Where to start with off idle bog

[Ian Turgeon]

I think it's time I fixed this as it's getting annoying, and I have the tools to fix the problem.

I'm sure theres a number of parts I could throw at the problem, but I'm pretty sure its the tune at this point. I'm running an ultimate (v7?) t1 22 chip, 20g-12cm, 2800k stall, Walbro, 3" JSM open downpipe.

The problem now: ever since the new downpipe, off-idle has been consistently boggy. My wb02 is registering in the 16-18 afr range when coming off a stoplight, corresponding to the dead acceleration I get in this zone. I am not sure what typical numbers are in this condition, but it seems really lean.

Now that I think about it the truck has exhibited similar problems for a long time now, even before the converter and dp, just not as consistent and pronounced. I can remember a few occasions years ago where I would be braking for a turn, with my foot off the gas, then switch back to the gas to accelerate again, and it would bog for a short time. I always thought it was something with the trans at the time...

I guess my question is what table should I be looking at?

 

[MRKING]

Re: Where to start with off idle bog

Your dipping into parts of the fuel map that have not been refined on your chip . Get tunerpro rt working so you can datalog and watch where the bubble goes during the times you say it does this . Add a little fuel and try again . Youll have it in no time if you jump right in .

 

[91blazins10]

Re: Where to start with off idle bog

Time to mess around with code 59, I had nothing but problems with my old ultimate chip, truck would stall all the time, always had a stumble. Now I just open up tuner pro, turn on data tracing and watch where the AFR would be lean, then beef up the f29x table. Now I actually drive my truck everyday and it drives just like any other car would.

 

[MRKING]

Re: Where to start with off idle bog

Code 59 does have a few stater bins to get you started . Complete a few autotunes to get you close and then you can sell your ultimate . Or I believe dig , paul ,or jeff can even transfer your chip into a code 59 bin so youll be close to where you are now .

 

[ashman]

Re: Where to start with off idle bog

my truck bogs at anything approaching 17afr when loaded. get your fueling back up and you'll be golden.

BTW, jeff converted my original custom $58 tune to $59 and I did some tuning with it. never really felt that it was 'right'. So, i grabbed one of the starter bins and made a couple of adjustment to get afr's good at idle and left the remaining cell alone. this has proven to be FAR better than anything i had with the custom tune.

 

[Ian Turgeon]

Re: Where to start with off idle bog

I haven't done any tuning yet, just read over some of the write-ups and listened to Hood a couple of times. I don't think i want to jump into 59 just ye. Everything else is acceptable at the moment, and I'd just like to fix this one problem so It isn't such a pain to drive round town.

What tables am I looking at? I tried to locate in Jeff's 101 post but all i can find is:

"Word of caution. If you have off idle stumbles, bogs when accelerating, engine goes rich when slowing down chances are NON of the above changes will help much. The above tables are mainly for steady state driving not large changes in Kpa (boost), rpms, or throttle positions. That is for another section."

 

[Tooky]

Re: Where to start with off idle bog

The basics of fuel tuning the VE tables involves first logging/noting the RPM, KPA, and AFR in the problem zone. Let's say your problem is that it goes lean just off idle, mainly in the 60-80 KPA range, from 1200-2000 RPM. Try selecting that entire zone (rectangle) in the F29 table and add 10-20% fuel. Then retest and see what happens. If it's terrible, go back to your original BIN.

In TunerPro you can select that zone and bring up the Toolbox and click "Multiply.....by a factor of 1.2" 1.2 = 120% of the original value. Which obviously gives us our goal of "20% more fuel".

 

[MRKING]

Re: Where to start with off idle bog

Im sure youve been working on it all night since you have no kids and have some good news to report so far ? :lol:

 

[JSM]

Re: Where to start with off idle bog

In a stock based, non code59 chip you want to look at F29 table. This is the main fuel table for all conditions. It will be labeled from 0-100kpa, I would look for the low map (high vacuum) and above idle rpm range. If you datalog and watch the bubble move you will see it move up in rpm first before it moves to the right, that first section MIGHT be where your stumble it.

There is also a F29c table which is for idle. If those 2 tables don't match you can get a stumble also.

(code59 enlarges and combines these tables and has proven to make this transistion much smoother)

Now the other thing it could be is acceleration enrichment not enough.

The larger dp will flow more air, so it doesn't suprise me it is a tad lean. One of those 3 will solve the problem. But if you have the tools what are you scared of with code59? Have you seen anybody convert over, then want to go back? Are you scared of actually having a well tuned truck or learning something.

 

[TYTILIDIE]

Re: Where to start with off idle bog

Agreed, Code59 is waaay more user friendly. Especially if you can get away with making small changes in the simple XDF.

Jeff, in Code59, if the Closed Throttle table doesn't match F29x, this will cause strange issues? I have been having some issues ever since Closed Loop on my Alky tune with the truck doing very close to what Ian's is doing except that my truck stalls in the day time a lot.

