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Thread: Fuel cutoff settings- Softer rev limiter?

  1. #1
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    Fuel cutoff settings- Softer rev limiter?

    Hi guys, I've got a question!

    I haven't changed my fuel cutoff/rev limiter settings in my LSA Sky for quite awhile but I recently have been thinking about experimenting again. The stock CTS-V LSA file uses the throttle, I turned that off long ago because it seemed to make it dump too much power and be too slow to regain rpm/power after it hit the limiter. So for the last couple years I've been running it with only ignition timing and fuel cut, more like the LS9's do. But the LS9's don't use ignition timing control, which I kinda like since it's fast and more "controllable".

    To clarify, this is only for situations like when doing silly stuff like donuts or burnouts. lol. Obviously I don't like to sit on the rev limiter, but there are times when things are happening too quickly to worry enough about rpm control. So like when drifting a turn in second gear, I want it to be able to run right up to 6k or so, but not dump power and rpm so drastically that it throws the car back and forth when the wheel speeds change. (Naughty drivers problems. haha) These settings I've been using have been working ok, but I want them better! We all know, it's ALWAYS a never ending quest to make things better!

    Anyway, can you guys look at what I've been running and maybe we can get a discussion going about what everyone is doing for rev limiting? I think it would be cool to have it setup so it basically sits at an even 6k or whatever you want it to be at, without the up and down power and rpm's of a "normal" rev limiter setup. I've also made my main ignition timing dump drastically at around 6300 on up so if it does go towards 6400 or above, it won't be able to make enough power to rev any higher. I'm thinking I'd almost like it to only be controlled by dumping the ignition timing so it would be easier to keep it at a certain rpm in those situations, but that's not how any stock limiters I've seen are setup. BTW, I actually wanted to look at an LS9 file with PTM, but I only have LS9 files up to '11 and I think that started in '12?

    Thanks guys!

    Here's the settings I've been using. It's been years since I came up with these so I don't even remember my thinking on any of the numbers I put in! It's been working pretty well to control the rpm's, I just think it can work better with some more knowledge from you guys and some re-experimenting.


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  2. #2
    if you are on the limiter for long periods, throttle is definitely the nicest on the engine. Long periods of high RPM timing retard will overheat exhaust components pretty quickly. Just something to keep in mind.
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  3. #3
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    Quote Originally Posted by Chris@HPTuners View Post
    if you are on the limiter for long periods, throttle is definitely the nicest on the engine. Long periods of high RPM timing retard will overheat exhaust components pretty quickly. Just something to keep in mind.

    Excellent point Chris! And thanks for jumping in here, I really appreciate your insight.

    So maybe what I'll try experimenting with is trying throttle only, or maybe throttle and fuel cut. The thing that's weird is the LS9's use fuel cut ONLY. (The '11 file I was looking at is a PTM car.) I know fuel cut is extremely fast acting and in theory(?) there shouldn't be an actual combustion taking place in the cut cylinders or firing times but it still makes me wonder if cutting fuel at redline is a good idea? When I see my wideband go to 2.0/full lean during fuel cut it scares the cr@p out of me!

    So I'm going to lower the limit rpms down to like 4k for experimental purposes so I don't have to flog this thing to death in the process. I think I'll try throttle only and see if I can get the torque limit numbers right so it will control the rpm without huge power/rpm swings. So can you make sure I have the theories behind these tables correct here? I'm assuming table 12073 basically sets the maximum torque value that is allowed during limiting? So if my calculated torque reading in my scanner is 800, and I set the max at 400, it should cut somewhere around half the power when the limiter is active? And table 12070 sets the amount of torque allowed in relation to the rpm error? So setting table 12073 to all 6000 would make the limiter not do anything? I think I'm ok on that one, it's the Delta table I need help with. The delta table 12070 says "The commanded torque value based on rpm error", but is it actually adding to or subtracting from the desired torque? So if I raise the positive numbers on the left side of the table the limiter will have LESS effect? And if I make the negative numbers on the right side MORE negative it will have a stronger effect of limiting power when the rpm's are OVER the limit number? Do I have that right? lol.

    Stock '11 LS9 table values...


