Forum Discussion
otrfun
Mar 18, 2014Explorer II
OhhWell wrote:I totally and respectfully disagree. Please reread my previous posts referencing HP = Torque x RPM /5252. Using this formula, please explain why you would choose a 400 HP, 200 ft. lb. of torque engine that has to rev over 10,000 RPM as a practical truck engine. Until you address this, then I don't believe you have a credible argument.otrfun wrote:I do not have horsepower and torque confused. I was wondering if perhaps you did? Torque doesn't pull ANYTHING is it a measure of force. It is a very important measurement but doesn't have squat to do with acceleration or top speed. If these high torque diesel engines could rev as high as gassers do, they would have insane amounts of horsepower.OhhWell wrote:You're jokin', right?! If not, is it possible you have horsepower and torque confused? There's a reason why diesel engines are so popular--it's NOT because they have horsepower--it's because they have TORQUE. Again, torque pulls the trailers, hauls the goods, does the work in the realworld. If horsepower was doing all these great things why don't we see Indy 500-type engines powering big trucks? They're small, lightweight, and they produce 700+ horsepower. There's a reason why you'll never see one in a big truck--it's because they have very little torque.otrfun wrote:I would pick engine 1 any day of the week. I might actually have to climb a hill at some point. I'm assuming that in this scenario, the same exact transmission isn't forced on both engines?OhhWell wrote:I get your technical point; however, I believe you missed my point.otrfun wrote:Who in the heck says that? Torque is a measure of force and horsepower is a measure of WORK.
As they say, torque does the real work, not horsepower.
You can multiply torque through gearing. You can't increase your horsepower through anything besides upgrading the powerplant.
Definition of horsepower
It's just a case of semantics. Notice my use of the word "real" work. I'm talking about work as defined by the average person:
"activity involving physical effort done in order to achieve a purpose or result"
If someone needs to haul or tow a lot, and wants to "achieve a purpose or result", which engine would be the better choice?
1. An engine with 400 HP and 200 ft. lbs. of torque.
2. An engine with 200 HP and 400 ft. lbs. of torque.
I think most would choose engine #2. Why? Because in the above scenario an abundance of torque allows them to "work" at "achieving a purpose or result" much easier than an abundance of horsepower.
P.S. I see your point about gearing down to increase torque. However, if this was an efficient process, can you explain why we don't see 700+ horsepower Indy 500-type engines powering big trucks?
The reason you don't see Indy Car engines in big trucks is due to longevity and fuel economy. Big trucks and diesel engine manufacturers don't spout out Torque numbers except (it appears) to the light duty truck consumers. Even there we are starting to see a horsepower push and race. Top speed calculations don't take torque into consideration at all, incline or not, it is all horsepower.
Luckily, diesel engines these days have more than enough horsepower as well so it's really all good. Your scenario you posed was too extreme. I wouldn't want to tow a heavy load up a decent hill with only 200hp no matter what the fuel type. You can scream TORQUE all you want but it isn't going to go very fast.
"The general point I'm trying to make (with this formula) is that there is a give and take in terms of HP, Torque, and RPM. Some seem to think that HP is the cat's meow all by itself--that an engine with tons of HP will some how perform better under all conditions without any regard to its torque characteristics--that is simply not true. Again, HP is the product of Torque and RPM. Change one variable, and the other one or two variables must change, too."
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