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| Does anyone else get fed up with Decel Enleanment kicking in? (Page 2/3) |
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Patrick
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JUL 02, 07:12 PM
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| quote | Originally posted by A_Lonely_Potato:
...for the majority of people it makes sense how it is.
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But why? I'm not suggesting that DFCO be completely eliminated.
| quote | Originally posted by sdgdf:
I know the Fiero DFCO disengages extremely early, like 1500RPM when on newer standard trans vehicles of mine it goes all the way down to idle.
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That makes a whole lot more sense!
| quote | Originally posted by pmbrunelle:
You have to bring the engine back to life at some point before it returns to idle, to avoid the risk of the engine stalling due to lack of fuel.
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What's the RPM of an engine when the starter is engaged? A couple hundred RPM? I see no valid reason for the Fiero's DFCO to be disengaging at 1500 or so RPM. I suspect there'd be no issue if the DFCO disengagement parameter was set to 800-900 RPM.
There's gotta be people on this forum who've altered this parameter! We need some first hand revelations! 
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pmbrunelle
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JUL 02, 08:41 PM
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| quote | Originally posted by Patrick:
What's the RPM of an engine when the starter is engaged? A couple hundred RPM? I see no valid reason for the Fiero's DFCO to be disengaging at 1500 or so RPM. I suspect there'd be no issue if the DFCO disengagement parameter was set to 800-900 RPM.
There's gotta be people on this forum who've altered this parameter! We need some first hand revelations! |
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I had a MegaSquirt 2 computer with a stock Fiero 2.8 engine. The MS2 is obviously not the same as the Fiero ECM, but I think they are both in a similar class of complexity/sophistication.
I played around with DFCO on the MS2/2.8 combo. 1500 RPM was pretty much where I had to start reintroduction of fuel to prevent stalling, or having the RPM crash and undershoot idle speed. Re-introducing fuel to the cylinders isn't a fast process; the dry intake ports need time to wet before they get loaded up with fuel.
Upon fuel re-introduction, there was a noticeable nudge, which I didn't like. I ended up disabling DFCO to avoid the transition.
Unless you have some strong reason to keep DFCO, I'd look into disabling it, rather than trying to adjust parameters to smooth the transition. I don't know if the Fiero ECM has tunable parameters which can help smooth the transition.
Generally speaking, upon fuel reintroduction, ignition timing can begin retarded (so the engine generates little torque), and then ignition advance can be ramped in over some time, until it reaches the normal amount of advance.
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A_Lonely_Potato
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JUL 02, 10:52 PM
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| quote | Originally posted by Patrick:
What's the RPM of an engine when the starter is engaged? A couple hundred RPM? I see no valid reason for the Fiero's DFCO to be disengaging at 1500 or so RPM. |
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oh wow i had no idea it was that high. i thought it was closer to idle. my tach reads 3k at idle in gear so i have no idea haha
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Patrick
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JUL 03, 03:25 AM
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| quote | Originally posted by pmbrunelle:
Unless you have some strong reason to keep DFCO, I'd look into disabling it, rather than trying to adjust parameters to smooth the transition. I don't know if the Fiero ECM has tunable parameters which can help smooth the transition.
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Oh, I definitely do not want to disable DFCO. It's a very worthwhile function. Not only does it greatly aid in engine braking, but it also saves fuel in the process. It's a win-win situation. There's no way I'd wish to disable it.
All that needs to be done is to set the parameter for DFCO disengagement to a low threshold RPM that wouldn't normally ever be reached while engine braking. I mentioned 800-900 RPM earlier, but heck, why not 500-600 RPM? The clutch would be disengaged long before the engine RPM reached that lower limit. As soon as the clutch disengages, the engine would then just idle at its regular RPM. There would be no apparent kick/lunge/lurch/nudge during the "transition" as the clutch would be disengaged. It seems so straightforward and simple! [This message has been edited by Patrick (edited 07-03-2023).]
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Mickey_Moose
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JUL 03, 08:47 AM
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These are the stock settings.
Of note, the deceleration fuel cutoff rate is different on the auto transmission (0.5 as opposed to 1.0 on the manual):
I can make changes you want - disclaimer - I am not familiar with tuning, I have the software, know how to make changes and can burn the chip. But you would need to tell me what changes you want specifically and it is at your own risk. You would just pay for the EPROM (unless you send me one) and shipping. However I am currently out of the 2732 EPROM and would have to order (I used my last on an arcade I fixed).
New (can also get slower chips (as slow as 450ns) from them a bit cheaper)
https://www.jameco.com/z/D2...pin-200ns_40109.html
Used (speed is known)
https://www.arcadepartsandr...s/eproms/2732-eprom/
I do not know what speed the factory ECM requires - original IC may state it's speed on it. If a faster IC is installed it doesn't make a differences - slower will most likely glitch.
Emailing me may give you a faster response as I sometimes don't check here often.[This message has been edited by Mickey_Moose (edited 07-03-2023).]
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fierosound
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JUL 03, 10:55 AM
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| quote | Originally posted by Mickey_Moose:
I have the software, know how to make changes and can burn the chip. But you would need to tell me what changes you want specifically and it is at your own risk. You would just pay for the EPROM (unless you send me one) and shipping. However I am currently out of the 2732 EPROM and would have to order (I used my last on an arcade I fixed).
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Good to know someone nearby is using Tunerpro RT as well.  ------------------
My World of Wheels Winners (Click on links below)
3.4L Supercharged 87 GT and Super Duty 4 Indy #163
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Patrick
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JUL 03, 01:55 PM
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| quote | Originally posted by Mickey_Moose:
These are the stock settings.
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Great, that's really helpful! 
| quote | Originally posted by Mickey_Moose:
I can make changes you want...
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Thank-you so much! Let me poke around a few tuning sites/forums to see if there's a "perfect" setting I should be striving for. I'll email you when I know what I'm doing. Thanks again! 
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Mickey_Moose
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JUL 03, 06:44 PM
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| quote | Originally posted by fierosound:
Good to know someone nearby is using Tunerpro RT as well.
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Using and knowing what one is doing are 2 different things. lol
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jelly2m8
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JUL 04, 02:00 AM
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Something easy to try if you have it is a 2.8 Auto ECM. Reason I say that is I drove an 87 for many years that I converted to a 5spd right away on the auto ECM and I cannot recall it doing that, pretty certain it would stall it's self out.
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Patrick
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JUL 04, 02:48 AM
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| quote | Originally posted by jelly2m8:
Something easy to try if you have it is a 2.8 Auto ECM...
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It would be helpful to know the default parameter settings on the test auto PROM. Reason being, if I didn't feel the "kick/lunge/lurch/nudge" at some point while slowing down, I wouldn't know for sure if DFCO on that PROM was actually enabled... although eventually stalling out would probably be a pretty good indication.  [This message has been edited by Patrick (edited 07-04-2023).]
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