    Last edited by gmtech16450yz; 03-03-2017 at 02:17 PM.
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  4. #4
    Been a long time since i looked at this code...

    The two looked up values are added together for the final torque request. You are correct that making the numbers more positive (or more negative) as the RPM error gets larger will make the response faster.

    The ECM will also switch from fuel/spark to ETC if the RPM limit timer exceeds the switchover delay table. The extreme limits are a hard fuel cut.

    Yes fuel cut is the fastest way to reduce engine torque. The injector doesn't fire so there's no fuel to burn, the WBO2 sensor will read lean for sure, its just air pumping thru the engine.
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  5. #5
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    Quote Originally Posted by Chris@HPTuners View Post
    Been a long time since i looked at this code...

    The two looked up values are added together for the final torque request. You are correct that making the numbers more positive (or more negative) as the RPM error gets larger will make the response faster.

    The ECM will also switch from fuel/spark to ETC if the RPM limit timer exceeds the switchover delay table. The extreme limits are a hard fuel cut.

    Yes fuel cut is the fastest way to reduce engine torque. The injector doesn't fire so there's no fuel to burn, the WBO2 sensor will read lean for sure, its just air pumping thru the engine.
    Again, you're awesome Chris! Thanks! BTW I know you're busy and I'm getting deeper into this so don't feel like you HAVE to read all this and respond! There's got to be others reading this and picking up some tidbits.

    What you said about the fuel cut being just air pumping through the engine is exactly what I figured, so that makes those super lean wideband readings a little less scary! I have noticed something though, If the fuel cut is active for very long, the boost levels rise A BUNCH. Like I just created a boost spike from 12.3 to 15.2psi by simply staying "in" fuel cut for a second or two. I'm not sure the actual explanation, but obviously having a few cylinders not getting any fuel for a period of time effects something in a way that it raises boost. I'm not smart enough to know why though! Maybe the air going through the engine cools down the chambers or exhaust since there's no actual combustion going on? Or maybe the un-combusted air is heavier and denser than combustion gasses so it restricts the exhaust a little bit more? I don't know, but it appears to be happening.

    "The extreme limits are a hard fuel cut." This is huge too, thanks for mentioning that. That means when I'm trying to make a "soft" fuel cut rev limiter at say 6k rpm, I need to make sure the extreme limit is higher otherwise I'll still be getting a "hard" fuel cut. Interesting.

    My goal is to make a soft limiter, but one that will absolutely not go over my limit by more than 100rpm or so. I played around with a few settings tonight and I'm definitely figuring it out! In table 12073 I went way lower than I had it and it resulted in a HARD drop in torque when the limiter hit. I went the other way with higher values and I could make the limiter basically not work. Ok, got that.

    I then figured out that in table 12070 the secret is to set the values in the +100 column on the right side to something small enough that it drops torque, but not by too much. With all other values the same, I went from -130 to -100 in the 100 column and it definitely made a softer drop. Ok, I'm in the right direction! haha. I actually made the values in the higher error columns MORE negative to insure that if the rpm's did go too high, the limiter would have enough authority to keep them in control. The theory is a soft initial torque drop but if it doesn't work, come in hard and dump a lot of torque.

    The other clue I learned was on that same table 12070, I had the values on the left side too high. Meaning when the rpm's started to drop back down after the limiter hit, it would add back in too much torque and that's why you get the big rpm oscillations. So what I did there was to make the increase of torque very slight and gradual. The theory there is if I get the initial torque drop close enough, it won't really need to be adding back in a lot of torque.

    So far I've got a log were it hit my limiter setting of 5500rpm and then it only dropped to 5200 at the lowest point. That's a lot better than the 700rpm drop and rise oscillations I was getting before. (I started experimenting with the limiter set at 3500rpm. Good idea when you're messing with the values enough to entirely disable the limiter function!) I'm shooting for getting it to hit the limiter at 6300, then drop and hold steady at 6100 or 6200. I think I can do it! I'll post up log screenshots and the table values I end up with later.
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  6. #6
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    sounds like some good testing, on my e38 LS2 boosted i use ETC only and mine seems to come in a couple hundred over limit and holds there and i can't even feel it engage and it just sits there no bouncing at all, but in saying that when i was on the dyno the limiter acted differently and cut in exactly on limit and u could feel the torque loss

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    Ok I made some progress and learned some new stuff!

