Help fixing lazy tune, not even 20* WOT, lots of KR

[happysem]

Howdy,

Been lurking for a while and still learning, but I need some help with figuring this out.

Car is an 06 LS2 Corvette, 6spd auto, has a teeny tiny baby cam, intake, and full exhaust. TR6 plugs, I think gapped around 55 EDIT: plugs at 40, I was remembering wrong, new plug wires, all mods done in last 7K miles, 138K on car.

After the cam install, I paid to have it tuned, both engine and trans. Car felt great at first, then felt more and more lazy over time. I finally got fed up with trying to get the tuner to respond and bought HPT myself.
Compared my tune to friends tunes and many stock samples, turns out he barely did anything. He didn't even touch the trans side. I think he just hit the relearn button. So now I'm trying to fix this myself and learn on the way.

The car honestly feels really good, it has run 12.01 @ 119 in about 700DA.

The first time I logged the car, I noticed it was only getting 15-19* timing WOT...this seems incredibly low. Should be mid 20's? Unfortunately, I didn't have the KR and Retard channels on, so I assumed it had no knock or retard with such low timing. Car has 93 gas in it.
I compared my tune to a friends big cam LS2 car, and added about 4* of timing above 4400rpm and .70 cyl air mass, since it looked so low, just to see what would happen, turned KR and retard channels on, and now its getting a lot of knock and retard, especially when it shifts.

Is this real knock? If so, something has to be mechanically wrong with the car right? Knock sensors bad?
Or did my OG "tuner" fart up the tune that bad?
With no KR in 1st, then like 4* as soon as I hit 2nd, and tapers down, then almost 8* when I hit 3rd and tapers down...this seems like a form of torque management or something?
However, the torque management advance channel shows nothing?

Please educate me!

Thanks!

[5FDP]

That's a big spark gap if that is true, I'd want it at .040 at a minimum.

Commanded fueling is really lean, I wouldn't ask for 13.0 on this engine. Aim for 12.3-12.5 for good safe fueling. You'll want to get a wideband o2 sensor to make sure that commanded AFR is matching the real time AFR in the exhaust.

If any part of the exhaust is touching the subframe or body, that can be picked up as a vibration/knock.

Both high/low timing tables shouldn't have matching values because if it does knock it can't take the timing away. The low octane table should always have at least 4-6 degrees less timing in it everywhere.

[happysem]

I'll pull a plug and double check, I could be wrong.

I have a WB gauge in the car, its around 12.5-13.0 WOT.

There very well may be something touching underneath, I straight up DESTROYED the exhaust running over a fold down spike strip thing, but I got it sorted out. Will double check.

Appreciate the insight, any other thoughts? I'll start there and see if anything is obviously wrong.

[happysem]

Checked, plugs are gapped at 40, I was remembering wrong.

The muffler case can hit the frame at the very back of the car, but only if I shove it over pretty good, so I don't think this is it.

Is there any other way to tell for sure if its knocking from that?
Has the knock or other retard portion of the tune been modified to be more "sensitive" maybe?
Is this tune worth working off of for WOT, or should I just start from scratch?

[happysem]

Update, filled up the car at a different station with 93 again, ran it in paddle shift, and regular mode to eliminate those, almost no change, lots of knock.

Went back to the original tune from my "tuner", and it gets 2* KR at tip in, but then nothing else the rest of the run. Solid 18-19* WOT timing.

Car seems really healthy, so I doubt this is real knock. Going to dive more into the tune myself with a lot more research and time and try to fix what I unfortunately paid for.
No way that's all the timing my mostly stock car can take.
Maybe knock sensors going bad?

Open to other thoughts and suggestions!

[383_Stroker]

It sounds like the tuner added timing until it knocked and then pulled it back a degree or two, which is how most people do it.

If knock is only present when you add more timing, it is probably real.

If you really need to test it, put some better fuel in and see if it knocks with the elevated timing with a higher octane fuel (Boostane or something similar works well for this kind of testing)

[happysem]

I think you're right. But you would think an experienced tuner would realize not even 20* WOT on a very mild LS2 is not normal.

I would also think that if it was knocking, it would continue knocking more and more with RPM, not less as my log shows.

I'm playing around adding more fuel and lowering the knock sensitivity just a bit, will update with results.

[ZincGT]

If I was tuning this car, based off the data that you logged I would add at least 5% to the MAF curve at WOT (you need to log maf hz to figure out where to add the fuel) and disable burst knock then re-log.

[TheMechanic]

Update, filled up the car at a different station with 93 again, ran it in paddle shift, and regular mode to eliminate those, almost no change, lots of knock.

