davepl

Given that everything I've read indicates our cars have to pull timing with 92 octane once they warm up, sometimes I wish I had a light on the dash to indicate knock. By that I mean a light that lights up when the computer has heard knock and is going to pull timing - so that it'd flicker or flash with each knock detection event, or light up if it were constant.

I can think of two ways - the first is simpler if possible, hooking into the knock sensor circuit itself somehow.

The second would be to monitor the datastream on the ALDL port like a little mini scan tool that then lights up an LED. That'd take a little bit of hardware, but is likely safer.

Has anyone heard of any pre-existing solutions or products that do anything similar? I found this MSD product, but you'd need a bung to screw it into the block, and I'm not even sure we have a spare hole!

https://www.summitracing.com/parts/msd-8964

ajrothm

You can get the Dash Logic/Dashboard commander, it will report knock retard and display it on the DIC while you drive. That's the easiest way to do what you want. You can also display/read through a lot of other data points the PCM utilizes.

davepl

Thanks! That sounds fairly deluxe, I'll check into it!

IM3CPO

I like your idea! Let me know if you end up with a final "product". Out of curiosity, any idea how much octane is needed before knock is essentially eliminated on the stock tune? I realize IAT, load, etc., are all variables but curious if there was a general consensus similar to how 92 causes knock.

phantasms

Agreed. I love my Dash Logic controller. It let me know to sell my cold air intake due to my other mods.

Best,
Gene

ronsc1985

Not according to the company. This is the response I received about DIC display.

Hello,

Dashcommand does not put any data on the vehicle DIC, it can only transmit OBDII data to a smart phone or tablet. With Dashcommand you can make a log, then email it and view it later using our ScanXL software.

phantasms

Uhhh.... I realize that you of course would trust the company who makes it over some guy on the internet you don't know BUT I am definitely right and they are definitely wrong. Do a search on some threads about the controller. Many of the threads are people discussing the layout of how they make the data show in the display. You set the display to Navigation and it takes over that section. You use the door lock buttons to cycle through the pages. Damn that's a dumb employee over there.

Good luck!

Best,
Gene

Check out out.... https://www.corvetteforum.com/forums...p-control.html

ronsc1985

Maybe the confusion is I contacted the wrong company. In this thread the product was described as Dash Logic/Dashboard commander. This is provided by a company called Palmer Engineering. In the link you provided the product was made by Autometer.

Strangely the Palmer site does state you can put PIDS on the DIC but it is not compatible with 2017 models. Maybe that is why I received the aforementioned response.

Aside from all that does anyone know if the Autometer product works with a 2017 model? Their website states 2014-2016

CandyRed77

I bought one late last year for my 2017 GS to find out it did not work Tried the unit on a 2016 Z06 and it was fine. I emailed Autometer and asked for 2017 software but nothing was available back then... maybe you have more luck now, but I'd ask them first to be sure.

Sonny

dar02081961

Dave and all;
You may find a method to display a light when knock retard (KR) is encountered. But a light or warning when you get knock retard isn't giving you only the information you wish.

"Pulling timing" or more appropriately called "reducing advance" can be the result of several causes. Most of these causes show up in a data log as knock retard or "pulled timing".

If it is actually from 92 octane or lower quality fuel the PCM will use "knock learn" to slowly bias the timing solution towards the lower octane table by reducing the timing in the high octane table by a percentage in the area where knock was encountered.

Point is if you run 92 octane regularly as your normal fuel your car will learn where the threshold of knock is over time for 92 octane. And thus your "dash or DIC warning" will not occur once this happens. Or at least you wont be getting the warning for KR from the fuel.

To make the "dash or DIC warning" matter worse you would still get your warning every time traction control kicked in and every time torque management used spark to control torque. Because these events show up in a data log as KR. The PCM,TCM, active handling and eDiff can all use spark (or reduction of spark) as a way of controlling (limiting) power delivery. Anytime (which is fairly often) one of these events occurred it would set off your warning device.

