Knock Sensor readings

[Scott13SHO]

I finally got around to switching around the settings on my Interceptor gauges to display if the ECU is pulling any timing from the engine. I did my 15 mile ride into work today and I saw that the engine was pulling timing in low load applications at times (like low RPMs going over a hill or only using 25% throtal) but not when I floored it...I'm assuming this is fine since detontation more dangerous to an engine at higher RPM's and I've experanced knock on NA engines when "lugging it" at lower RPMs from "spark knock"?

I have a Livernous tune and an intake on the car...so discuss...

 

[Brucelinc]

Glad you brought this up.  I presume you talking about "knock retard" on your gauge, correct?  I have been monitoring mine, too, and 99% of the time, my gauge shows 0.00.  However, on a couple of instances it did show a negative value.  Like yours, it seemed to be low throttle, low RPM applications - like accelerating from 50 MPH in 6th gear - and then only for a second or two.  It doesn't do it at WOT or when cruising. 

I am not too concerned about this.  It seems to me that the system is doing it's job.  My car runs very strongly and gets good mileage.  I certainly do not hear any sign of pinging and I have had the tune for about 15,000 miles. 

 

[Scott13SHO]

Glad you brought this up.  I presume you talking about "knock retard" on your gauge, correct?  I have been monitoring mine, too, and 99% of the time, my gauge shows 0.00.  However, on a couple of instances it did show a negative value.  Like yours, it seemed to be low throttle, low RPM applications - like accelerating from 50 MPH in 6th gear - and then only for a second or two.  It doesn't do it at WOT or when cruising. 

Correct...

 

[geswek]

Doesn't a negative number indicate a knock?

I would think that we would pull reduce timing at low load; and full timing (as set in tune) at WOT.

 

[Brucelinc]

Yes, my understanding is that a negative number indicates a knock was detected and timing was pulled to correct it. 

The manual says:

Do not be concerned if your engine sometimes knocks lightly. However, if it knocks heavily while you are using fuel with the recommended octane rating, see your authorized dealer to prevent any engine damage.

Personally, if I heard any knock at all - lightly or otherwise, I would be concerned. 

 

[geswek]

Makes me wonder LOL; I haven't had any issues--but yet I have a LMS 93 octane tune (super early tune). I don't have anything to monitor knock at the moment.

 

[Scott13SHO]

From what I've been reading on other forums about Spark Knock or Burst knock as its called, its the ECU pulling the timing back to prevent an expected knocking situation to occur in the engine. Sounds like its interperting data from the sensors and trying to prevent something bad happening.

I can get my Mustang to ping if I'm lugging it in 5th gear at lower speeds...and I haven't blown it up at 120K miles on it.

 

[brettd4x4]

Negative number = added timing, a good thing
Positive numbers indicate knock/ping and timing is retarded

 

[Larrylu]

Negative number = added timing, a good thing
Positive numbers indicate knock/ping and timing is retarded

If this turns out to be the correct interpretation I'll be pleased as it is more intuitive than the reverse. We are reading a knock sensor so it's reasonable to think a positive reading indicates an occurrence...the fix for which the ECU would retard timing.

 

[ecoboostsho]

Negative number = added timing, a good thing
Positive numbers indicate knock/ping and timing is retarded

If this turns out to be the correct interpretation I'll be pleased as it is more intuitive than the reverse. We are reading a knock sensor so it's reasonable to think a positive reading indicates an occurrence...the fix for which the ECU would retard timing.

So in my experience this will vary by manufacturer or even how the guage "provider" has it set up.  On my GM cars a negative number meant it was pulling timing and that meant you were getting knock.  The interceptor gauges may work the same way.

With the PID we use in Torque you can get both positive and negative numbers and it is backwards from the above example...a negative number means it is adding timing and a positive number means it is seeing that many degrees of knock. 

If you don't like that you can modify the formula in Torque easy enough.

As you can see it can get confusing...

 

[Larrylu]

I'm not that fussy. Once it is definitively decided which way to interpret the pos and neg readings, I'll just adjust my thinking and get on with it.

 

[IHeartGroceries]

The Mazda PID algorithm is so that it displays positive numbers, in degrees; e.g. 3.0 degrees K.R., and it is generally (on the MZR platform) accepted that less than a degree is "noise" and is negligible.

Sent from my SM-N900V using Tapatalk

 

[JohnnyBravo]

Is there an answer to the question, "does a positive number mean knock was detected or does a negative number mean knock was detected"?

Aeroforce's website does not want you to ask them technical questions.  It requires to go to the forums, which are fairly out of date and certainly not vehicle specific.

Thanks,
JB

 

[Scott13SHO]

Is there an answer to the question, "does a positive number mean knock was detected or does a negative number mean knock was detected"?

Aeroforce's website does not want you to ask them technical questions.  It requires to go to the forums, which are fairly out of date and certainly not vehicle specific.

Thanks,
JB

I just posted a question their forums asking this specific question. I asked a question previously about the gauges and they answered in a timely matter. I'll post the answer once I get one from them.

 

[JohnnyBravo]

Is there an answer to the question, "does a positive number mean knock was detected or does a negative number mean knock was detected"?

Aeroforce's website does not want you to ask them technical questions.  It requires to go to the forums, which are fairly out of date and certainly not vehicle specific.

Thanks,
JB

I just posted a question their forums asking this specific question. I asked a question previously about the gauges and they answered in a timely matter. I'll post the answer once I get one from them.

Awesome.  Thanks, Scott.

 

[Brucelinc]

I look forward to the answer.  I have seen both pluses and minuses on my gauge but both are rare and only present for a second or so.  They appear to be fractional, too - presumably less than 1 degree.  Mostly the gauge just shows 0.00.

As Darrell Waltrip once said, "I don't watch the gauges.  I will just run the bi*ch until it blows up, anyway."

 

[crash712us]

I feel that much of whats said is speculation, and I will research more in depth. As I do believe I have how ignition timing is used on these cars. However seeing timing lessen under low load situations make perfect since, just like old vacuum advance systems would do. But I do recall reading something saying in certain situation timing is retarded.

 

[Brucelinc]

I noticed on the Aeroforce forum that Scott's question still had not been answered.  I PM'ed Todd at Aeroforce gauges:  Here is his response:

Positive is actual knock being detected, and timing is taken away.  Negative is timing added due to lack of knock.

 

[Larrylu]

I noticed on the Aeroforce forum that Scott's question still had not been answered.  I PM'ed Todd at Aeroforce gauges:  Here is his response:

Positive is actual knock being detected, and timing is taken away.  Negative is timing added due to lack of knock.

Simple straight answer and even better I like the logic so I have a great shot at remembering this!

 

[glock-coma]

Is this just for the aeroforce gauge? Or is it the same for torque?