    I had been running for a long time with fuel and spark cut and without ETC cut. As Chris mentioned, dumping ignition timing to control rpm isn't the best idea but it's relatively quick, quicker than ECT. The LS9's use fuel cut only, which works, but I kinda like the idea of using the throttle too since it's actually the "best" way to control torque.

    Here's another reason I didn't like only using fuel cut, I learned something about boost in this process that had been bugging me (and others). Boost climbs higher when the fuel cutoff is active. Why? I know it happens, I can see it happen. And I can MAKE it happen. When I was playing around with my rev limit set to 5500rpm, I was getting boost spikes as high as 3psi higher than normal. So if the boost was at a steady 13psi before the limit, as soon as the limiter was active it would jump to 16psi! Does anyone have an explanation for why the boost rises? (I put those parts in bold so they don't get lost in my "book" here. lol.) Temp? Pumping uncombusted air in the fuel cut cylinders raising pressure? I know it's not simply caused by the rpm because I could get the boost spikes just as high at 5500 as 6300.

    That was one of the reasons why I tried to get a better rev limiter operation. I didn't like the boost going that high, especially at those rpm's. That's where ETC comes in. Hardly any stock tune files use ETC for rpm control. I'm not sure why, maybe it's not as "safe"? Obviously if your throttle sticks and you only use throttle control to limit the rpm's, you're screwed! I wanted to use throttle, but also be as safe and "friendly" to my engine as possible. I decided on ETC and fuel cut only, no spark limiting.

    So my first tries with ETC enabled were too strong. Fuel cut AND ETC can cut a whole lot of power. So I worked on those torque tables. I was hoping the values jived with my indicated or desired torque readings, but they only kinda do. So figuring out what your particular torque numbers in these tables should be will be the hardest part. The calculated torque values obviously vary greatly when you mess with a stock tune. Surprisingly enough my indicated torque values appear to be VERY close to what my crank torque values would dyno at.

    The basic premise is this... Let ETC do most of the "work" of limiting, but only slightly decrease torque, don't dump it down to zero like most stock (and modified since most guys don't touch this stuff) tune settings do. As you can see in the first screenshot I'm going to post, the torque drops to almost zero when the limiter is active. F that! Table 12073, the torque limit table, is basically the "floor" that the torque will drop to when the limiter first hits. Raise these values and the limiter will hit with less throttle and fuel cut drop. Lower the values and it will dump throttle lower and fuel cut more cylinders when the limiter first "hits". I raised these numbers until the torque only dropped enough to let the rpm's drop 200 or 300rpm from the limit setting.

    The Delta table 12070 is where you stop the oscillations. The problem with my original settings, and most stock tune files, is the left side of that table. When the rpm's drop, the positive table values give back too much torque, which then hits the limiter and it dumps it back down to zero. Then it repeats over and over. That's what creates the "bouncing" off the limiter. What I did was to drastically lower the amount of torque that the dropping rpms can add back in. So basically it's ok if the limiter drops the rpm's 100 or 200 lower than the set point, the delta table won't add back in ANY until the rpm's drop lower than 300 below the set point.

    The right side of the Delta table is what saves your engine. haha. That's where you want strong values so if the rpm's DO rise too high, the torque is dropped drastically. I was considering letting the 100 column be super low, but I settled on -100 for the first drop as rpm's go higher than the set point. Just make sure you make the higher rpm error column values as much or more than your total torque so you're sure it's going dump all torque if the rpm's go that high. At 300rpm over the set point I'm already dropping below my "floor" in the torque table 12073. The higher values are really just overkill.

    Here's some screen shots...

    This is the situation that got me started on "fixing" my rev limiter. It's a tight turn and then up a hill, and then another tight turn. No time to shift, more fun to just drift it in second gear! The drastic "bouncing" makes it really tough to control the car though...



    ^Notice the torque, it drops to 26! Is that really necessary? That was with fuel and spark cut only.




