in and hold it in, the RPMs sometimes drop right through the floor and the engine stalls.

I have adjusted TC and TF and it has not stopped the problem.

The oem parameters don't have any values for TF and TC for 'In Neutral' and I even carried the 'In Gear' values over to those columns and increased them.

This question has been posed before without any resolution. Somebody knows exactly what needs to be tweaked to address this RPM drop through idle settings when the car is moving and the clutch pedal is depressed.

Help Please.

[SOMhaveit]

No help on this, obviously.

So I started thinking about this and the issue revolves around more cubic inch displacement because I had the FAST & 90mm TB before this and did not have the problem with plummeting RPMs.

It dawns on me that GM put the 90mm TB on larger displacement engines, so I look at stock tunes, and oddly enough, the timing in the high octane table is around 30 degrees. Can it be that simple, I ask myself. Who cares?

I bump my high and low octane tables as the LS2 Vette has, and voila! I can't make the car stall with the clutch pedal depressed.

Is it "right" to do it this way? I don't know and don't care. The bottom line is that it worked.

Now all of you pros chime in and tell me about gas laws and theory and how this is all wrong without offering any different solution.

[joecar]

I like the simplest solution... good job...

(I didn't have any ideas, but I have been reading along nonetheless).

[SSpdDmon]

No help on this, obviously.

So I started thinking about this and the issue revolves around more cubic inch displacement because I had the FAST & 90mm TB before this and did not have the problem with plummeting RPMs.

It dawns on me that GM put the 90mm TB on larger displacement engines, so I look at stock tunes, and oddly enough, the timing in the high octane table is around 30 degrees. Can it be that simple, I ask myself. Who cares?

I bump my high and low octane tables as the LS2 Vette has, and voila! I can't make the car stall with the clutch pedal depressed.

Is it "right" to do it this way? I don't know and don't care. The bottom line is that it worked.

Now all of you pros chime in and tell me about gas laws and theory and how this is all wrong without offering any different solution.

Did you try playing with B4310 before adjusting timing? My concern would be low airflow / light throttle surging may rear it's ugly head with more timing. If you don't get any bucking from upping the timing, I'd stick with the change you made. Otherwise, you're just trading one problem for another.