2015 ZL1 knock? Conclusion @ 4/27/15

[1KillerSS]

Originally Posted by angryBits

I think I will get it. But I'm unsure about which one to get.
I would eventually like to datalog wideband.

Two questions please:

#1: If I get the standard version, can I upgrade it to support wideband later or will I have to sell the standard and buy a pro version? If I have to sell it and buy a pro, then I think I'll just buy the pro now.

#2: I don't see my truck or my wife's car on the supported vehicle list. Can I still use this scanner to read standard OBD2 data and codes for non-supported vehicles or is it useless?

Thanks again and sorry for all the questions.

EDIT: I found the answer to #1 at the HP Tuners website. It costs $289 + shipping to upgrade from standard to pro.

You can upgrade from standard to pro, its more cost effective to just buy pro from the start, it will come with 4 credits if I remember correctly. You can rig your wideband through your AC input if you chose to buy standard and upgrade later. There are two problems with doing it that way, you will have to mess with the offset equation to get the wideband data to be correct. Other people wont be able to view your AFR data on your tables, only you will be able to see it. The AC input will come up as an unsupported parameter when they go to view your log. I just took screenshots and emailed them back and forth before I got Pro. Also the accuracy is questionable because the data travels through the PCM.

If you really want to set it up I can help you do it, but I recommend just going pro from the start.

Also if its not on the supported vehicle list just email HPT and ask them, they will shoot you an email back with a short to the point answer. Not all of there supported vehicles are on the list, at least as of two months ago.

[angryBits]

Originally Posted by 1KillerSS

You can upgrade from standard to pro, its more cost effective to just buy pro from the start, it will come with 4 credits if I remember correctly. You can rig your wideband through your AC input if you chose to buy standard and upgrade later. There are two problems with doing it that way, you will have to mess with the offset equation to get the wideband data to be correct. Other people wont be able to view your AFR data on your tables, only you will be able to see it. The AC input will come up as an unsupported parameter when they go to view your log. I just took screenshots and emailed them back and forth before I got Pro. Also the accuracy is questionable because the data travels through the PCM.

If you really want to set it up I can help you do it, but I recommend just going pro from the start.

Also if its not on the supported vehicle list just email HPT and ask them, they will shoot you an email back with a short to the point answer. Not all of there supported vehicles are on the list, at least as of two months ago.

Thank you!

[Chrispy]

Originally Posted by white ZL1

It shouldn't, because that's not really how it works. You seem to be completely overlooking the part where there is a max timing in the programming. The car cannot continue to adjust timing up to compensate for ANY octane.
There's actually two different timing tables, high and low octane, and the car has the ability to slowly yet continually adjust between the two of them.
I have dozens of datalogs of my car when it was stock, and typical WOT timing was in the 23 to 24 degree range. Sounds like you're in that same ballpark.



You certainly shouldn't. A stock car should not see any actual retard with 97 octane in the tank. That should be more than enough octane on a stock car on stock programming.
False knock, yes. Burst knock, yes....on quick throttle transitions.
But never real knock retard unless something is wrong.

I wish you were closer, we'd scan it with HP Tuners and see if the KR is consistently coming from one cylinder or another. Would quickly help narrow down what the problem might be.

We were actually saying the same thing. It doesn't advance timing forever until it hits knock, it'll advance up to the max timing that's allowed in the stock tune.

You can raise that timing ceiling with a custom race gas tune.

Make sense? Sorry I wasn't clear earlier.

[angryBits]

Originally Posted by Chrispy

We were actually saying the same thing. It doesn't advance timing forever until it hits knock, it'll advance up to the max timing that's allowed in the stock tune.

You can raise that timing ceiling with a custom race gas tune.

Make sense? Sorry I wasn't clear earlier.

I got that the max wasn't infinite. I figured that was a given

I was more interested in the fact that the computer would adjust the timing more aggressively when running higher octane gas.

If the car was designed to run on 93 octane and the computer runs an approximate expected timing for 93 octane, will it adjust the timing to be more aggressive for 100 octane gas, or will it just run the same timing?

What I thought I was reading was that the car would adjust the timing to be more aggressive for 100 octane.

If that is the case, then the car will likely adjust the timing to the point of minimal knock detection and then dial it back a bit. This says to me that the car will mostly not knock but may still knock on rare occasion even with 100 octane gas. UNLESS the max timing is for something resembling 95 octane, in which case it may literally never knock when running 100.

Did that make sense?

I have no idea if that's correct -- but that's how I understood it.



The only reason I'm so interested in this, is that it could explain why my car still gets some occasional knock when running ~97 octane and it would suggest there's hope still that theres nothing wrong with the car

[1KillerSS]

Originally Posted by angryBits

If the car was designed to run on 93 octane and the computer runs an approximate expected timing for 93 octane, will it adjust the timing to be more aggressive for 100 octane gas, or will it just run the same timing?

Nope it will only be as aggressive as your high octane timing map settings.

[angryBits]

Originally Posted by 1KillerSS

Nope it will only be as aggressive as your high octane timing map settings.

Okay. Darn.

