I can't get idle IGN Advance to change. Also some idle issues.

Customers vehicle. Having a couple issues I'm having a hard time dealing with. 98 LS1 98 Camaro/Pcm/Wiring Harness, this is a swap vehicle. Blower cam, .600 lift 240/240 ish 114lsa. Specs are from memory, it's been a while. Magnacharger, making 9 lbs of boost. 42lb injectors.

Set my spark tables, IFR table and related tables. I dont have the Banish tables but I'm certain I'm close. Modified all the other little things here and there.

I did the 2bar OS and the Cobalt baro sensor, all is well, logging/tuning went great. Tuned the VE from low to high on the dyno and on the road. Put over 100 counts in every possible cell, blended results into the VE table. Did this 3 times. When I enable closed loop, fuel trims are under 5% almost everywhere :yay:

PE is commanding 1.26 (11.56) and I'm hitting it right at 11.5-11.6 on the dyno all the way to the top even after adding and reducing load. I'm fairly certain VE is as dialed in as it's going to get.

At 9 lbs of boost through a 4x4 trans/transfer case, truck axles and 32" wheels/tires, it put down 430hp and almost 500 ft/lbs

I used the RAF histogram found somewhere around here, it spit out some low looking numbers for this cam but I used them and it runs fairly well. I have LTFT's disabled.

PROBLEMS: I need help tuning the cracker/follower, it comes down to idle faster than the pcm can catch it and will typically hunt than stall, mostly noticeable with the a/c on. The truck it's in (JEEP) can not idle up the motor, so I have idle around 875 and when you switch the air on it will hunt then settle around 800. To get the most torque at idle, I enabled bidirectionals, and took the afr to around 13.8-13.9 and around 33* it pulled the most vacuum and idled the best. in the 40-55kpa area and 400-1200 columns I set the timing to 33* and blended in surrounding areas in the High/Low timing tables and in the IDLE--->IDLE SPARK ADVANCE tabs, did the same. It still idles at 26* no matter what.

To richen it up, I set PE from 400-1200 to 1.05 and set TPS PE Enable to 0 from 400-1200, from what I understand this should force it into open loop at idle and hold it around 13.9. However, when I scan I still see STFT's working and spark advance staying at 26-27* I did a write entire also, still didnt change anything....

I reduced the idle/overspeed spark timing by 50% so it can't swing as much, that helped alot. It doesnt hunt for idle like it was. I still think it's trying to come down to idle too fast.

Am I missing anything ?

I've attached the file, I dont have a log on this PC.

If you haven't logged STIT's, do that and get them Zero'd out from a cold start. A common mistake is to not make accommodations for the electric fans and A/C. If you get the STIT's zero'd and then the fans kick on and kill your STIT's, don't adjust the RAF. Adjust the fan airflow tables. You can use the bi-directional controls to turn them on and off to get the proper compensation set.
Another mistake I see is folks adjust timing for maximum vacuum by using the wrong control in the bi-directional controls. You don't want to lock in the timing at a solid value. Use the other one that pushes the value up or down, but doesn't lock the timing value and do it in closed loop. This allows the overspeed/underspeed to work properly. What I expect you'll find is that your 33° idle timing value is way too high. When you push it that high, it doesn't allow for any cushion for the over/underspeed to work.

The follower is what will slow the RPM descent back to Idle, so log it and raise it.

Can't look at your tune from this computer, so that's as far as I can address it.

Thanks i will do that with the idle. Using the histogram config here for RAF, the raf requirements doubled with the a/c on. The truck its in has no way of sending the a/c request to the pcm for idle up and additional advance. The a/c switch is basically engaging the compressor clutch and nothing else.

I ran the raf histogram with the a/c off and the a/c on and just averaged the 2 and used that for my raf table. It sounds/feels like its choking with the a/c on sometimes.

Oh and i was using the spark adder in the bidirectionals when i was checking for best vacuum, not just the static spark setting

Can you clarify what you meant about the Jeep and it's target idle? I see in the tune you want it to idle at 860rpm's across the board which is a little odd, but that's why I'm asking.

I noticed all tables regarding spark at idle RPM's have the same general shape of a mountainous peak...you have idle transitions going from 35-36* to the next column at 7*. Perhaps try smoothing out and blending the areas around your peak idle columns to eliminate the severe dip caused by moving to the next cell/column.

Also, I'm not sure how your cooling fan setup is but a few of those settings look askew depending on what you've got.

Thanks Patrick. Im aware of the timing mountain. Its strictly there for testing/troubleshooting. I have no intention of leaving it like that. But with the mountain there in the idle tables and hi/low tables, it still idles at 26* all the time.

That 860 should be 850, typo on my part.

By jeep, this combo is in an 04 wrangler.

The a/c pressure switch is there and working, i can read the voltage in the scanner, but theres no request wire hooked up. Is there a way for me to tune it for a/c on/off with just the a/c pressure ?

Its set that high, because with a/c on, it pulls the idle down to 650 like that. Occasionally, it will surge and have a fit. A blip of the throttle settles it down.

A couple observations... First, setting the timing way up near MBT leaves no torque reserve for the PCM to be able to add timing in to bump RPM. So if you have an overspeed table with say 12 degrees in it at a certain RPM error, the PCM will try to add 12 degrees to the 33 you said you commanded at idle.

