Found a solution more or less accidently when I logged a ride. Helped fine with my XB12, but will not neccessarily work with every bike.

When the throttle is closed in overrun, fuel get's reduced according to the deceleration correction settings, by default 96%. (All images shown below are made with a much lower setting (40-60%), to get rid of excessive exhaust popping in overrun.)

When the throttle is opened again, there's a small lag until the deceleration condition ends and fuel will be delivered again. This is what makes riding at low speed quite irregular.

Image 1: logfile as logged when letting the bike run with a closed throttle.
http://ecmspy.com/download/gunter/images/decel_log1.jpg

Watch the pink line in the marked area, how it drops below the blue line (showing the fuel map's value). As soon as the idle region is reached (rpm < 1350, load < 20), fuel will be supplied again and the bike suddenly bounces forward. This also happens very similar if the throttle is opened, as seen in the event just left from the marked area.

Deceleration correction is defined by a value and by a region, where it is applied. Both engine speed and load must be below the line, defined by the four points of the deceleration correction region:

Standard setup of the deceleation region:


My attempt was to make it impossible to enter deceleration correction at low speed, by setting the load to 0 at an engine speed higher than will apply at the targeted speed:


When logging another ride with the deceleration region adjusted as above, riding was much smoother and throttle reaction more predictable as before. Especially slow turns will benefit from this refinement.

http://ecmspy.com/download/gunter/images/decel_log2.jpg

The marked spot shows where fuel kicks in again, as a much higher speed than before, where the change is much less noticeable.

_________________
"It is often said that before you die your life passes before your eyes. It is in fact true. It's called living."
Terry Pratchett

What did he say?

gunter,

So it's been about a month. Have you left the settings the same?

Bryan

Oh yes, and I am not going back to stock settings.

I additionally applied some other changes to make the bike act smoother, as shown in the comparison here:



TPS voltage range was adjusted to a value as measured, decel region as described before, decel fuel correction down to 60% (better engine breaking), front cylinder correction set to 100% for all engine temperatures, because the O2 sensor is still installed in the front header, calibration mode O2 transitions reduced to 13 for faster response, noise abatement switched off completely. Exhaust valve settings can be ignored, as the silencer currently installed has no valve.

Map comparison (stock vs. current) here:



Fuel maps are adjusted in closed loop. Didn't have a wideband sensor handy at that time, so I only checked WOT fuelling wasn't lean. Timing tables - IIRC - are halfway between the stock BUEGB and a BUEZD, but I reduced spark advance significantly at 2000 and 3000 rpm @ load below 60. Advance was increased at 1000 and 1350 rpm @ load = 30 and 45 - although I do not assume, this would make a real difference when riding.

The result is amazing. The engine can safely be run at 1500-1800 rpm now without stuttering, jumping or coughing. The vibes will still shake the fillings out of your teeth, but these are good vibes now, because of the low engine speed. No hesitation when throttle is opened, be it slow or fast. I'm not sure how much this has to do that the O2 sensor is installed in the front header. I noticed several times, that this position makes the engine run smoother, but I do not have a technical explanation for this. Maybe it's just a coincidence, as I start adjusting the rear cylinder first, then move the O2 sensor to the front header and continue adjusting fuel there. Therefore, at this time, one map is always adjusted already, which could make all the difference.

_________________
"It is often said that before you die your life passes before your eyes. It is in fact true. It's called living."
Terry Pratchett

Only for my confirmation, if I'm going the wrong way

Data taken from my Uly2006 with IB310, calibration 76 EU:

EcmSpy TPS-Voltage for fully closed throttle: 0.91V
EcmSpy TPS-Voltage for fully opened throttle: 4.68V (max reading)

Difference: 4.68-0.91=3.77V (decimal) => 377 (*0.01 translation) => 0179 (hexadecimal)

ECM Data (OEM H-D):
Line 010, row 04: 6B
Line 010, row 05: 01
=> hex 016B => 363 (1/0.01 translation) => dec 3.63V

So I have to program:
Line 010, row 04 -> 79
Line 010, row 05 -> 01

Am I right ????

That's how I did it. To make it perfectly, measuring the butterfly opening angle would also be required, but I decided to believe the stored value (this time). Load (0-255) is mapped on this voltage range, as well as TP in degrees (0-85 by default). I don't think it will make things really run better, but it won't hurt, and it's an adjustment easily applied.

_________________
"It is often said that before you die your life passes before your eyes. It is in fact true. It's called living."
Terry Pratchett

Thanks.

I have just read your work on low speed surging and I have not got a clue, as I am not the most technically minded.
Is there anyone you can recommend in the North east who could do this for me ?

Hi Gunter, is there a way to do that without having to install the full version of ECMSpy 2?
Great job BTW.

I suppoes, that you could use any tool of your choice.

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"It is often said that before you die your life passes before your eyes. It is in fact true. It's called living."
Terry Pratchett

Ok, I found it in TunerPro RT, "Parameter Tree" - "Functions" - "Table: Deceleration Correction Region"

I guess it will only be to make the changes and save it to the EEPROM

Having just starting riding V-twins, specifically an XB12S Lightning, and finding it really hard to be smooth at low speed I was reading with growing excitement Gunter's initial post, that was until I realised it's a pretty technical job to do .

I take it that to do this you need to a) have access to a computer with the correct software that can connect to your bike and b) know what the heck you are doing?

As I unfortunately don't have either of those how would I go about having this done?
Is it expensive and is it reversible?
I've never been into tinkering with my cars or bikes but this sounds like the only must do 'mod' to my bike to help me ride smoother.

Any / all help with this would be greatly appreciated.
Thanks

Visit ecmspy.com, read the tuning and the users guide. Almost all of your questions are covered there.

_________________
"It is often said that before you die your life passes before your eyes. It is in fact true. It's called living."
Terry Pratchett

Awesome, thanks Gunter

Top Work Gunter