I ran a test last week that I thought would tell me which of my engines was the best performer and walked away scratching my head instead of with a solid answer.
I tried to keep as many variables consistent during the test. Used the same gearing, same kart setup, same clutch, same tire pressures for every run and ran the test between 1:30 to 3:30 in the afternoon to keep weather change to a minimum.
What was weird was the engine that produced the best lap times ( by .3-.4 seconds per lap) turned 200 RPM LESS and generated less EGT than the other motor leaving me wondering what I did to sku the results and still leaving me wondering if the motor that turned more RPM is the better one still.
So if I read between the lines what trends do I need to look for in the data to really determine which engine is stronger? I just assumed the quicker lap times would result in the engine turning the most RPM. Since that didn’t happen I’m looking to understand what did happen.
Some engines just function better at different RPM ranges. The KA engine I ran last year and won with at GoPro really liked lugging the RPMs, so we were able to run lower gear than a lot of people and stuff have plenty of speed off the corner. We’ve had lots of engines from HPV to Yamaha to Leopard that prefer different RPM ranges. Also, some engines can pair with a certain carb better too, so if you ran the same carb on both engines, that could be a difference as well. Plenty of instances in the past where me and a teammate were on totally different gearing and were going the same speed. When we tried to run each other’s gear, they didn’t work with our engines, we went slower.
It might be worthwhile to try and even the RPMs up with some gear changes so you can see if that changes the lap times or how the engines perform. Otherwise, your test sounds like it was conducted in the best way you could.
One engine might have a slightly different powerband, making it more suited for one type of track than the other. In the end, the stopwatch should be the final judge. A difference of .3-.4 is pretty significant.
If you have access to data with your MyChron, I would review the RPM and speed traces of the two engines and see if you can see where the faster engine is making up time. From there you can predict why it’s better a bit easier. RPM doesn’t necessarily mean speed.
Are you logging speed? Pull up delta on speed and you’ll have an indication on whether and/or how much the engine made in those lap times. You might find it was exit speed or any combination of things not related to engine.
Highest RPM is not related to fastest lap. Sometimes it can be, but there’s no absolute correlation whatsoever.
Remember you hit peak RPM maybe a couple of times a lap but you have to accelerate out of turns multiple times.
Also the slope of the speed trace is acceleration.
Look for differences in slope at different rpms.
The steeper the slope the highest the acceleration, and hence the higher the torque.
Try utilizing the engine rpm analysis feature on race studio…it calculates hp/tq on track …if you had mychron 5 on both karts it could help in seeing if one engine was making more power/tq than the other at a certaim rpm