Can someone look over my tune

[98 SLP]

Bought my 1998 M6 SS Camaro about a year ago. Things I know about the car are, 98 SS with all SLP options, Pacesetter LT's and catless y pipe, SLP loudmouth exhaust, LS6 intake and ported stock throttle body, Unknown cam (seller didn't get the specs on it when he bought the car), Patroit gold valve springs and retainers. After pulling the tune it looks like the ecm has been swapped for an 02 model year.

Issues I'm having with the car are, It's a little slow to drop rpm's after revving and seems to pull itself down the road when I let off the gas. Thanks for any insight.

My 98 SS base tune.hpt

[JasonS5555]

Hey Mike,

Your idle airflow looks like it "might" be a little high. See what the car actually wants with the Russel K idle procedure.

I would look at changing the throttle follower decay and cracker airflow as they are still stock values (under engine - idle - airflow). Look at the top of this forum and read about tuning a car with a cam for specifics.

HTH,
Jason

[98 SLP]

Okay. Thanks for the tips.

[nkautz]

It's probably idle airflow or IAC park position airflow

[98 SLP]

After running the Russ K idle config I came up with the same values except for minor differences in the 25 and 46 degree cells. One other thing I've noticed is that the throttle body has been drilled. Should I toss it and buy one that hasn't been drilled before continuing to try and tune out my lazy rpm drop?

[68Camaro]

don't get rid of your throttle body. its common practice to drill the throttle body on cammed iac cars to bring the iac counts down to an acceptable range at idle at operating temperature (60-100 iac counts is good in park or neutral at operating temp). your base running airflow looks acceptable to me also. try working with your throttle cracker and throttle cracker decay tables - they look like the numbers in them are excessive

[98 SLP]

Ok. I was a little concerned when I got the same figures after running the Russ K config twice. Thanks for the reply.

[98 SLP]

Ok. So I've messed with with the throttle cracker tables and have seen no change in the idle down speed after revving the engine in neutral. I cut these numbers in half and still saw no change. I've been unable to road test to see if the car still pulls itself along when I let off the gas. Poor weather conditions is preventing this.

[shoaf85]

Have you tried changing the throttle follower tables at all?

[98 SLP]

No, I have not. I'm still researching the function of that table and how much to adjust it. I don't want to just start throwing random figures at it blindly.

[98 SLP]

Should I just highlight all values in these tables and X by -0.2 until I start seeing a change or is there a specific procedure for these tables?

[mowton]

Can you get another stock throttle body to try out....not for the drilled hole, but for the porting....notorius for f'n up idle and coastdown.

The hole should be "sized" to maintain a closed throttle TPS value of .5 to .65 volts and 40-50 IAC steps.

Ed M

[98 SLP]

I'd need to buy one or steal the the Nick Williams off my wife's WS6.

[mowton]

I'd need to buy one or steal the the Nick Williams of my wife's WS6.

Try your local Camaro club, sure someone would have one to try. Nick Williams brings in another set of variables.

Ed M

[JasonS5555]

In addition to the TB, if hanging RPM is the issue would also look at increasing the decay values in the throttle cracker and follower decay tables. You can get pretty severe in your adjustment, the only side effect will be the car trying to stall as the RPMs drop too fast instead of too slow. If you get that, adjust the decay values back down.

Jason

[mowton]

Log TC and TF and see what they are doing at you issue area and adjust the decay like advised. Easy test. TB more difficult.

Ed M

[01SLPSSM6]

After you get your throttle follower and cracker sorted out you should re do your VE table. I was looking through your tune and noticed the VE table is all over the place, most likely from street tuning that wasn't done at steady state. Also if you select the entire VE table and smooth it that should give you a good starting point.