Trying to wrap my head around a Full open, 100cc , ported, geared to turn approx 16500, open slippy pipe, not completely blowing away a fairly stock, 100cc reed jet with an IR2 pipe turning 13,800. What am I missing here?
I read a good quote somewhere back in the day. Might have been the book about Mark Donahue. Anyways it was something to the effect of:
“Horsepower sells motor cars, torque wins motor races”
I’ve always believed a motor with good torque in the right range is better than a little more horsepower in a very narrow range which I believe is how most opens are.
TQ is for pulling stumps out of the ground.
HP = TQ x RPM / 5252
The question is too complicated to answered completely, because we’d need to have both complete power curves just to start. But the short answer is, you want HP.
The fact is that TQ as a number, by itself, doesn’t tell you much. What is 500 ft/lbs? It’s a fat guy jumping up and down on the end of 1 foot wrench connected to a crankshaft. That’s not going to win any races. You need more information than just TQ. The missing number is Time. How quickly can he jump up and down on the wrench? one time per minute… 1 RPM or 16,000 RPM?
That’s what HP tells you. It’s a number that takes both TQ and TIME into consideration, accounting for both and allowing you to decide which is better.
Motor A. makes 5 ft/lbs @ 13,800 RPM = 13.13 HP
Motor B. makes 5 ft/lbs @ 16,500 RPM = 15.7 HP
Motor B makes the same amount of TQ, but at an RPM that is 20% higher, 16.5K vs 13.8K. It also makes 20% more HP, and because it can rev 20% higher, it can run gearing that is 20% higher… which is where TQ really comes into play. NOT how much TQ the engine makes, but how much TQ actually makes it to the ground.
Imagine Motor B, it’s generating the same 5 ft/lbs of TQ, but at 20% faster intervals AND running 20% higher gearing. Now, this is not an real world example (Motor A / Motor B) I don’t know what levels of power they make at what RPM.
If Motor A is running a 10/82 gear, Motor B can run the SAME track with a 98.4/10!
Muscle cars pay a price for that low end grunt in engine weight. Its very difficult for a normally aspirated car to make lots of torque without forced induction, or more cubic engines. But adding RPM is almost free. Not increasing compression, not adding weight, just doing things faster!
In the 3.0L V10 days of F1 cars, they were revving to 19,000 RPM, making lets say 850 HP. If that 850 HP came at 19,000 RPM, then they were also making only 234 ft/lbs of TQ at 19,000 RPM. When they upshift, revs dropped maybe 2,000 RPM. That means the fastest circuit racing cars in the world were driving around producing TQ levels found in a mid-sized ford pickup. Engine TQ doesn’t win races. Small, light weight, high revving engines win races.
What open engine are you running if it is a older engine they don’t have ports that the reed jet engines do the open engines that I ran back in the yearly 90s was just starting of the new port design that they all use now that was a big improvement over the older port design.
Buddy, new H2o Vortex, new port design. BTW, I sure miss your dad! Keep in touch!!
YEA me too Ric , then the new engine depends on the port timing that plays a lot in to it
both set ups work just half to pick and go and work with it on the short tracks I ran RPM
set ups on the tracks were more speed for a long period of time was needed then I went went toward the torque set up.
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