Bucking Returns

[Happy Jim]

Hi,

I have recently leaned out my off load areas and the dreaded Bucking has returned :bad:
I could of course just revert to my old tune.....but where would be the fun in that :hihi:

Would a kind soul let me know what PIDs I should be monitoring to check what's happening with the Spark Timing at low rev/low load (only happens at 1500-2000 RPM).

COS3, WBo2, no O2's, No EGR/Air, No Aircon, No Cats etc etc 224/230 TR230 LSA111 Cam.

Thanks

Jim

[DrkPhx]

Why is the Commanded AFR so lean? That's part of the problem. Looks like the bucking is on decel. I have to believe the combination of the Commanded AFR and DFCO is causing the problem seeing the WB reading is between 18-20 AFR.

[dfe1]

Looks like you did more than lean out the mixture. You also altered a number of timing tables. Since you're timing is jumping around like a politician being pressed to answer a question honestly, look at the timing changes you made. Your idle overspeed/underspeed timing corrections look too aggressive for the camshaft you're running. Log DynCylAir_DMA so you can see the timing table cells that are relevant to your log. I primarily looked at your log for idle conditions and it looks like one of the issues may be a big discrepancy between values in your primary spark tables and in the idle spark tables. That combined with the overspeed/underspeed settings is a big part of the idle/low speed spark inconsistency. Although there are slight variances in air flow, they aren't large enough to cause the spark bouncing around to the degree it is.

[WeathermanShawn]

What everybody else said. I buck if I go that lean. I can handle the DFCO lean..but I would richen it up in those other areas..along with all the extra great advice on spark.

Curious, you say no MAF or you are running MAF? Don't see a DTC Code on it? I know you are Open-Loop..but something to think about..


If you don't get a MAF DTC then it will still run from the MAF...

Good luck.

[Happy Jim]

Thanks for the advice, I'll Richen it up a bit.

Maf is fitted and working (guess I need to update my footer :doh2:)

Dfe1 - thanks for tips, I'll work through them tomorrow and see how it goes.

Many thanks

Jim

[Happy Jim]

Had a brief run out with some of the suggestions enabled and logged the results....and then realised that I hadn't programmed the correct PIDs - hey ho! - then got distracted by the hot weather (very uncharacteristic in England :-)).

Anyway, just had a good look through S&T and selected a bunch of PIDs and did a quick 30 sec log to make sure I've got the right ones...

Question - have I got DynCylAir_DMA in there? (if so, I'll go drive and log) I couldn't see it in S&T so selected what I thought it might be?? (or do I have to manually do it via Options.txt?)

Thanks

Jim

[WeathermanShawn]

Had a brief run out with some of the suggestions enabled and logged the results....and then realised that I hadn't programmed the correct PIDs - hey ho! - then got distracted by the hot weather (very uncharacteristic in England :-)).

Anyway, just had a good look through S&T and selected a bunch of PIDs and did a quick 30 sec log to make sure I've got the right ones...

Question - have I got DynCylAir_DMA in there? (if so, I'll go drive and log) I couldn't see it in S&T so selected what I thought it might be?? (or do I have to manually do it via Options.txt?)

Thanks

Jim

Jim:

Your OS should have DYNCYAIR_DMA available. Look under 'Tune" in your Pid Selection File (see attachment).

Did you get rid of the bucking?

[Happy Jim]

Shawn, thanks...found the little bugger now :-)
It's been a long long time since I used the Scan tool to play with PIDs, I'm struggling to program them into the V2 (only vaguely remember doing this with the V1) - The "Programme selected PIDs into Flashscan" is greyed out which I'm sure is telling me I've got something wrong (sequence of connecting the V2 to car/pc maybe??).
The bucking never went away with the tweaking I did above, although it did improve. I've gone back to my "best" tune and can actually feel the bucking in the same area - guess I'd just got used to it and drove around the problem (it's not bad, just noticable). Once I've got the right PIDs loaded I'm going to use my "best" tune as the baseline and then apply the adjustments mentioned above (changing the base spark table seemed to make the biggest difference (SOTP).

Regards

Jim

[joecar]

Jim, to program pids into V2 you have to use the S&T software.

[Happy Jim]

Started with "GD J1m 10 May Start.Tun", changed the Idle over/underspeed settings (set them to 50% of previous max value and then a linear ramp to zero), changed the base spark table to be the same as the High Spark - went for a quick run, definate improvement SOTP (I'd say 85% of it has gone), haven't looked at the log yet but will in a min.

Thanks for the pointers guys, much appreciated.

Jim

[Happy Jim]

Jim, to program pids into V2 you have to use the S&T software.

Joe - thought so, but have low self trust given that I'm no expert! just had another play in S&T....Is DYNCYLAIR_DMA now known as DYNCYLAIR_M? if so I'm good to go tomorrow morning for another run :-)

[joecar]

Yes, in V2 BBL the _DMA pids have been renamed to _M.

[Happy Jim]

Great stuff, I must have missed that bit in the chatter. I'm now off for a play :-)

Thanks

Jim

[Happy Jim]

Went out and had a play - it's miles better, the Spark line is a lot smoother (although there is still a small amount of bucking at very light load/1500RPM, but I might just be asking too much :-)) - Hugely happy now.

Thanks all

Jim