Went back to the original tune from my "tuner", and it gets 2* KR at tip in, but then nothing else the rest of the run. Solid 18-19* WOT timing.

Car seems really healthy, so I doubt this is real knock. Going to dive more into the tune myself with a lot more research and time and try to fix what I unfortunately paid for.
No way that's all the timing my mostly stock car can take.
Maybe knock sensors going bad?

Open to other thoughts and suggestions!

Use the comparison tool with the Ctrl+5 View Comparison Log. It will give you exactly what was changed.

[383_Stroker]

I would also think that if it was knocking, it would continue knocking more and more with RPM, not less as my log shows.

Timing is sensitive to cylinder pressures, not so much RPM. Its not uncommon for higher rpm ranges to take more timing than mid range will without knocking

[happysem]

IDK what happened, but whatever parameters I used in the engine side of the tune (trans stock) it locks the trans in like 4th gear. No warnings or anything. Takes off in 4th, stays in fourth in D, S, or paddle shift mode.
I'm trying to band-aid this tune since it runs well and I don't know a lot. But it looks more like I need to just learn more, and start over.

If someone can point exactly how to add a little more fuel to the tune posted above, I'd be happy starting there.
Haven't quite figured that side out yet.

[happysem]

Update, I barely know anything, but now I'm dangerous...

IDK if this is how you should do it, but I changed stoich boxes and PE to get a solid 12.6 afr out of it, and now it has 24* of timing. Only played with timing above 4k rpm and .7 air mass, also dropped some KR sensitivity.

Based on all the data that HPT can churn out, tq/hp estimation, time stamps, etc... it shows I made a definite improvement. So I'm happy with that, time to see if it translates to any better on the track tomorrow.

EDIT: in case anyone finds that weird problem in my last post about trans staying in 4th gear, sorry but no idea how I fixed it.
Instead of changing 20-30 things, I changed 1 or 2 things, made sure it worked, datalogged, then rinse and repeat. So I'm convinced that I messed with some field that my car didn't like, but it wasn't anything obvious.

[Pekka_Perkeles]

Offtopic, but...

Both high/low timing tables shouldn't have matching values because if it does knock it can't take the timing away.

This is common misunderstanding.

Knock detection (capability) is not in any way dependable of low octane timing table. Or any other timing modifiers, such as IAT, ECT and so on.

In other words, even if PCM would be using low octane table as a starting point for ignition advance at certain situations, the knock detection is still there and will remove timing if it detects knock. Unless it has been disabled from the tune altogether.

The low octane table should always have at least 4-6 degrees less timing in it everywhere.

Yes, if you want to use low octane gasoline or if there are things like gas quality issues. However, that will of course need knock detection capability not being disabled in the tune, as fuel octane estimation is based on how much knock there has been previously.

[jsllc]

Offtopic, but...

5FDPBoth high/low timing tables shouldn't have matching values because if it does knock it can't take the timing away.

This is common misunderstanding.

Not true. Is 100% correct. If you set both tables to be the same it has no room for the Low octane detection to pull timing. Yes it will still pull some timing based on modifiers but if it does try to settle into a low octane mode that table should be at least 4 degrees less.

[Pekka_Perkeles]

Still offtopic...

When I started tuning with HPTuners about 15 years ago, someone said it's the Scanner that is the most valuable tool. At that time I didn't believe that too much, I just wanted to tune my Vette...

Not true. Is 100% correct. If you set both tables to be the same it has no room for the Low octane detection to pull timing.

Well, again that might be the "forum truth", but just check your own logs.

Meanwhile, see below these two screenshots. This is very track-oriented car, but also a street car. It competes successfully against best of the Europe Supercars, such as Mclaren, Porsche GT3 RS, GT2, Lamborghinis and so on. It has very tight suspension, sequential gearbox etc. to be able go very fast around track. It has also a tendency to get false knock because of that.

Now, as you can see from the tune file, low octane table has 27 degrees of timing at 1400 rpm @ 0,40 grams of cylinder airmass. No IAT retard, no ECT retard, no AFR retard, burst knock disabled. But about 6.7 degrees of knock retard. And the final advance at that point is 20 degrees of timing.

So this is a knock detection functionality and it does retard timing, no matter what is in the low octane table.





Finally, I've written many times wrong information in this forum. Most of us do the same thing. It's a long learning curve to get everything right.

[RobZL1]

Pekka, I might be wrong, but I think the point was the ECM will just go right back to the timing you had in there with no adjustment capability between the two tables if they are set the same. Sure, it still will have knock retard, but the KLF won't have anywhere to take the timing. So if you have a batch of bad gas, it will just keep knocking and retarding, instead of adjusting the timing down.

