Calculating Horse Power and Torque through 50-80 MPH runs

[Infinitiguy19]

A while back Q45Tech mention he could calculate how much power a Q makes at the wheels by using the stop watch times from 50-80 MPH. If you know me then you would know I have searched every resource at my disposal to find the answer but I have come up short.

Obviously feet above sea level, temperature (Humidity?) and weight matter and would change things significantly.

Now Dennis I don't care if you post something like this:


And then expect me to solve for E. I will find the answer eventually, Because with a little help and a lot of will power anything can be done.

This method is supposed to be more accurate than a dyno because it takes place in a real world environment. Of course this test is done while the car is rolling in second gear so you have no wheel spin. Unlike on a dyno where the tire may slip on the metal drum and you have no aerodynamic resistance.

[Infinitiguy19]

I think I may have it actually:

Force = weight of the vehicle: 4100 LBS.

Distance = The distance covered by the vehicle (In feet) from 50-80 MPH.

So when you multiply those two together you get your answer in Foot Pounds of Torque.

[SanCarlosQ45]

I think I may have it actually:

Force = weight of the vehicle: 4100 LBS.

Distance = The distance covered by the vehicle (In feet) from 50-80 MPH.

So when you multiply those two together you get your answer in Foot Pounds of Torque.

From any physics class Force(in this case weight) x distance = work. Now horsepower I believe is work over time whereas torque is calculated as a force to rotate an object at some radius. What you are trying to calculate is linear motion if the car was being dropped vertically the distance you measured.


work=force applied(or weight if moving vertically)xdistance
torque=force applied x radius (such as radius of tire or flywheel)

[OwnerCS]

In about 3 hours driving time, you can take a spin over to Rensselaer Polytech in Troy NY and take a tour. I bet you could get some dyno time..

[elwesso]

actually you can quickly determine HP from acceleration.. A G-Tech pro or whatever is out there now does a pretty dang good job of estimating wheel HP. If you had an accurate 1/4 mile time you can also estimate wheel HP.

All you really need to calculate HP is a distance and the time it took to travel that distance, the weight of the vehicle. Tons of calculators out there to help estimate this.

Really wheel HP is the only true way to compare because each car has a different loss factor, so you can be "close" by saying the Q has a 15% drivetrain loss, but it might be 10% or it might be 20%.

HP is simply work per time.. Ft-Lbs/Sec.. Torque is an "instantaneous" value..

The actual "HP" number statically is not very important, and will often vary +/- 15% or so depending on the measuring equipment used (even the same kind of dyno but a different physical machine). IMO, the HP numbers are really only useful when COMPARING them, say a before and after comparison when doing mods..

IN other words, you could go put your car on 5 different dynos and probably have a swing of about 10-20HP.. 20 HP sounds like a lot, but in a car its hardly noticeable.. After all 20HP is only 15% of 300HP.

[OwnerCS]

IMO, the HP numbers are really only useful when COMPARING them, say a before and after comparison when doing mods..

Ahhh Wes go ahead and say that four letter word.. TEST.. :-)

It was interesting to see this car on the dyno at Rensselaer deliver a whopping 38 HP at the wheel with its rated 60 HP air cooled 274 cubic-inch six-cylinder overhead valve engine.