 

[JSM]

Re: Where to start with off idle bog

Jeff, in Code59, if the Closed Throttle table doesn't match F29x, this will cause strange issues?

F29c will ONLY be used in code59 if you do not have it selected to use just f29x. All the base bins posted I believe are setup to use ONLY f29x. You can make it use both via the flags if you want but I doubt you have.

Just to clarify this.

GM code as designed had 2 VE tables. F29 and F29c F29c is for closed throttle basically 0% tps. aka IDLE. As soon as you give it gas f29 takes into effect so the ecm jumps from the 1 table to the other. If the VE #'s are not real close you get a drastic change. I will say 90% maybe more aftermarket chips didn't tune f29c much, and if they did chances are they don't match f29 to give a smooth transistion. If they didn't change f29c, then for sure the transistion won't be smooth.

For its time the Ultimate was just that. It far exceeded anything sold by ATR, Superchips, KenneBell, etc. But keep in mind that chip was developed ~7yrs ago now. The software just wasn't very strong back then and tuning involved Diacom logs and Promgrammer changes along with a UV light that took 30 minutes to erase a chip and then the chip was reprogrammed, and tryed again. If someone did 50 burns it was considered a lot. Today I might make 50 changes to a chip within the first hour of tuning. The software and realtime bubble, etc was all dreams back then.

Dig said something I found funny several weeks ago. "All the fast guys are doing custom tunes" I think that really speaks here, but I will go further and say it isn't all about being fast. Honestly tuning in 90% making it run smooth, 10% being fast. Just because your goal isn't to be FAST, or the Fastest don't be afraid to learn to tune.

Jumping off the soapbox, it is early and only got 4 hrs sleep last night...:tup:

 

[Ian Turgeon]

Re: Where to start with off idle bog

I'm not really afraid of it per say, I just wanted to make a few quick changes without digging too deep for this weekend. I'll be spending more time with 59 before too long.

 

[turbodig]

Re: Where to start with off idle bog

You can tune the standard ultimate bin too... you'll spend a whole bunch more time, but you can do it.

1) Shut off closed loop o2

2) Sit at idle, foot off the gas. Tweek the F29 closed throttle table so that your AFR is where you want it (pick 14.5 as a good start, unless the motor is still cold). Do a bunch of A/C on/offs, and a bunch of Park -> Drive and Park -> R transitions, all with no throttle. Note the AFR at these different load points, and change as necessary. You probably won't be able to do 14.5 at these higher load areas- might even be in the low 13s. Gotta see how it runs. Also, when doing the transitions, be aware that RPM drops as you do them, so you're actually getting into the row of cells below your idle RPM. Adjust these cells as nescessary.

3) If you really want to be thorough, change the desired idle speed table to a value ~200 RPM higher, and repeat the above. Keep going up in RPM (and repeating the transitions) until you get to a ridiculously high idle RPM. If your truck allows, you might even want to do a lower RPM than your original idle.

4) Once you've done all this, take a look at your F29 closed throttle table, and look for obvious big jumps in adjacent cells. Smooth the table out, where possible. Once you're done smoothing, go back and re-check your work with another set of transitions. If it's all good, you're done with this part.

5) Advanced topic- you can start playing with low RPM timing here, with the goal of reducing overall IAC needed and fuel delivered. Once you start doing this, you get into a cycle of change timing -> do the transitions -> change fuel -> change timing. It's a lot of things to juggle. Tunerpro's running change log helps, in that you have notes of where you've been, and where you're headed. Watch engine temp closely while doing this- you can booger stuff up with low RPM timing if you get too crazy.

6) Assuming you have the idle stuff sorted out... you can move to the F29 open throttle VE. For the most part, you'll want to do some off-idle transitions, watch the data, and bump up fuel as necessary. Do some with A/C and full electric power load on. If you don't have too loose of a converter, get some ballast (Engine parts, chubby friends) and repeat the off-idle transitions to get into the higher load points. Also, do some off-idles on slight downgrades (although, the converter usually stalls too high to get much use of this - YMMV.).

7) Do some tests of the inverse - simulated stop-sign pull-ups, parking-place pull-ins. Big Mall parking lots on Sunday AM are good for this.

8) Turn closed loop 02 back on. Recheck your work to make sure the o2 sensor isn't making it do anything funny.

With enough experimentation, you'll find the AFR your truck likes (or, rather, the leanest it'll tolerate smoothly) . Your goal is to get the AFR to be as smooth as possible when transitioning from one load area to another. It's less about the actual number, and more about being smooth.

If you put the time in, you'll be amazed at how nice they run. They never really ran well from the factory. (They had to worry about emissions when doing the above... a whole other set of rules applies there...)

The same processes apply to code59, although you only have one table to deal with.
Really, this process applies to any ECM or management system, in terms of a driveability tune.