Deceleration

RK4000 · **Posted:** Mon Mar 09, 2020 5:08 pm

mrf582 wrote:

RK4000 wrote:

So, I have an interesting problem.

The issue is this: If you were to very slowly decrease the throttle in this same situation, the moment it closes, the fuel cuts immediately and ignition instantly retards fully. This makes a very jarring "twitch", since it sends a shock through the driveline. This is even more pronounced if you are driving downhill with very little throttle, and slowly close it, it will very annoyingly and abruptly twitch.

In the logs, I see that in the first example ignition will first start gradually retarding, then after a bit less than a second, fully retard and shut fuel injectors at the same time. Even though in the logs, the injectors are still shown as firing, the econo gauge in the cluser shows they aren't, and the exhaust note clearly changes indicating that there is no fuel being burnt. But in the second example, ignition instantly jumps to fully retarded, without that gradual slope and fuel is immediately cut. This is probably what shocks the driveline and makes the car twitch. Again, it only does this if you very slowly close the throttle, and moreso if going downhill.

Is Fast Decreasing Throttle responsible for this? If anything, I was under the impression that it should be the exact opposite: Retard ignition immediately if FDT is detected, but retard it slowly if FDT is not detected. I am attaching the map of the car in question. FDT should be disabled anyway below 4500RPM on this map, and this problem does happen in the entire rev range.

Correct, FDT is not the issue. If you log Switch LV_PUC, I believe you'll see a 1:1 correlation between it and the effect you're seeing.

The Dashpot function affects fuel cut as well as the IACV. One of the checks for transitioning to fuel cut is whether any of this dashpot is still in effect or if it has completely diminished to 0.

In your tune, the values may be too low in the 2.3% column (2nd TPS column). You could also add some non-zero values to the 1st column to add some more 'damper' effect when transitioning to closed throttle from an already very low throttle.

Unfortunately, the ECU doesn't know when the engine is disconnected from the trans via Neutral or Clutch switch so this dashpot can only apply to one or the other. Recommend you tune it for proper operation in gear. Again, not knowing exactly which gear isn't ideal. The strength of this dashpot 'spring' needs to suit the amount of engine braking for a given gear.

Same applies to your Decreasing TPS - Step Size for really low loads. No reason to allow for timing to get reduced so rapidly at low loads.

Thanks for the info!

I messed with the settings some more (even before this reply) and came up with a pretty viable solution. I'll post the .bin when I get the chance. Basically, I restricted the IACV's "damping" function as much as possible at these low revs, so the throttle completely throttles back the engine - my reasoning for this being that if there's no air going in, the engine can't twitch when going to fuel cut, because very little combustion was happening anyway. The throttle responds much more directly on deceleration, and my friend says he very much prefers it this way. It may be a bit too aggressive for most people, but in this case it's great, especially with the boat anchor dual mass flywheel. There's still a little bit of a "twitch" sometimes, but nowhere near as drastic as before. I'll try to employ some of your suggestions to fix this.

Speaking of which, I am very curious about these various "checks" the ECU does before going into fuel cut mode. Are they defined anywhere? How many of them are there? Is there any documentation explaining them? Changing the conditions the ECU deems necessary for transitioning into fuel cut sounds really useful. Looking into them might also explain why this particular car would do this "twitching", even when I tried a map where the only difference to the stock map was ignition step size, which, logically speaking, should not make it "twitch" per se, rather, just make it start decelerating faster.

fre.fre · **Joined:** Thu Dec 07, 2017 3:10 pm **Posts:** 14

Hi
I read 29 page of deceleration post and seem that some one want shot flame when you change gear.
Let me know if I'm wrong.
So I attach a wiring that could work.
I think If we swich off the spark when we push the cluch on full gas we made a huge flame.
What do you think?
There is some one that know if the engine control unit know if we made this trick for the time that we make a gear change?
Please write in a simple english because I have gap languge. Thanks

Attached wiring

GAdam40 · **Posted:** Sat Mar 28, 2020 8:03 pm

fre.fre for pops when shifting gears, do what 328i-sport-rossi did. Do some retard in ignition base map. Decel maps leave untouched. Disadvantange of this is that you must have gently pressed gas pedal to stay injectors on.

Decel pops are too slow and i don't know how to get faster retard ignition in decel mode

Dade · **Joined:** Sun Apr 26, 2020 1:57 am **Posts:** 4

Hi,
can someone please help me add pop and bang to my ecu
MS41 328i

GAdam40 · **Posted:** Thu Apr 30, 2020 5:17 am

I just discovered how to get few second pops. It depends on how fast you relase throttle. Slowly relase throttle = longer pops, Faster relase = short pops or none

You can adjust "sensivity" with hysteresis delay counter.

