flyrod

I'm seeing some weird stuff trying to tune a K with hondata. I tried registering on their forum but I can't get it working. I've not had much luck with them in the past getting support anyway, so maybe some fellow tech-ers here have some ideas.

Basically, how useful is the knock sensor? I was getting a lot of knock count at part throttle, but it's still there after pulling gobs of timing and putting in race fuel. I don't think it's anything loose or rattling. At this point I don't think the knock I'm logging is "real" because it's not very repeatable and it doesn't go away with less timing or more octane.

I can understand that the knock level varies and when it gets high enough relative to the knock threshold a "count" is recorded. What I don't understand is why the threshold would be jumping around? Here is what I'm seeing:




If you look at the top plot, you can see the knock threshold drop, and the count pile up. Also note the ignition is only 18deg at part throttle, and the time is 12 minutes into a drive and it starts "knocking" at fairly steady state conditions that don't "knock" before or after this for another 20 minutes of driving.

Here is some more weirdness. Below are two consecutive periods of coasting (TPS is 0, injectors are off, A/F is high):



Look at the knock level. On the second period of coasting the level jumps up, but it simply can't be knocking because there is no fuel?!?

Ideas?

98vtec

is this a stock internal motor?

check this out:
http://mtggraphics.com/bigmoosesubpages/knock.htm

flyrod

I think there must be some kind of vibration causing the spikes in the knock level, but I still don't understand why the threshold is jumping around.

flyrod

After putting a hole in the timing there I had a "flat" spot in the throttle response. I put the timing back to around 32deg and that fixed the flat spot with almost no change in the "knock count" so I don't think it's real knock.

flyrod

also, decelerating with the car in gear produces knock at around 2500. must be some kind of vibration, but what does the threshold do?

Turbogixxer

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by flyrod &raquo;</TD></TR><TR><TD CLASS="quote">also, decelerating with the car in gear produces knock at around 2500. must be some kind of vibration, but what does the threshold do?</TD></TR></TABLE>

Thats what I would check into. I have seen this happen a lot with swapped cars.

sander

The threshold sensitivity is not user adjustable.
I dont know if they still have this problem, but a while ago ALL the kpro cars that I did had a "knock" around 3000 - 3500 rpm at low load. Obviously this was not the case as it is near impossible to have detonation in column 1 - 3. I usually wont look at the K count if I do a car (which must ALWAYS be on a dyno with K engines). If the car continues to make power under load and the plugs do not show any signs of detonation then all is well.

-sander.