Hi everyone, I have recently set my bike up with a detonation counter. I want to know how many detonations are acceptable/desirable per kilometre or mile. The bike is a track/race bike.

I read somewhere that a very high 'on edge' level of tune would see 10 per kilometre for an RS250. Does anyone have any NSR-specific knowledge on this?

Sorry no, I never got round to fitting one when I was racing.

Does the manufacturer of the counter have any advice?

As far as i can make out 1 per km is what you strive for but getting to that point across two cylinders is a lot of trial and error.

I am talking RS250 here...

It's all a matter of longevity anyway, the less dets the better the fuelling is and therefore better for the combustion chambers.

Iv'e got it all to learn, just had one fitted.

....Is it April already?
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Dave Ett wrote:Sorry no, I never got round to fitting one when I was racing.

Does the manufacturer of the counter have any advice?

No advice, I guess like this site they try to steer clear of giving advice that doesn't take into account all the variables and different conditions etc.

simono wrote:As far as i can make out 1 per km is what you strive for but getting to that point across two cylinders is a lot of trial and error.

I am talking RS250 here...

It's all a matter of longevity anyway, the less dets the better the fuelling is and therefore better for the combustion chambers.

Iv'e got it all to learn, just had one fitted.

Is that right, where did you get that info? I assume Honda RS250?

Hobbit210 wrote:....Is it April already?

No? Have I missed something obvious??

I believe HRC says 1 to 2 per KM. But I am sure the track can affect this. Wouldn't tracks with longer straights potentially have a higher chance of detonation then tracks that you are not at/near maximum power for short periods of time?

Not sure on your knock meter, but the ones that are normally fitted to cars, just bold to the block, and measure detonation as a whole across the whole engine opposed to individual cyclinders. They basically measure vibration.
They normally have a big range, and you just keep an eye on it. Normally running might see a number in the low hundreds, while a big knock might be around 300 plus (audible pinging).
Not sure how one would go on a 2stroke bike though.
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Thanks for the feedback guys. Next time at the track I will jet to achieve around 2 per kilometre (for lack of more NSR-specific figures). Last time out I had a couple of sessions seeing around 30-35 in a run (approx. 15 km), followed by a minor change in setup that saw me getting more dets than ideal. In particular I was seeing 3,4 or even 5 in a row as I accelerated hard out of a 1st gear corner.

All detonations were at or above redline, so will go up in mains and see if I can get back to that 1-2 per km figure.

Oh and try not to run out of fuel and lunch the engine as well...