Apex dyno time

[DYNAREX]

dont forget to multiply engine torque by clutch reduction=1.23
so 80 is really 100 at the clutch

 

[jtssrx]

???

when you calculate torque numbers on the apex do you use clutch rpm or engine rpm

example
150 hp * 5252 / RPM * 1.23

If you use engine rpm "10100 it is 95.94 pounds of torque

if you use clutch RPM "8200" it is 118.17 pounds of torque

 

[RED800]

are those real torque#'s cause,a few dyno's in the mag's said torque#'s were in the 80's...or are the production units that much stronger..

 

[Yammerhead]

Torque = Power * 5252 / rpm.
Power is not affected by rpm, it is constant regardless.

For example; 100 hp @ 1000 rpm = 525.2 footpounds.
Now lets gear that down 2:1,
100 hp @ 500 rpm = 1050.4 footpounds.
Or lets gear it up to 1:10,
100 hp @ 10000 rpm = 52.52 footpounds.

Now lets go for some more interesting real world numbers;
Taken from a dyno sheet for CPR turbo on RX1 http://thespeedshop1.com/Turbo Chargers.htm;
PEAK TORQUE is 113.4 footpounds at 6100 rpm where it makes.... 113.4 * 6100 rpm / 5252 = 131.7 hp. Their sheet actually reports 131.6
PEAK POWER is 192.1 @ 9900 rpm where it makes....192.1 * 5252 / 9900 = 101.9 footpounds. Precisely what they report on the sheet.

NOW to add to this, lets pick our speed.... 50 MPH....
9 tooth driver, 2.52 pitch = 22.68 inch, 1 inch = 1.579293*10^-4 mile, 1 driver revolution = 3.579*10^-4 miles.

50 MPH = 0.8333 M/minute / 3.579^-4 = 2328.4 rpm

Ok, we've established 2328.4 rpm.


Now this is what we've got;
at PEAK TORQUE (you'll check above) we have 131.6 hp.
131.6 * 5252 / 2328 = 296.9 footpounds torque ("forward acceleration").

at PEAK POWER we have 192.1 hp.
192.1 * 5252 / 2328 = 433.4 footpounds torque.


Now just to make you happy, lets calculate this through using gear ratios and torque instead of power;

at PEAK TORQUE 113.4 footpounds we have 6100 rpm geared down to 2328 rpm at a ratio of 6100/2328 (overall). 113.4 * 6100 / 2328 = 297.1 footpounds torque.... same as we got in the last calculation.

at PEAK POWER 101.9 footpounds we have 9900 rpm geared down to 2328 rpm at a ratio of 9900/2328 (overall). 101.9 * 9900 / 2328 = 433.3 footpounds torque. Again thats the same as calculated above.


For anyone having a hard time following that math (its really easy math BTW), take careful note of the fact that we obtained MORE driveshaft torque from LESS crankshaft torque at the same speed. In particular, at any speed, where it makes the most POWER will result in the greatest driveshaft torque.

LESSON TODAY: WE DON'T CARE ABOUT CRANKSHAFT TORQUE, ONLY IN HORSEPOWER BECAUSE WE CAN ALWAYS GET MORE DRIVESHAFT TORQUE BY GEARING DOWN FROM PEAK POWER.

So, by going what you show here, when you connect a dyno to the output shaft of the RX-1 motor (where the clutch would be) the dyno sheets will actually show the torque on the crankshaft, not the output shaft, right? (Not that torque really matters though, Ha! Ha!) Is torque then always a calculated value by the Dyno as opposed to measured?

What you say makes sense. We all try to clutch for peak power RPM, not where peak torque is. When everyone refers to the flat torque curve of the the 4 strokes, all that means is that as the engine speeds up, the ratio between output power (HP) and RPM is remaining the same. The only advantage I can see with that is that the clutches would maybe be more efficient at shifting in a nice linear fashion. If the torque was more "peaky", the clutches would have to shift out faster and more erratically to maintain the highest possible torque at the track. Feel free to correct me if I am wrong???

Cool thread.

I never really thought the whole horsepower vs torque thing through
before......

 

[Viper34]

Torque = Power * 5252 / rpm.
Power is not affected by rpm, it is constant regardless.

