300 HP Cummins Diesel

[EZRider800]

Originally Posted by A Traveler

Say WHAT???
.

I don't want to seem like a know it all but I've been selling diesel engines for 30 years so I know a little bit about them. And there IS a difference in HP in a gas engine and the HP in a diesel engine because if your gas engine comes from the factory with 300 hp you are stuck with 300 hp. There is no box to check to uprate the hp on a gas engine.

But with a diesel engine (especially in class 8 big bore trucks and some high end RV's) just because the engine came from the factory with 300 hp doesn't mean it has to stay there. With many diesel engines you can "turn up" the hp with the electronics or with the fuel pump (on older diesels). When you are spec'ing a new truck for a customer the SAME ENGINE may have 4-5 different HP ratings to pick from as long as you stay in the same torque family. Gas engines can not be ordered this way. To get more HP in a gas engine you have to order a larger engine, add a turbo or a supercharger or other performance parts like different heads at great expense. Diesel engines can be ordered with 300, 325, 375, 400 HP for instance and nothing changes except the price. But this HP range is limited by the torque rating of the componants of the driveline. Cummins and Cat and Detroit make their money by selling HP. It's the same engine but if you want 375 hp instead of the standard 300 you pay an additional $2000 for instance. This is why I say HP is not just HP because there is a huge difference between ordering a gas engine or a diesel engine.

My comment to Gary was because he said HP is HP but then he didn't want to even talk about torque, basically dismissing it like it didn't matter. But the fact is if you order a 300 hp gas engine you'll only get about 300 pound feet of torque. But a 300 hp diesel engine might have 450 or 500 lb/ft of torque with the same hp rating!! That is huge!!

Anybody that really knows how to spec a truck or in our case an RV, knows that pulling 30,000 - 80,000 pounds up and down the hills and towing additional vehicles and trailers behind them knows that it really doesn't matter how much HP you have because HP does not move extreme weight like what we are dealing with. Torque is what moves the weight. You have to get waaaaay up the RPM range before the HP takes over in an engine doing the kind of work we are asking them to do. And even then if you don't have enough torque to go with the HP your transmission will shift itself to death trying to multiply the torque to get the job done.

[chuckftboy]

Originally Posted by A Traveler

Say WHAT???

Horsepower is horsepower, no matter what is producing it. The only difference between a gas engine and a typical diesel is the RPM at which the horsepower is produced. The Ford V-10 will have to rev to about 4,000 RPM to produce its 362 hp. The 6.7 liter Cummins diesel produces its 360 hp at about 2,300 RPM.

The formula for Horsepower is TORQUE x RPM / 5252. In other words, and engine with higher torque (diesel) will produce its horsepower at a lower RPM than an engine with less torque. That engine has to rev faster to produce the same horsepower, but as I said at the top of this post, horsepower is horsepower, no matter what is producing it.

Traveler is still correct in that 300 HP from any motor (even electric) is still 300 HP. I agree that you can get more out of the same diesel motor but that doesn't change the fact that 300 is the same when its only 300 for each

[A Traveler]

Curtis, what you posted about diesels being "dialed up" to higher horsepower is very true. I've done it myself. However, you have missed my point about exactly what "horsepower" is. Horsepower is a measure of how fast a given amount of work can be done. The laws of physics don't care what is developing that horsepower, because it doesn't matter. Horsepower is horsepower no matter whether it's gas, diesel, steam or electricity generating the power.

Everyone always focuses on the torque spec when looking at engines. They assume that an engine with higher torque will have more power. But that is simply not true. Torque is nothing more than a twisting force. You can have all the torque in the world, but if the shaft is not turning, there is ZERO horsepower being developed.

A diesel engine develops its maximum horsepower at a lower RPM than the typical gasoline engine. A typical 360 HP diesel develops it's maximum hp at 2,000 – 2,200 RPM, where the 362 hp Ford V10 has to rev to over 4,500 RPM to develop that same level of horsepower.

What everyone misses in this discussion when it comes to motor homes is gearing. Because the diesel can develop its maximum horsepower at around 2,000 RPM, a diesel-powered motor home typically does not have to shift down to a lower gear to climb a hill. When cruising the interstate at 60-65 mph, a diesel engine already is running very close to its horsepower peak RPM.

A gas powered motor home running in top gear at the same speed will also be cruising with the RPM somewhere near 2,000. However, that RPM in the gas engine is far below its peak horsepower RPM, and THAT is the difference! In order to climb a hill at speed in a gas-powered motor home, the driver has to shift down to a lower gear. The lower gear will allow the driver to get the engine RPM up to the horsepower peak of around 4,000+ rpm to get all the horsepower that engine can develop.

The driving technique between diesel and gas coaches is different, but my original premise remains the same. Horsepower is horsepower no matter what is generating the power.

[EZRider800]

Originally Posted by chuckftboy

Traveler is still correct in that 300 HP from any motor (even electric) is still 300 HP. I agree that you can get more out of the same diesel motor but that doesn't change the fact that 300 is the same when its only 300 for each

I agree that 300 hp is 300 hp technically speaking. I mean it doesn't magically change the formula just because it's in a diesel engine. But to ignore the torque side of the equation is uninformed at best or ignorant at worst.