    ^This is an example of the boost spikes I'm talking about. Notice the boost, wideband and narrowband readings. Seems kind of scary doesn't it? This is basically what just about any LSA or LS9 boost would do when you hit the limiter. Why it happens I don't yet know, I just know it happens. So when your overdriven blower is running at a steady 15psi and you think everything is fine, in this situation it might be OVER 20 PSI! Yikes.




    ^This is one of my first tries with ETC enabled. The first torque drop was better at 137 instead of 26, but not good enough. Adding in ETC makes the limiter effect stronger so I had to go even further with my table changes.




    ^Now we're talking, the initial torque drop was only down to 374! Oscillations are still too high though.




    ^This is third gear. I'm almost there! This is my goal, a torque drop that's just large enough to stop the rpm rise, but not so low that it starts "bouncing". You can see after the initial limiter hit, it actually stays at steady rpm/torque/fuel cut/throttle amounts. And also notice how much happier the boost and wideband readings are. MUCH safer! I made some more changes after this log that I think might be my final settings. This is pretty close and a helluva lot better than it was! Here are the settings I'm hoping will be my "final" values. I'll see the next time I do a little drifting! BTW where are all the smart guys? Jump in here and let me know if this is no big deal and I'm an idiot for not already knowing it, or wow it's amazing! lol. I know it's something very few guys mess around with. From what I've already found I think there's a LOT of room for improvement in this area of our tunes, especially in boosted applications. Thoughts?

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    I'm actually very appreciative of you doing this Sooo, I'm just sitting here taking notes...

    I had a bad experience with SCT a few years ago where I changed some torque limits for neutral and it killed the rev limiter all together - these tables aren't in HPT and I advised SCT to remove them Never the less - I never caught it at the time and wasn't paying attention - over revved and kissed some valves... I tend not to mess with actual torque settings for rev limiters much anymore...

    I do see and understand all of your points and on a side note in reference to your boost question - I can prove time and time again that with a load on the engine a belt driven pd supercharger builds more boost just because its spinning up slower - explain that one when you figure out why they build 3 more psi hitting the rev limiter - perhaps the answer is one and the same I think it has to do with the physical air molecular makeup and how it flows as to a degree it has a weight, but no clue?

    I was noticing one thing - wouldn't you want more pulled in the lower gears as they are hit quicker and theoretically would require a quicker or stronger hit?
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    Quote Originally Posted by GHuggins View Post
    I'm actually very appreciative of you doing this Sooo, I'm just sitting here taking notes...

    I had a bad experience with SCT a few years ago where I changed some torque limits for neutral and it killed the rev limiter all together - these tables aren't in HPT and I advised SCT to remove them Never the less - I never caught it at the time and wasn't paying attention - over revved and kissed some valves... I tend not to mess with actual torque settings for rev limiters much anymore...

    I do see and understand all of your points and on a side note in reference to your boost question - I can prove time and time again that with a load on the engine a belt driven pd supercharger builds more boost just because its spinning up slower - explain that one when you figure out why they build 3 more psi hitting the rev limiter - perhaps the answer is one and the same I think it has to do with the physical air molecular makeup and how it flows as to a degree it has a weight, but no clue?

    I was noticing one thing - wouldn't you want more pulled in the lower gears as they are hit quicker and theoretically would require a quicker or stronger hit?
    Interesting point on the slower the rpm climbs the higher the boost. My simplistic guess/explanation might be this- if the rpm's are staying the same, not rising or dropping, the blower's output is "matched" to the rpm the engine is running at. So say at 5000rpm the blower is producing enough air to result in 10psi. If the rpm's went higher but the blower speed stayed the same, that same amount of air would result in a pressure of say 9psi at 5100rpm. (That's basically the whole point of changing pulleys obviously, to make the blower produce more air than the engine rpm's can take.) But what if when the rpm's rise so quickly that the blower's output is somewhat "behind" the engine's rpm or ability to flow that volume of air coming out of the blower? In other words, at a particular ms of time, the blower could be producing enough air to result in that 10psi at 5000rpm, but by the time the air actually goes from the blower to the intake or combustion chambers the engine rpm has actually risen to 5100rpm? Does that make sense? So if the rpm's are rising very quickly the overall boost will be lower. But if you make the rpm's stop rising by doing something like a rev limiter's fuel cut, the boost pressure "catches up" with the engine's ability to flow and the pressure rises? Maybe? H#ll I don't know!

