edumacate me on horse power

[john_bud]

what year 6.6 do you have? i have a bunch of parts for them just no senders



my happy place is diving into the the dirt with all 4 wheels spinnin

It's a 2003. Been a pretty nice truck, but the guys in the electrical department need to be slapped around some. I've had to redo the ground connection for the brake controller 3 times. Who in there right mind would put a critial ground connection to the body where road salt is constantly flung up on it? (probably the same one that chose the contact metal in the sender!)

I agree with you on the diesel option to a point. I got it to pull my trailer around better with less strain on the truck and on me driving it. Bigger trucks are easier to drive heavy than lighter trucks. But, hey if you have the $$ and want the diesel --> get it. This is America and if you can afford it - that's justification enough. If we could only have what we could justify - most of us would be issued shoes and a bus pass.

It's -11F here today. Enjoy your warmth!

jb

 

[SPYDERLK]

workinallthetime quote: this guy wants to know about hp but you cant talk about it with out torque.

See post 7. Diesel torque reaches a max around 1500rpm and declines slowly with increasing rpm, then falls off sharply after max HP rpm. The diesel "gears" down as it slows down. This characteristic, where HP remains virtually the same as it slows, is more pronounced in a diesel than in a gas engine.
Larry

 

[workinallthetime]

Gas vs Diesel Hp vs Torque

started a new thread for this since we are way off, lol.

Diesel for work gas for play, if you need it you will find a way to buy it, if you want it you will justify needing it, lol

 

[bx23barry]

<So you are saying, I could put a 21 hp gas engine in my tractor with the same gearing and same hydraulics with no difference in work produced?>

Did you skip over the last part for any reason?
“HP is HP. It really doesn’t matter if it is gas, diesel, steam, electric, air, or hydraulic powered (some may last longer, use less fuel, need different gearing).” The fact is 21 hp does indeed produce the same amount of “work“ no matter how it is produced. HP is defined by work produced. From your link: “Horsepower is defined as work done over time.” All the talk about diesel vs gas, car vs tractor, torque vs speed has little to do with hp only how it can be produced and/or measured differently. Lifting 66,000lbs ½ foot in one minute is the same amount of work as lifting 11,000lbs 3 feet in one minute. Both one hp (if my math is any good).

 

[SPYDERLK]

<So you are saying, I could put a 21 hp gas engine in my tractor with the same gearing and same hydraulics with no difference in work produced?>

Did you skip over the last part for any reason?
“HP is HP. It really doesn’t matter if it is gas, diesel, steam, electric, air, or hydraulic powered (some may last longer, use less fuel, need different gearing).” The fact is 21 hp does indeed produce the same amount of “work“ no matter how it is produced. HP is defined by work produced. From your link: “Horsepower is defined as work done over time.” All the talk about diesel vs gas, car vs tractor, torque vs speed has little to do with hp only how it can be produced and/or measured differently. Lifting 66,000lbs ½ foot in one minute is the same amount of work as lifting 11,000lbs 3 feet in one minute. Both one hp (if my math is any good).

The diesel will be a little more easy to work with because it will produce the 21 HP over a broader rpm range than the gas. Because of this you will be able to get more work/T out of the diesel unless you maintain the gas engine very close to the rpm where it provides its peak HP. This is tuf to do. Its much easier to keep an engine between 1500 and 2100 than between 1900 and 2000.

 

[john_bud]

The diesel will be a little more easy to work with because it will produce the 21 HP over a broader rpm range than the gas. Because of this you will be able to get more work/T out of the diesel unless you maintain the gas engine very close to the rpm where it provides its peak HP. This is tuf to do. Its much easier to keep an engine between 1500 and 2100 than between 1900 and 2000.

SpyderLK,

I think you may be suffering under some "urban legend" mis-information. I did post that Ford for one made the same size engines (same bore and stroke) in both gas and diesel and that the diesel was less powerful at all rpm's.

Here's the dyno curve published in 1963 by ford as part of the sales lit for a 4000 Heavy-Duty Industrial tractor.

As you can see, the gas engine may loose torque faster than the diesel (10 ft-lb VS 5 ft-lb) over the same rpm span of 1000 to 2200 rpm. But, the gas engine has more torque and HP at every rpm. In fact, the gas engine has more torque at 800 rpm than the diesel has at it's peak.

What's it mean? The manufacturers can tailor engines to suit tasks very well. Gas or diesel.

jb

 

[cp1969]

Horsepower = torque x rpm/5252.1

It's just a calculated number arrived at by multiplying the torque an engine is producing by the rpm it's turning, then dividing by 5252.1 and is intended to represent an engine's ability to do work. More horsepower means an ability to do more work--but--you have to gear it correctly for the application.

 

[bx23barry]

The diesel will be a little more easy to work with because it will produce the 21 HP over a broader rpm range than the gas. Because of this you will be able to get more work/T out of the diesel unless you maintain the gas engine very close to the rpm where it provides its peak HP. This is tuf to do. Its much easier to keep an engine between 1500 and 2100 than between 1900 and 2000.

This may or may not be true depending on many engine design factors. The truth is most diesel engines operate in a much narrower RPM range than most gas engines. While torque is usually higher at lower rpm on diesel engines hp is a function of torque and speed so hp is equal to a gas engine producing half the torque at twice the speed and that hp # can often be held over a larger rpm range (albeit higher, maybe 3500-4500). But again, it all depends on the engine design. The advantage of diesel power is efficiency not power production. A normally aspirated gas engine will almost always produce more hp than a normally aspirated diesel engine of the same displacement purely by the fact it can turn higher rpms.

