VE tables squared away. I am right at 14.7/1 on WB when closed loop. BLM's looking good.

Manual trans in 2 gear of 4 when no load on engine I get moderate to heavy bucking at slow speeds. To avoid it I need to drop to first gear or upshift to 3rd. Neither is desireable. Seems too improve I need to look at timing tables at that RPM and Map where it occurs and have a datalog of that event.

Q? Should I remove timing or add? And how much to start. Also should I smoothen the surrounding SA cells? Using stock EBL tables. I am at 1600-1800 rpms and 40-50 map. My SA is 27 at 1600 9both map) and 28 at 1800 (both map).

Edit: I just reduced the proportional gains. Previously was about 80% of stock EBL now more like 50%. A search suggested that. I do have VAFPR reducing FP from 20 to 15 at idle.

 

Hi

I tried to fix this issue for 2 years ( car is a 6spd -91 vette ). I whas closed to give up.
But im happy to said I solved it.
I hade both mechanical and tuning probleme. First I hade clogged injectors. After I replaced those the car whent from un-drivabel at low rpm to drivabel, but far from "smooth".
What I hade to fix in the tune whas first, the timing tabel. I hade to tweak the low map, low rpm area alot. For me it whas like a switch, over 2000rpm it whas smooth, below the car whas bucking.
And it whas whery sensitive, 2 degrees here and there made alot of diffrence.
I also ended up tweaking the closed TPS spark tabel. Everyone said that the closed TPS spark tabel should match the main timing tabel ( where you let of the throttel ). But I hade to increase the closed TPS timing well abow the main table. At idle RPM and below, my closed TPS timing table is 25, all other areas are around 35 or more.
I also tuned the VE tabel to be on the lean side at whery low MAP/rpm. The reason for this is that I thought I could hear some "popping/gurgeling" in the exhaust during low rpm crusing, going from closed tps to little tps. Like in stop and go traffic.
And then finally I tweaked the proportional gains, after a tips from Rbob.
This made the car good to drive. I wount say perfect, im still aware that the cars EFI is 17 years old. And im far, far from stock.
But I dont think I can get it to run better under the current circumstances. And to be honest, im the only one that will reflect over it. Put another driver in the car, and he/she will think its stock ( before you go WOT that is ; ).

Hope this help any, and you can understand my bad english.

//devil...

 

Thank you. That is what I expected to hear. On closed throttle deaccelleration I am at 123 BLM and WB should the expected enrichment with fuel pull off walls on intake then I seea decent A/F. So I think I will leave that alone. This event as stated is CL and A/F is right on. So spark is the option. I am uncerttain of I have "closed throttle" SA tables in EBL. Regardless this is not a CT event. I will add 2 deg SA in areas of RPM/MAP I see issue and blend up the surrounding cells. Lately I see KC only on startup(89 octane) so I can afford more timing lower in SA table. I idle at 20 SA and it ramps up from there.

 

Even thoe your A/F is "dead" on, 14.7:1 is perhaps not ideal A/F for that engine at that rpm/map? Have you tried to run the car in open loop, and adjust for another A/F and se how the engine react?
I have tried to run the car at a leaner A/F then stoich in open loop, and the drivability is better, more crisp. But as I use a cat, that is not a option for me.
I could "cover" some of this with the prop gain setting.

Good Luck, and let us know how it turns out for you.

 

Actually my WB shows 14.7/1 but that is stoich for 10% ethanol as WB is calibrated for "good gas". So I am right at stoich for ethanol blend or 14.3/1. Yes I did run OL for a month and fuel mileage was in the toilet. Now in Sept here the morn commute is like 50 deg and afternoon is 70's so dont want OL just now. I was thinking of adding fuel by running OL under 13 MPH as that is where bucking is? Just a thought. That would be enrichment to 13.7 on WB. But I just added 2 deg SA at that area and 1 deg SA in surrounding cells. Will try that out today. Thanks.

 

Which way did you change the gains? I have read that the farther away the O2 is from the engine the lower the gain.

