Anyone want to look at my tune? Cam surge...

[rosey]

So I've been at this for a couple of days now and I can't seem to crack it. As of now the car idles pretty decently, and seems to drive alright for the most part, but it turns into a bucking bronco at low throttle/no throttle in the idle-2000rpm area. Once the RPMs get a little higher, or if I give it a little gas, its smooths right out, but cruising down the street is hardly possible under 2000 rpm. Starting from a stop isn't bad, but once the clutch is fully engaged <20% throttle and under 2000rpm is just bucks a little, and then gets worse an worse until I have to either give it gas or put the clutch in.

AFR is in the mid/low 14s, I've tried a little richer and it didn't seem to matter. Spark advance in in the mid 20s to low 30s, and I've gotten it to stay pretty steady when I'm getting the surging, I've tried adding a little timing, then more timing, until I started to get to the knock threshold, and it hardly even makes a difference. I've done the RAFIG process a couple of times, tried adding a bit to the desired airflow, no change. Right now the desired airflow is about +0.5 from what I've gotten logging the pid. I've tried playing with the throttle cracker/follower, but I'm having trouble figuring out what to change, but so far nothing I've done has done much to help the surging. I've also drilled a bigger hole in the throttle body, and the IAC counts are around 50 at a warm/no load idle.

Car is 3000lbs, with a 4.1 final drive, 232/240 112+4 cam, stock heads, bolt-ons motor. Running open loop speed density until I can get the tune mostly worked out.

I'm guessing the car just wants more air in that area, but I really don't know how or where to give it...nothing I've tried so far has made a bit of difference

Thanks

[TAQuickness]

Welcome to the forum Rosey. SSpdDmon has some good info here that may help you out.

Be patien with the idle transition tuning. It can be very frustrating as you're trying to find the perfect balance of spark, fuel, and air (throttle cracker & follower) to smooth things out.

[rosey]

Thanks, I've already read over that thread and tried most of the things mentioned - some helped a bit with my idle, but surging while driving is still the same. Doesn't seem to be a problem in the transitions as much as just light throttle/decel at low rpms. I'll keep at it, reading and trying things, but I'm running out of ideas.

[The Alchemist]

Just been doing one myself Rosey....check out my posts from 2 weeks ago. Bascically you have to alter the T/C and T/F settings to add airflow at light throttle openings. I found that about 11 to 11.5g/s of FINAL AIRFLOW kept the car going with no surging. Takes a while to set up though but I got it right > Thanks to SSpdDmon.

Mike

[SSpdDmon]

Try this one. You can use the compare feature with the tune you uploaded to see what I changed. Don't be concerned about the spark looking low at part throttle. Just make sure there's no knock at WOT and your fueling is in line (12.8:1 or so). If there is knock, you may have to back it down a little. Otherwise, keep it and let 'er rip. It's a good idea to do the RAFIG process once more after uploading this tune.

Jeff

BTW - This looks like a pre-01 car converted to and 02 OS. What year was it?

So I've been at this for a couple of days now and I can't seem to crack it. As of now the car idles pretty decently, and seems to drive alright for the most part, but it turns into a bucking bronco at low throttle/no throttle in the idle-2000rpm area. Once the RPMs get a little higher, or if I give it a little gas, its smooths right out, but cruising down the street is hardly possible under 2000 rpm. Starting from a stop isn't bad, but once the clutch is fully engaged <20% throttle and under 2000rpm is just bucks a little, and then gets worse an worse until I have to either give it gas or put the clutch in.

AFR is in the mid/low 14s, I've tried a little richer and it didn't seem to matter. Spark advance in in the mid 20s to low 30s, and I've gotten it to stay pretty steady when I'm getting the surging, I've tried adding a little timing, then more timing, until I started to get to the knock threshold, and it hardly even makes a difference. I've done the RAFIG process a couple of times, tried adding a bit to the desired airflow, no change. Right now the desired airflow is about +0.5 from what I've gotten logging the pid. I've tried playing with the throttle cracker/follower, but I'm having trouble figuring out what to change, but so far nothing I've done has done much to help the surging. I've also drilled a bigger hole in the throttle body, and the IAC counts are around 50 at a warm/no load idle.

Car is 3000lbs, with a 4.1 final drive, 232/240 112+4 cam, stock heads, bolt-ons motor. Running open loop speed density until I can get the tune mostly worked out.

I'm guessing the car just wants more air in that area, but I really don't know how or where to give it...nothing I've tried so far has made a bit of difference

Thanks

[SSpdDmon]

For those without time to examine the changes above...

Adding in a little air to the follower is also a positive way to cure light throttle surging if the spark and AFR is in line. You can tell if spark is a culprit because it'll be jumping around quite a bit. 1* of timing swing at low load, low rpm can be a real PITA. Anyway, I used the stock Throttle Follower Airflow Table and increase the Throttle Follower Multiplier. Keep in mind, if you increase the amount of follower airflow, you will have to play with the decay rates too. More air decaying out at the old rate will cause the idle to hang up until it all decays out. So, you need to increase the rates.

[SOMhaveit]

SSpdDmon. Would you email that file to me. I don't have whater you guys use to post php files so I can't open it off the post.

[SSpdDmon]

SSpdDmon. Would you email that file to me. I don't have whater you guys use to post php files so I can't open it off the post.

You should be able to download it. If it wants to save it as a .php, you have to override it in a sense. Change the file type to all files and rename it to sspddmon.tun before saving it. It should work still. The file should be 475K when you download it.

[SOMhaveit]

Thanks. That worked.

[rosey]

Well, I tried SSpdDmon's map and it helped a bit, the surging still isn't gone, but its a lot better than it was. I didn't do a RAFIG again yet, just took it around the block. It is a 00 tune sent over to a 02 OS. It looks like you put the spark tables back to stock(or close to it) any main reason for that?

I'll play with it a bit more tonight once the roads are more clear, it at least feels like I'm heading in the right direction now, thanks a bunch!