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Thread: Big off idle stumble, whatt first? IFR? calc.vet? Something else I'm missing?

  1. #121
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    O2 problems were fixed a couple of months ago. Ended up being a ground lug spot weld failed for the heater circuit. I reattached it and the sensor has been working great since then, even seems to have fixed the switching latency. For the first time in eons the truck doesn't throw any codes, even the ones that don't throw a MIL. Back in September I did something I've wanted to do for a long damn time: I changed over to hydroboost. This is how the truck should have been stock. It wasn't without some 2nd order effects though as the blower inlet severely interfered with the HB accumulator and brake master cylinder. I ground enough off of the blower inlet to eliminate static interference, but I could still hear it when hitting bumps, taking corners, or hitting the brake pedal in reverse down my driveway so I removed the blower and had the inlet modified by a local shop. While I was at it, I also opened up the blower outlet as there was an orifice cast into it so I hogged it out.

    https://photos.app.goo.gl/ZpRDvCCzqsrTjfBi8
    https://photos.app.goo.gl/wqd4k2sHGLdsvf388

    I don't recall what the airflow was when I first put the blower on and my old logs seem to lack timing advance of all things so I don't have a before dyncylair picture. I know NA and pre-CALC.VET the max dyncylair was .64. My MAP from the initial post-modded blower datalog last week showed almost no boost (~95kpa with ~79 being atmospheric), so I removed the blower and tweaked the bypass valve preload. After that, I had to remove it again to further clearance the inlet and zinged through a weld with the hammer and grinder so back to the shop it went. I got it back a few days ago and got it all back together this time with excellent clearance and was showing boost similar to what I saw pre-porting (109 kpa pre porting and 107 kpa then) so I was pretty disappointed there. Tonight all I did was globally add 2 degrees of timing to the high map (and copy/pasted the low map to match) yet somehow mustered 110kpa. The difference that really caught my attention was in airflow. I showed a consistent 1.00 g/cyl right after porting, but tonight am showing a consistent 1.12 which is right at the top of the table for timing. Strange that this table tops out before pegging the MAF, this will definitely cause issues at lower elevations. Were I to skew VE/MAF/IFR I'm guessing I could buy myself some headroom in B5913. The thing that makes my brain hurt is the handoff between it and A0010 since one is MAF referenced and the other MAP. Below is a log from the other night. My big question from all of this is how do you explain the increase in dyncylair with MAP staying pretty much the same?

    Attachment 23125
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  2. #122
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    As for the transient fueling, here's the latest. I was running that B3406 table from Alouicious and his COS3 Whippled truck from 100 years ago and it was WAY better, but with 1 tiny problem. The truck would want to stall after firing on a restart. It did the same thing when I tried maxxing out the table when incremental changes were proving ineffective. The only way I can figure to smartly fix this table is to plot AFR against ECT and MAP, then filter by MAP changing more than 5kpa/sec or something along those lines? Does anyone have a smarter way to address this?
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  3. #123
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    So I tried this last night and the map wasn't as effective as I'd hoped. Looking at the data plotted in 2D, however, was helpful. Another epiphany I had was seeing how the impact factor affected starts. It seemed that it had a much more pronounced effect on starts than tip in fueling. Duh. TP isn't changing on a start, but MAP is, so if changing impact is making starts worse then this must not be the right place to try fixing my tip in issue. As expected, the results of trying to get it right via impact table alone was not the right way to go as the truck would not run this morning. Similar to how I maxxed out the table a couple years ago and the truck wouldn't run, only not as extreme. I trimmed impact back almost to where it was, and started bumping the stomp table. The title is very misleading. On a cold winter morning the truck works well, but then as it starts to warm up just a little it gets bad quick, then once warmed up it's tolerable. The reason for this appears to be that the table is flat up to 20 degrees C, then drops off very quickly after that. For now, I'm slowing this taper with 10% bumps. It's going to take a few cycles to see if this is the right way to do it. To ballpark it, I really don't need to log because I can watch the wideband flick lean any time I poke the gas. That and I forgot to plug in the wideband on my last log. I decided logging BEN as ECT vs MAP was a better idea for the colder temps. Nos sure how I'll make a 2D table to capture stomp once I'm closer, I figure I'll just make a single column but what to make it is the question.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  4. #124
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    I went and horsed around with Stomp and wasn't really seeing any effect. I blew well past the EFILive limits for that table and the truck still never got a rich tip in. I'm going to put it back where it was mear maxxed out and leave it there. I was about at my wit's end, then decided I should try to boost the Impact table in the high MAP areas. I realized the lean spike I was going after was happening at 70+ kpa for the most part, and the Impact table is the only one that breaks it down that way. Again, in parts of the table I blew well past EFILive's limits, but was well within the GM limits. I finally saw an observable improvement, though it wasn't extreme. On the last drive, it looked close, but AFRs were jumping around quite a bit. Since I left the 20, 30, and 40 kpa columns alone, the truck was still happy to restart.