    On the lower gears comment, I agree totally and thought of that. There's two reasons why I didn't make the gear rows very different- The first is that on my particular car the second gear situation actually ended up being too much torque drop and the 3rd gear situation ended up actually better with the same amount of torque reduction. So that actually goes against what we both would think it should be. Perfect on MY car might actually be LESS torque drop in the lower gears and MORE torque drop in the higher gears. WTH? lol.

    The second reason is that with a manual trans where the gear position is calculated in the ECM instead of it knowing the actual gear, I've found it doesn't always "know" the correct gear. So for a lot of tables with gear rows or choices, I tend to keep them all the same in case the ECM is "confused" on what gear it's actually in. With an auto it obviously works a lot better and you can depend on the different values being used in the correct gears.

    I think I have a pretty good handle on the rev limiter, I'm almost more interested in this boost phenomenon! There's got to be some people way smarter than me that can explain why it's happening. And you're right, what you've seen and what I've seen could in fact be caused by the same laws of physics or whatever.

    Thanks for jumping in BTW!
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  10. #10
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    Quote Originally Posted by gmtech16450yz View Post
    Here's another reason I didn't like only using fuel cut, I learned something about boost in this process that had been bugging me (and others). Boost climbs higher when the fuel cutoff is active. Why? I know it happens, I can see it happen. And I can MAKE it happen. When I was playing around with my rev limit set to 5500rpm, I was getting boost spikes as high as 3psi higher than normal. So if the boost was at a steady 13psi before the limit, as soon as the limiter was active it would jump to 16psi! Does anyone have an explanation for why the boost rises? (I put those parts in bold so they don't get lost in my "book" here. lol.) Temp? Pumping uncombusted air in the fuel cut cylinders raising pressure? I know it's not simply caused by the rpm because I could get the boost spikes just as high at 5500 as 6300.
    Here is my explanation. The reason boost pressure spikes when on fuel cut is the engine isn't working as it should when it's not combusting a/f mixtures. The exhaust velocity is exponentially higher when it's hot burnt exhaust. This effectively scavenges inlet air from the manifold/blower. So when a cylinder doesn't fire that means it's only using the piston to pull air in and push the cylinder of air out the exhaust effectively making the intake portion more restricted.
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    Quote Originally Posted by LSxpwrdZ View Post
    Here is my explanation. The reason boost pressure spikes when on fuel cut is the engine isn't working as it should when it's not combusting a/f mixtures. The exhaust velocity is exponentially higher when it's hot burnt exhaust. This effectively scavenges inlet air from the manifold/blower. So when a cylinder doesn't fire that means it's only using the piston to pull air in and push the cylinder of air out the exhaust effectively making the intake portion more restricted.
    From my post above-
    Maybe the air going through the engine cools down the chambers or exhaust since there's no actual combustion going on? Or maybe the un-combusted air is heavier and denser than combustion gasses so it restricts the exhaust a little bit more?
    Yep, that was one of my thoughts, and the one that makes sense to me. This also explains why when you get high rpm misfires the boost goes up. I wonder how many engines have been killed by a lean condition at high rpm WOT not only causing knock or misfires, but the boost levels also creeping up at the same time. Double whammy.
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    Ok I wanted to make this a separate post because...

    I DID IT!!!

    haha. Ok I just went to lunch in my car and on the way back I had a little fun. Those last settings I thought might be my final values worked AWESOME!!! This first screenshot was in 2nd gear, slight incline. What it basically did was to spin up the tires to redline, and then it just sat there spinning at right around 6k rpm. Brainless burnouts! lol. No more "bouncing" off the limiter and the rpm's and wheel speeds going drastically up and down. This isn't a replacement for actually modulating the power/wheel spin with my foot, this is just for when situations happen way too fast to control a very short wheelbase high hp roadster without a little "intervention". By using the power that's in our ECM's to do some of this work it ends up being WAY easier on the engine also.

