lighter flywheel idle problems

[jkieffer46]

good evening folks.
i have an 01 vette with an lq4, procomp heads and torquer 2 cam. have an ls2 manifold and tb. texas speed longtube headers. that should be it so far as my problems are concerned.

having problems with the idle catching it at 7-800, where i'd like it to be. while driving and coming to a stop, it'll fall on itself down to 3-400 or just stall.

the other problem is when i blip the throttle to maybe 4k, it takes it's sweet time getting back to idle- maybe 5sec or more.

i was having blackbear tune this via email, and after about 6mo i can say i'll not ever have him tune another car with a lighter flywheel. i'm pretty tired of it and know i can do it myself, so since ive heard more people happy with hpt than efilive i took the plunge.

[Ben Charles]

Throttle follower needs to be adjusted.
Lighter Fylwheels can be a pain in the ass, you'll need to play with TF.

[jkieffer46]

Wow that really fixed it. Still tries to die when it drops to find idle after a rev. Where should I look for that?

[Ben Charles]

IF you slow TF after a rev and it still tries to die, then it may need more air, add some TF air at low TPS. Is idle solid?

[jkieffer46]

Im not sure how to do that- at low tps? im seein throttle follower related to p/n or gear and vs speed. Yes idle is great. Is there a certain rpm i should be idling? I can crank the thing down to 500ish and its still ok. Have it at 750 now when warm.

[jkieffer46]

Is there a minimum tf that i want to use? After about 4.000 im not noticing a difference in how the rpm falls. It says max is 64.000 though. is there a problem with jacking it all? he way to 64?

[WS6FirebirdTA00]

Depending on the rest of the setup, throttle follower may or may not resolve it.

Some OSs will not run stable idle with throttle follower enabled while cruising and there could also be some cases where it is not active or quickly zeroed. The reason your idle won't come down well is because throttle follower is too high. This is another issue with trying to "fix" the issue with throttle follower. It can only do so much.

In some cases where the RPM drops very fast the throttle follower is less likely to help.

I have the exo-skel clutch on mine which is light and has a much lower inertia. I had to raise my idle. On mine I had to leave throttle follower and cracker at 0 near idle or else it would go unstable. My adaptive spark goes active so I was able to use the over speed and under speed spark tables to make the biggest impact. Worst case I have always found was a free rev in the driveway and as the idle was coming down I turn the steering wheel to full lock. This way the car didn't shut off on me while I was driving.

Basically if I tried to idle it too low it never wanted to run right. I have mine at 1175 RPM right now with a 236/244 cam on a stock bottom motor. This is really the extreme case as just a lighter flywheel shouldn't be as bad. I made adjustments to the PID control so that it would not try to bring the idle down quite as fast. You have to be careful here because you can screw up a lot more than you fix if you don't know what is really going on. Although I am 100-150 RPM higher than what I would like to run this cam at, but I am confident the motor RPMs won't drop at all on me.

Also make sure to drive the car and do a couple key cycles when doing this. I have had mine where I thought it was good, shut the car down and then went back out and the issue was still there. We still have not got an answer on what is going on with that in some computers. It tends to be a commonly reported issue.

[WS6FirebirdTA00]

After seeing your tune, step 1 is to put the idle up at a more reasonable value with that cam and flywheel. Stock is 800, you are 750, I would want to idle that around 900 RPM but it may need between 900 and 1000.

Many guys are willing to sacrifice driveability to get the lower idle loping sound with a cam. If you are one of these guys you will need to learn to live with some of the idle dip as it will be harder to clear it all up. Just my opinion.

Also, why do you have 10º of idle spark?

[jkieffer46]

Ok so jack to 900+ or live with dip. Can handle that, cant handle stalling. Im just getting into this is why its at 10deg. Blackbear was tuning this via email and its literally been 6mo+ working on it that way with him. Im tired of it and want to learn how anyway. I dont even know at what degree idle spark should be.

the other question- is there a such thing as too much throttle follower? Says max is 64.000. im assuming that means no tf. Is that detridetrimental?

[Russ K]

Had an aluminum flywheel in my car for 2 months. Spent many hours tuning the idle tables including the proportional, intergral & derivative tables as per a Motec tutorial video.

Finally re-installed the stock flywheel, no more hunting & stalling, was able to lower the idle back down to 950 plus the neutral gear rattle is gone!

Never again will I use an aluminum flywheel in a street car, and for the claimed ~10 rwhp it's just not worth it,

Russ Kemp

[WS6FirebirdTA00]

I tested mine before and after, 13 RWHP on a skimpy dyno believe it or not.

