Trying to dial out a minor surge, please help.

I'm trying to track down this minor surge, but I'm running up against some confusion. At constant speed, 30mph, fairly constant TPS (as steady as my foot can hold the throttle) the car seems to be switching from the high octane table, to the idle table...at least I think that's what it's doing. When it's on the high octane table there's 41 degrees of advance, and the car is smooth as glass, then it ramps over to the idle table for some reason, and it seems to oscillate between 18 and 22 degrees of advance, and it's very noticeable in the drivers seat. LTFT remains very steady while it's doing it and the behavior of the STFT even appears very similar when it's smooth to when it's surging.

It seems to be when my foot gets to 14% ETC, but 15% appears to keep it smooth. Ignore the wideband data, the sensor isn't in the car.

I disabled spark smoothing for now, because I haven't gotten a good grasp on tuning that yet, and it makes some surging far far worse when it's enabled.

Any advice? Check between frame 6500 and 6900 for a really clear example of it happening.

i think ,,
i am not sure
i think its the decceleration fuel cutoff
its the only thing that you have messed with it
try to disable it and have a go ,, or get the numbers back to stock numbers

also u have a varibale camshaft on the ls3
so this might do this business ,, you need to zero all the timing adders and control it yourself if you know what are you doing ,,
this is not a sulotion ,, but this is a point you might wanna start on

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Originally Posted by vette_c6

also u have a varibale camshaft on the ls3
so this might do this business

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No, the LS3 has a regular cam gear. In fact mine has a 3 bolt LS7 cam gear and a C5-R chain. :)

good ,, then disable the table that added timing

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Originally Posted by vette_c6

good ,, then disable the table that added timing

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That's all stock GM tables, and it's not using them.

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Originally Posted by vette_c6

i think its the decceleration fuel cutoff

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DFCO is remaining disabled while it surges. It's one of the status bits I'm logging, and you can see injector pulsewidth actually stays the same before and during the surge, and the narrowbands are showing there is combustion.

Log your dyn cyl air, and determine what area of the timing tables you're in. Then make all the timing tables the same in that area. Done. Surge gone. You can send me a check now LOL

There's something funny going on in frames 4220-4270. Something is yanking all the advance it can until it hits the minimum allowed.

it is funny ,,,

mmmm copy paste the High octane to Low Octane

i think this will solve your problem :D

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Originally Posted by edcmat-l1

Log your dyn cyl air, and determine what area of the timing tables you're in. Then make all the timing tables the same in that area. Done. Surge gone. You can send me a check now LOL

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I did that...and then I had to re-learn the idle air stuff...and now it's actually driving really nice, BUT, when I first start it, it wants to die...if I blip the throttle for a moment it catches itself and it's fine...and it returns to idle really nicely even if I just stuff the clutch in at speed. I think I need to soften up the startup flare control spark to cure it, I did a little and it seems a little better, I'll go a little more and see.

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Originally Posted by Nodnarb

There's something funny going on in frames 4220-4270. Something is yanking all the advance it can until it hits the minimum allowed.

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I didn't even notice that before. I can't feel it when I'm driving, but you're right, there's definitely a few ridiculous spikes. Similar conditions to when it surges later on. 30 mph, ~1200 rpm, ~14% throttle. I hope I can figure it out. I've got it driving a LOT nicer now than I did earlier this afternoon, but not perfect yet.

Quote:

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Originally Posted by vette_c6

it is funny ,,,

mmmm copy paste the High octane to Low Octane

i think this will solve your problem :D

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No. It's pulling to even less spark than the low octane table...and I like leaving that there should I wind up with a tank of junk fuel from somewhere...I run 16-17 gallons through this car every 2-3 days...I drive a LOT, and I'd rather leave the PCM every chance it has to save the engine.

I'm having the same thing happening... I was able to tweak the idle and main spark tables to get rid of damn near all cam surge between 1200 - 1800, but now I get retard when in 5th or 6th and accel. And I am also seeing weird advance pulses with a steady TPS.

I also was having some trouble with start up air flow. I had to add quite a bit to get the engine to start, but then after it fired up, it would want to drop in rpm too much and stall after setting minimum idle air flow. I ended up moving startup time over / under speed to 4 seconds. This seams to give the engine enough time to settle out after it fires up. I don't particularly like this, as it's a bit obnoxious.

