I bracket race this car and every so often I get strange issues pop up like this one yesterday. For some reason just after launch, it goes to torque source 4 for a split second, closes the throttle blade, then recovers. It's obviously not hitting a rev limiter. Can anyone suggest what to adjust in the tune to keep this from happening? Thanks.
FYI, car has a transbrake and a 2-step module installed.
torquesource4.jpg
Not sure its the exact same issue but my car does something very similar but i've never been logging a pass when it occurs. It feels like a stumble but recovers instantly.
I currently tune on SCT but may make the switch soon....
I'm actually experiencing the same thing. 2013 GT/auto. Mine manifests itself exactly the same you describe (torque source 4 logged) while closing throttle to 28deg briefly. Instant hiccup then recovers. Except mine is doing it as I try to exceed 7500 rpm, regardless of gear. So long as I don't try and exceed 7500, it never occurs. Try to raise the shift schedule mph's and/or WOT gear limits to go beyond 7500, I get this same type of uncommanded brief throttle close, repeatedly. Not sure where else to look as all the parameters I have access to should allow it to rev higher. Interested what others may suggest.
Torque source 4 is "Engine Speed Limiting"
http://www.hptuners.com/forum/showth...-Torque-Source
Yep... I think my issue and the OP's are different, even though the symptom is the same. My limits are all raised to 7900 everywhere, so it is something else.Originally Posted by AKDMB
Looks like you guys have a "patch" you can apply to GT's that experience a hard rev limit at 7600-7700. Pretty sure that's where I'm at although I'm not aware of what "the other sides" fix is for that....grrrrr.......
OP's issue looks load/torque table related possibly?
Thanks for the replies. I looked closer at the datalog and it appears that the car spun the tires a little just before it went to source 4. Could this be some hidden traction control feature? Before each run I hold the traction control button down for 10 sec until it says "advance trac off" on the display.
Any thoughts?
^ I would disable all that in the tune completely. I've seen funny stuff happen just using the button.
Actually take a look at my thread about (OL) Inj Cut I just posted. We are seeing the exact same thing. My torque source is RPM limit when I see it too.
Not sure if related, but I have had vehicles re-enable the traction control even after to complete disabling of advance track via holding the TCS button down. It seems to happen most on a violent wheel spin, or on dyno.... That said if torque source 4 is "engine speed limiting" is it possible there is a table for modified rev limit based on engine acceleration we just don't have access to? I know GM uses a table such as this, to limit engine speed to below the actual hard rev limit if the PCM sees engine RPM increasing at a faster rate than the table outlines. My 2013 Regal GS 6spd, E39a processor required this table to be adjusted
A hidden limiter for rate of acceleration would explain what I've seen. Hopefully someone (Eric) can confirm/deny.
I see these parameters listed here which are not in our copperhead definitions. Could one of these be the limit?
http://www.hptuners.com/help/vcm_edi...uel_cutoff.htm
RPM Limit vs. Output shaft RPM: RPM Limit in relation to output shaft RPM.
For this one, I see the manual definition but I don't see the auto definition:
RPM Limit Neutral Cutoff Auto: Above this RPM, injector fuel cut will occur for auto transmissions in neutral.
Also it's not just when spinning. I'll get this RPM limit right after I launch (around 4mph) sometimes even when I hook hard. I know others see it in these cars too. I've had people come up to me at the track who have the same year Mustang and ask if my car sometimes takes a dive on a launch. We're all seeing the same thing I'm sure. Maybe changing the Fuel Cut Torque Ratio to 1 for RPM limit will stop it. I'll give it a test this coming weekend.
I tried setting all 1's to the fuel cut torque ratio including DD and RPM Limit this weekend and it had no affect. Still getting the rpm limit when coming out of burnouts and every now and then on a launch.
