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Unread 05-09-2013, 03:21 PM   #11
Rich Z
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Arghh... I took the car out for a drive today with test tune #25 loaded in. Still had the problem with high idle speeds, regardless of the changes I have made. Pulled into the local Walmart parking lot and made a few more changes in a new tune, but they didn't change anything. Soooo, I went all the way back to tune #12 and loaded that one in. Idles fine now coming to a stop. But I'm sure I'm going to have that cold start stalling issue back, and I felt the lope back a bit at slow speeds. But I guess I'm going to have to just make one change at a time to tackle each problem. Going to be damned tedious, but the way I've been doing it is obviously producing unintended consequences that are then harder to figure out and fix.

But at least I can look over the tunes I've done since #12 and have a better idea of what I need to change that MIGHT have the effect I want.
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Unread 05-12-2013, 01:53 AM   #12
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Got some better results today by modifying table B4307 (Desired Airflow). I copied the table from a much earlier tune into my current working tune and reducing the values in the ECT (engine coolant temps) regions of 90 degrees and above by 10 percent. I also increased the airflow 10 percent in the lower ECT cells. Idle RPMs dropped down to a much better 925 to 950 rpm when I would take the transmission out of gear to coast to a dead stop.

I made some of these changes while out on a drive to log data, so I need to do a cold start up in the morning to see how everything reacts to a gas pedal blip. I made other changes to this same table last night, and noticed that the recovery time after blipping the gas pedal was greatly reduced. Went from 18 seconds to just 2 seconds. So that told me that I am likely on the right trail.

My guess is that the changes I had made to this table a while back were allowing too much air at idle, and when I would blip the gas pedal, the airflow and timing were fighting each other trying to keep the engine from stalling. Another obvious sign was that the RPMs were revving too high coming to a dead stop, which apparently was being caused by the throttle blade being open too much because of the commands from that B4307 table.

Just guessing, but I'll know more with more trial and error testing.
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Unread 05-16-2013, 12:12 AM   #13
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Haven't done one of these boring videos of me taking the car for a test drive for a while. Just fiddling with the tuning to iron out some minor issues. Startup is much improved. Unfortunately I left the wideband plugged in over night, so it started up kind of sluggish. But at least it didn't have to crank over a bunch of times before starting up. Still getting a little bit of instability after blipping the gas pedal, but it's gradually getting better. And the coasting to a stop when out of gear is much improved too, as the RPMs drop down to a much lower level than before.

Cranked it out in second gear a little bit when I got out onto the highway. Only hit 52 percent throttle in second gear and it felt like the rear tires broke loose. One of these days I've really got to try 100 percent throttle to see what happens.

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Unread 05-16-2013, 11:15 AM   #14
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Quote:
Originally Posted by Rich Z View Post
Cranked it out in second gear a little bit when I got out onto the highway. Only hit 52 percent throttle in second gear and it felt like the rear tires broke loose. One of these days I've really got to try 100 percent throttle to see what happens.
SWEET! It's going to be very interesting seeing the trees going past the
windshield when that beast goes sideways.... I'm looking forward to seeing THAT
video! Do you have any intentions on putting it on a dyno when you get the tune
where you want it to be?
Andy
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Unread 05-16-2013, 11:49 AM   #15
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Quote:
Originally Posted by navy2kcoupe View Post
SWEET! It's going to be very interesting seeing the trees going past the
windshield when that beast goes sideways.... I'm looking forward to seeing THAT
video! Do you have any intentions on putting it on a dyno when you get the tune
where you want it to be?
Andy
I wonder if there are some tweaks I could do to the suspension to keep the rear end from wanting to swing around to the passenger side when the tires lose grip? The suspension is real stiff, as the car doesn't even budge when I get in and out of it. I don't know if that stiffness makes things better or worse for that problem. Stickier tires would help prevent them from breaking loose of the pavement so quickly, but that introduces additional stresses on the drivetrain. I guess I'd much rather have the rear tires be the "fuse" in the drivetrain instead of the driveshaft popping under load.

As for the dyno thing, Mike Carnahan said I can bring the car up to him whenever I'm ready (and his schedule permits) and he'll put it on the dyno for me and fine tune the WOT tuning. I'm just not ready to trust the car for that long of a trip quite yet, though. If I get more familiar with creating MAPs in EFILive, I might be able to get some of that done myself. But when boost kicks in, I don't see how I'll be able to hold it there for very long to get some good data collection for the MAP cells.
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Unread 05-16-2013, 03:04 PM   #16
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I must say you exercise restraint better than I could Rich.....
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