any tips to tune out an off idle stumble?

jsmcortina · Post by **jsmcortina** » Wed Mar 29, 2006 6:48 am

whittlebeast wrote:Eventualy I think it would be good to move all of the AE tuning to one screen but this would most likely involve Eric, MS2 and Extra. With extra this would also invole moving all the AE settings to one page in flash. I hear this is all rather involved to accomplish.

That custom screen would indeed involve a re-write of Megatune to support it. I'm afraid I can't help with that.

Moving all the data to one page isn't a big deal really and the recent XML data save format in Megatune makes it a lot less painful to import slightly older MSQs to a new structure.

James

woh · Post by **woh** » Wed Mar 29, 2006 6:55 am

Would changing the labels to "Accel time/cycles" help matters?

Yes. How about the units. Are cycles in number of engine cycles?

whittlebeast · Post by **whittlebeast** » Wed Mar 29, 2006 1:53 pm

woh

When using RPM based AE there is a choice of MAPDot triggered or TPSDot triggered. Once activated then the code looks at the RPM/ms table to deliver the correct ms of AE. This version of code has just one trigger point as dictated by the map threshold or the tps threshold. Stabbing the throttle even harder does not change the amount of MS of AE.

AE

mikesb · Post by **mikesb** » Wed Mar 29, 2006 4:08 pm

whittlebeast wrote:Stabbing the throttle even harder does not change the amount of MS of AE.

Which, so far, is the other thing that makes RPM AE problematic for me. At idle if I stab the throttle I need more enrichment than if I use a lighter touch.

If I had my druthers, I'd like the original AE to start calculating the correct mapdot immediately (from 0) instead of using the first bin. I think it'd help me at lower RPMs. If I get ambitious I may try making that code change. A 4x4 matrix to combine RPM AE with MAP/TPS dot AE would be cool, but probably overkill for my situation. I think, if I could set the initial bin lower I could get everything I need - MAP and TPS dot w/ cycles pretty much compensates for higher RPMs because the throttle is already open. Seems intuitive 'cause the accel pump seems to work pretty good with carbs and that's a very similar problem.

James, yes, changing the label would help, and the units too: Accel time (seconds) / cycles (cycles / 10) might be right. I'm pretty sure 1.5 in that field == 15 cycles (it could mean 7.5 cycles, if a cycle is measured as an ignition event on my 4 cylinder).

Werner: req_fuel = 9, Injector Opening Time = 1.0ms

Andy, you've got mail

.

jsmcortina · Post by **jsmcortina** » Thu Mar 30, 2006 4:06 am

mikesb wrote:
whittlebeast wrote:Stabbing the throttle even harder does not change the amount of MS of AE.
Which, so far, is the other thing that makes RPM AE problematic for me. At idle if I stab the throttle I need more enrichment than if I use a lighter touch.

Same here. I drove to work with 029L and rpm based AE. I wish I'd brought my laptop so I could turn it off and go back to MAPdot or TPSdot.

I had upped the kpa threshold to prevent mistriggering but now light throttle movement (that need enrich) are too weak.

James

daxtojeiro · Post by **daxtojeiro** » Thu Mar 30, 2006 10:05 am

James,
I would guess youve not got the threshold high enough now, as Ive tuned 3 cars now with rpm based and it is superb, I can only detect the slightest problem if stabing it really quickly, but 99% of driving it works great for. I would like to put another threshold in the code so it was 2 rows wide to allow for variants in the throttle but I havent got round to it yet and I must confess I didnt feel it would be that easy to tune then, where as this can be tuned in a matter of minutes and its easy to understand, etc, etc
Phil

whittlebeast · Post by **whittlebeast** » Thu Mar 30, 2006 10:14 am

Did you start with the hints here.

http://www.msefi.com/viewtopic.php?t=16087&start=0

AW

mikesb · Post by **mikesb** » Thu Mar 30, 2006 8:34 pm

I have, and just had another look to double check. For me, using RPM AE by following those instructions works great for higher RPMs but around idle it doesn't work at all. I need a rich setting for idle or I get big time lean pops when I hit the throttle to accelerate away. But with those settings with the gearbox in neutral, if I blip the throttle or open it slowly the engine floods and stumbles. Then vacuum rises triggering another pulse - this floods it right out and it stalls.

I did a bit more thinking about what would work best for me. A couple of changes could work for RPM AE and the original AE, and I suspect they'd work better for most everyone.

1) Get rid of the dot thresholds
2) Change the AE algorithm to start right away rather than using the first BIN for the first cycle
3) Provide a "sustain" function to keep AE on for a short time even when the dot goes -'ve.

This would give me the best control over AE, it would work very similar to a carb accelerator pump. If the AE algorithm calculated dot right from the first TPS/MAP movement I could set the first entry to 0. Then the trigger thresholds aren't needed - even if the TPS/MAP is noisy, the size of the AE pulses triggered could be set very low. The slope of that line could be increased after the threshold. This would also solve my biggest remaining problem - a lean spike because a slow throttle increase at high speeds isn't recognized so accelEnrich isn't triggered. It would also help my other problem - too rich of a pulse when AE is just barely triggered because I need to set a richer bin than I'd like.

For RPM AE, I'm looking foward to trying Hybrid BG/RPM based, but I think I'd still like to have the above changes.

whittlebeast · Post by **whittlebeast** » Fri Mar 31, 2006 3:58 am

Mike

Try this trick. The upper left section of the VE table is only in effect on a quick throttle stab off idle and can often be made far richer that you would normaly think. Watch the VE table as you do one of the stabs off idle and the cells that are in effect for a very short time period. This will normally cover for the lean hole. The other thing is that under normal driving I seldom stab the throttle from 800 RPM. MS2 will soon have a way to fix all this.

Hope this helps

mikesb · Post by **mikesb** » Sat Apr 01, 2006 6:30 am

Yeah, it's a good technique - it worked really well when I was using Alpha-N.

I'm using it for the middle part of my table - it helps with the slow throttle increase at mid speeds - in around 1800-2500 rpm in 3rd for in town cruises, coming off of speed humps when I'm too lazy to downshift, and 2500-4500 in 4th on the highway. I'm trying to limit how far I go 'cause those bins overlap a little with my cruise bins.

For off idle using speed density it's trickier. I could tune out the pops, but then I found two big problems. One was with starting off - letting out the clutch would drop the vacuum, those bins would kick in and run really rich. The other problem I found was cold starts - my lower RPMs would be way too rich and she'd struggle to get the vacuum down and idle properly.

Trouble is I need AE for only a short time after the MAP changes and if I'm still in those rich bins when it ends, she bogs down big time.

I think I'm going to try a code modification - I'd like to ignore the thresholds for AE and start calculating & using MAPdot from an assumed bin of 0/0. If I can I'll leave the thresholds in place for things like the Gego calcs.

This picture might help show what I mean. It's shows the accelEnrich PW on the left, time (of the AE event) on the bottom. Green is rich, red is lean.

I need the larger PW events to start higher rather than at 2ms - those are from idle (the log resolution makes some look like they start higher). You can see how green the events are around 2ms - those are at higher RPMs - the 2ms start point is too high but I can't lower it without hurting the events from idle - that's the threshold & first AE bin problem.