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# Horsepower ratings exaggerated

Bear in mind that the transmissions in these trucks have more of a parasitic loss than the ones you'll find in cars. That 5.3l number does sound mighty low, though. Rear wheel HP for the 6.8l Ford V10 was recently measured at 170 (against an advertised 275) but that was on a motorhome chassis with HD transmission, rear end, etc.

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This discussion has been closed.

## Comments

2,721606582If you want power get a Vortec 6.0 300hp the most powerful V-8 in the world!

1,021I think we all should drive the various trucks more and read the idiotic magazines less. You all must know that the winner of these shootouts are the trucks with the most money in the glove boxes.....

2,721606Aah, why do I bother...

2,7211,110Ehh, i've developed the same attitude as you Stanford. i know a few places where there is discussion with substance.

3,516And stanford is absolutely right about horsepower ratings vs torque figures. Perfect example would be my last two trucks: my current Ram 3500 Cummins, and a 1993 Ford F150 302.

Here are their respective engine ratings:

Cummins: 180 hp/420 lb-ft

302: 185 hp/270 lb-ft

Believe me, the Cummins is a hell of a lot stronger, despite having 5 fewer horsepower, and both trucks can hit and hold 95mph. If both engines were in the same truck, the Cummins would outrun the 302 with a load (bed or trailer).

2,7211,110Not being demeaning, but I think those equations are a bunch of hooey. In the engineering world, you can solve just about anything with dimensional analysis. the world of physics follows it. And first look at your equations show no coherency really. not disregarding, they may be upper level math derivations, which would be impressive, but I'm really skeptical of total lack of gear ratio, tire size, and for dear goodness WHERE THE HELL IS TORQUE??!! you're saying that a '99 v6 with 200hp could run the same as '92 chevy 350 dodge 361 with 200 hp. Nope, sorry, I don't buy it.

6062,721Cdean, I need to quote you from your post because I am replying to a specific point about "I'm really skeptical of total lack of gear ratio, tire size, and for dear goodness WHERE THE HELL IS

TORQUE??!!"

The answer is that torque is already represented by the horsepower term of the equation for calculating ET and MPH. So is gear ratio and tire size. How? Because horsepower itself is nothing more than a calculation with terms for torque and rpm. Same for gear ratio, it gets reduced to the term RPM. Horsepower is equal to torque at the rear wheel times rpm at the rear wheel. The actual equation is:

HP = Torque*RPM/5252. The number 5252 is a units constant. When you work at the rear wheel like the chassis dynomometer does, it measures two things, torque and rpm. The result gets plugged into that equation, so horsepower is a calculated result. The key point is that without both torque and rpm together, no horsepower is measured or produced. Why does this matter? Because you have stated it's your opinion that the equations I posted earlier for ET and MPH (not my equations BTW) don't work because they don't consider gear ratio, tire size and torque. What I'm saying is that those factors are indeed included already when you enter the number for horsepower into the equation. If it's still hooey to you, you can keep that opinion if you want, but already, there is proof to me the equations have merit because they support the numbers that Truck Trend produced. One last question. In the same post you asked, "you're saying that a '99 v6 with 200hp could run the same as '92 chevy 350 dodge 361 with 200 hp. Nope, sorry, I don't buy it."

I said no such thing, and for you to infer that I did is a misunderstanding on your part. You may not be buying it, but I wasn't offering that opinion for sale either.

606Then again, I think we've beaten this particular horse half to death. Agree to disagree?

6061,110I made up the little example about the 200 hp engines, meaning two different same HP engines with different torque. I thought your equation was saying you put in HP (200 in my example) and you would get an ET or whatever, and I was trying to say how different torque motors with same HP would run very differently. all goes back to misunderstanding which HP goes into equations.

I'm on the same page now. still a skeptic though. And yes, I think the horse is dead.

3262,721Cdean, you have it! I'm a skeptic too. That's why I get into this.

Stanford, you asked several questions, all good. The chassis dynomometer does not care what gear, or axle, or tire you are using. The horsepower will measure the same no matter what gear, or axle, or tire you are using. But torque, on the other hand will be much greater in first gear than in overdrive. But opposing this, rear wheel rpm will be much lower in first than in overdrive. The net result is that torque goes down by as much as rear wheel rpm goes up when you up-shift through the gears. The horsepower stays constant through the driveline, but the amount of torque gets multiplied with each gear ratio. The chassis dynomometer can measure your maximum horsepower and torque just as easily in overdrive as in first gear. The torque the dynomometer measures will be greater in 1st gear than in overdrive. But even though torque is measured at the rear wheel, it is expressed back to the crankshaft. Thus for example on the V10 Triton, the actual rear wheel torque measured on the dyno, in whatever gear the transmission was in, the number measured was divided by the overall ratio of the transmission and driveline to arrive at the published specification, expressed at the crankshaft, which was 280 ft/lbs at 3000 rpm.

3,516"We got another one for ya"

326Hey quadrunner, what was that, the eulogy?

Oh, Wilbur!

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