Kinda, but I don’t believe you read the other posts to have context for what is being said.
The misunderstanding is between the Gen 1 and Gen 2 Tillotson Engines. The assumption was that Gen 2 made more power because it was faster than Gen 1. The dyno proves there wasn’t much change between the two generations of engines(I should point out that this was the same engine or bottom end, with the only changes being the updates.) The question is, then, where did the extra speed come from?
The speed didn’t come from an increase in power but an increase in rpm. Comparing the Tillotson and the 2-cycle engines was to make the point that more power doesn’t always equal more speed; if that were the case, the Tillotson would be as fast as those engines.
The gear ratio is a torque multiplier. If you did not change the current gear ratio, you would achieve more mph with the same acceleration due to the additional 1000rpms. That’s not typically what happens. Instead, the gear ratio increases and torque is multiplied by the axle to improve acceleration and mph and reduce lap times.
Horsepower is a derivative of torque, which makes your statement about torque being irrelevant a contradiction. Torque is often a misnomer to mean the low end of the powerband, except an engine only makes torque. Horsepower is literally for non-technical marketing. When miners and farmers couldn’t comprehend what torque was and the effectiveness of a steam engine, James Watts created the equation to compare engines to the work produced by a cart pony. Torque x rpm / 5252 = Hp
You probably meant the difference in rpm since the engine’s power (horsepower/torque) at the crankshaft is different than the torque at the axle, which is the point we’re both trying to make. However, power is just as relevant as the gear ratio and rpm because they’re all part of the same equation. For example, the gear ratio means nothing if the KA100 or X30 turns less than 10,000 rpms; it doesn’t make enough torque to get out of its own way, and without 15-16,0005rpms, it wouldn’t have speed.
Rather than making assumptions about the final power output, we can do some math to figure out the difference between the KA100 and Tillotson 225.
If our kart’s rear tire has a circumference of 34.6” and our goal is 65.5mph, the KA100 would need a 7.5 ratio at 15000rpms. The Tillotson would need a 3.75 ratio at 7500rpms. If we multiply our gear ratio by our peak torque, the KA100 7.5 x 11ft-lbs is 82.5ft-lbs at the axle, and the Tillotson 3.75 x 13.75ft-lbs is 51.56ft-lbs at the axle. That means the Tillotson has to make 60% more power to equal the torque while matching the mph of the KA100.
However, that is just at the peak torque of each engine. That percentage could shrink significantly if the KA100 torque falls off more than the Tillotson, which is likely considering there are only 500rpms between peak horsepower and peak torque. So we can’t say that the KA100 makes three times the power at the axle as the Tillotson because it doesn’t.
Considering all things equal(chassis, grip, etc), If a load is transferred directly to the engine, say from flex in the chassis, before it gets multiplied by the gear ratio, you only have the torque of the engine to overcome that load since that load is on the engine directly and not the drive line. That would mean on track, you experience a difference in power not seen on the dyno. Old man, EC made the point long ago that we race karts, not dynos. My point is there are many variables to consider regarding speed.