Jake brake feel

[Don D]

Got an 06 Softail here for work. Tuned by a good tuner familar with the SERT
Has one annoyance. It feels like the fuel is cutting off at 0 throttle between 1500 and 2500 rom when coming to a stop. Feels like a Jake. Is this a map characteristic or can the values be tweaked to get rid of this. I was thinking the tuner may have done something to get rid of decell popping but IME we added fuel there. Would be nice to be gone with it.

[WVULTRA]

Don:

Sounds like a characteristic of some maps that shut the injectors off during decel, then bring them back on-line just before coming to a stop.  Previous '05 RK with Stage II 95" was notorious for this using the recommended SERT map.  Friend gave me a Tuned map for similar setup that started with a Dyna/Softail SERT map, and the issue was gone.

A data recording with all the data exported to excel clearly showed the injectors shutting off (0pw) at 0 throttle/decel for as long as 6 seconds.  You'd be decelerating to a stop, and just before coming to that stop, the bike would have a slight "buck" when the injectors came back on-line.  Sorta felt like slightly blipping the throttle.  And it would happen just below 2500 and IIRC would come back on-line ~1500rpm.

I'm sure Herko, Bob, Steve, Doc, or some of the other tuners here can shed some expert light on the situation.

I could feel it on the '07 Ultra with PZ176.  VTuned with PS176 modded, and have yet to have it happen.  I'm sure a competent Dyno Operator can tune this out; but that's just my opinion.

HTH's

[Herko]

What I've found is that this decel fuel cut happens on only certain Cal Files.
The cut being a shutoff (0.0ms) of the injectors.
Yes, it can have a more pronounced compressing braking effect.

I actually prefer this zero fuel for decel pop control.
So, I do not know if richening the VE's/AFR's with these particular Cals will in fact keep fuel delivery in tact with at least some fuel delivery throughout decel. Easy enough to find out though.

Ends up some Cals decrease down to a flat 1.50 ms during decel. This is pop city on some pipes.
Richening would cure though.

Another Cal file category in this vein is Cals with decel fuel values of random amounts based on VE/AFR Tables for that area. Seems to be the majority and would coincide with the prescribed procedures for curing decel pop.

IMO, using 0.0 decel fuel is a clean and effective way to control decel pop.
The trick was to find a way soften the fuel re-introduction surge to a point of being unnoticeable.
Warm up enrichment has to have timed out to enable the 0.0 decel fuel btw.
There are also certain RPM plateau values that need to be reached to initiate 0.0 decel fuel.

I've inquired about which Cals do what on decel and the answers were somewhat inconclusive.
Apparently it's something that Delphi puts in the firmware and not consistent throughout the different Cal files.
I assume it would take someone with the skills (and time) to look into the forbidden partitions of the Delphi ECU's and the Cal files to sort this out.

Assumption is that 0.0 fuel on decel is a fuel economy/emissions feature while controlling decel pop.
For closed loop bikes, another personal preference is the less unburned fuel thrown on the unheated O2 sensors during decel the better.

IIRC the TMax has settings for decel fuel cut.
Maybe someday we'll have something similar for the TTS to enable control for beginning/ending and re-introduction quantity etc. of 0.0 decel fuel. This of course being a table in addition to the Decel Enleanment table. DE effecting the fuel values for only about a second or two.

BTW, what Cal file is in the 06 bike you speak of?