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Discussion Starter #1 (Edited)
Hello all...
I’m a relative newbie to the tuning arena and would like to see some new discussions on the forum in the PCM Programming/Engine Management section.
I’ve seen some old threads covering these settings and was wondering if anyone has been doing any more work on this since then.

Marky has been helping me with several tuning options and configurations, while he’s been very helpful in guiding me through a very comprehensive tunes and setups, I’d still like to hear what others have to add to a discussion that’s 12 years old now.

I use JET’s DST as my tuning platform, while Marky uses TunerCAT.
His extensive knowledge covers both but there are some minor differences between the two, and the previous discussion is so outdated, I’d like to hear what others have done in this area recently as far as the numbers being used, and their experiences in using more recent configurations.
Especially with the DFCO Entry Spark Blending %, since the old thread addresses it as the DFCO Exit Spark Blending % and even then it didn’t really go into any detail regarding it’s settings.
Also, I can’t even find the DFCO Enable MPH configuration line in DST as a CONSTANT...
I think it’s called DFCO Enable Vehicle Speed vs. Baro. in the Fuel Tables’ tab, whatever the Baro. part means...
What does air pressure or Kpa vacuum have to do with the Enable MPH setting at 18 - 20 mph???

I‘m trying to breathe some new life back into the tuning portion of ISSF and look forward to hearing what any of the more experienced members have to add to the discussion.
Any and all responses will be appreciated and I will be responding back to whoever has an interest to pitch in and be of assistance.

Thank you all for your time and efforts, you all know who you are and I appreciate all you’ve done responding to my other questions in the past...
Tune or Die...
 

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I think it’s called DFCO Enable Vehicle Speed vs. Baro. in the Fuel Tables’ tab, whatever the Baro. part means...
What does air pressure or Kpa vacuum have to do with the Enable MPH setting at 18 - 20 mph???
Baro - you probably found is barometric pressure or atmosphere pressure. It helps fine tune fuel and spark calculations based on it. If you were an old timer tuning carbs, racing at high altitude tracks required different jetting and spark because of the thinner air. Now a a days, the HEGO will compensate for fueling changes, but it's after the fact. And the MAF measures actual air so also less important. Unless you drop into speed density mode. So think of it more as an altitude table. Not everyone lives at sea level. I recall how much sluggisher cars were in Albuquerque with it's roughly 5000 foot elevation. It was the thinner air.

So in all likely hood, the table probably delays DFCO longer at lower pressures (higher altitudes) without seeing it.
 

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Discussion Starter #3
Baro - you probably found is barometric pressure or atmosphere pressure. It helps fine tune fuel and spark calculations based on it.

I recall how much sluggisher cars were in Albuquerque with it's roughly 5000 foot elevation. It was the thinner air.

So in all likely hood, the table probably delays DFCO longer at lower pressures (higher altitudes) without seeing it.
Thank you 91ss, that makes sense and pretty much makes it unnecessary except for the fine tuning in Speed Density mode as you‘ve pointed out.
I recall having to reach down and set my idle/air mixture a little leaner and bring up the idle while riding my motorcycle over crests at Yosemite at 10,000’ of altitude, so now I understand the concept

I’m still kinda left wondering why the Stock tune Table line item to adjust is in MPH, as opposed to a rpm range being adjustable in the program cell. I’m thinking Dinosaur.... 96-97 OBDII
But...
Since I do have a MAF and my MAP correcting for it, I suppose it’s of little consequence to me.

I appreciate the response.
 
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To move a car at whatever speed takes so much energy. Which is fuel. And since it's really a fueling function, it easier to determine when to turn on or off based on how much fuel you're using --> speed. With RPM, you also need know LOAD to figure out how much fuel is going to be used. Are you accelerating etc etc.
 

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Also, you want the car to have a certain amount of momentum so it can sustain running things like steering and ac. And that's not an rpm function.
 

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Discussion Starter #6 (Edited)
Also, you want the car to have a certain amount of momentum so it can sustain running things like steering and ac. And that's not an rpm function.
Ok. I understand it a little better now, thank you 91ss.
My interest in DFCO isn’t fuel savings, but engine braking when letting off the throttle quickly at higher rpms, I’m looking to get some engine braking, and not having the transmission immediately up shift at the higher MAP vacuum inputs.
This involves not only the DFCO adjustments but the TCC lockup’s and release settings as well.

I’ve noticed how my car responds to the settings mentioned in that thread from 2006 having tested them, however I only use 17.5 degrees of spark in the Constants Spark Retard cell so there’s no significant strain put on the transmission, just enough to feel it kick in and out while I’m trying to figure out how to get the engine braking point results I’m after.

I‘ve read the threads where people discount the effect of spark in DFCO, but I know from playing around with it testing tunes, that the higher value the Spark Retard adjustment, the more engine braking I can feel.
I don’t know the exact reason for this, just that there is a difference, and since it’s included in the DFCO settings so did GM.