By raising your timing to MBT, you'll make the motor quirky. Try lowering the timing a good bit, and adding airflow instead. The motor will be more steady with the additional airflow. The RAF tables will need reworking of course.

The PCM would need to know that the AC is on. I didn't look at your tune or scans, but basically there has to be either a signal wire from the AC switch, or a signal created by clicking on a relay or something that's tapped into the AC clutch wire. Or if the PCM works off of AC pressure, then it should work if the pressure switch is in there. Not sure what method your PCM/tune is using for AC engagement, but a look at the wiring diagram should clue you in to whether or not the AC switch signaled the PCM originally.

As previously stated, the RAF tables with and without AC should be tested. And remember, that blower is getting turned at idle, creating drag. You'll have to add more RAF than a stocker to compensate for the blower, and any large cam you've added.

As for throttle follower, hold the engine in neutral at 3500 and then let off the gas. If it drops too fast, right past idle, add some throttle follower in the bottom end of that table.

Basically, I think that it's your RAF tables with lack of AC signal, combined with the fact that you're using lambda and timing to increase idle torque, when you likely need to use RAF instead.

Okay, I will add a little RAF. According to the histograms, the motor required almost twice the RAF with the a/c on vs. a/c off. I took the a/c off values than ran it again the next day from cold a/c on, averaged the numbers and used them. They still "look" low for a big cam and blower. When I monitor the "A/C Request" Status bit in the scanner, it doesn't do anything when I switch the a/c on and off. BUT I can see the pressure/voltage working just fine in the scanner. It intermittently doesn't like to run with the a/c on. Other times it's fine.

Sounds like your AC request comes from an AC switch (which is normal), not pressure variances. You'll have to find the wiring diagram for the PCM and see how you can signal the PCM that the AC is on. I'm thinking you could run a relay that triggers off of the AC relay trigger source, or maybe just the AC switch itself. There's no load on an AC request circuit going to the PCM, so it shouldn't be a problem tapping into the switch.

I think you're finding the AC on/off so finicky because of how you're getting the power to idle your motor. By using timing and air/fuel ratio instead of just increasing the load via more IAC, you've basically maxed out what the PCM can do to control idle speed while at the same time not given the PCM what it needs to compensate for the AC.

Your car had a roots blower on it, right? It should take considerably more airflow at idle than a stocker to offset the blower drag at idle. I would guess maybe 12 - 18 g/s as a guess.

Also, you need to figure out why your ignition advance is locked. The first step would be to make sure the TPS is in 'idle' mode, so check the TPS voltage. You may need to close the IAC with the scanner, and manually idle the car down with the throttle body stop screw until you hit minimum airflow/rpm. Then make sure the TPS reads an idle position, and turn it back on in the scanner. Remember, the IACs job is to control airflow from the minimum RPM at idle up til the maximum RPM at idle. The throttle body's stop screw controls airflow up until the minimum RPM/airflow. If you adjust that minimum airflow screw, you've got to make sure the TPS still sees your new position as 'idle'.

Setting the idle timing way down should help with the steadiness and power at idle. The over/under tables should help from there. HPT just recently updated the scanner to include some new idle timing PIDs, so that may be helpful to get the latest beta. That was a result of another thread I was in, where the guy was having idle timing issues (timing 5 degrees too low all the time). Chris @ HPT revised the scanner to help with diagnostics of the issue. The scanner now shows what "mode" the TPS is in, the base idle spark from the idle timing table, and the actual idle spark. Since your timing is so high, I would keep a small eye on the knock sensor retard too, just in case.

Well, the truck had to go. I went in there and removed the excess timing, worked with the follower a bit, made a small correction in VE, increased RAF about 20% and bumped the idle to 875. It idles steady around 850 like that, comes down nice and predictably, doesn't surge, and transitions into a/c nicely. Customer was satisfied. I'm primarily a ford shop, but I enjoy the occasional GM work. I never did get the a/c request figured out, but the increased RAF and follower airflow helped a lot, it runs very well. Heres a WOT video. The sound is terrible, it's dual 3" exhaust, straight through mufflers. It immediately overpowered the mic in the camera.

http://www.flickr.com/photos/mobiled...ns/6065432323/

Final numbers last night, I tossed a bag of ice in the blower for the last pull.
439hp 498 ft/lbs DynoJet (SAE) at 9lbs, 17* timing, 11.5 afr.. Through the 4x4 drivetrain and jeep axles.. It does wheelies in 1st/2nd if you roll into it. Forget turning while in the throttle, it picks up both front tires every time. You can predictably carry the front tires without dumping the clutch or being dramatic with it, lol.. It's so dumb, I'm happy to see it leave. It was cool to drive for 5 minutes, it's just obnoxious.

Interior is 100% stock, a/c-p/s still work, factory column, factory jeep cruise still works, a/c controls, the whole jeep cluster was converted with gm gauge guts and works, has fabbed long tube headers, mcleod twin disc clutch, etc. etc. Jeep ECU is still in there and working, just moved all the engine controls to the camaro ecu/harness

Nice! Sounds like a blast to drive.