I thought the general consensus from most KA runners in here was to stay above about 15800 RPM. Most things I have read here say below 15500 is too low to be optimal for speed. I have put together laps where my minimum RPM is 8500, but usually that is on new tires, so I am probably close, but I feel I may need to go up a little.
I mention the 15k as a point of interest. Personally, I am over 16k for about 2 seconds on the straight, but really what I am more worried about is the RPM out of the tightest corner. Below 7k there isn’t much happening.
Yes, this his a high speed circuit with only 2 “Hairpins” But minimum speed is about 34 mph so not really a slow speed corner on the track. I feel like at 34 mph I should easily be able to keep RPMs above 8500 around the whole track. I just don’t know what sprocket to try out next. I don’t want to order 5 different sprockets necessarily.
Actually you might see the same or lower top speed but you’ll gain some extra power coming out of turns. It may be faster, it may not. You’ll have to try and see.
Carburation plays a big part too.
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I would call similar top end with more low speed torque a win. I only want to buy 2-3 sprockets at a time. Do you think getting a 76/77/78 would be a good 3 to try from a 74?
When I’m looking for the right gear, I always adjust by 2 teeth at time. 1 tooth could be 150-300 RPM so it’s really a fine tuning thing when you’re only going 1 tooth at a time. However, at 15,300 max RPM for you, I would say you can easily throw on 3-4 teeth no problem. As noted, the KA will spin 17-18k if you need it. At Dousman which is a pretty twisty technical track, I’m usually 16.5k + depending on track conditions.
You’ll have to test where your specific engine likes to run. Every one is a bit different. Mine screams up top but is maybe a tick weaker on the bottom end than some others I’ve had. I tend to run a lot of gear on this engine. I’ve had other engines that really worked well running low RPM.
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I would suggest 72, 76, 78 to give you options in both directions. Its always good to have extra sprockets anyway!
Min RPM…and a little bit of local knowledge are more important than Max RPM.
Histogram in Race Studio 3 is your friend if you know what the power curve of a KA looks like.