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Discussion Starter #1
Well, things are going on slowly to get DFCO as agressive as I can. I don't know how much interest there is here, but I know I have search the net over to find very little meat on DFCO.

DFCO Enable RPM: 1300 RPM
DFCO Disable RPM: 600 RPM
DFCO Enable MAP: 20 KPa
DFCO Disable MAP: 36 KPa
DFCO Disable RPM Decrease: 3750 rpm
DFCO Enable Coolant Temp: 20 Degrees C
DFCO Enable MPH: 18 mph
DFCO Enable Delay: 0
DFCO Spark Retard: 23 degrees
DFCO Exit Spark Blending % TPS vs RPM: **
DFCO Enable % TPS vs RPM: All 0
Throttle Follower IAC Offset vs MPH: All 1

What I have learned is that the key to getting DFCO to kick in, it having the MAP pressure CROSS the DFCO Enable MAP. If you can't get the vacuum to cross it, it won't turn on. I wish it was as simple as make it railed high or low and keep it on all the time, but it won't work at all then.

** I haven't messed with Exit Blending yet, but my initial start is to run it all to 0 and then see how it reacts.

Having DFCO Disable rpm as low as you can tolerate keeps it turn on for as long as possible. I try to get it to nearly idle. As you approach idle, MAP goes up (towards 100) and will cut off when it hits the MAP Disable threshold. But, setting this high will also cause DFCO to not turn on. It almost seems that the vacuum before you attempt to enable it must between the Enable and Disable MAP to even have a chance to turn on.

I'll post more notes as I get time...
 
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Discussion Starter #2
RamAirRocket:
Are these the latest and greatest numbers? I know you say 21 for enable now, not 20, right? Are you saving fuel noticeably with this? Have you ever stalled out, like when heading for a dangerous curve and you really need your power steering NOW!!?
 
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Discussion Starter #3
Yup, these are latest and greatest.

Never once had a stall or even come close, not even any stumble. It seems to either hit rpm limit (I have it set very close to idle or desired idle) or it hits the disable MAP limit. I have had it hit both and shut off, it seems to be close to hitting them around the same time. I try to keep them pushed to the limit.

20 seemed slightly better than 21. Now I get it to engage almost every time I back off, it engages. mpg is close to the same, but I don't drive a LOT of drivin city, mostly highway....

Originally posted by producers_kid:
RamAirRocket:
Are these the latest and greatest numbers? I know you say 21 for enable now, not 20, right? Are you saving fuel noticeably with this? Have you ever stalled out, like when heading for a dangerous curve and you really need your power steering NOW!!?
 
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Discussion Starter #4
Correct me if I'm wrong (I know someone will), but these settings will allow for actual compression braking on deceleration won't they?

SStewart
 
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Somewhat, it definately help on decel. I can go down a hill now and back off the gas and slow down slightly, where before I would have to tap the brakes to keep speed from increasing. It is much easier on the brakes and much easier to maintain speed accurately.

Originally posted by Murf'sDad:
Correct me if I'm wrong (I know someone will), but these settings will allow for actual compression braking on deceleration won't they?

SStewart
 
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Discussion Starter #6
I read somewhere that, when the gear selector is in OD on a stock setup, it is not good to make a 4L60E drive the engine. Something to do with the overrunning clutch not being engaged and putting strain on parts.
 
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Discussion Starter #7
Any trans experts know?

It doesn't really much, in OD, you can't get DFCO below around 40 mph anyway, it just won't because the rpm's get too low and at that point, KPa is going up and will hit high limit and cutoff, but rpm limit usually hits first. When DFCO is on, rpms drop significantly more than when fuel is being added, even at close throttle.
 
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Discussion Starter #8
Originally posted by RamAirRocket:
DFCO Spark Retard: 23 degrees
What have you found with the amount of spark retard? Is it the more retard the more of an effect, or the other way around?
 
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Discussion Starter #9
Sorry for the delay in reply, I wasn't able to login for some reason, now finally fixed...

I messed with lower and higher and for my combo (pretty much stock) seemed to give the best decel feel (what I wanted).

Honestly, I don't know how ignition timing has any effect if fuel is cut off anyway. If anyone has insight on that, please share!

I have made a lot of changes up and down with DFCO settings to get where I am, and it seems to work pretty darn good now. I can't complain and mpg isn't bad at all for a V4P car and my long commute. Seem to be hanging in the 18.5 to 19.25 range back and forth, at least 4 WOT blasts a day, several healthy accelerations getting into traffic, and right now, lack of cruise control. I put on around 100-120 miles a day depending on my route. Longer is a little higher in mpg than shorter, but they both balance out. I have been keeping to my shorter route primarily lately, it just has lots more stops and starts.

Originally posted by SStan:
</font><blockquote>quote:</font><hr />Originally posted by RamAirRocket:
DFCO Spark Retard: 23 degrees
What have you found with the amount of spark retard? Is it the more retard the more of an effect, or the other way around? </font>[/QUOTE]
 
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Discussion Starter #10
Originally posted by producers_kid:

<snip>
Are you saving fuel noticeably with this?
<snip>
The point is not saving fuel but saving brakes. And being able to decellerate just by backing off your right foot instead of having to move the right foot over to the brake.

