It appears that I must change gearing on the KZ for Amp. My s2 time is always exactly the same despite my overall laptime getting lower and lower. Since s2 is basically a full throttle straight, I’m guessing I’m spending too long on limiter.
Here’s lap so u can listen. https://youtu.be/cS-J3EuYT-c
How do I change gearing in the KZ? What should I do to start? I am guessing mess with rear sprocket? What am I shooting for? Hit limiter at EOS?
Two teeth is a huge change for a gearbox engine. I normally only go one tooth or less by using a different combo of front and rear sprockets. How long are you tapped out in 6th before braking? A gear change will also change your shift points on the rest of the track. The best way to find the right gear is getting your hands dirty and trying different combinations based on your needs. There will always be some give and take with gearing. Also, make sure you are getting the proper revs out of the engine before making a gear change if the only issue you are having is one straightaway.
What gear ratio are you running now? In the 4:1 range, one tooth on the axle (+/-) is worth about 100 RPM on the top. So if you’re hitting the limiter right at the end of the straight, you’re going to hit the limiter a little sooner by adding one tooth.
Something to try. Hitting the limiter before the end of the straight might be good. Having that lower gear throughout the rest of the track might be the ticket? You going to get onto the straight quicker and accelerate quicker, that’s got to be good.
Thanks Al,
So the deal is that the second sector is basically a straight. My sector time remains unchanged despite dramatic decrease in overall lap times.
Ergo, my assumption of incorrect gearing.
“Having that lower gear throughout the rest of the track might be the ticket?”
Maybe but I think not. I am currently 4th USA but my s1 time is world #3. My s3 time is consistent with my leaderboard peers. My s2 time is off pace and it has been pegged in exactly the same speed to the hundredth since I was 8th USA.
In order to answer your question about ratio, I will look when I get home. I am guessing I will need to know how many teeth front and back to calculate this?
7/28 = 4.0
8/32 = 4.0
So you’re right, the RPM changes are different with a one tooth change on the axle. Don’t know what I was thinking, I must’ve missed the part about the 430 chain.
I’m afraid not, it’s 42 pages long, just send a request and see for yourself, it is free you know! I keep no mailing list if you’re wondering about that. lol
This is less relevant to KartKraft really, but nonetheless… Here’s the folder of gear calc sheets I have for various shifter motors.
Based on sheets John Denman originally made for the CR125 and CR80, I’ve created sheets reflecting the individual input and internal gear ratios of various KZ engines and the CR250.
One tab lists gear ratios sorted by numerical value, so you can see what the next “increment” in gearing looks like.
Second tab you input your overrev and shift RPMs along with the sporcket gear ratio to get a sense of how it might look in terms of speed in each gear, top speed etc etc.
Naturally the very top speeds (115MPH+) are not attainable without a laydown body or a significant draft.