To further complicate the issue. There are several modifiers to the base timing table that advance and reduce (pull) timing. When these tables modify timing they can significantly adjust the final timing solution and not show up as KR because most are included in the final solution for timing commanded (for lack of a better term). Or said another way they may be able to reduce your timing and not trigger your warning device.

So yes you may find the tool you are looking for. Just understand KR can be activated (used) by the PCM for many things and KR doesn't necessarily mean the engine is "pulling timing" due to knock or bad fuel.

davepl

Good point - most of those are OK, but torque management showing up as knock retard would mess up the data.

Isn't there a "knock count" you can watch? Then you wouldn't see torque management or traction control commanded retard, just observed actual knock?

The MSD unit screws into the block and reports separately, so it wouldn't be interfered with by any of it. But I'd bet the factory sensor system is much more accurate and specific.

ronsc1985

According to the email I just received from Autometer there is no current compatibility with a 2017 C7 or any date for a new release.

IM3CPO

Thanks for sharing this... Definitely changes things!

I wanted to ask you about how the car learns over time if knock is happening due to fuel, then pulls timing in that area, etc., and if you use the same fuel all the time those changes essentially become "normal" for the car. First question: Say you use 92 octane exclusively in the car and drive "spiritedly" 50% of the time and do regular small burst of full throttle. How long/how many miles will it take for the car to "adapt" to 92 octane?

Second question is now that is has learned 92 octane. What should the process be to clear the old settings if you now decide to run 96 octane fuel full time in the car (under similar driving conditions as previously stated)?

dar02081961

That's kinda what I was getting at. In my past experience these data streamers provide KR as a single parameter and don't take into account the things KR is actually comprised of. They may have gotten smarter about it by now I don't know.

When I use HP Tuners software I log several parameters for Knock, all of the modifiers and any parameter I can that controls spark. Then I can see what is being added (or subtracted) and determine what is actually KR from the knock sensor vs other sources.

If your scanner/device can pole these parameters as well then you could set up filters to filter out the other BS. Then you would have the accurate and usable device you are looking for.

dar02081961

Great questions.

These ECM/PCM factory programmers are smart folks. They know fuel quality varies from pump to pump and area to area. So they built a system smart enough to compensate for a bunch of stuff so we can drive these cars anywhere and pretty much be ok and get the most consistent performance available for the atmospheric conditions and the fuel.

1. You have 2 Spark advance timing tables, 1 is called the high octane table and the other is called the low octane table. Of course the high octane table has the more aggressive timing. Our cars are set up to always use the high octane table if able and assumes the owner is going to run 91-93 octane. Those 2 points aren’t major and there are many instances where you could run 91 and not have “timing pulled” due to knock. In this case “knock learn” will not engage and adjust base timing at all.
So if you were to put 93 octane in it you would still get all of the timing the base table calls for (excluding any other modifiers). No news there.

But what if that 91 octane you put in does cause some knock? Well a few things can happen depending on how bad and how long the knock stays around.

First there will be knock retard and the algorithm will pull timing based on the severity of the knock. Since we are discussing the difference between 91 octane and 93 octane we know it shouldn’t be that severe.

So let’s say the PCM pulls 1.5 degrees of timing at 5000 rpm under WOT and knock goes away. The PCM will attempt to give you back the timing (go back to what the base table calls for) as soon as possible. Now during the same run you are at 5500 rpm at WOT and the PCM hasn’t detected any further knock for several milliseconds, so it slowly allows the 1.5 degrees of advance it took out to come back in.

This can happen several times during a single run as well as several times during your daily drive over any given period of time. In this scenario “Knock learn” hasn’t learned anything either. And all is well because timing will continue to dance at the threshold of knock regardless of the octane whether its 91, 92 or 93. This is more often the case when you burn 91-93 octane. 1-2 degrees of KR from spark alone is normal to see. You will likely see 3 or 4 degrees but not all of that will be from the knock sensors.

Second is what happens if the PCM sees MORE than about 2 degrees of knock from the knock sensors for an extended time. Say several seconds (for this discussion we will call this “severe” knock, though 2* isn’t severe). In this case the PCM realizes there is definitely a fuel quality problem. It knows this because all of the other conditions that can cause knock are accounted for and compensated by additional timing modifier tables.