A possible downside is that the brake lights won't be on. A possible mod is to make the brake lights come on when the throttle is closed.

Please keep the info on maximizing the DFCO coming.
 
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Discussion Starter #11
Will do. Current settings are definatly a big improvement over stock. I can go down a hill and in most cases decelerate down the hill, not coast on and not slow down. It is nice.

Toss in those settings, you'll like it.

Pretty much the MAP values seem to be the hardest to dial in. Take lots of data logs and see what triggers DFCO and what does not. Takes time to analyze to get it right.

I can say brakes would be saved, for sure, it is very nice not needing to ride them much anymore.
 
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Discussion Starter #12
I did put those settings on the 9C1. It made a noticeable difference. It's nice not having the DFCO go away as I decellerate through 22 mph in second. Also, knowing that I need to be above a given MAP for it to start working will let me use it more. You've helped me. Thank you.

On my 9C1, the DFCO Enable RPM was 1400 RPM. Since that seems to be an upper limit, what would be the advantage of reducing it to 1300? Or is it like the MAP and the engine has to be above that RPM for the DFCO to begin cutting off the fuel?

Thanks again.
 
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Discussion Starter #13
Originally posted by Rowland Hill:
A possible downside is that the brake lights won't be on. A possible mod is to make the brake lights come on when the throttle is closed.
I wouldn't do that...my car slows down AWESOME on the DFCO but it's still nothing compared to hitting the brakes.

If you're after brake and fuel savings, the best mod you can do is the T56. My LT1 car does 30 mpg pretty consistently, and if I think ahead for slowing down, I can just keep rev matching my downshifts (no wear on the clutch) and let the DFCO keep slowing the car down. Added benefit to that is it's always right there if the light turns green, or the lane I'm in opens up in front of me, don't have to wait for a downshift.
 
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Discussion Starter #14
I was trying to push it down as much as I could, but below 1300 rpm when DFCO would kick in, it would hit the low limit and turn back on, hit high limit and turn fuel back off, and on and off.... Makes for nice surging. So 1300 was about best I could get without any surging.

The reason I posted is I couldn't find any solid numbers out there that worked. I can't tell you how many iterations I went through that just never turned on DFCO at all, so I had to drive 60 miles home without it. That sucks!

The tough one was why it would turn on sometimes, and not others. That is where I found it was DFCO Enable MAP/Disable MAP and that you had to be in the middle to get it to trigger. If they were true just enables, I should be able to set one at 0 and one at 100 and be in DFCO anytime I backed off the gas, but that disabled it completely.

I hope I can help people at large to have good DFCO, save some brakes and possibly some fuel. This is how GM should have set it up in the first place.

They always say GM does some of this stupid stuff based on what people complain about. So lets start complaining that DFCO is setup soo bad I can't decel and it never kicks in properly. Maybe they will start coming back our way. Maybe just complain on the 2.5 second delay. A friend of mine has a 2003 Bonneville and claims the delay is nearly 5 seconds. He is screaming.... Even in 3rd gear decel it will hold speed almost like you had your foot on the gas.

The 99 Tahoe we had at work would nearly get you into an accident because you would nail the brakes and the DFCO would keep adding fuel and actually FIGHT you till the delay was over. I would disconnect the IAC once warm to eliminate much of that. Wasn't the true fix, but helped a lot. I am guessing agressive throttle follower settings on it that aren't good....

You may need to tweak some, mine is fully intended at 3.42 gears and my cruise MAP readings, so some tweaking may be needed, but I doubt much.

Tom

Originally posted by Rowland Hill:
I did put those settings on the 9C1. It made a noticeable difference. It's nice not having the DFCO go away as I decellerate through 22 mph in second. Also, knowing that I need to be above a given MAP for it to start working will let me use it more. You've helped me. Thank you.

On my 9C1, the DFCO Enable RPM was 1400 RPM. Since that seems to be an upper limit, what would be the advantage of reducing it to 1300? Or is it like the MAP and the engine has to be above that RPM for the DFCO to begin cutting off the fuel?

Thanks again.
 
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Discussion Starter #15
To monitor the DFCO working with data logging, do you look for the injector duty cycle to go to 0?

Thanks in advance.
 
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Discussion Starter #16
There's a DFCO status bit you can monitor or you can watch the injector pulsewidths go to 0.
 
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Discussion Starter #17
You see the O2's drop to 0.004 to 0.009 volts, that is how you know it kicked in, which is what I always watched for. I think BPW (Base Pulse Width) does not drop to zero. I can double check my datalogs again, but that is thinking off the top of my head. It might and I am just not remembering it right now....
 
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Discussion Starter #19
Nobody have an answer about possible side effects on the transmission?

I wouldn't mind trying this, but I don't want to put any added stress on my already old trans..

I love the way my exhaust sounds when DFCO kicks in..
 
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Discussion Starter #20
I have stock exhaust, so I don't even hear it. :(

But in OD I don't think it hurts, but in D the overrun clutches are locked so it will add straign there.

Any trans guru's comment?
 
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