So that means w/ a stock tune -- I should not be seeing any knock whatsoever with ~97 octane. Poop.

So much for hope...

EDIT: (except for false knock)

[1KillerSS]

Originally Posted by angryBits

Okay. Darn.

So that means w/ a stock tune -- I should not be seeing any knock whatsoever with ~97 octane. Poop.

So much for hope...

EDIT: (except for false knock)

Not necessarily, I have had knock with my factory tune with high octane fuel before, granted I'm an LS3 guy, but that is just an example of what were talking about. People told me I should have ni knock, when it was definitely present. I could log it with hpt and see it for myself, it wasn't much knock, and I could not hear it with my ear, yet the funny thing is that a few of the tuners I talked to would not have any knock in their tune at all, let alone a little. To be more to the point if a tuner saw the knock that was displayed in my factory tune they would most definitely tune it out. As of today I don't have even .5 of knock anywhere in my car.

[Russell James]

Originally Posted by angryBits

Okay. Darn.

So that means w/ a stock tune -- I should not be seeing any knock whatsoever with ~97 octane. Poop.

So much for hope...

EDIT: (except for false knock)

There's no reason to run 97.

And you're paying way too much attention to knock.

You're going to have lots of knock under boost and heat with 91. You'll have less knock with 93, but still some as conditions vary. Don't sweat that little bit. The PCM is constantly adjusting for it.

It can be like a person with no medical training constantly monitoring their EKG. And occasionally there is a skipped heartbeat. And numerous meds, surgeries, diseases are contemplated...

When a cadiologist would look at that situation and say... don't worry about, get out and enjoy. Do things to improve your breathing like excercise (CAI), eat better (93)... but don't sweat a minor blip that is pretty much a common occurence.

[angryBits]

Originally Posted by Russell James

There's no reason to run 97.

And you're paying way too much attention to knock.

You're going to have lots of knock under boost and heat with 91. You'll have less knock with 93, but still some as conditions vary. Don't sweat that little bit. The PCM is constantly adjusting for it.

It can be like a person with no medical training constantly monitoring their EKG. And occasionally there is a skipped heartbeat. And numerous meds, surgeries, diseases are contemplated...

When a cadiologist would look at that situation and say... don't worry about, get out and enjoy. Do things to improve your breathing like excercise (CAI), eat better (93)... but don't sweat a minor blip that is pretty much a common occurence.

I get what you're saying -- I'm overly paranoid about knock. I'd agree with you except that mine (when using 91 octane gas) is audible and happens every time I WOT and it doesn't go away until I let off. If nothing else, its annoying enough for me to worry about. But I really think an audible knock is something to fuss about anyway.

EDIT: I forgot to mention. The reason I'm running 97 is because I'm trying to see at what point the audible knock begins. I started high and will work my way down. You're right that a minor blip is a common occurrence, but is it common on 97 octane? I bet not. Thus the concern.

[angryBits]

Pulled the trigger on a HP Tuners Scanner "Standard", I didn't get the suite and I didn't get the "Pro". Cheapest is best right now -- If I use it enough maybe I'll upgrade.

In any case, it should arrive Monday.

In the mean time -- anyone have any pointers on what steps I need to take to actually measure KR reported for each cylinder?

Also, what are some potential conclusions I could draw from the number of cylinders w/ KR?

Here are my guesses -- I'm not an expert:
1 or 2 cyl could be a bad spark plug or plug gap.
1 or 2 cyl could be a imperfections in the cylinder wall (unlikely).
1 or 2 cyl could be bad injector, 1 cyl running leaner? guessing?
1 or 2 cyl could be gasket spill over
6 to 8 cyl likely bad gas
6 to 8 cyl maybe bad fuel pump? causing lean? guessing?

A reason why bad gas or bad fuel pump may only be 6 or 7 cylinders rather than 8. Lets say the gas is a little bad but 1 or 2 of the spark plugs is running cooler by mistake, then those cylinders may be more tolerant of the bad gas and not knock. Totally theorizing -- I've got time to kill before my HP Tuner arrives

I welcome and encourage any criticism of my guessing -- I'm just looking for probable causes so I can make good decision once I get real data.

Thanks for your help!

[1KillerSS]

If it were me, I would get a hold of white ZL1 or ZO6 bryan and see if they have a config file already set up for you to scan with. I have a different PCM and am not sure it will work on your car. Setting them up can be kinda tedious sometimes. I am sure either one of those guys will be glad to help.

[angryBits]

*crossing fingers*

[angryBits]

*bump*

I'm expecting my HP Tuner to arrive today. Would love some advice on how to measure KR reported from each individual cylinder.

Thanks guys.

[angryBits]

*UPDATE* 4/27/15

I received my HP Tuners scanner and plugged it in and logged some data.

It was really cold and foggy and damp outside so I wasn't willing to push it too hard.

The car is running approximately 93 octane during this run.

Attached below in the .zip is my scan. I wasn't pushing it hard for too long but I was still easily able to produce KR every time I stepped on it.

EDIT: Oh yeah! Can someone tell me how to find the KR per Cylinder? Thank you!