That equation is only good for playing mathematical games. HP is a linear motion, a engine produces a rotary motion, that is why torque is measured and HP is always calculated.

 

[LazyBastard]

The dyno will show the torque on whatever shaft you plug it onto since the dyno measures torque. You use the torque and rpm to calculate the power, which can be used to determine the final torque based on whatever ratio you are in.

To give you a vision of what a dyno machine actually does, invision this; A BRAKE of some sort mounted on heavy springs. When you apply the brake, it will twist the mounts on the springs. Based on how far the springs twist, you know the amount of FORCE being generated by the engine - that is the torque.

If the dyno is mounted on the clutch shaft, then to find the torque on the actual crankshaft, you need to compensate for the initial reduction gear by multiplying the torque by the gear ratio (as mentioned above by DYNAREX). Those dyno sheets shown are either from mounting the dyno on the crankshaft, or have been compensated - you can tell this by the fact that the power, torque and rpm line up correctly by the formula.

Now about the flat torque curve... with a flat torque curve comes a linear power curve, which means that by increasing rpm by x% you are approximately increasing power by x%. Means that the power comes on very smoothly, and yes, makes it simpler to clutch because you don't have to follow a non-linear power curve.

 

[LazyBastard]

Torque = Power * 5252 / rpm.
Power is not affected by rpm, it is constant regardless.

That equation is only good for playing mathematical games. HP is a linear motion, a engine produces a rotary motion, that is why torque is measured and HP is always calculated.

Torque is measured because you CAN measure torque. You CAN'T measure power.

I can assure you though, that if you had a 1 hp engine that made a MILLION footpounds of torque, it would NOT win any races.

 

[LazyBastard]

Re: ???

when you calculate torque numbers on the apex do you use clutch rpm or engine rpm

example
150 hp * 5252 / RPM * 1.23

If you use engine rpm "10100 it is 95.94 pounds of torque

if you use clutch RPM "8200" it is 118.17 pounds of torque

You're a little off there.150 hp * 5252 / 10100 = 78 footpounds of torque ON THE CRANK.

78 * 1.23 = 95.94 footpounds ON THE CLUTCH.

You can also get that by this;
150 hp * 5252 / 8200 = 96.1 footpounds ON THE CLUTCH.

 

[Viper34]

Torque is measured because you CAN measure torque. You CAN'T measure power.

Thanks for restating that. However, HP CAN be measured, but not on a engine.

 

[Viper34]

I can assure you though, that if you had a 1 hp engine that made a MILLION footpounds of torque, it would NOT win any races.

Obviously, but it could pull a freight train real slow!

 

[LazyBastard]

Torque is measured because you CAN measure torque. You CAN'T measure power.

Thanks for restating that. However, HP CAN be measured, but not on a engine.

This is real fun. Contradict me and then agree with me about the SAME point is the SAME SENTENCE.

I can assure you though, that if you had a 1 hp engine that made a MILLION footpounds of torque, it would NOT win any races.

Obviously, but it could pull a freight train real slow!

You could pull that freight train a lot faster with a 100000 hp engine that makes 0.1 footpounds of torque.... AND you could get it up to the same speed a lot faster.

 

[DaveyBoy]

Just look at a F1 car and the #`s they make no torque to speak of But make 1500 hp ah yes they turn 18000 rpm too i know but they measure the same no torque to speak of but tons of power

 

[welterracer]

Ill make it simple for ya..

Tell your friends your Apex only has 149hp and 80ftlbs of torque..

Then watch your friends bewildered when you smoke them.. LOL

When realistically its all how you measure the torque on a apex with a gear reduction..

 

[Slush Monster]

I think you guys NEED some snow!!! BAD!!!

You guy's would get a kick out of the massive torque my peterbuilt dump truck puts out as compared to the horsepower. In the equiptment world torque is king.

 

[LazyBastard]

Its a different application. You're looking for a much greater EFFICIENCY and LIFESPAN - you could get the same job done just as easily by strapping in a bunch of RX engines, but they would blow more fuel than you would care to think about and wouldn't run for as many years of constant pulling. Slow spinning diesels are more efficient than fast spinning sparkers and last longer. There are also the different characteristics of the transmissions to consider. Snowmobiles can get away with a lot because the belt clutches can keep the motor spinning at its best speed.