Question About Modified Engines?

[Terry Heddin]

What is meant by the phrase "This engine is set up for heat racing"? I have seen it in a couple of modified engine descriptions.

 

[john v]

A gas engine that is set up for heat racing would hopefully have some low end torque for cornering and speed for the straightaways
A saw motor is setup for top end speed and these racers are usually not concerned too much about low end.
Saw or straight a way time trials motors are from what I am told are timed higher than a heat race motor
I do not run saw so I can imagine there will be other views on this

 

[LohringMiller]

Actually the maximum over rev rpm is the most critical for SAW engines. Because prop pitch is limited, the maximum SAW speed is limited by the maximum rpm. Propeller improvements have helped, but the relation between our Quickdraw speeds and Zenoah speeds was around the difference in 20,000 maximum rpm for Zenoahs and 23,000 rpm for Quickdraws.

Maximum power sets the acceleration of the boat. Normally you should prop for the maximum power rpm (around 16,000 rpm in modified 26 cc Zenoahs) at the exit of the turn. The shape of the power curve after that determines how long this acceleration can be sustained. Low drag hulls don't need as much power to keep accelerating as do high drag hulls. That means high drag hulls benefit from a flatter power curve after the peak while low drag hulls benefit from a higher peak with lots of over rev.

Lohring Miller