 

Yeah, try that. The reason I used open loop whas to se trends. You know, when noting seems to work. And the results from that lead me to the prop gain change, as I have to use the darn 02 to keep the cats happy.
Good luck
----------
The proportional gain vs airflow table is used along with the proportional gain vs O2 error table.
The prop gain vs O2 error table is at $4DE.
The values from each table are multiplied together and divided by 256. The result is the proportional gain.

( thanks again Rbob )

Cheers..

 

I reduced the prop gains about 50% from stock .bin. That did not help in bucking however. I believe it helped idle surge. Idle surge just about gone but I need to idle at 850 rpms. May drop idle speed again with TSS. IAC still not functional si plugged.

I added SA as stated yesterday and it appears to help somewhat with bucking. Still present. Driveline slop may be contributor.

This issue is not a biggy but I noticed moreso when I got stuck in rush hour trafffic a few days ago and needed to drive in 2nd gear at a crawl for about 4 miles.

 

I tried to elimintate the IAC throttel follower, and that made my car more "jerky" to drive. Just a ide. I compared a auto bin with a manual car bin. And there where changes that involved the IAC.
Do you have the same probleme with a working IAC?

CHeers

 

IAC passage is temp plugged. For a while I did not remove IAC routines from .bin. Then I realized maybe I should remove the added fueling. I since did. My issues are with a steady throttle so IAC I dont think is a factor?

Long story. never had functional IAC. when I pulled the crossfire manifold the 7.4L TBI IAC apparently had differing wiring. I tried every combo recommended but not successful in getting it to function correctly. I have a suggestion for RBob on wiring and another as well as a 454SS member. Have not yet had time to attempt those. It does respond but in ways one would not want! I have a manual modded .bin. I just wonder how much slop in driveline. Original drivetrain cept clutch 109K miles.

 

hmm. I do belive that iac has effect on drivability, at low rpm, low speed. I can se the IAC step "follow" the throttel at low rpm. And for me that use a converted lt1 intake. It also allow air to travel the "right" path.
Se pic
http://z28.reanimator.org/stuff/intake/bottom.jpg

But I dunno if this apply in your case.

Devil.,.

 

I agree on the IAC following a change in TPS%. If throttle is locked as mine was in logs I would not expect IAC changing steps. I plan on reattaching the IAC soon. Just so many other things come up. Was going to work on that this week. cant find my soldering iron !

 

Just one more note on prop gain. I hade to tweak this a bit to find the right combo ( a romulator helps alot here ). To much hade the same as to little.
Also is it possible to se a log, as well as your timing tabel?

Cheers

 

I can do so Sun PM. Can I send to your email address? If so give me your email address. I have flash ability so I can play with timing pretty easily. Prop gains today about 50% reduced of stock EBL.

 

you got pm..

 

Got it ! will send from home tonight !

 

I've had this problem a few times.

Not any more.

Let me know if you want some help.


MAP calibrations try to do too much..

-- Joe

 

Anesthes: What info need I provide? My datalogs are done with EBL. Datalog Analysis shows a graph which I could email to you? As stated I added 2 deg SA where it occurs and smoothened by pulling one deg in surrounding cells. seemed to help a bit. But still there.

 

I found the following permanently cured the bucking:

A ton more advance
A ton of idle advance
ZERO all RPM error iac crap
Adjust throttle blades to produce 0 steps at idle
Reduce how much PW is added with battery voltage changes.

This is on the '730 $8D.. I know you're running that '747 based EBL thing.

Does it have a closed TPS advance table ?

What does your advance look like?

Mine looks like a vac advance dizzy.. 24* idle, 26* wot (blower mind you), high 40s in all cruise areas. Idles at 49-50kpa.

-- Joe

 

Look at your minimum and default Pulse widths these are set at 1.59 ms for stock GM 22#, but if you are running fords or newer style injectors, they are set at 1.05 ms.

This is one reason people get a rich idle that can't be fixed. A big injector has to be able to shut down more.

