Torque vs. Horsepower

[thgoodman]

My '06 Beaver Patriot Thunder has a C-13 Cat rated at 525hp. The guy parked next to me last week had a similar size MH (looked like a Prevost but wasn't). It also had a Cat C-13 but it was rated at 475hp but with more torque. I know Cat can change engine ratings both mechanically and electronically (i.e., injector timing?) but I don't know why the coach builders' design specs call for different ratings.

What I don't understand is how the torque/horsepower trade off affects vehicle performance and if there would be any advantage to going back and paying Cat to making a change to my engine specs (what would I ask for?). How do the changes affect hill pulling, towing, city vs country driving, fuel mileage, etc? Could the average Joe sitting in the driver's seat even feel the difference if the modifications were made?

[bobman]

The combustion temperature is determined largely by the correct mixture ratio of fuel to air if the boost goes up ( meaning more air is being packed into the cylinder ) then the computer must compensate by lengthening the time the injectors are open to inject more fuel and keep the proper mixture

If that didn't happen the engine would run lean and if lean long enough the exhaust temp will exceed the rating the valves are designed for

[davebrown]

bobman wrote:
With two engines of identical displacement it has to be different boost levels or the hp is rated at a different rpm or some combination of those two factors

Fuel delivery has to match the combustion volume to keep the valves in the correct temperature range

not really what the op was talking/asking about but first time in my life I heard that
quote:Fuel delivery has to match the combustion volume to keep the valves in the correct temperature range

can you explain how this works? how does one correct the temperature of the engine valve and how does one know when its incorrect?

[bobman]

With two engines of identical displacement it has to be different boost levels or the hp is rated at a different rpm or some combination of those two factors

Fuel delivery has to match the combustion volume to keep the valves in the correct temperature range

[Altern]

I see what you are getting at but its a bad idea to downrate your coach.
Did you know for example, an earlier, Patriot Thunder can run circles around your 2006 model?
Even the earlier 475 HP, 1550 lbs torque models could leave you in the dust climbing a hill......Why?
Its all about HP to weight ratio.
The earlier Thunders were much lighter, maybe 8-10 K lighter.

By the way thats a lovely coach... :C

[davebrown]

thgoodman wrote:

ScottG wrote:

2oldman wrote:
Torque horsepower 2010
Torque horsepower 2012

I'm curious to see an answer to the OP's question as well but not curious enough to read through 75 pages of text.

Maybe someone can provide a more condensed or specific answer to the OP's question on his C-13.

Well said, Scott. Thank you. I guess I should have been more clear. My actual question was kind of buried it the end of the post. "Could the average Joe sitting in the driver's seat even feel the difference if the modifications were made? "

I don't get your question? Your 525HP Cat has more HP and More torgue than a older 475 one to begin with.

[ScottG]

2oldman wrote:

ScottG wrote:
I'm curious to see an answer to the OP's question as well but not curious enough to read through 75 pages of text.

Threads like these always turn into what I posted.

I was attempting to answer his first two questions. Feel free to ignore all of it.

Oh don't worry my old friend, I did. :W

Scott

[2oldman]

ScottG wrote:
I'm curious to see an answer to the OP's question as well but not curious enough to read through 75 pages of text.

Threads like these always turn into what I posted.

I was attempting to answer his first two questions. Torque v horsepower is always a complicated subject. See the post above mine?

If you want to criticize further, go right ahead.

[steveownby]

thgoodman wrote:
My '06 Beaver Patriot Thunder has a C-13 Cat rated at 525hp. The guy parked next to me last week had a similar size MH (looked like a Prevost but wasn't). It also had a Cat C-13 but it was rated at 475hp but with more torque. I know Cat can change engine ratings both mechanically and electronically (i.e., injector timing?) but I don't know why the coach builders' design specs call for different ratings.

What I don't understand is how the torque/horsepower trade off affects vehicle performance and if there would be any advantage to going back and paying Cat to making a change to my engine specs (what would I ask for?). How do the changes affect hill pulling, towing, city vs country driving, fuel mileage, etc? Could the average Joe sitting in the driver's seat even feel the difference if the modifications were made?

I'm surprised at hp being lower and torque being higher. The most common occurrence is for them to increase together but torque at a lower rate than hp. Many times the torque rating will be the same over 2-3 hp ratings. This particular situation may be due to a design change in the fuel system or electronic controls.

Torque and hp are linked. The actual force measured on an engine test stand or a chassis Dyno is torque and the hp is calculated from that. The big "heavy hauling" performance advantage a diesel enjoys is due to the much lower rpm range that a diesel produces both torque and hp. Your C13 likely develops peak torque at around 1200 rpm and peak hp at 1700. The torque curve will stay pretty flat up to 1500 rpm or so at which point the hp will be at 85-90% of peak. Your 6 speed Allison 4000 multiplies available torque and enables the rpm to stay in the sweet spot over a large mph range.

My guess is that you would notice very little benefit in a re flash to increase your power.

[thgoodman]

ScottG wrote:

2oldman wrote:
Torque horsepower 2010
Torque horsepower 2012

I'm curious to see an answer to the OP's question as well but not curious enough to read through 75 pages of text.

Maybe someone can provide a more condensed or specific answer to the OP's question on his C-13.

Well said, Scott. Thank you. I guess I should have been more clear. My actual question was kind of buried it the end of the post. "Could the average Joe sitting in the driver's seat even feel the difference if the modifications were made? "

[ScottG]

Here: C-13 specs are Hp/torque specs. It looks to me like you have 100 lb/ft more torque than the 470 version (?).

[ScottG]

2oldman wrote:
Torque horsepower 2010
Torque horsepower 2012

I'm curious to see an answer to the OP's question as well but not curious enough to read through 75 pages of text.

Maybe someone can provide a more condensed or specific answer to the OP's question on his C-13.

[davebrown]

thgoodman wrote:
My '06 Beaver Patriot Thunder has a C-13 Cat rated at 525hp. The guy parked next to me last week had a similar size MH (looked like a Prevost but wasn't). It also had a Cat C-13 but it was rated at 475hp but with more torque. I know Cat can change engine ratings both mechanically and electronically (i.e., injector timing?) but I don't know why the coach builders' design specs call for different ratings.

What I don't understand is how the torque/horsepower trade off affects vehicle performance and if there would be any advantage to going back and paying Cat to making a change to my engine specs (what would I ask for?). How do the changes affect hill pulling, towing, city vs country driving, fuel mileage, etc? Could the average Joe sitting in the driver's seat even feel the difference if the modifications were made?

your C13 525HP should be around 1700lbs torque? I doubt the 475 vertion is higher or as high?
you at 525/1750 have more hp/torque than most any RV out there as it sits now so doing anything would be a waste of time and money

[2oldman]

Torque horsepower 2010
Torque horsepower 2012