[jsllc]

Still offtopic...

When I started tuning with HPTuners about 15 years ago, someone said it's the Scanner that is the most valuable tool. At that time I didn't believe that too much, I just wanted to tune my Vette...




Well, again that might be the "forum truth", but just check your own logs.

Meanwhile, see below these two screenshots. This is very track-oriented car, but also a street car. It competes successfully against best of the Europe Supercars, such as Mclaren, Porsche GT3 RS, GT2, Lamborghinis and so on. It has very tight suspension, sequential gearbox etc. to be able go very fast around track. It has also a tendency to get false knock because of that.

Now, as you can see from the tune file, low octane table has 27 degrees of timing at 1400 rpm @ 0,40 grams of cylinder airmass. No IAT retard, no ECT retard, no AFR retard, burst knock disabled. But about 6.7 degrees of knock retard. And the final advance at that point is 20 degrees of timing.

So this is a knock detection functionality and it does retard timing, no matter what is in the low octane table.





Finally, I've written many times wrong information in this forum. Most of us do the same thing. It's a long learning curve to get everything right.

It will always pull timing base on the other modifiers. No one was arguing it didn't. However, setting the two tables the same does not allow the low octane routines to work. Meaning: you are relying on the knock sensors instantaneous adjustments to fix the fuel issues. This system works much like STFT and LTFT. You can run run your car without LTFT but it had better be a more accurate tune if you do. There are compete routines is the ECM that will force the ECM to use the low octane table if persistent knock appears. Put this with the instantaneous knock detection and you have a safer more reliable fuel variation tune. "The low octane table should always have at least 4-6 degrees less timing in it everywhere." is very good advice and correct unless you are 100% certain that you do not need it and you know what the end result of changing it will cause. Usually an unwanted boom. Example :Ford Shelby truck went boom. It was running the stock tune with the stock pulley pulling a 3000 lbs. boat down a freeway with less than a 1% grade. Shot oil out the back of the motor. 5 of 8 pistons were destroyed in just 30 miles of detonation. Ate holes right through the pistons.
blown.jpgblown2.jpg

[5FDP]

Maybe my wording wasn't the best but the main thing I was trying to get across what about the knock learn factor. Having them both the same doesn't let the KLF work anymore.

So it would be at 27 degrees of timing, knocks 5 degrees, down to 22 and slaps 27 degrees of timing right back in it. With the KLF working it would slowly ramp timing back in based on the value in the KLF.

[Pekka_Perkeles]

Maybe my wording wasn't the best but the main thing I was trying to get across what about the knock learn factor. Having them both the same doesn't let the KLF work anymore.

So it would be at 27 degrees of timing, knocks 5 degrees, down to 22 and slaps 27 degrees of timing right back in it. With the KLF working it would slowly ramp timing back in based on the value in the KLF.

Yes, exactly.

With N/A track oriented car and a customer who understand what is quality fuel and why it is required, there's really not much need for a low octane learning factor (KLF). It is too slow to learn back in cases like road race usage.

[Pekka_Perkeles]

However, setting the two tables the same does not allow the low octane routines to work. Meaning: you are relying on the knock sensors instantaneous adjustments to fix the fuel issues. This system works much like STFT and LTFT. You can run run your car without LTFT but it had better be a more accurate tune if you do. There are compete routines is the ECM that will force the ECM to use the low octane table if persistent knock appears. Put this with the instantaneous knock detection and you have a safer more reliable fuel variation tune.

That was a very good comparison.

I think it is a more about tuning strategy, i.e. how you want to do things with certain engine setup, intended usage and end user preferences. For example, if there is also a meth injection, there should always be a plenty of octane. But those pumps have tendency to fail if being unused longer time (winter time etc.). So in my case it always depends on those three things. And fuel quality isn't really an issue here.

"The low octane table should always have at least 4-6 degrees less timing in it everywhere." is very good advice and correct unless you are 100% certain that you do not need it and you know what the end result of changing it will cause. Usually an unwanted boom. Example :Ford Shelby truck went boom. It was running the stock tune with the stock pulley pulling a 3000 lbs. boat down a freeway with less than a 1% grade. Shot oil out the back of the motor. 5 of 8 pistons were destroyed in just 30 miles of detonation. Ate holes right through the pistons.

I think some stock forged induction 2003...2004 Mustang Cobra's had knock sensors disabled because supercharger was so noisy... :-) Buy yeah, towing has not been intended usage of the cars I've tuned.