So “Knock learn” (KL) will apply a knock learn factor. This multiplication factor is a number between 0.1 and 1.0. This factor is applied to the difference in the high octane table timing value for a particular cell vs. the low octane table value for the same cell.

To keep the math simple let’s say at 5000 rpm at WOT the high table calls for 24 degrees of timing. And at 5000 rpm at WOT the low table calls for 12 degrees of timing. And you have encountered “severe" knock. Knock to the tune of your KL factor being .20 or 20%. That KL factor (KLF) will be applied to the difference between the high table and the low table.

So in our example the difference between the high table and the low table at 5000 rpm is 24-12 or 12 degrees. They then multiply 12 degrees by the KLF of .20 to come up with 2.4 (12 x.20=2.4). This result will be the amount of timing removed from the high table in the cell that corresponds to 5000 rpm at WOT.

In our example (24-2.4= 21.6) so the cell will now call for 21.6 degrees of timing advance 5000 rpm WOT. This is how timing is learned down and as you would guess this is fairly aggressive.

What is not so clear is how fast and when this KLF is learned away back towards the original high table base number. Some say it learns up at 1/10th the rate as it learns down if no “severe” knock is encountered.

To answer your specific questions.

1. If your car doesn’t “severely” knock on 92 octane (which normally it shouldn’t) you won’t have a KLF at all. Your timing will just “dance” around (retard, probe and recover) below the 2 degree threshold of KL and never learn a KLF. So in essence it continually adjust in real time and there is nothing learned about spark. Your car will give you max timing for 93 octane until it hears knock at which time it will remove up to 2 degrees and try to forget that it did so.

2. This is an excellent question because without a scanner we can never know when a KLF is being applied and what it is. And since we really don’t know how fast the KLF is forgotten (learned away) if we wanted to take advantage of that 96 octane it might be best we reset the KLF to 0.

How do you clear the KLF if you think/know your car has learned one (which as explained above it may not have)?

The only way I know for sure to do this is to load a tune, any tune even the same tune, into the PCM. I have heard disconnecting the battery resets the PCM and all of these type remembered parameters but I have not specifically looked for KLF on the rare occasion I have disconnected the battery. I know fuel trims are supposedly erased but KLF’s I don’t know.

Perhaps others can chime in if they know. Regardless if you have a scanner and determine the KLF is 0 nothing is required to take advantage of the 96 octane.

Last point. There are times when you get poor fuel from even your favorite place (high water content or whatever). So if any of us were to scan our cars we might on occasion see a small KLF even though we only burn 93 octane or the best we can find and shouldn't have a KLF at all.

Thanks for listening, this may not be 1000% correct but you can grasp the principle.

davepl

So what -would- be an appropriate parameter to watch in the DIC with a DashLogic to be informed about knock?

I actually above thought you could watch knock COUNT, which I assumed to be how much knock it saw, not the amount of retard. Wouldn't that work?

Knock count doesn't -mean- it's pulling timing yet, but it does tell you something about what the engine is "hearing" for knock, doesn't it? And it should be separate from traction management and torque management and so on...

dar02081961

Knock count might do the trick Dave. I am not sure if a "count" consist of only actual knock. My gut tells me that's should be the case.

I am not that familiar with the Dash Logic.

I will take a look on their site when able to see what I can find.

Regardless if you can log KR, IAT spark retard, Tq management spark retard, and TCM spark retard or anything they have similar to these, you should be able to figure it out.

6Speeder

The Interceptor gauge sold by Norcal will monitor knock, and record it, for later display.

http://www.aeroforcetech.com/files/I...AL_rev_2_4.pdf

Pacembellum

How about knock sensor active in the log? Using the torque to check different gas types. 91+boostane to make 93 and regular 91.

Pacembellum

I'm not at the track or i would. What should advance be at full throttle? I think i logged .25 degree knock retard earlier today. Just getting started with torque app.