*Fuel restore rpm - default value
*Fuel cut hysteresis max - 3488 rpm, so 3488 + 1056 = -+4544 rpm (below this value i get pops)
*Fuel cut hysteresis min - default value
*Fuel cut hysteresis delay counter - 1000 injector cycles
*ECT threshold - default value

The point is to set fuel on by "Fuel cut hysteresis max" table and adjust time of pops with "Fuel cut hysteresis delay counter" table

I set 4500rpm becouse i want to keep fast decreasing mode.
I set 1000 injector cycles but you can decrease "time of pops" if you want shorter pops

Don't forget to decrease values in "Ignition retard decreasing tps" and "Ignition retard decreasing tps (closed)" tables!!!

Have fun

tdehrmann1 · **Posted:** Sat May 02, 2020 1:08 pm

GAdam40 wrote:

fre.fre for pops when shifting gears, do what 328i-sport-rossi did. Do some retard in ignition base map. Decel maps leave untouched. Disadvantange of this is that you must have gently pressed gas pedal to stay injectors on.

Decel pops are too slow and i don't know how to get faster retard ignition in decel mode

You can get faster ignition retard with "Ignition Retard - Decreasing TPS - Step Size". In the first Load column change the Step Size in your preferred RPM range to 10 degrees or any other higher value than stock. I have 10 degrees in my files.
Also i am logging the Engine Load while deceleration and edit Ignition Base in this Load and RPM range to 19,90° and Ignition Retard is at -48°. If all values are correct you can control both with the AC Button. If you want to change the "popping noise" lean out the fuel table at the range of load you logged in decceleration

i played a lot with decel but my problem is to explain it to somebody else. Hope its understandable what i want to say.

Sorry for my bad english

Attachment:

little DECAT Escalation.zip

<-- a few tries from last winter

Dade · **Joined:** Sun Apr 26, 2020 1:57 am **Posts:** 4

someone can help
to get pop and bang?

Dade wrote:

Hi,
can someone please help me add pop and bang to my ecu
MS41 328i

GAdam40 · **Posted:** Tue May 05, 2020 1:58 pm

Dade wrote:

someone can help
to get pop and bang?

No! Everything you need to know is here. Spend some time to learn how to do it. Or pay a local tuner.

busterhax · **Joined:** Wed Jan 22, 2014 6:54 pm **Posts:** 1773

Lol is it time to close deceleration after almost 500 posts or will there be more innovative modifications to further improve slowing our cars down?

mrf582 · **Posted:** Tue May 05, 2020 5:31 pm

busterhax wrote:

Lol is it time to close deceleration after almost 500 posts or will there be more innovative modifications to further improve slowing our cars down?

I agree...
...but it is a good n00b catcher, lol

ET89 · **Posted:** Sun May 10, 2020 12:03 pm

I just followed MRF's, Enabled and busterhax's discussion in the beginning of this thread.

I have normal acceleration and deceleration when i just punch it and have some nice crackle
when i do a rev matched down shift, and sometimes it even pops a bit.

blipping the throttle during decel also creates a light crackle.

this way it isn't obnoxious, since it doesn't happen if I don't want it too, and enhances the driving experience because it is fun when you get the downshift just right.

reason for this is because i have been driving an LS this week and I was happy to be back in my e36,
but I liked the downshift drama.

Ed Hardwood · **Joined:** Sun Mar 03, 2019 2:38 pm **Posts:** 10

I'd just like to say thanks to those that posted values, and helped explain things. I managed to get my tune exactly like I wanted it, and have two versions.

One is a normal daily tune, doesn't make the fuel consumption much worse, but has nice pops and cracks on decel, or when feathering the throttle.

The other tune is something that ups the car from 11L/100 to 13L/100, but is more for car meets and showing off. Has the occasional flame, but nothing big (would like to change that), but will pop on the entire rev range.

I've uploaded both maps for those that want to take a look at. I'd also love suggestions, as I'm sure I've made some mistakes.

Car is a South African 328i. No O2 sensors at all from factory. M50 manifold is the only performance mod done, other than a decat and a more free flowing exhaust.

GAdam40 · **Posted:** Tue Jun 09, 2020 6:31 pm

Ed Hardwood daily and loud are exactly the same files

Ed Hardwood · **Joined:** Sun Mar 03, 2019 2:38 pm **Posts:** 10

GAdam40 wrote:

Ed Hardwood daily and loud are exactly the same files

Fixed!

thirtysix · **Posted:** Sun Jun 28, 2020 1:02 pm

Hello,

I'm currently working on a PopsandBangs tune for a MS41.0. I only want the pops to happen when the AC is turned off. I've had it working but now the car sometimes randomly starts to burble when the AC is on. My question is, does the engine use the tables according to the button in the car or does it use the tables according to the AC compressor? (If compressor is engaged or not)

RomRaider

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