cruising gets jerkier as PCM learns
10-08-2014, 02:30 AM
#1
cruising gets jerkier as PCM learns I'm starting to get into tuning my own car. Just did 24x on my LT1, bought hptuners, bought the Greg Banish books that are currently in transit. I want to ask if there is an easy answer for what's going on though. The tune I'm running came from hpt's repository for an Impala SS 396 that also did 24x. I'm running everything from this guy except I changed the injector sizes and some other small things unrelated to my problem.
What happens is whenever I drive the car after either disconnecting the battery long enough to reset the PCM or reset the fuel trims with hpt, it runs so smooth and perfect for a few minutes. Then as the PCM begins to learn and adjust, the car will jerk/surge while cruising. It's not too violent or anything, just irritating for a DD. Any ideas what's going on?
What happens is whenever I drive the car after either disconnecting the battery long enough to reset the PCM or reset the fuel trims with hpt, it runs so smooth and perfect for a few minutes. Then as the PCM begins to learn and adjust, the car will jerk/surge while cruising. It's not too violent or anything, just irritating for a DD. Any ideas what's going on?
10-16-2014, 03:24 AM
#3
They are off. I'm running a sort of Frankentune right now that's a combo of a file I got from an hptuners user, a file from hpt's repository, and pcmforless. I was running the hpt user's file for a bit and was having the same jerky problem at cruise. STFT's were between 0 and -10 at all times. He also had me running MAF only. I've been doing some trial and error experimenting with the injectors lately, I think he had me running rich. Now my STFT's are between 0 and +10 at all times on bank 1 and -4 to +4 on bank 2 while cruising. Still jerky anywhere below 60mph though.
Last edited by AdsoYo; 10-16-2014 at 05:08 AM.
10-17-2014, 05:19 AM
#4
I dialed in my VE table with the help of this guide: http://gmtune.ru/hptuners-tuning-guide. LTFT's are +/-5 at all times which is pretty exciting. It's nice to see some form of progress. The jerkiness was still there so I made some changes to the injectors. With the help of calculators around the internet I adjusted flow rate vs. kpa, offset vs. volts vs. vac, and short pulse adder. After all that the jerkiness was still there, it was just... different. At this point I think the solution lies in the injector calibrations.
Does anyone have or know where to find info for Ford 30# red tops (the fat ones/ older ones). I would love to be able to compare my numbers to someone else.
This has easily been the most time consuming part of learning to tune. Through all my searching it seems like there was a surge of diy tuner activity about 7-10 years ago and then it all disappeared. There's so many dead links and unfinished threads from 2004-2007!
So if anyone can help me with these injector tables I could sure use it.
Does anyone have or know where to find info for Ford 30# red tops (the fat ones/ older ones). I would love to be able to compare my numbers to someone else.
This has easily been the most time consuming part of learning to tune. Through all my searching it seems like there was a surge of diy tuner activity about 7-10 years ago and then it all disappeared. There's so many dead links and unfinished threads from 2004-2007!
So if anyone can help me with these injector tables I could sure use it.
10-28-2014, 02:19 AM
#5
Made some more progress again these last few days. Read this marathon thread about EOIT and used the Excel worksheets to figure mine out: http://www.hptuners.com/forum/showth...ereencing-what My "actual normal" values for EVC, IVO, ISP EVC, ISP IVO are 6.48, 5.88, 6.29, 5.69. I've tried multiple values from 4.54 up to 6.55 and 6.29 seems to feel the best. The bucking is still there but ever so slight. It made a noticeable difference in torque and throttle response which is nice. This probably made the most noticeable difference out of everything. Would still like to have bucking gone 100%. Can anyone tell me what the ISP stands for? Can't seem to find it's meaning anywhere.
To recap, in trying to smooth out cruising I've worked on dialing in the VE table so all LTFT's are +/-5, then re-enabled the MAF and dialed that in to keep LTFT's at +/-5. Then adjusted spark to where I was seeing the lowest MAP and feeling the least amount of bucking. Now I've adjusted EOIT to finish with a closed exhaust valve (I think) instead of spraying at who-knows-when in the cycle, most likely sending a lot of fuel out the tail pipe. Adjusting EOIT didn't seem to mess with LTFT's any either.
What I'm still experimenting with is throttle follower and cracker. In my logs, throttle follower is pretty active and I can't tell yet if higher or lower values feel better. Throttle cracker I haven't messed with and it's activity pattern is a mystery to me right now. It only activates at very particular times it seems, even though the description makes it sound like it should always be on and adjusting according to speed and rpm.
I'm still hoping for some answers with my injector settings, too. I've found 3 excel calculators that all throw out different numbers and different-shaped slopes. Does anyone know what vehicles the fat red tops came stock on? There was a lone post out in the internet wastelands saying they came on Ford's turbo 2.3 but that has been a dead end so far.
To recap, in trying to smooth out cruising I've worked on dialing in the VE table so all LTFT's are +/-5, then re-enabled the MAF and dialed that in to keep LTFT's at +/-5. Then adjusted spark to where I was seeing the lowest MAP and feeling the least amount of bucking. Now I've adjusted EOIT to finish with a closed exhaust valve (I think) instead of spraying at who-knows-when in the cycle, most likely sending a lot of fuel out the tail pipe. Adjusting EOIT didn't seem to mess with LTFT's any either.
What I'm still experimenting with is throttle follower and cracker. In my logs, throttle follower is pretty active and I can't tell yet if higher or lower values feel better. Throttle cracker I haven't messed with and it's activity pattern is a mystery to me right now. It only activates at very particular times it seems, even though the description makes it sound like it should always be on and adjusting according to speed and rpm.
I'm still hoping for some answers with my injector settings, too. I've found 3 excel calculators that all throw out different numbers and different-shaped slopes. Does anyone know what vehicles the fat red tops came stock on? There was a lone post out in the internet wastelands saying they came on Ford's turbo 2.3 but that has been a dead end so far.
11-01-2014, 09:02 PM
#6
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
I found that when I drove the mixture lean (by O2 switchpoints)
the cruise started to buck a little. I backed off some and it quit.
Just keep playing with mixture and timing (although getting rid of
bad data comes first, unless you like wasted effort).
the cruise started to buck a little. I backed off some and it quit.
Just keep playing with mixture and timing (although getting rid of
bad data comes first, unless you like wasted effort).
11-02-2014, 05:14 PM
#7
Thank you so much for that tip jimmyblue! Made a HUGE difference. I set the switch point down to 451 in the airflow modes where I cruise (10-12) and the bucking is almost non-existent. I'll keep playing with it to see if I can eliminate it completely but even if I had to drive it in its current condition forever, I'd be satisfied.
Last edited by AdsoYo; 11-02-2014 at 05:23 PM.