COBB,

I have tried calling your company, e-mailing, etc. and as of today, I still have yet to get a solid answer to a question I have.

If the answer to my question is unknown, then that's fine, but I'd just like to hear a "We don't know yet" so I can relax until it's figured out.

In the AccessTuner EVO tuning guide for the EVO X, you reference "Knock Sum". You say "We have seen that an occasional logging of 2-4 Knock Sum is acceptable".

I NEED CLARIFICATION ON THIS.

In the Accessport, there is no Knock Sum. There is Knock Correction (CA), and there is Learned Knock which is usually always at 100%.

When you say 2-4 Knock Sum is ok, is that 2-4 instances, or is that 2.0 - 4.0 (CA)?

I have been told that a Knock Correction (CA) of anything over 0.5 will pull timing. I get plenty of 0.35's, some 0.7's, and every once in a while, a 1.0+, one time at the worst (with more boost) I experienced a 3.1.

Does anyone at COBB or anywhere else truly know what this (CA) number REALLY represents? What does CA stand for any way? Crank angle?

I'm going back to the dyno soon to touch things up with my tuner, and would really like to understand this piece of the puzzle. It's hot this time of year, and my car is not pulling 100% smoothly to redline like it did when it was cooler out. Pulled timing is not acceptable to me on a normal basis, so if that means that only 0.35's are acceptable, then that's where I need to get to. Thanks in advance for your time.

- Louis

PS. I am running an upgraded turbo, with plenty of fuel (11.0:1) and a max of 10-12 degrees of timing by redline.

 

After doing some extensive reading and researching this more, it appears that in the latest tuning manual (v1.7) for AccessTuner, the Knock Correction (CA) is simply the amount of timing that was being pulled by the ECU for whatever reason.

With that said, a 0.35 or 0.70 event is under a degree of timing being pulled which is not material enough to worry about. Your input would still be appreciated.

Thanks!

- Louis

 

Louis,

I have forwarded this thread on to one of our tuners and I will endeavor to get back to you in a timely manner on this topic.

Knock Sum is the total amount of timing being pulled for a knock event.

Knock Correction is the timing adjustment made when knock is dectected

Knock Learning is a long term adjustment when repeated knock is encountered. 100% means there is no knock learning. The smaller the number, the more knock learning is being applied.

Travis
COBB Tuning

 

Travis, I appreciate it.

Based on what you just explained, there is no difference between Knock Sum and Knock Correction, right? They are both timing adjustments made to prevent further detonation. With is the (CA)? Actual degrees of timing pulled based on Knock Sum?

Sorry to beat a dead horse, but I'm clearly trying to understand the differences here and most importantly, what my AP is trying to tell me.

I look forward to one of your tuners replies.

Best Regards,

Louis

 

Cobbs knock(CA) is knock sum *.35

so
1 = .35
2= .7
3=1.05
etc etc

 

HB, that's helpful.

Is the 0.35 increments actual timing in degrees that is pulled?

 

afaik yes

 

I'm a bit confused, but that doesn't seem like it would be true. For example, knock sum in evoscan (mode23) is not the same as degrees of timing pulled. Sometimes you can get 1 knock sum and see either 0 timing pulled, or 1 degree pulled. Sometimes 2-3 knock sum will result in 2 degrees pulled.

If Cobb's knock correction (CA) is really knock sum * 0.35, then we should never see timing pulled when there is only 1 knock sum right? Can anyone clear this up?

 

sometimes that happens when transitioning between cells with higher timing than the one before. Its strange but in COBB's software thats what it is ( Knock sum*.35)

I tune with both and have used both loggers on the same tune on the same car

the ecu does all sorts of strange knock activities, i watch timing more so than knock, if it follows my timing curve then all is well

 

Thanks, so knock sum is correct as we know it (indication of knock detected). It sounds like Cobb tried to simplify things for the users by creating knock correction as knock sum * 0.35. My guess is the ECU never uses the 0.35 multiplication factor to determine number of degrees of timing to pull - I would guess the ECU has more complex algorithms to determine how much timing to pull based on the knock sum value. I could be completely wrong though

 

Yeah, still very curious to see what COBB themselves have to say about it. For simplicities sake, I'm hoping that the 0.35, 0.70 etc. is actual timing pulled, but for some reason, I don't think it is... the reason being that I can FEEL the cars power surging a tiny bit on/off in higher RPM... it's not a smooth pull like when it was 25 degrees cooler out (way less humidity then, too).

I know engine preservation is a great thing, but it also kind of sucks to not have a consistent car depending on its mood and the weather, you know?

- Louis

 

Hello? COBB tuners?

 

...

 

Knock sum is actual degrees of timing advance subtracted from the map.

From the tuning guide:

Knock Retard (CA) – Degrees of timing actively removed by the ECU when engine noise indicates possible detonation – This is a CRITICAL parameter to log whenever tuning or road testing. Low values or zero values indicate safe operating conditions whereas positive values indicate detonation. Small values (less than 2 degrees) are not optimal but are also not dangerous. Larger values indicate that the calibration needs to be made less aggressive.

What this is saying then, is that if you see that the ECU is pulling more than 2-4 degrees of timing with proper fueling, then you will want to remove timing from your map. We do not log individual "knock" hits, but the amount of timing the ECU is pulling in response to detected knock.

 

In evo land:

1 KnockSum = 0.35 timing retard

Which is why a lot of guys only see 1* timing retard on 3 KnockSum

My guess is Cobb's "Knock Retard (CA)" is just "KnockSum * 0.35"