So how much different is the L98 auto vs manual tunes?

Hopefully someone can enlighten the subject.



Amended : Maybe someone can share their 86 4+3 tune?

 

Here are some general differences that I've noticed:

Idle rpm is typically increased for manuals by 125 rpm or so. Some idle related parameters are slighty different for rolling in gear, etc.

Spark advance tables are different. Autos showing more advance at light loads, with manuals a bit more advance at heavy loads differences of 7-12 degrees in some cases.

TCC related parameters are different between 4+3 and autos and not applicable for 6 speeds.

The O/D behavior will be screwy if you mix and match them.

 

TTT

Amended first post

 

I'll agree with tequilaboy.

Also add this: I'm running two TPI vehicles right now - the '85 vette (with a vortec head crate motor using the SDPP base manifold and edelbrock runners, etc..) automatic car, and an old ('78) chevy 4wd pickup with a TPI setup on it - basic mild 350 and the TPI is an '85 style system - to keep it interchangeable with the vette. The truck is a 4 speed.

Essentially the only differences I have in the chips between the two vehicles are higher idle RPM's and IAC positions in the truck, mostly so that I don't get a low MAF code if I let the RPMs drop too low in the truck when chugging it off the line with the clutch. Otherwise the two prom programs are about identical.

The automatic car idles happily and feels about right at 600 rpm or so, maybe 650. The 4 speed Truck - you can't even tell it's Running if it's that low. In that I have it idling at 800-850, which the seat of the pants says is normal.

I do have a bit different shape to the timing advance in the car, mostly to help with "issues" caused by the cam in that vortec crate motor - the thing will want to shake if there is too much advance in it at light loads about 2000-2100 rom, and will also shake bad at about 1300 rpm and very light throttle. I don't know how anyone could live with this cam/motor combination and a mechanical advance distributor...

The Truck, on the other hand, is a "stock" 350 with a small "RV" type cam - no overlap and lots of low rpm dynamic compression with that - it'll want to knock pretty easily. The timing in That program is a direct copy of the "factory" tables for the '85 vette. No changes. Seems to work fine like that. It does get into knock retard a Lot - even with "good" gas in it. I need to get that darn cam out of there.

Lots of other differences in the two vehicles, of course, the Truck is geared a Lot lower (3.73's, but with 31-10.5's on it also), is heavier and a Brick going down the highway. The thing is turning almost 3000 rpm at 70 mph! I would have expected to need a lot of changes in the PROM program - turns out not to be the case.

 

JrRifleCoach:

What are you trying to do that would involve an 86 4+3 bin? Maybe I can help.

If its for an 86 auto trans car, a normal 87-88 or 89 auto bin may be a better choice for an upgrade.

You can always pm me if you want to discuss (unless my box is full).