 

Good info. Did reduce the PS based on Volt change do "alot" for you and the trouble you experienced?
And could I se your timing tabel. It would be interesting to compare to my own

Thanks

 

My tables are attached. I had to user tunerpro to display them because I don't have tunercat on my work computer.

The batt voltage correction table I think might be ok for stock motors but on mine it seems to make the idle go way too high. For example, when the fans come on my idle would raise like nuts.

There is another table somewhere not defined in the TDF that I need to find - that seems to raise IAC counts under similar conditions. I'm still working out that stuff - but it needs a PW reduction for sure.

I'm running a TON of advance and the motor loves it. If you want I can email you a datamaster log ($8D).

Oh, NO PE advance either. On this bin I don't have the closed tps hack enabled, so I am running off both that and the main table. I've tried it both ways and I may leave it this way (using the closed tps table)

-- Joe

 

Thanks.

Its whery much like my own timing tabel. But I use even more closed TPS spark advance. I hade to ramp the timing down fast at whery low rpm and low map, to decrease bucking in stop and go traffic. But my timingtabel is like a switch at 1400 rpm. Abow 38 degrees, below 28. But hey, it works

Well back to topic.

Ronny, i will look at the files this weekend

 

I idle at 22 degsa. That is set in bin. But in datalogs it shows as 20 sa? I changed in bin from 20-22 and datalogs for reasons I dont understand did not change.

During bucking event I am now at 29-30 and bucking severity I will say is reduced by half. I will add 2 more deg in idle SA and same in that cruise area where buck occurred. It would seem I need to blend in the surrounding cells by adding a degree. Maybe I should use TP "smoothing" function for all SA table afterword. (just done).

I cannot posttables here at office but my SA-maxSA is 41 deg. In main tabkle my SA shows max at 60 map 3600-6000 rpms. Then it rams diown to 24 deg at 1000 map. PE adder for gear zeroed out.

SA-RPM error? Dont see that one(EBL.xdf)?

PW vs Volt. Dont see that either. But my V is steady. New battery and new Delco alternator. Volt reg not sure.

closed tps adv table. none.

IAC zero steps already. Idle at 900 rpm.

PW at idle steady 1.6 msec(vafpr). PRP gains reduced 60%.

I dont see those idle tables? But my issue is in a different area of no load 2nd gear crawling in complex so not to disturb neighbors(Aerochambers).

 

Ronny, the SA RPM error is the idle SA compensation & multiplier tables. Four of them, "SA - Idle High Compensation" is one. Then there is the MAP multiplier for it, along with the same two tables for low idle. Note that these tables will have no affect during a traffic crawl. They are only used in idle at a stand still (0 MPH).

You may want to set open loop, then see if the bucking changes. Also, the prop gains are not used in open loop. So don't touch those while using open loop fueling.

Bucking can be caused or corrected by either SA or fueling.

RBob.

 

I zero out all that idle spark error stuff. I'd rather run off the main closed throttle, and main spark advance table.

-- Joe

 

I reduced PRP gains earlier this season. then restored them to stock EBL. then about 3 weeks ago reduced them again. the car seems to run better with them reduced. So I will leave them. I think they are about 60% reduced from stock EBL. I understand not affecting idle. I idle OL. I will seach for a CL trigger over a certain speed. Did not find.

Idle SA comp. I just set idle high to zero. I idle 35-40 map. idle high mult is 100% so did not change. set idle low to zero. idle low mult at 0 so no change done. I know this has no effect on buck but wanted to see what happens to idle. Maybe should not have done since I just upped idle SA 2 deg so making two changes there!

OL running will kill my gas mileage. This AM temps are 55F and this PM around 80F. I tried OL a couple years ago and mileage sufferred. I drive car about 120 miles a week. I would like to set CL above 12 mph. But dont see that?

Running BLMs at 126-130 in logs where buck happens. I will double check that. WB shows 14.7-15.0/1.

I think SA is the cure. How about driveline slop?

 

I run open loop at idle only, it switches to closed loop around 1400RPM.

I guess you could probably change one of the 02 lookups to a VSS signal and change the relating constant to get your 12mph CL enable.

-- Joe