gothic_sera

I'm trying to get my motor running nicely and I'm struggling to get a nice stable idle.

Approximately what idle spark advance should I be running with my cam?

236/242, .621/.612 lift, 112LSA

CR is about 10.8 with forged pistons and heavily worked over 317 heads.

Also, what are people finding good target idle RPM's and AFRs with similar cams?

Sera

JakeFusion

iTrader: (7)

Disable the MAF - see the HPT help site for how to disable MAF to tune in SD.

Once done, take your VE table... multiply the 400 by .6, the 800 by .8, and the 1200 column by .9. Then select all out to 2000 and smooth it. Change your idle to 1100 in the colder cells stepping down to 950 at 150+ degrees. Change your timing to about 25 degrees in the idle table. Save that file and upload it.

Check your idle. With HPT, bi-directional controls, lean it out from 14.7 to 15.2 or so and keep going til the idle stabalizes and it starts to chop. If that number is 15.8 in the bi-directional controls, divide it into 14.7... 14.7/15.8 is .93. Multiply your 800 and 1200 columns by that number (.93), save and reflash. You should be idling around 15.5:1 at that point and the cam should like that. You don't even need your wideband. Watch your narrowbands. When they are under 100mv... down to 30-50mv, you're lean enough. The sound also gives it away. You can also add timing... 26-28 may be ideal. Add timing until the kPa readings drop to 65-70 with that cam. Then back off a degree or two. That'll give you the "smoothest" and strongest idle.

Works on every big cam I've tuned. Takes literally about 2 mins to dial in the idle enough that you can start tuning... but first wait until the next day.

Next day after the car has cooled off, restart it and put it in gear but don't drive it or touch the gas (also disable the fans in bi-directional controls - you don't want airflow adders). In fact, go ahead and zero out all your adaptive airflow tables as well. Use the stock imperial HPT cfg. Let it warm all the way up. Take the base airflow numbers in the histogram and update the Base Running Airflow table in idle. Reflash (putting the stock adaptive airflow numbers back in). Then check and see if your mv for the O2s changed significantly since you changed the airflow model. You may need to mess with the bi-directional controls again, but it will be close. Now you can go for a drive and it'll stay alive and shouldn't die or stall too much.

If the throttle response is a little less than ideal, add 2% fuel to the 1200 column. Then you can start really tuning the VE table. Just drive it around with the wideband or you can use the narrowbands. Don't get into PE mode. Just drive around keeping it near 14.7:1. Update. Drive. Update. Do that 4-5 times and the VE will be dialed in pretty close below 4k RPM. You'll be able to drive to tuner and get WOT dialed in if you plan to do that. MAF can be dialed in on the street as well using the same method.

gothic_sera

Thanks very much, very useful, even though I am running Megasquirt.

I've got it idling much better, found that I had a dodgy idle valve too which wasn't helping things

I adjusted the injection timing as well as setting the idle spark advance to 20deg. It idles happily now around 950rpm. AFR about 14.