    Here's the 2nd gear run...



    You can tell when it first hits the rev limiter by the yellow TPS trace dropping. Look at the torque, it's relatively flat and well controlled. The boost is a reasonable 9 or 10psi and you can see by the wideband readings that the actual injector fuel cut isn't very strong because the exhaust isn't getting full of unburnt air making the wideband peg at 2.0. This is the smoothest I've ever seen an LS engine sit on the rev limiter, stock or modified. I would think the drift guys would love this!

    Here's a 3rd gear pull from today also. Look at how flat the rpm trace is. In both of these situations the highest the rpm's went to was 6350, 150rpm's over my limit setting of 6200. That's better than I've seen a lot of stock tunes control rpm. I can live with it sometimes hitting 6300 or even 6400, that's still relatively safe for an LSA. Especially when it's a flat rpm instead of bouncing between 5500 and 6500. And I also REALLY like using ETC for torque control. Like you said Chris, it's the easiest on the engines that's for sure.

    3rd gear pull with settings from the tables above...

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    That is good rev limiter fueling and boost control... Is there anyway to use a harder throttle control or is that completely impossible with this approach? I can't have it over shooting the limiter and I know that's very possible with just throttle cut if not setup aggressive enough...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

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    Quote Originally Posted by GHuggins View Post
    That is good rev limiter fueling and boost control... Is there anyway to use a harder throttle control or is that completely impossible with this approach? I can't have it over shooting the limiter and I know that's very possible with just throttle cut if not setup aggressive enough...
    I'm using both throttle cut AND fuel cut. You can pretty much dial in as much or as "hard" a cut as you want. By putting certain values in these tables you could basically make the power go to zero and STAY THERE after it hit the limit setting. I'm pretty impressed with the control you can have with the options available, at least in an E67 Gen 4 ECM. It would be nice if you could separately and directly control ETC vs. fuel cut, but just dialing it in by the torque numbers seems to create a pretty good blend of ETC and fuel cut automatically.

    So as far as being able to keep the rpm's from overshooting, I think it's entirely possible to set up these tables so they have BETTER control over rpm than most factory settings. Even the LS9's are only using fuel cut, which results in higher boost and a more "violent" torque control. It's got to be harder on the engine than using a combination of ETC AND fuel cut like I'm doing here. So far I'm not seeing a downside to changing these from factory settings, especially when the engine itself is modified and making more torque than these settings were meant to see.

    edit- I know I write a lot and it's hard to take it all in so I'll copy paste part of it that relates to what you were worrying about...

    The right side of the Delta table is what saves your engine. haha. That's where you want strong values so if the rpm's DO rise too high, the torque is dropped drastically. I was considering letting the 100 column be super low, but I settled on -100 for the first drop as rpm's go higher than the set point. Just make sure you make the higher rpm error column values as much or more than your total torque so you're sure it's going dump all torque if the rpm's go that high. At 300rpm over the set point I'm already dropping below my "floor" in the torque table 12073. The higher values are really just overkill.
    So if you put a value like -500 or -700 in the 100 and up columns of that delta table, believe me your engine isn't going to over-rev! That's basically telling the ECM to cut ALL torque if the rpm's go 100rpm higher than the set limit value.
    Last edited by gmtech16450yz; 03-10-2017 at 08:10 PM.
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    nice work, great result!
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    if only the traction control was as easy to adjust, but this has given me some ideas for it to test out, do the limiter and traction adjustments interact or are they a totally different area of control..?

  17. #17
    Quote Originally Posted by 07GTS View Post
    if only the traction control was as easy to adjust, but this has given me some ideas for it to test out, do the limiter and traction adjustments interact or are they a totally different area of control..?
    the traction control torque request come directly from the EBCM (ABS) module
    I count sheep in hex...

  18. #18
    Tuner in Training
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    so I take that the switch over delay is set pretty low to make this work properly?

  19. #19
    Advanced Tuner
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    Quote Originally Posted by russ472 View Post
    so I take that the switch over delay is set pretty low to make this work properly?
    Good question. And I don't have the answer actually. haha. Here's the explanation of that table...

