LT1 tune advice - dfco
Thread Starter
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Joined: Sep 2009
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From: st louis, mo area
LT1 tune advice - dfco I'm trying to get my dfco tuned correctly. My tune had a lot of delcel popping and backfiring that I've gotten rid of by playing around with dfco. Now I'm trying to get it to operate smoothly.
Problem 1: When coming to a stop with the m6 in gear and dfco active, when I depress the clutch the engine will idle down to 500-600 rpm for about 2 seconds, then go to the proper commanded idle. If dfco is active, it doesn't matter what rpm or speed I depress the clutch at, it will always idle down to 500-600 rpm. Commanded idle is 975, so when it idles that low, it almost stalls. On the other hand, if I want to come to a stop and depress the clutch before dfco kicks in, then it will idle just fine all the way to the stop. How can I get it to exit dfco cleanly in this situation?
Problem 2: When exiting dfco (for instance, decelerating for a red light that turns green before you have to stop), I have a bad flat spot and some popping at throttle tip-in. I want tip-in to be smooth & uneventful. How can I make it happen?
I've got dfco set to enable at 2000 rpm and disable at 1200, with a 12 degree retard. It's working good when it engages. I'm getting smooth decel with no popping or lurching. The IPW goes to 0 and the wideband goes dead lean.
Log:
https://docs.google.com/leaf?id=0Bw7...jktYzk2MS00MzM
Problem 1: When coming to a stop with the m6 in gear and dfco active, when I depress the clutch the engine will idle down to 500-600 rpm for about 2 seconds, then go to the proper commanded idle. If dfco is active, it doesn't matter what rpm or speed I depress the clutch at, it will always idle down to 500-600 rpm. Commanded idle is 975, so when it idles that low, it almost stalls. On the other hand, if I want to come to a stop and depress the clutch before dfco kicks in, then it will idle just fine all the way to the stop. How can I get it to exit dfco cleanly in this situation?
Problem 2: When exiting dfco (for instance, decelerating for a red light that turns green before you have to stop), I have a bad flat spot and some popping at throttle tip-in. I want tip-in to be smooth & uneventful. How can I make it happen?
I've got dfco set to enable at 2000 rpm and disable at 1200, with a 12 degree retard. It's working good when it engages. I'm getting smooth decel with no popping or lurching. The IPW goes to 0 and the wideband goes dead lean.
Log:
https://docs.google.com/leaf?id=0Bw7...jktYzk2MS00MzM
the problem is that you don't have the DFCO enable or disable settings correct. why would you not want it to be active at higher rpms to slow the vehicle down and also conserve fuel?? typically set the DFCO disable to around 2K. This allows the engine to transition from DFCO to normal operation more smoothly. Of course if the VE tables are set correctly and the MAF is calibrated accurately the engine should be able to nearly instantly move from one to the other without any surging.
The popping in the exhaust you are having is from a couple of different problems/concerns. One is that with an unrestrictive exhaust you will almost always have some sort of popping when dfco is active. The nearly only remedy to it is to add timing. but that also decreases the engine from slowing you down as fast.
properly set the active/inactive table and you will have a much smoother operating engine.
The popping in the exhaust you are having is from a couple of different problems/concerns. One is that with an unrestrictive exhaust you will almost always have some sort of popping when dfco is active. The nearly only remedy to it is to add timing. but that also decreases the engine from slowing you down as fast.
properly set the active/inactive table and you will have a much smoother operating engine.
Thread Starter
Banned
Joined: Sep 2009
Posts: 213
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From: st louis, mo area
I understand that the dfco enable setting at 2000 rpm will activate it at any rpm over 2000, which is what I am seeing in the cars operation. I'll set the disable setting a little higher to see if that fixes it.
You have it backwards. The enable rpm is the maximum rpm you want it to be enabled. and the disable is when you want it to stop. You dont want it to be too low because it will cause stalling/stumbling issues. You also don't want it to be too high and every time you run up to 5k and let off the gas it stalls or stumbles. A good idea of where to set the DFCO is to look at where you tend to rev it to when you are driving a "little" spirited. That rpm is where you should set the enable setting to. I say "little" because your probably not in a situation that would be harmful to the engine to go as lean as DFCO enables the A/F.
Now if you have a stall then you should put the disable between 2500-2000. If not stalled then around 1800 seems to give the most leeway; keeping the engine from stalling.
Now if you have a stall then you should put the disable between 2500-2000. If not stalled then around 1800 seems to give the most leeway; keeping the engine from stalling.
Thread Starter
Banned
Joined: Sep 2009
Posts: 213
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From: st louis, mo area
According to the log, I'm getting dfco at 2500 rpms. Using your logic, that should not happen. I still think the enable is a threshold value, and any rpm over the enable will let dfco happen. Ay any rate, I've raised the threshold to 2200 from 2000 and raised the disable to 1500 from 1350.