When I go out and play, I do what would be considered more along the lines of autocross driving, not drag racing, where I upshift manually at WOT, and let off quickly at higher rpms for braking, before getting back into the throttle gently when needed for smooth downshifts...
Knowing that what I’m after is engine braking, and controlling the up shifts from happening... Not mileage...
Any advice ?
 

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Discussion Starter #7
I don’t use these tunes for daily driving, just for when I want to go out and play...
Then I put my DD tune back in when I’m finished.
 

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I get you. I'd say you're on the right track using spark advance. Not familiar with OBDII tables and i'd have to fire up my old laptop to refresh the caprice OBDI tables in my head. The ford spark table (few of them) maps LOAD vs RPM. Lower LOAD roughly equates to higher manifold vacuum if that's what your tables are in. Your lowest row(s) (or highest) depending how you're displaying, would be conditions of high vacuum/low load that only occurs during decel. That's where I would drop the spark ask much as you can tolerate. Making sure you're not in a very light cruise area. Which if strictly an autocross tune, wouldn't be an issue. With fords, we can rescale the column and row values. I doubt the DST allows that kind of manipulation. So you need to log and try to find the right row (assuming rpms are the column headings) One thing to be conscious of is that a lot of retard will put the heat down the exhaust and can potentially over heat the cats. So you need to make sure you're reducing the fueling when you do this. Or run test pipes for the event.

Another area to help engine braking is to stop air going in. Reduce as much as you can that is. Your throttle blades are fixed at closed throttle, but you may be able close them a little bit more. And to added, have the ISC position set to the lowest (steps as i recall in GM tuning) when at high rpms. In fords it's a function of opening vs rpm and called a dashpot function. Normally used to avoid engine stalling on obrupt lifting of pedal at low speeds. You'd need to increase idle steps to compensate for a more closed throttle for idle conditions (steps vs coolant OBDI) and then see if you have a similar dashpot function or table to address the higher rpm steps

Hope this helps some..
 

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Discussion Starter #9
I get you. I'd say you're on the right track using spark advance. Not familiar with OBDII tables.
The ford spark table (few of them) maps LOAD vs RPM. Lower LOAD roughly equates to higher manifold vacuum if that's what your tables are in. Your lowest row(s) (or highest) depending how you're displaying, would be conditions of high vacuum/low load that only occurs during decel. That's where I would drop the spark ask much as you can tolerate. Making sure you're not in a very light cruise area. Which if strictly an autocross tune, wouldn't be an issue.
Yes, that makes more sense and sounds easier to configure...

With fords, we can rescale the column and row values. I doubt the DST allows that kind of manipulation. So you need to log and try to find the right row (assuming rpms are the column headings) One thing to be conscious of is that a lot of retard will put the heat down the exhaust and can potentially over heat the cats. So you need to make sure you're reducing the fueling when you do this. Or run test pipes for the event.
Hope this helps some..
Actually DST does allow the “Scaling” of the Table Cell entries, however most of its DFCO adjustments are done as Constants, which makes it a bit more difficult to fine tune for my intended purposes.
It’s mostly about getting the MAP and RPM enable/disable values to cross in order to activate DFCO, then dealing with TCC lockup and release settings to control the transmission.
Here’s the adjustable elements of the TunerCAT/DST platform.
I used these as the initial setup values in my test tune as shown in the old 2006 thread.
CONSTANTS:
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
TABLES:
DFCO Entry Spark Blending % TPS vs RPM: 0
DFCO Enable % TPS vs RPM: All 0
Throttle Follower IAC Offset vs MPH: All 1

Just to help you recall OBDI (TunerCAT) & OBDII (DST) ways of configuring the DFCO area’s of a tune.

I’ve made some changes to them so they’re more applicable to the engine braking I’m after, as opposed to gaining better mileage.

Thank you 91ss for your time and energy in responding.
I appreciate any and all information provided, as well as the time and energy it took.
👍
 

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I don't disagree with any of those constants, with the following caveat:
More DFCO Spark Retard = harder engine braking.
Track oil consumption if this number is over OEM, especially over 26°.
If your engine is already consuming oil between oil changes, maybe LOWER this number.
Gentler engine braking is ALWAYS safer for longevity and durability.

They'll still make replacement brake rotors and pads and drums and shoes.
For whatever dumb reasons (fights over reverse cooling), no one makes any more LT1 blocks.
(PLEASE, correct me if I'm wrong - we'll have something to celebrate.)

Apart from the above constants and tables, the trick to DFCO, assuming the TCC is already locked, is in writing the 00.00% downshift speeds and the 00.00% TCC unlock speeds to keep the TCC locked as long as reasonably possible.
 
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Discussion Starter #11
Thank you Marky...
I always appreciate your input and advice.
 
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