Hi All,

I found this ages ago, but only just understand it now.

Now we all know that 0x24 (36) is the maximum knocksum the ECU will allow!

However this isn't the full story.

When you are UNDER the Load in the "Knock Load Threshold" table the ECU will actually use the following formula to limit your maximum KNOCK_SUM:

MAX Knock_Sum = 3 * (High_Oct_Ignition_Map - Low_Oct_Ignition_Map)

This is why when you increase your High Oct Map without touching your Low Oct Map you seem to get MORE knock in low load areas of the map.

It's not actually more knock - it's the same - its just the ECU is allowing more of it to be converted into "knocksum"

I dont know what this means in terms of tuning? I think it's best to leave the Low Oct Ignition Map alone anyways

But now you know

Cheers
D.

 

That's interesting... Thanks David for that!

 

I still am trying to work out why I get BIG knock in LOW load during the first 10 mins of my journey...

Even well after the ECT has come upto temp :|

I dont think its real knock, but it would be nice to pin it down

 

Thanks tephra! Makes sense too based on what I've seen in the real world. Bump up timing a bunch on the high octane table and not on the lower one and suddenly knock goes through the roof! Doesn't really make sense....gotta keep the spread even-steven or adjust it accordingly.

 

I never figured out why the low end knock at start up between like 1000-2500 rpm from first gear. I assume TOB noise picked up. Dunno...

 

Ok, so you are saying that if I made the High Octane and Low Octane maps the same, I would never get part throttle knock (or should I say less than Load Threshold Knock)?

Could this be why Dino's car was seeing crazy part throttle knock a while back? I'm not sure if he tuned it or not.

Anyways, good find.

BTW, I do adjust my Low Octane Maps to be a static count less than my High Octane Maps. I should never really use the Low Octane Maps.

 

so if you set your load threshold to 0 it won't use that formula to calculate knocksum?

also will you be adding an "Alt Low Octane Timing" Map to your mod for those that want to use it on their alternate maps?

 

That should be correct.

No alt low octane map

keep in mind this is ONLY for LESS THAN 100 load - anything above that and your knock system is normal

 

So if I set Low oct. map identical to High oct map in 0-90 load, I will never get ignition timing pull in that area?

This would be helpful, cause I see almost always 1-6* pull (measured on AccessPort) in that area in low RPM during moving from lights at 1st gear -from idle. I have my High oct map about 4* higher in that area without knock at cruise, just at the moving from idle.

Is there any danger in making the maps identical in the low load?

 

Dave, does this formula also apply to earler models or just the X?

 

xhomm02 - I believe that would be correct, you wouldn't get any measureably knocksum anyways - give it a go.

personally I would NOT do that thou, you probably dont notice the 1-6* pull in low load, it will only happen randomly, and generally never after the car has been running 10 mins...

GrayW - I don't think so

 

BTW: my car has been running for many months with the exact same timing in both high and low timing maps in the 0-90 load range. I get 1-5 knocks all the time. (Clutch noise taking off)

 

Yup, like I have been saying for a year. TOB noise or clutch noise. It does not matter what motor mounts you have. Seen in stock EVO X's.

 

My point was that since:

MAX Knock_Sum = 3 * (High_Oct_Ignition_Map - Low_Oct_Ignition_Map)

And my tables are equal:

MAX Knock_Sum = 3 * 0

You would think I would get 0 MAX Knock_Sum.

 

Yes, if you see up to 5 knockcount, it looks like the formula must be more complex.