Horsepower is horsepower?

I am not into the tech statistics part of this thread at all but it is surprising to me how many folks dont believe how much better a diesel truck pulls then a gasser just generally speaking. Lots of arguments and I totally see the value in a gasser 1- if you dont want to spend the extra money or 2- if you are hauling light enough / are happy with the gasser performance. It really is fine. But that does not mean it performs as well. All I can say is find someone who has a diesel and try it. I promise it will only take one time of sitting behind the wheel of a diesel pickup with a heavy trailer to make you realize that V10, Big V8, etc, there just is no comparison when it comes to pulling. WIth that said, each person should buy what makes them happy!

I am surprised that people do not understand the difference in power output from a diesel engine and a gasoline engine for a pickup truck.

A 2013 Ram pickup with the diesel engine is providing 850 ft lb of torque at the rear wheels. The 2013 Ram pickup with the gas engine has 400 ft lb of torque at the rear or less than half that of the diesel engine.

Comparing one company's diesel powered pickup with another company's gas engine is plain dumb. Sometime is better to keep you mouth closed and have people think you are stupid, than to open it and have them know it. Same applies to the OP.

Engineer9860 wrote:

mowermech wrote:
"If you look at a dyno graph, HP = Torque at 5252 rpm."

but...but...
My old Cummins was redlined at 2900 RPM!

The 8V71 Detroit Diesel was not turbo-charged, and it made LOTS of torque in logging trucks at 6000 ASL.
Of course, it was a 2 cycle SUPERCHARGED engine (a gear driven Roots-type blower).

There was an 8V-71 turbo charged version. It is called the 8V-71T:

There was also an aftercooled version, the 8V71TA. I drove a bus (GMC PD4106) with an 8V71T (no "A"), and it moved!

wilber1 wrote:

Water-Bug wrote:
Wow! 121 posts and nobody has stated that "horsepower isn't always horsepower". There is horsepower and brake horsepower. Two different measurement systems that come up with different numbers for the same vehicle/engine. Just thought that I would stir the pot while I refill my popcorn.

What would be the point, there are many ways of calculating and measuring horsepower, far more than just two. The important thing for this debate is everyone using the same method.

Europe doesn't even use horsepower to rate their engines any more. They use kW.

Yip and it takes roughly 1.5hp to make a KW. A hp=745 or 750w, I forget which been to long since I messed with gensets and electric motors.

This whole discussion has now come close to real boring.

It's time for some genuine, but non-RV, fun ... with a demonstration of pushing the horsepower versus RPM versus torque versus engine cubic inch efficiency envelope to the limit. Try clicking on the 2nd photo down from the top - but first turn your speakers way up high (... and by the way, this engine is double-supercharged, so it can maintain it's power at all kinds of altitudes):

http://www.racedepartment.com/2012/10/best-engine-sounds-ever-brm-v16/

Hannibal wrote:

4x4ord wrote:
Horsepower and torque ratings are both an indication of the power of an engine. People often bring up the fact that torque is a measurement of force where as HP refers to the rate of doing work, but when you are talking engine torque you are talking torque at a specified or at least implied rpm which indicates power.

Exactly. I'm interested in the whole picture. The rate of doing work, aka horsepower. In our case, miles traveled in one hour. Then you can break it down into what rpm you think you need to run and how much you're willing to pay to run at that rpm. That's when torque value comes into the picture. If you want the necessary horsepower to move a load a certain speed at a lower engine rpm, you have to increase torque to produce the necessary horsepower at a lower rpm. In the end, it's still horsepower (the sum of torque X rpm/5252), not torque alone, not rpm alone, that determines speed. Doesn't matter if it's a dragster or an 80k lb OTR tractor trailer. The rate of doing work is horsepower.

My 'depends on lots of things' is AKA 'the big picture'...

The actual architecture of the ICE (gasser, diesel, small block, big
block, forced fed, direct injection gasser, cam profile and another
huge ETC) the fuel itself (alcohol, bio, etc) and another huge ETC

The tranny type, manual vs automatic (then on that, what does the
software algorithms look like), the numbers of gear and their ratios,
the thermal management attributes, ATF capacity, and another huge ETC

The other gear boxes in the food chain...like folks don't know that
the diff is a gear box. Is there another gear box in the drive line?
A 4x4's transfer case is another gear box and then whether full time,
part time, viscous coupled, etc

Most of the above have losses and how that is managed has a bearing
on the HP delivered to pavement.

Finally, longevity. So many read here do not understand that, really
don't understand that. They are the ones who go back to the OEM
complaining it broke, but don't understand that the tuner they
used went over the longevity line...

Oh...another finally...personality and likes/dislikes. I don't like
high rev'ing ICE's on my TV. Love it in my 2 seater and the Morgan
going to be getting soon. Also don't like diesel...looking into it
but that not really liking them and the SMOG freight train coming
down the tracks in the late 90's reading clinched or killed that thought.
I love big blocks for my TV. Not so much for 'my' sports cars. Had
a L88 in my Vette...loved the torque, but knew would kill myself out
on the track because it twisted the body so it went 'that-a-way' when
I wanted it to 'that-a-way'...

I think the simple answer to the original question is that spec peak HP isn't always operating HP and that spec HP isn't spec HP at altitude.

Water-Bug wrote:
Wow! 121 posts and nobody has stated that "horsepower isn't always horsepower". There is horsepower and brake horsepower. Two different measurement systems that come up with different numbers for the same vehicle/engine. Just thought that I would stir the pot while I refill my popcorn.

What would be the point, there are many ways of calculating and measuring horsepower, far more than just two. The important thing for this debate is everyone using the same method.

Europe doesn't even use horsepower to rate their engines any more. They use kW.

Wow! 121 posts and nobody has stated that "horsepower isn't always horsepower". There is horsepower and brake horsepower. Two different measurement systems that come up with different numbers for the same vehicle/engine. Just thought that I would stir the pot while I refill my popcorn.

Engineer9860 wrote:


There was an 8V-71 turbo charged version. It is called the 8V-71T:

As ugly as that thing is, it's a beautiful mechanical work of art! Like musing over an old Harley.