I'm now 90% sure this must be some sort of a neutral or launch RPM limit in fuel->cutoff->RPM Limits that maybe isn't available in the software currently. I've attached another log. Look at the log on my launch. You'll see where I'm on the converter at 2,000 RPM's and then I launch. The RPM limit hits at right around 3500 RPM's and my speed is right at around 3MPH. That seems to be the behavior I see each time I get this random RPM limit.
I see in the software "neural exit speed" and "neutral cutoff". Both of the descriptions say they are for manual transmissions. I tried raising both with no effect.
Here though I see auto PID's listed:
http://www.hptuners.com/help/vcm_edi...uel_cutoff.htm
RPM Limit Neutral Cutoff Auto
Any thoughts by anybody? Eric, do you have any thoughts on this?
I raced this weekend making 7 passes. Never had the issue. Car did spin a few times out of the hole, but never went to torque source 4. It's annoying as it seems so random on my car.
I agree, it's very annoying. I have a feeling these cars are on the edge wherever that RPM limit is coming from. Most of the time you won't spin the RPM's up fast enough to hit it, but it's still too often.
This is what I think is happening when you spin which is why it shows up there more often. When you spin right after launch, the RPM will spike up, as the tire gains traction, the MPH will drop dramatically to the actual speed the car is going, but the RPM might still be high. Based on what I'm seeing, being above about 3500 RPM's and at or below 3MPH seems to trigger this fuel cut.
I did some experimentation yesterday. The neutral cutoff does work on my Auto with my car in park and neutral. So now I'm not so sure it's related to the neutral cutoff or neutral exit speed.
Yesterday at the track the exact same pattern. Every burnout I come out of when the tires "hook" I get this RPM Limit. I also got it on one launch out of about 10 runs. So the same pattern. Tires hook on burnout, RPM"s/MPH are dropping as the tires hook and at some point below about 3600 RPMs I get this RPM limit.
On a random launch, at right around 3500 RPM's and very early in the acceleration (around 3MPH) I will randomly get this RPM Limit. Where the heck is this RPM Limit coming from? Maybe something with driveshaft speed vs RPM I'm considering now? It's very frustrating for sure.
I'm going to email Eric to see if he has any ideas on this too.
I need to do something about this phantom RPM limit at about 3500 RPM's. Happened to me twice again tonight at the track and cost me another win and almost cost me a second one but luckily my opponent missed the tree badly. I've tried a bunch of different things to stop this RPM limit. But nothing works. It's the same patterns. I get it immediately after launching at about 3500 RPM's.
Until this can be figured out, I think I might try band aiding this issue with the RPM Limit randomly occurring by setting the Fuel Cyl Cutoff to Stoich and my WOT Lambda in the appropriate cells where I see this limit occurring.
Having the Exact same issue. I haven't noticed it in the burn out, but right on the hit. I'm a bit more aggressive with the rpm, my 2-step is at 3500. The torque source 4 happens at 4000 rpm, and 3.5 MPH. Happens randomly, can't seem to find a pattern to make it repeat. Need to get this fixed, or find some way to cheat it. I might try turning the 2-step down and launching off line-lock to see if it has any affect.
Unfortunately I don't think lowering the launch RPM will help. I only launch at about 1900 RPM's on a 3600 stall and I still have the problem. We're definitely all seeing the exact same thing on our launches though.
My idea of defaulting the Fuel Cyl Cutoff to stoich and WOT lambda didn't work unfortunately. I also tried setting RPM Limit ETC Hyst to 0 hoping then that the RPM wouldn't drop at all but that didn't work either. I still see the RPM limit (torque source 4) at about 3500 RPM's, the fuel injector cut happens and the RPM drops about 200-300 before the fuel injector cut stops and the car starts accelerating again.
Eric help!!We know you can figure out this phantom RPM limit between 3500-4000 RPM's since you were able to reverse engineer the high side RPM limit over 8,000 RPM's. There must be some RPM limit when the car accelerates faster than the ECU thinks it should. Or the RPM is higher relative to MPH than the ECU thinks it should be.
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