    [ECM] 12069 - RPM Limit Method Delay vs. Gear: If RPM limiting has been active greater than this time then control method with switch from Spark/FuelCut to ETC.
    The stock value comes up in seconds, and most stock tunes are around 5 seconds. (or 4.13359788359788 ftn if you're using that scaling. lol.) I figured 5 seconds is an awful long time to be sitting on the rev limiter so I arbitrarily set it to all 2.0 seconds. I actually was expecting the throttle cut to then come in 2 seconds AFTER it first hit the limiter, like the description seemed to say, but it didn't seem to work that way. Throttle cut comes in immediately even with the setting at 2 seconds. Now this may be because I already have ETC enabled, but honestly it worked so good on my first tries that I never experimented with that delay table any further. For what I wanted I didn't really want to delay ETC cut anyway. So to answer your question... I don't know! I think that table is more of an extreme case fail safe kind of thing anyway. I know I've had it at 2 seconds for years with ETC disabled and I never saw throttle cut in any logs. I doubt I've ever sat on the limiter that long though.


    07GTS, Also a good question! Again, I only know what I know, and I don't know much about traction control because I never use it!!! lol. I turn it off whenever I get in any car. When I built my LSA Sky I had a CTS-V EBCM that I was going to use so I could have full traction and stability control, but the ABS, brake bias, pedal feel, power, etc was so perfect with the stock Sky EBCM running all by itself I never put the V EBCM in it. That way I never have to turn it off! Yep, no traction or stability control in a ~750whp ~3400lbs car. I love it!

    Anyway, Chris is right, the EBCM is what decides the traction control part of things. I do have a question though, is there a chance that the EBCM makes the "request", but the TCS settings in the ECM do effect the ultimate amount of torque? So has anyone messed around with the TCS settings in the ECM itself and had it directly effect traction control events? I haven't experimented with that stuff at all because like I said, I just don't use it. There are a LOT of TCS and torque settings and tables that we have control over in the ECM, they should have an effect on something! On that I have no idea. I know where I'd start though... Does anyone have any logs of an LS9/ZR1 during PTM situations? It sounds like fuel cut when it's happening, but in stock LS9 tunes fuel cut isn't enabled in the TCS settings, only spark and ETC. I'd like to actually see what's happening during a ZR1's traction limiting situations since that "should" be the gold standard.

    Last but not least... THANKS AGAIN Chris!!! You posted 4 little words. I REALLY appreciated them! It's really interesting how this software you've created has changed how I feel about working on cars. I've been fixing cars for 4 decades now. It gets old. lol. I actually just "retired" from my dealership job after 32 years. But this tuning thing is so far beyond changing jets and modifying distributor springs and weights that even for me I'm learning new things constantly. Making "discoveries" like this are so freakin cool! I didn't like something about how my car acted, I experimented for awhile making it better, then worse, then way better. The end result? I get more enjoyment out of my driving experience and I exercise my brain cells in the process. And the best part of all? With the power of the internet and these forums, I can share what I've learned with others and not only can they benefit from it too, they can add their knowledge to mine and I learn MORE! I love it!

    So I'm sorry if this sounds a little sappy, but I couldn't do it without you Chris. lol. Seriously, thank you so much for your decision years ago to get into building this software and company. It absolutely has changed how this old wrench turner feels about something he's been doing for way too long. In one of my posts above I put "I did it" in bold. I posted it that way because I was excited. So when you or your guys are sitting in front of a computer trying to reverse engineer all that code, just remember your efforts make a difference in the lives of random guys on the other side of the world! Thanks!
    Check out my V8 Sky build video. It's pretty cool!...

    https://youtu.be/2q9BuzNRc3Q

    https://www.youtube.com/user/gmtech16450yz

  20. #20
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    i think there may be more involved with the traction side because mine worked fine (all tho a little harsh from factory imo) but when the blower was fitted all it could do was flash up on the display but couldnt control anything, so i just disabled all the control methods, now ive had a look at some LSA traction settings and all the settings are exactly the same as my stock settings but i assume the traction control can stop the LSA from spinning but it cant with mine so there must be some more involved that we cant get to or see