Chronicles of idle tuning LS1/big cam

[Rinkrat456]

Hey folks, I'm creating this thread so I have somewhere to go in a few days when I start trying to tame the idle on a friend's LS1/t56 in his Mazda RX7. He hired my services to tune the engine and so far we've got VE and spark tables fairly dialed in. It's got stock 241 heads, stock compression, but ARP head studs, ARP rod bolts and the necessary valve train to wind up to 7000rpm's. The cam is a 236/236, .569/.569 on a 112LSA - and it feels like it too. ALL high end power, but it's a fair-weather only car meant for fun. We'll be working on it all summer so this thread is just a place to go for questions along the way.

I'll be sitting down with the car in a couple of days to log and data collect during a cold start situation. My goal is to really nail down idle perfect. For him, it's been rough trying to keep the car from dieing so that's my main focus. The car likes to die when coming to a rolling stop.

For starters, here's the latest tune file. If you see anything out of obvious wack feel free to correct me. In a few days I hope to spend a lot of time on idle.

[5_Liter_Eater]

Have you done the RussK idle config on it yet?

[The_Bishop]

Anyone have a pointer to where the Russ K idle config is? I've been searching and not getting anywhere... Possibly I've gone blind.

[SmokedOutZ28]

Post # 2

http://www.hptuners.com/forum/showth...ss+idle+config

[The_Bishop]

Great, thanks.

[Rinkrat456]

Did not run the Russ K config before posting, read up on it, learned where to find it, but I'm still not sure what it does. Per the directions from Russ K himself, I opened the config file in the scanner and started recording the cold start.

This is what I got. Not quite sure what to do with this info.

[Rinkrat456]

To double check that you guys could open my attachment, I downloaded what I uploaded and something went amiss. I started scanning before turning the car on and recorded all the way until ~215*F. I saved the file as 522 (yesterday's date) and when re-opening it, the file is basically blank. Unless I'm not seeing the "play" button to review the 10 minute log, I'm not sure what's going on here.

[Rinkrat456]

NVM, figured out my mistake with saving the file. I'll have to do another cold start and report back.

[SmokedOutZ28]

Did not run the Russ K config before posting, read up on it, learned where to find it, but I'm still not sure what it does. Per the directions from Russ K himself, I opened the config file in the scanner and started recording the cold start.

This is what I got. Not quite sure what to do with this info.

I know you said you got it but to be sure... What I found in searches was you take the #1 histogram chart and plug those numbers into your RAF table (Base running Airflow) and your all set.

[Rinkrat456]

I'll have to try that out tomorrow, thanks for the tip. So, from what I understand about the Russ K config is that it monitors whatever is "off" about the cold start up until operating temp and then pasting the "fixes" into the RAF table corrects for whatever is wrong?


I have three main focuses right now for the idle.

1st and foremost, my commanded 1000-950rpm target idle speed doesn't actually happen until the engine is warm. On a cold start, per the tune, engine rpm should start high and gradually slow down as engine temp rises (until the opposite happens and starts overheating of course). What the 5/22 file would have shown is the cold start idle at 450-500rpms until at least 115*F, where then the car slowly increases idle as it becomes more stable. That part is confusing the hell out of me.

2nd issue concerns drive-ability. After a good episode of tuning, with the engine nice and warmed up, sometimes the engine will die when coming to a stop with the clutch pressed in or the M6 in neutral. This drop in RPM (950 to 250-350) happens every time, and the engine dies probably once every five occurrences.

Lastly, I can see during the log that spark is all over the place during a cold start until engine temps come up above around 150*F. The engine seems to stall, then over correct, then stall, then over correct...the spark looks like a sine wave from Calculus class.

Again, this is my buddy's car and I want to do a good job for him so to avoid having to connect multiple times I try to do as much fore-thought and pre-planning in the tune as possible.




EDIT: Here's the most recent tune in case anyone's wondering.

[Ben Charles]

Little off subject, but what program is the russk idle file written in? Looks like some weird script on my computer?

[Rinkrat456]

Here's this morning's cold start log file. I removed the traditional 40% fuel at 400rpms, 20% at 800rpms and 10% at 1200rpms from the VE table. The car did not like that, wouldn't fire no matter what. Went back and added back half the fuel to 20/10/5% reduction, still wouldn't fire, so I added 3lb/min to the base running airflow to get it to at least start.

Again, the car for some reason starts idling low and builds up to target idle so I'm confused why it does that instead of the opposite (starting high and gradually lowering to target idle at running temp). Any helpers on that?

Also, when coming to a rolling idle (or pressing in the clutch at speed) the car still wants to idle low around 550-650, sometimes stalling to 300 or less.

I made the changes called for from RussK's idle config and pasted them to the RAF table. Seems like a lot, check out that table in the tune and let me know what you think. Seems like a far way since stock.

[69lt1bird]

Something on your end must be wrong. I looked at the scan and it shows this.

Labels    -40    -18.4    3.2    24.8    46.4    68    89.6    111.2    132.8    154.4    176    197.6    219.2    240.8    262.4    284
     4.50                    4.60    5.30    5.30    5.30    5.30    5.30    4.00    3.80

IAC is frozen at 310 too.

[Rinkrat456]

Could you elaborate on what's wrong? I saw that data too.

[Rinkrat456]

Bump for today. I'm hoping to finish this car soon, and we're meeting up on Sunday to do some more logging.

[Rinkrat456]

Still working on this car. It's become a "tune as we have time" project, as it's not his DD.

Still have a few issues and not sure which tables address each issue.

1) Clutch in rolling to a stop, the idle drops to almost nothing. By nothing I mean 200-250rpms and the engine shakes like crazy. Eventually it comes back up to half of what commanded idle is (900-950) and it never comes back fully.

2) Idle to 1600rpms the engine is running pig rich, but as I take fuel away it becomes more and more difficult to start.

3) 9 times out of 10 we need to step on the throttle to get the engine to fire. Somewhat related to issue #2.

Any help?

[mecanicman]

Your IAC is maxed out at 310 all the time, this is causing a large portion of your problems. You do not have enough bypass air. Open the throttle blade up. Wait until its fully warmed up. Add tps voltage to the scanner and start opening the throttle blade up with the set screw slowly as the IAC position will change slowly. Adjust it so that it is 70-80 at hot idle. You want to keep the tps voltage under .76 v I believe, if it climbs over before you get your iac position correct try loosening the tps and rotating it back. You may have to drill a hole in throttle blade if this does not work, but that is last resort. After you have all this adjusted, turn key off, unplug IAC and TPS, turn key forward for 10 seconds, then shut off and reconnect.

Then rerun russk idle config and you should be in a lot better shape.

[Rinkrat456]

Thanks for the advice. When we reconnect I'll try what you mentioned. I'm glad that you spoke up when you did because I've been reading about adjusting the set screw all morning.

[mecanicman]

Also, your ltit are way out of wack because of this. Once you have completed the tps/iac adjustment disconnect the battery for awhile to clear.

[Rinkrat456]

I'll be spending quite a few hours with this car Thursday and Friday morning. Unfortunately right now the coldest MN gets is in the low 50's so I'll have to do a Russk idle config Friday morning. I'm still sketchy on how to use that feature, I wish there was a pictorial how-to for us newbs.

Edit: Forgot to ask, I keep reading how important the Primary VE table plays in idle quality so I'm wondering how the best way to tune for those 400-1600rpm cells when the car really doesn't go down there often? It's got a T56 manual 6 speed with 4.10's and 25" tires so it's quick to move up the RPM band. I'd basically have to tour side streets in 6th gear below 30mph to hit those kind of cells. Any tips on making this easier?