Oil & Fuel Diesel HP vs Gasoline HP

[MikePA]

<font color="blue"> If a HP is a HP, then the tractor with the Chevy engine should out pull the tracor with the Cummins. </font>
Whoa, wait a minute, Dave! /forums/images/graemlins/smile.gif Your original question asked about diesel vs gasoline horsepower. The answer to that was 1 diesel hp = 1 gasoline hp.

What a vehicle can 'pull' is a whole 'nuther question. That has to do with torque and guess what? 1 diesel pound foot of torque = 1 gasoline pound foot of torque. /forums/images/graemlins/grin.gif

'Out pulling' has to do with a lot of factors;

How much torque an engine produces
Where in the rpm range it produces it
How flat the torque curve is
How broad the torque is

So swapping engines, even engines with the same hp and torque figures, does not mean they will perform the same. Notice I said hp and torque figures, which are usually the peak numbers for an engine. All the aforementioned factors, plus many more, come into play when you ask the question which engine will 'out pull' another engine.

Drag racers have been 'debating' this question for years. /forums/images/graemlins/cool.gif

 

[BillyP]

I'll add one more thing.

The main reason a 90 HP tractor can out pull a 290 HP truck is the gearing...
What's the speed of that tractor at 2,600 RPMs?
What's the speed of that truck at 2,600 RPMs?

25 HP gas vs 25 HP diesel = difference in torque and torque curve.

As far as stating the Torque instead of HP on the side of the truck, Jerry pegged that. The everyday person would look at the torque figure and scratch their head.

OK..OK... so I can't count /forums/images/graemlins/tongue.gif

 

[jinman]

</font><font color="blue" class="small">( Can I modify the P/U ?? )</font>

You mean make it more like a tractor?? /forums/images/graemlins/wink.gif

 

[slowzuki]

I'll muddy it further, you guys are talking about a bunch of things here:

Draw bar power - Power that can be put to the ground via pulling

Draw bar pull - This is the force you can generate to get some thing moving

Engine power - its all the same units, engines have different curves of torque vs rpm

Engine torque - the twisting force and engine can produce


1 hp is a hp, but if you don't have enough drawbar force to get something moving, you can't generate any drawbar power. This is because power is force X velocity.

A vehicle can be geared such that 2 equal hp engines can do the same work. As we know the engine with the flatter torque curve and therefore power curve too is much easier to work with.

Anyone try to put a lumpy cam in their old gas tractor? Reving it and popping the clutch trying not to stall with a load on it would be crazy!

 

[GareyD]

When I went to Dyno school for Motorcycles a couple of years ago...
the instructor explained it like this...

Horsepower = how fast you are going to hit a brick wall ...
Torque = how far you will go through it.. /forums/images/graemlins/blush.gif

Makes it real easy for me to keep them straight /forums/images/graemlins/smile.gif

GareyD

 

[PineRidge]

GareyD very well said. /forums/images/graemlins/grin.gif

 

[Egon]

Yup that's it. Different gearing, different tires, more weight but just leave the engine the same.

Egon

 

[Nasty135]

Just one more thought for the gas vs. deisel debate the reason the for the hp ratings is as since the dawn of the internal combustion engine they needed a reference point to relate the amount of work or pull you could get out of any given engine (hence the horse power rating) Now with that said with the need for torque over hp in heavy equip. where speed is not a requirement .
Gasoline is a fast burn fuel so the combustion process is more of a pop for the given amount of gas needed to make the piston travel(depending on compression),where the deisel is
a slow burning boom with more ability to push the piston futher longer stroke= more torque. gasoline engine has to rev much higher to equal torque of a chugging deisel. Generally the longer the stroke the more torque also faster piston speed in the cylinder for any given rpm because of the longer stroke(rpm's equal distance traveled w/longer stroke piston speed increased ) that's why 2800rpm in a deisel not only sounds tight but with that long stroke it is tight! the amount of swing on the crank = lots of leverage.
That's why deisels all have forged steel cranks& rods vs. the cast stuff thats put in most automotive equip. unless its high performance.
Did I say way tooo much! or just too much /forums/images/graemlins/grin.gif

Wait I'm on a roll , I do like to discuss engines and the dynamics of any given setup (yes I'm a gear head) okok ill stop for now ,hope it helps??

 

[MossRoad]

Hey, if you replace that horse with a hampster, that's what I've got under the hood of my Power Trac /forums/images/graemlins/tongue.gif

 

[MossRoad]

<font color="blue"> Horsepower = how fast you are going to hit a brick wall ...
Torque = how far you will go through it.. </font>

That's a great explanation! /forums/images/graemlins/smile.gif