Well, I get only get single instantanious dips in timing for no reason whatsoever, I lose as much as 20 degrees but it rebounds instantly, but still I get a surge. Your log has what I used to complain about, but mine was shorter, and occured mostly during off idle/takoff. Disabling "Smoothing" seemed to help it, when it was only during slight off idle takeoff's, but I still get the drop in timing for no reason when cruising with everything constant, no knock, change in throttle, load, etc.

I can see your speed reading is affected by it, so it's severe enough.

If you dont get an answer, start flattening out some of all of the "affecting" tables for spark or airflow... sooner or later you might find out what's causing it.

If nothing stops it, then you just found a new table for HP Tuners
to look for.. I did this with the old LT1 Edit software and was finally able to safely boost a stock LT1 PCM (found the Baro Reset this way).
.

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Originally Posted by 10_SS

Well, I get only get single instantanious dips in timing for no reason whatsoever, I lose as much as 20 degrees but it rebounds instantly, but still I get a surge. Your log has what I used to complain about, but mine was shorter, and occured mostly during off idle/takoff. Disabling "Smoothing" seemed to help it, when it was only during slight off idle takeoff's, but I still get the drop in timing for no reason when cruising with everything constant, no knock, change in throttle, load, etc.

I can see your speed reading is affected by it, so it's severe enough.

If you dont get an answer, start flattening out some of all of the "affecting" tables for spark or airflow... sooner or later you might find out what's causing it.

If nothing stops it, then you just found a new table for HP Tuners
to look for.. I did this with the old LT1 Edit software and was finally able to safely boost a stock LT1 PCM (found the Baro Reset this way).
.

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I remember getting John at TC to add that to the LT1 definitions...a LOT of the LT1 definition file for TC was added because of my questions haha. In fact, I think I remember threads long ago when you were scaling an LT1 to run a 2 bar MAP too.

I've gotten the car behaving a lot nicer, but it's tough to find time during the week.

Do you have a stock cam in your car or something else?

Return the Idle Adaptive Spark Control > Underspeed > Coast back to stock as yours is backwards.

Also zero out the AC Torque > Torque Reduction table.

Russ Kemp

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Originally Posted by MikeOD

I remember getting John at TC to add that to the LT1 definitions...a LOT of the LT1 definition file for TC was added because of my questions haha. In fact, I think I remember threads long ago when you were scaling an LT1 to run a 2 bar MAP too.

I've gotten the car behaving a lot nicer, but it's tough to find time during the week.

Do you have a stock cam in your car or something else?

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I have all stock, 0 changes so when I see this dip in timing, I know somethings up.

But yea, TC was pretty awesome, I told him what was happening and instantly they knew where to look and released new code in 1 day. LT1_Edit never cared to check, or didn't have the capability. Megasquirt is also awesome, 1 day turnaround.

Still waiting months now for my standalone datalogging to work. New chip ID. Apparently takes months to add it to code.

Hello there, I'm fairly new to the hp tuner, and am working on a 2010 camaro with an crate ls7 intake and fuel injectors LSX454, k&N cai,borla headers and cat back. It's doing the same minor surge at the same speed and rpm range. I've been looking at everything and can't seem to find the problem.
Can anyone take a look at the the file and the log to maybe give me an idea what might be missing.
Thanks for your time

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Originally Posted by Russ K

Return the Idle Adaptive Spark Control > Underspeed > Coast back to stock as yours is backwards.

Also zero out the AC Torque > Torque Reduction table.

Russ Kemp

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That spark table is still stock...I've noticed it's way different in the Camaro than it is in other cars and I don't understand why.

Why do you zero out the AC Torque Reduction table? This surge happens when the AC/Defrost is off or on (yes I'm still dealing with it)...it seems like anything I do that fixes/smoothes the surge, totally screws up the way the car starts and idles...and anything I do to fix that, makes it surge again...and I can't get the idle while rolling in neutral with my foot off the clutch to be right either...I'm very frustrated with the car. I'd be so much more willing to mess with this until I figured it out if I could start the car after I flash it...that bug is still there too. :(

Email me with your detailed mod list and the file. You know my email.

I'll put it together at work today

Hey Mike, try a Write Entire.