I posted graphs a while back. Still, not worth it though really.

Yes, there is such thing as too much follower. It will cause idle to hang.

[jkieffer46]

When you say hang you mean at the top of the rev or hesitate while its tryin to find idle?

[WS6FirebirdTA00]

Top of the rev.

[Frost]

something I haven't seen mentioned is that there is discussion related to more than one platform here... Lightweight TBs, while a pain on F-bodies, are (and this may be the ONE exception too) actually easier to get right on IAC cars than many ETC cars.

On an IAC car, you can work the steps vs. effective area to pad the return to idle to keep it from falling so fast. After you've done one or two, they don't seem bad at all.

Now.... on the other hand.... some of the biggest tuning headaches I've ever had are centered around lightweight flywheels on the ETC C5 cars. By headache I mean amount of time spent. Part of it stems back to us, with many OS's, seemingly having on one STIT limit, and that's an upper limit, but a lower limit to the remembered range would work better. The OS's that won't do something like remember -2 or -3 g on the STIT can be 'padded' in the idle airflow region. When the car returns to the idle position, the STITs THEN move negative. If they remember -3 though, it's gonna fall like a rock and then continue untill stall from re-applying the negative STIT when approaching the target idle area. If you are unlucky enough to have this style OS (seems 01-up it's the most likely) then you just have to get ALL, I mean ALL of your ducks in a row. The VE fueling must be right, especially below 12-1400 as well as the MAF. You will have to build in spark to that clutch in decel area to help slow it down and you will have to be all over your idle adaptive spark to make it do work without going into oscillation ('ringing' if you are a controls guy).

Log ALL of your idle related parameters to even see what's going on here. I haven't seen any details from OP past word of mouth description. To give help without seeing idle logs is tough unless something is just really wack in the base that is being used.

[WS6FirebirdTA00]

I used the same methods on my car and a 2001 Z06, FWIW. We had the same clutch. I think that OS seemed to want throttle cracker though, but I had to drop back the follower.

[jkieffer46]

ok the snow finally broke so i could get out and drive the thing. doesn't stall anymore, but still dips down to about 200. scary. what exactly does the throttle cracker do? also- is there a sticky somewhere i'm not seeing on an idiots guide to tuning for newbies? i am one and don't want to bother everybody on the forum if i can find it somewhere else.

if i'm logging/saving the wrong file please tell me. once again- very new to this.

[edcmat-l1]

Now.... on the other hand.... some of the biggest tuning headaches I've ever had are centered around lightweight flywheels on the ETC C5 cars. By headache I mean amount of time spent. Part of it stems back to us, with many OS's, seemingly having on one STIT limit, and that's an upper limit, but a lower limit to the remembered range would work better. The OS's that won't do something like remember -2 or -3 g on the STIT can be 'padded' in the idle airflow region. When the car returns to the idle position, the STITs THEN move negative. If they remember -3 though, it's gonna fall like a rock and then continue untill stall from re-applying the negative STIT when approaching the target idle area. If you are unlucky enough to have this style OS (seems 01-up it's the most likely) then you just have to get ALL, I mean ALL of your ducks in a row. The VE fueling must be right, especially below 12-1400 as well as the MAF. You will have to build in spark to that clutch in decel area to help slow it down and you will have to be all over your idle adaptive spark to make it do work without going into oscillation ('ringing' if you are a controls guy).

It would be nice if there were some way to keep it from memorizing the low point in the idle airflow. That and if there were a MPH switch for the throttle follower, that way we could allow it to decay slowly while moving, same as it does when sitting still. Maybe the crew at HPT can find this? Would be nice. Would make tuning these much easier. I know I'm considerably balder due to tuning these pain in the asses LOL.

[ElecTech]

I can't open your file right now, but check that you are on the latest OS for your Vette. I just battled a car for a week with similar issues and everything I used in the past would not touch it. Turns out GM had an update for that very issue that covered 01-02 Vettes and it all but cured my headache. Check your VIN in TIS and make sure you are on the latest. The fix was in a table(s) we don't see.

Hope this helps.

[Zo6 4 Me]

I can't open your file right now, but check that you are on the latest OS for your Vette. I just battled a car for a week with similar issues and everything I used in the past would not touch it. Turns out GM had an update for that very issue that covered 01-02 Vettes and it all but cured my headache. Check your VIN in TIS and make sure you are on the latest. The fix was in a table(s) we don't see.

Hope this helps.

Hi,
I have a 02 zo6. How do you tell if the OS has be up dated? I have HPTuners, can it check it?
Thank you,
Christian