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Knock Sum


praedet

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Anybody want to explain exactly what knock sum does, and means, in the newest logger definitions?

 

Also, thoughts on loggin the new 4-byte parameters? Are they worth using vs. their original counter parts? (AF Sensor #1 for example)

:spin:
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The 4-byte parameters are not new for the most part, they are renamed from "direct" parameters from before. If you want the highest precision at the cost of an increased sampling interval, then you would want to log the 4-byte extended parameters. If there is a corresponding engineers logging parameter (double asterisk and listed as 2-byte or 1-byte), then you can log that with some loss of precision (and sometimes a capped max), but with reduced sampling interval (see the logger release notes for details - engineer logging parameters are new with this release). Standard parameters (which have no asterisks), are always 1-byte parameters (except for MAF, RPM, and rear o2 are 2-byte), so they have the worse precision and in some cases, have a capped limit (for example, manifold relative pressure at 18.4 psig and manifold absolute pressure at 37 psia).

 

For tuning, the engineer's logging parameter, if available for ECU and the parameter you want to log, is your best choice overall. Logging 4 1-byte parameters would have the equivalent sampling interval as logging 1 4-byte parameter.

 

Knock sum is a counter that is incremented when the knock signal changes from off to on. It is cleared when it reaches 35. The knock signal is always referenced to make the final decision to make changes to the FBKC, FLKC, or the IAM when conditions warrant a potential change to any of those elements. So, the knock sum can be very useful, although it will not increment with consecutive knock events - only the first knock event in a sequence of consecutive knock events.

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Reasoning? I haven't experimented with it much but find it a bit misleading.....

 

It is not misleading. It is the BEST way to determine if the ecu thinks there is knock.

 

FLKC is misleading. The only way to tell if FLKC is indicating knock is to keep track of it which is a pain in the ass.

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I've been watching knock sum on my car (which is still on the stock tune) and it increments a lot more than I expected. Learning view still shows zero in all but one cell.

 

It's still a great thing to be able to watch, I just think it's interesting how much activity there is, even on the stock tune. On a 2.5-hour drive yesterday it worked it's way up to about 20. Most of the increments were in the 'cruise' area, around 2500 rpm and low load (closed loop), just because that's where I spent most of my time.

 

So, I'm very curious how much activity other people are seeing.

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Use pivottable in excel to create a statistical summary. You'll see where the enginee is "noisy" but the ecu is ignoring the knock.

 

Frankly, I was expecting to see the knock sum incrementing a lot in the low load (<0.5 g/rev) region since SOA deactivated FBKC below 0.5 g/rev. I figured they must have deactivated it due to the noise.

 

However, when I beta tested this for merchgod, I rarely saw it incrementing. Actually, it made it hard to beta test.

 

I think you guys have noisy engines or something is loose.

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It is not misleading. It is the BEST way to determine if the ecu thinks there is knock.

 

FLKC is misleading. The only way to tell if FLKC is indicating knock is to keep track of it which is a pain in the ass.

Got a little time this weekend to check this out more, excellent little parameter!

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  • 3 weeks later...

So does it start at ZERO or ONE?

Either I have a knock right after startup or it starts counting at 1. I usually get 2-3 KS increments before I get out of my driveway, but that could be my LWFW and clutch(I hope). After that I've gone up to 2 hours and 146 miles of mixed driving and only get a total of around 5 in the KS.

The only events that occured were when I'd give it some pedal in 5th from about 50mph or low 2Kish rpms and hold it until about 3Kish rpms. I just had to adjust timing a little in that rpm/load range and all is good, but I still get knock before I ever get out of the driveway or parking lot.

I'm fine as far as WOT goes and don't get any mystery knock while cruising, just those couple low RPM or off idle instances that don't flag FLKC or FBKC.

Let's kick this pig!
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It starts at zero.

Thanks Infamous. I kinda figured that one out last night. It acutally stuck at zero and stayed there for about 20 miles until I started pushing the high load, low rpm areas again.

 

So what is everybody's average KS over a given period?

 

Like I said, I might see a couple ticks when backing out of the driveway from a cold start and then it might pop up to about 5 by the end of a couple hours of driving.

Let's kick this pig!
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I've only logged once with this. Got knock sum up to 14 just backing out of my garage and driveway and getting to 5mph in 1st. After that I drove 15 minutes, with several WOT sprints. When I got home it had incremented once more to 15. I'm not concerned about the knock sum happening upon getting out of the driveway.

My '05 LGT

My '07 Supercharged Shelby

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I'm thinking it's just hearing the FW and clutch when it's cold cause I don't knock on the move either. Just in the driveway or parking lot. I can force a knock at low RPMs in 5th, but that's about it.
Let's kick this pig!
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I'm thinking it's just hearing the FW and clutch when it's cold cause I don't knock on the move either. Just in the driveway or parking lot. I can force a knock at low RPMs in 5th, but that's about it.

 

I get the same sorts of knock sum as you do. In the winter just backing out of the driveway makes mine go crazy!

 

I would look into your knock in low rpms in 5th, maybe you have to adjust your boost targets or timing cells there a bit. It is not uncommon to reach a few timing cells that you don't normally in a 5th gear low rpm run.

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I get the same sorts of knock sum as you do. In the winter just backing out of the driveway makes mine go crazy!

 

I would look into your knock in low rpms in 5th, maybe you have to adjust your boost targets or timing cells there a bit. It is not uncommon to reach a few timing cells that you don't normally in a 5th gear low rpm run.

 

Yup, going on a roadtrip today, so I'll play with it on the way. It's right there on the upper right hand corner of the table on the outside edge of where I come through in 3rd WOT. Got several logs of it. I dropped a few cells a couple degrees in that area and will see what she has to say when I hit the road.

Let's kick this pig!
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Yup, going on a roadtrip today, so I'll play with it on the way. It's right there on the upper right hand corner of the table on the outside edge of where I come through in 3rd WOT. Got several logs of it. I dropped a few cells a couple degrees in that area and will see what she has to say when I hit the road.

 

If it does nothing, it is most likely noise. I would make sure to add it back to insure you don't take a hit in mpg's.

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If it does nothing, it is most likely noise. I would make sure to add it back to insure you don't take a hit in mpg's.

 

So you don't take a hit (at 2500 rpm in 5th at 2.3 load) in mileage, you know for when you are pulling a boat up a 10% grade and don't want to downshift.:rolleyes:

 

:lol:

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