 

[SPYDERLK]

SpyderLK,

I think you may be suffering under some "urban legend" mis-information. I did post that Ford for one made the same size engines (same bore and stroke) in both gas and diesel and that the diesel was less powerful at all rpm's.

Here's the dyno curve published in 1963 by ford as part of the sales lit for a 4000 Heavy-Duty Industrial tractor.

As you can see, the gas engine may loose torque faster than the diesel (10 ft-lb VS 5 ft-lb) over the same rpm span of 1000 to 2200 rpm. But, the gas engine has more torque and HP at every rpm. In fact, the gas engine has more torque at 800 rpm than the diesel has at it's peak.

What's it mean? The manufacturers can tailor engines to suit tasks very well. Gas or diesel.

jb

jb. Thank you for posting this! It is good info on a gas engine well done. Sorry tho, I do not mean to detract at all from it, but with perusal it bears out what I have said. In the following pls pardon occasional appearances of curtness. I have difficulty in efficient polite expression sometimes.

1st, the issue is HP for HP not displacement for displacement.
Now look hard at the curves. Youll notice that the diesels are flatter. Move the gas engine curve straight down over the diesel. see what i mean? See the linear rise and significant bulge in the diesel curve around 1400?
Notice how, altho the gas starts higher, the HP curves continuously converge as rpm drops, becoming identical at 800.
Imagine that the displacement of the gas engine were reduced so that the peak HPs coinsided. In such case the gas engine would be in a higher state of tune - a more highly optimized state. Its peaks would be more prevalent and thus it would show obvious points in the rpm range where the power was below that of the diesel.
Now imagine that the 172 gas was optimized for peak HP production at the same HP as the 172 diesel. Would the gas curves be as flat as the diesels? Maybe, but I think not. You would have to verify this, but I suspect this is a low compression diesel - less than 18 to 1. Nowadays they go 19 or 20 to one unless turboed. You can do this with a diesel system and the high compression favors the advantage described. The gas engine cannot be run at the high compression ratios, that would allow it to compete over the full rpm range [11 or 12 to 1] without destructive detonation, unless at a high rpm and using special gasoline. This would also entail the need for a differently geared transmission.
The diesel is just ideally suited for heavy work due to the tractability that is inherently provided by the principles of its function. The coup de gras is that it is burning a lubricant!
Larry

 

[john_bud]

jb. Thank you for posting this! It is good info on a gas engine well done. Sorry tho, I do not mean to detract at all from it, but with perusal it bears out what I have said. In the following pls pardon occasional appearances of curtness. I have difficulty in efficient polite expression sometimes.

1st, the issue is HP for HP not displacement for displacement.
Now look hard at the curves. Youll notice that the diesels are flatter. Move the gas engine curve straight down over the diesel. see what i mean? See the linear rise and significant bulge in the diesel curve around 1400?
Notice how, altho the gas starts higher, the HP curves continuously converge as rpm drops, becoming identical at 800.
Imagine that the displacement of the gas engine were reduced so that the peak HPs coinsided. In such case the gas engine would be in a higher state of tune - a more highly optimized state. Its peaks would be more prevalent and thus it would show obvious points in the rpm range where the power was below that of the diesel.
Now imagine that the 172 gas was optimized for peak HP production at the same HP as the 172 diesel. Would the gas curves be as flat as the diesels? Maybe, but I think not. You would have to verify this, but I suspect this is a low compression diesel - less than 18 to 1. Nowadays they go 19 or 20 to one unless turboed. You can do this with a diesel system and the high compression favors the advantage described. The gas engine cannot be run at the high compression ratios, that would allow it to compete over the full rpm range [11 or 12 to 1] without destructive detonation, unless at a high rpm and using special gasoline. This would also entail the need for a differently geared transmission.
The diesel is just ideally suited for heavy work due to the tractability that is inherently provided by the principles of its function. The coup de gras is that it is burning a lubricant!
Larry

Larry,

Don't worry about polite expressions, as long as you don't slash my tires, I probably won't even notice. Looking closely -there isn't anything even remotely impolite much less offensive. Just good factual discussion.

This is becoming quite edumacational for me, I hope it isn't too far afield for the original poster (sorry for the highjack!). Good discussion. Subtle points being raised, quite interesting. Taking your lead, I modified the picture to cut the torque curve for the diesel and moved it up so the max rpm end (max hp) would match the gas. (it was easier to cut the flatter curve). Ignore the BHP curve as it isn't modified.

The gas engine is fractionally higher torque from about 1400 to 2200 rpms. The Diesel is losing less torque as rpms drop, so it has more retained torque below 1400 rpm and thus more hp.

Obviously, I think this may indeed bear out your points in large degree, if not completely. yes?

However, my minor point that the manufacturers can tailor an engine to suit the application is also relevant. There isn't a significant difference in the hp between the gas and theoretical diesel, with the maximum being 0.76 hp at 800 rpm. It might have been interesting to compare the 134 gas engine to the 172 diesel. I don't have those curves, just thinking with my fingers. On that tack, I wonder what the fuel consumption of a de-displaced gas engine would be compared to the original diesel?

Oh, the hp is not the same in the original at 800 rpm -- but at the low rpm the small difference in torque divided by 5252 is a small number. Under the resolution of the copy's fat lines that had been copied, shrunk and posted. I would expect that on the original, the hp curves flop at some point between 800 and 525 (min rpm).

And once again, you were correct on the CR of the diesel. 16.8:1. Being a converted gas engine, it wasn't put up to a higher CR. Possibly cylinder wall or head gasket concerns. My rebuild with a 0.02 overbore raised it to 17.0:1 --> slightly better but in the "big whoop" category. The gas engine is also low compression at 7.50:1 so it can take full throttle for hour after hour and not self destruct.

Cheers!

jb