    I'm thinking about revisiting IFR and doing another calc.vet to have a good starting point. I also made some changes that I thought I'd made years ago recommended by statesman. I changed the O2 switch point to 450 mv and the min duty cycle to .9, so I need to do a log before thinking about changing the evap time for a rich lift condition, though that's much less of a priority than this other stuff. I thought I'd been running semi-open loop all this time and it turns out I wasn't, I'd only disabled idle STFTs but closed loop was free to come on. That explains why it never seemed to work. But these jumpy AFRs really have my attention right now and I think that's where I need to focus. Right or wrong, tip in is much improved while retaining a truck that's happy to restart. I've also gotten the truck in a better mechanical state than it's been in years. Since it doesn't feel like a piece of crap anymore, I'd like to finish addressing this tune that's fallen to the wayside for far too long. After the calc.vet I need to type up some notes so I can modify the IAT VE multiplier. I've seen significant AFR swings WRT IAT. Every time I reread the COS tutorial I remember how half baked this thing really is.

    So after all that rambling, I have 3 big questions: 1, what happens when you exceed an EFILive limit but stay within the manufacturer's limits? 2, my values do not seem sane compared to stock. Is that unusual on a modified vehicle? The injector trajectory is significantly different that stock. That, plus the baby blower I have on there really screw with the tip in fueling. 3, is that tip in spike transient related or should I be looking elsewhere seeing how far I've gone to get where I am with the transient fueling? Below is the current tune and the latest log, both subject to change depending on how motivated I am.

    Transient Log 19 Post Impact Bump 100kpa blend 40-100.efi
    411 Transient Round 18 Impact Bumped at High MAP 25 percent and blended 40-100 linear.ctz

    18 tunes and 19 logs since last night. For a lot of them I knew they were junk the instant I cracked the gas and it took longer to get back to a parking spot than it did to flash a new attempt.

    To be clear, I did a restart at 130 degrees and the truck drove great up to operating temp of 180. It's the wideband jumping around that drives me nuts at this point. Plus I have to see what it does from a 30ish degree cold start tomorrow.
    Last edited by Supercharged111; December 27th, 2019 at 04:09 PM.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  5. #125
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    Quote Originally Posted by Supercharged111 View Post
    I've also gotten the truck in a better mechanical state than it's been in years.
    That's not good enough. Being better than crap doesn't mean it's good.... and you can't tune an engine until it's good. Smoke test your intake, put in a fresh set of spark plugs, check your spark wires and replace if not in great condition, check your air filter and replace if needed, replace your fuel filter and check your fuel rail pressure (if you can). Then come back and tell me you know for sure that the engine is mechanically good.


    Quote Originally Posted by Supercharged111 View Post
    18 tunes and 19 logs since last night. For a lot of them I knew they were junk the instant I cracked the gas and it took longer to get back to a parking spot than it did to flash a new attempt.
    And what exactly did you learn from that? Spitballing tunes is fine as long as you're keeping track of the changes you make and what effect each change has on how the engine performs. A lot of people learn to tune that way, but you have to try to learn from the changes and not just make random changes which are discarded and forgotten about if they don't work.

  6. #126
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    A lot of the improvements aren't tune related, but my O2 sensors seem to both be working and I discovered a couple vacuum leaks, one was the evap vent valve of all things. At this point, I don't think there are any issues being tuned around. I sprayed carb cleaner at the intake manifold and no change. Filters are relatively new, but I should check fuel pressure. This morning's drive revealed that the values I felt weren't sane aren't, those were the cold values. The factory has a large disparity between cold and warm impact factor and this trial and error tweaking of mine seems to imply the engine wants less of a disparity. For instance, if it gets cold enough, tip in works fine. As the engine warms up, response gets worse, then fully warmed up there is only a slight hesitation. The 80 C values in there now have excellent response but the data shows a lean condition at tip in. Not sure what to take from that. I've kept track of my changes from stock, to a globally bumped map, to the concoction I have now that's getting scrapped. I've searched and searched for ways to methodically alter these tables and found nothing. I even tried one of my own and feel it was worthless. I can see a lean dip on the 2D graph over time, but the way the AFRs jump around I feel I need to address that first. If you have a way to methodically alter these tables I'm all ears.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  7. #127
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    Are you using the latest version of EFILive?

  8. #128
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    Ha! Yes I am! I finally got off my ass on that one.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  9. #129
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    Post the stock tune you've been using as your reference.

  10. #130
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    This is what I pulled off the PCM when I first got it. I bought this 411 from Justin at Blackbear 100 years ago and had him flash an 01-02 Chevy Express tune (12212156 OS) on there with COS5 plopped on top of that. Bear in mind this would have had a GenI 5.7 like my truck and not an LS based engine. I wonder if that's why you noticed so many things that seemed wrong.

    411 Base Tune.tun
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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