Surging when Coasting
I've had a good look over your tune now and WOW... you really are putting a lot of air into your engine with your throttle cracker and follower. With that much airflow, your decel is more like an off throttle coasting. I can see why you need that much spark in your decel.
We need to figure out what's causing you to need so much airflow. Your VE table doesn't look quite right to me... maybe a symptom of bad injector data, but I don't know if that's enough to cause this.
See if you can get a log for me.
We need to figure out what's causing you to need so much airflow. Your VE table doesn't look quite right to me... maybe a symptom of bad injector data, but I don't know if that's enough to cause this.
See if you can get a log for me.
Thread Starter
Joined: Aug 2004
Posts: 11,258
Likes: 146
From: Pace, FL
Just as an update. Here is the latest tune file and log. Lorentz with LSX Power Tuning has been helping. Still a little bit of a bounce off 1000 RPM when coming to a stop (I wonder if this is more a symptom of the converter than the motor?)... and still a bit of surge with foot off the gas (probably going to live with it until I put 3.70s or 3.89s in the car). But everything is much cleaner now.
Plan to do some WOT tweaking and then hit the 1/8 mile in the next couple of weeks.
Plan to do some WOT tweaking and then hit the 1/8 mile in the next couple of weeks.
Thread Starter
Joined: Aug 2004
Posts: 11,258
Likes: 146
From: Pace, FL
So I have a question on where the PCM pulls the timing based on my logging.
I've been messing with the timing. I added timing in the 1400 cell from 22 to 26 to get it to smooth out low throttle bucking in the .20 to .32 airmass cells. It helped.
However, for decel, I don't know which table it's pulling from. I've adjusted both the idle spark advance tables below .20 and the main spark tables below .20, but it doesn't always seem to pull from main spark. When I let off the gas, it seems like it pulls from the idle spark table, even above the idle spark routine cutoff mph.
Is it taking a mix of them? I put main spark at 26 in the lower airmass cells and put idle at 22 across the board... and low and behold, it's 22 degrees on decel. Is it supposed to pull from the idle table? Or a mix?
The car seems to like 22 degrees off-throttle. I got a noticeable reduction in the bucking. still some cam surge, but damn, I could so live with it like that.
One final thing - in CL at least, it still wants to bounce off idle returning to a stop. Not much mind you. I zero'd out the 400 cell of the cracker table. Still is a bit wobbly going back to idle. In OL it doesn't seem to happen as pronounced. Any ideas?
Btw, thanks to statesman for giving me the idea to lower the decel timing below spark timing (though I have that question on where it's pulling the timing) and to zero out the cracker 400 rpm column.
I've been messing with the timing. I added timing in the 1400 cell from 22 to 26 to get it to smooth out low throttle bucking in the .20 to .32 airmass cells. It helped.
However, for decel, I don't know which table it's pulling from. I've adjusted both the idle spark advance tables below .20 and the main spark tables below .20, but it doesn't always seem to pull from main spark. When I let off the gas, it seems like it pulls from the idle spark table, even above the idle spark routine cutoff mph.
Is it taking a mix of them? I put main spark at 26 in the lower airmass cells and put idle at 22 across the board... and low and behold, it's 22 degrees on decel. Is it supposed to pull from the idle table? Or a mix?
The car seems to like 22 degrees off-throttle. I got a noticeable reduction in the bucking. still some cam surge, but damn, I could so live with it like that.
One final thing - in CL at least, it still wants to bounce off idle returning to a stop. Not much mind you. I zero'd out the 400 cell of the cracker table. Still is a bit wobbly going back to idle. In OL it doesn't seem to happen as pronounced. Any ideas?
Btw, thanks to statesman for giving me the idea to lower the decel timing below spark timing (though I have that question on where it's pulling the timing) and to zero out the cracker 400 rpm column.
Thread Starter
Joined: Aug 2004
Posts: 11,258
Likes: 146
From: Pace, FL
I messed with it again on Saturday. Played with A/F and timing... and too much timing (34 degrees at 1400-1600 rpm) had me cruise controlling. So I brought it back down to a more manageable number ~ 28. From there, what made the biggest difference was airflow. I took out more from the cracker and rolling idle airflow. That allowed the car to return to idle more smoothly. I also cut my adaptive idle down to 1/4 the original values. If it drops down to idle too quickly, adding 15 degrees of timing will make it bounce. 4 degrees is plenty.
And finally, I took out airflow from the base airflow. I had run RAF, but it was still too much airflow. I had around 5.1g/sec... took it down to 4.8g/sec and that helped in the operating temp range. That also allowed the IAC counts to lower down a little bit. The key there was the A/C. When I turned the A/C on, I was adding significant airflow to the model. So I logged A/C airflow with Cracker and Throttle plus total airflow. Overall, the drivability got worse with A/C on, so I started taking out airflow and that helped a lot.
The point is, airflow and timing changes affect one another. So it takes time to just try one and see what happens. It also affects A/F. Now that I got the timing pretty well set, the airflow model came together and helped. A/F changed some, but it was only be 1-2%, so I'm okay with that as CL can compensate for that. Also, surprisingly, the bank-to-bank differences were less than 5% which was better than it was before. So getting it all aligned, made everything work better.
And finally, I took out airflow from the base airflow. I had run RAF, but it was still too much airflow. I had around 5.1g/sec... took it down to 4.8g/sec and that helped in the operating temp range. That also allowed the IAC counts to lower down a little bit. The key there was the A/C. When I turned the A/C on, I was adding significant airflow to the model. So I logged A/C airflow with Cracker and Throttle plus total airflow. Overall, the drivability got worse with A/C on, so I started taking out airflow and that helped a lot.
The point is, airflow and timing changes affect one another. So it takes time to just try one and see what happens. It also affects A/F. Now that I got the timing pretty well set, the airflow model came together and helped. A/F changed some, but it was only be 1-2%, so I'm okay with that as CL can compensate for that. Also, surprisingly, the bank-to-bank differences were less than 5% which was better than it was before. So getting it all aligned, made everything work better.
Last edited by JakeFusion; Mar 28, 2016 at 11:00 AM.
