Race cars - Torque vs Hp - The Undiscovered Country (for many)

[zanick]

I never said that you would have more power in a lower gear, I said if you had the same power at 1:1 or 100:1, the speed of the vehicle would be totally different. but, if the speed of the vehicle was the same, Yes, you would have much less hp with 1:1 gearing. How can you compare the two? You also said that If you did gear it, one would be doing work more slowly but "doing more work". (see your quote below). I said, at the same HP, both would be doing the same amount of work over a given time. I think you might have just made a small unintentional error below. did you ? what I was saying is that for any same speed of the vehicle, the 100:1 gear ratio could allow for operaton at near max hp, while at that same speed, using 1:1, you would have much less hp at that same vehicle speed. See the difference? I am keeping my comparisons at the same vehicle speed, you are not. I don't think the discussion makes much sense unless we keep the speed and mass the same.


You said this:
"This defines the amount of work a given engine can do. The POWER OUTPUT IS SET IT DOES NOT CHANGE DEPENDING ON THE GEARING. So if you geared it 1:1 you'd have the same power at the rear wheel as if you used a 100:1 gearning. It would be going this work more slowly, but it would be doing more work."

So, what you are wrong about, is that if a car had 1:1 or 100:1 gearing and the same HP with each, the rate of doing work would be the same. one would be doing the work more slowly, but the work (Fs) would be the same over the same time period even though one would use a higher force less frequently vs a lower force more frequently

Just for the hell of it, you keep saying you have more power in a lower gear. And that I am wrong in sayin that you have the sme power whether you have 1:1 or 100:1 ratio.

Prove me wrong, do some calculations and post them. Please TRY to show I am wrong. Dont just state it.

 

[xxChrisxx]

you are correct i didnt mean more work, i meant more load. just going round this iritating debate is now staring to annoy me and I am beginning to make stupid errors in my haste to correct you.

so more load at lower speed,
less load at higher speed.
all the same work.
you don't have to keep the speeds the same to compare power.You are correct in saying that 100:1 would allow you to have more power at the same speed. THE ONLY REASION YOU HAVE MORE POWER IS MORE TORQUE.

I cannot state it any simpler than this. you can find this out from the HP curve, but once you are dividing by the speed you are really looking at torque at the reat wheel. just like if you were using torque nd then applied an angualr velocity you are taling about power.

call it what ever the hell you like. do it howeverthe hell you like. You wanted to be correct in the physics and several poeple have attempted to correct you. You clearly don't give a flying arse about being correct in the physics, you just wanted someone to affirm what you are saying.so purely to lay this thread to rest.

What you are doing with the horsepower curve will work, maximise Hpseconds for maximum go. Use that terminology.

good day

 

[russ_watters]

It might be simple but it is one of the most confusing for most in the racing world. (except the very top engineers). You have to understand, that sometimes we only have dyno graphs to go off of, so that addresses you last point, because the resultant torque and HP measured, is at the rear wheels, incorporating the effeciency losses. [emphasis added]

That's not the scenario you gave in the OP:

I posted a set of engine HP/torque curves... [emphasis added]

In the first quote, you're talking about performance measured at the wheels, and in the second you are talking about performance at the crankshaft. Now the wording in the paragraph from the OP (the rest of it) is clumsy enough that I can see you might have meant the measurements were taken at the wheels, but that isn't what you said. As chris has said, most of this thread has been an attempt to get you to correct your clumsy thought process and presentation of the issues. I think we've beaten this issue to death. Thread locked.

[edit] Actually, just to clarify that one last little confusion between you and chris - if the output of an engine in HP (and therefore rpm and torque) is fixed, the gearing (assuming equal drive losses) produces equal HP at the wheels. A 100:1 gear ratio produces 100x as much torque and 1/100th as much rpm at the wheel as a 1:1 ratio. But the speeds and accelerations are different, which is the point being made: You can't ever view HP as independent of other factors. You must combine it with rpm and when you do that, you're just rearranging that equation that relates the three.