Dyno hp max in 4th or 5th gear?

[chex]

So when you put your car on the dyno, how should you proceed to make max hp without damaging the engine?

 

[Bullet488]

When you take your car to the dyno, the dyno operator (read: NOT you) will dyno the car in 4th gear. It's a big drum that you are accelerating to measure horsepower - nothing more. The dyno WILL NOT hurt your engine. Overrevving or running a bad tune WILL hurt your engine, whether you're on the dyno or not.
Scott

 

[Jack B]

If you use fifth gear the drive line stresses would be much higher. I guarantee you that a high hp sc or nitrous car wouldn't do many fifth gear pulls before hatching the half shafts. The same applies to high hp cars starting a pull before 3000 in fourth gear.

If you take a look at a log of a run at the drag strip, you really don't ever see less then 4000 rpms except at launch. Some cars won't even see less then 4000 at launch.

 

[Big Medicine]

If your goal is to measure the highest possible HP on the dyno, I'd suggest using first gear.

The dyno measures torque and converts the measure into horepower figures.

If you are interested how torque develops throughout your RPM range (e.g. horsepower), you would want to use 4th gear since it's a 1:1 ratio.

Any gear lower multiplies the engine torque, any gear higher depreciates the engine torque.

 

[Makara]

If your goal is to measure the highest possible HP on the dyno, I'd suggest using first gear.

The dyno measures torque and converts the measure into horepower figures.

If you are interested how torque develops throughout your RPM range (e.g. horsepower), you would want to use 4th gear since it's a 1:1 ratio.

Any gear lower multiplies the engine torque, any gear higher depreciates the engine torque.

It measures torque and a rate. Going to first increases torque but lowers rate. Because 1st is more lossy than 4th, you will get a lower hp with it than 4th, not to mention that traction may be an issue with a viper on a dyno in 1st gear.

 

[Big Medicine]

Lowers rate of what? Acceleration? My car accelerates much faster in 1st than in 4th.

Rate final minus rate initial divided by time elapsed? Is that what you are saying? The rpm of the dyno drum? O r the slope of the curve getting there?