In our application torque is what is needed to get our heavy Class A motor homes moving. HP is almost irrellivant. If HP was the most important we would all be singing the praises of gas engines even though they have much less torque. But we all know that isn't the case don't we??

[Gary RVRoamer]

In our application torque is what is needed to get our heavy Class A motor homes moving. HP is almost irrellivant. If HP was the most important we would all be singing the praises of gas engines even though they have much less torque. But we all know that isn't the case don't we?

The difference is strictly the rpms where the horsepower and torque are developed. You can't have a meaning ful performance conversation without including rpms. Gas engines have to rev higher to get their rated Hp and torque, but few drivers are comfortable running at the higher rpms needed. Therefore the typical or usable Hp of a gas engine is much less than the rated Hp. You get to use all 300 of the diesel hp in all common driving scenarios, but a 300 hp gas engine, even a big block V8, is typically getting by using 200 or so hp. Small wonder it seems to perform less. Especially from a standing stop where the initial rpms are so low.


The net is that diesels produce more usable horsepower at the RPMs whre most driving is done. That makes it an excellent choice for vehicles that need a lot of horsepower to move well.

[EZRider800]

Originally Posted by A Traveler

Curtis, what you posted about diesels being "dialed up" to higher horsepower is very true. I've done it myself. However, you have missed my point about exactly what "horsepower" is. Horsepower is a measure of how fast a given amount of work can be done. The laws of physics don't care what is developing that horsepower, because it doesn't matter. Horsepower is horsepower no matter whether it's gas, diesel, steam or electricity generating the power.

Everyone always focuses on the torque spec when looking at engines. They assume that an engine with higher torque will have more power. But that is simply not true. Torque is nothing more than a twisting force. You can have all the torque in the world, but if the shaft is not turning, there is ZERO horsepower being developed.

A diesel engine develops its maximum horsepower at a lower RPM than the typical gasoline engine. A typical 360 HP diesel develops it's maximum hp at 2,000 – 2,200 RPM, where the 362 hp Ford V10 has to rev to over 4,500 RPM to develop that same level of horsepower.

What everyone misses in this discussion when it comes to motor homes is gearing. Because the diesel can develop its maximum horsepower at around 2,000 RPM, a diesel-powered motor home typically does not have to shift down to a lower gear to climb a hill. When cruising the interstate at 60-65 mph, a diesel engine already is running very close to its horsepower peak RPM.

A gas powered motor home running in top gear at the same speed will also be cruising with the RPM somewhere near 2,000. However, that RPM in the gas engine is far below its peak horsepower RPM, and THAT is the difference! In order to climb a hill at speed in a gas-powered motor home, the driver has to shift down to a lower gear. The lower gear will allow the driver to get the engine RPM up to the horsepower peak of around 4,000+ rpm to get all the horsepower that engine can develop.

The driving technique between diesel and gas coaches is different, but my original premise remains the same. Horsepower is horsepower no matter what is generating the power.

I agree with almost everything you just said and I do understand the difference between HP and TQ. I guess my comments were more about how engines are actually ordered from the factory and the ratings they have. When ordering a 300 hp gas engine it's NOT the same as ordering a 300 hp diesel engine and what you get is totally different. You have to consider the APPLICATION the engine will be used in. This is why I say 300 hp is not 300 hp.

To prove my point 95% (?) of all automobiles have gas engines. This is the best engine for the application. Compared to diesel engines, gas engines make relatively little torque. Also 95% (?) of all Class A RV's and Commercial Trucks and Pickup Trucks heavier than half ton use diesel engines. Why? Because of the application. Because of the need for TQ. HP is irrelevant (for the most part) in a towing or heavy load carrying application. Look at the new Ram 3500 dually pickup trucks. They now have 1000 lb/ft of TQ and will tow over 33,000 pounds!!! No where in the ads for this truck will you see anything about HP. Why? Who cares? HP will help you go fast (in simple terms) but who cares how fast you can go when pulling 33,000 pounds??? It's all about the application. By the same token look at the ads for the Dodge Hell Cat or Demon. 747 up to 900 HP depending on the engine package. Do you think they mention TQ in their ads?? NO! Because it's irrelevant. Nobody buys a Hell Cat to pull a camper so who cares about how much TQ the 392 Hemi has? It's all about application. But you knew that too..........

[EZRider800]

Originally Posted by Gary RVRoamer

The difference is strictly the rpms where the horsepower and torque are developed. You can't have a meaning ful performance conversation without including rpms. Gas engines have to rev higher to get their rated Hp and torque, but few drivers are comfortable running at the higher rpms needed. Therefore the typical or usable Hp of a gas engine is much less than the rated Hp. You get to use all 300 of the diesel hp in all common driving scenarios, but a 300 hp gas engine, even a big block V8, is typically getting by using 200 or so hp. Small wonder it seems to perform less. Especially from a standing stop where the initial rpms are so low.


The net is that diesels produce more usable horsepower at the RPMs whre most driving is done. That makes it an excellent choice for vehicles that need a lot of horsepower to move well.

Exactly Gary! On paper, or for a pie in the sky theoretical generalization type conversation, if you didn't have to consider RPM's or fuel economy, or speed limits, or towing capacity or GVWR or GCWR then you could say that you always want to have the most HP possible, regardless of any other factor. But in my industry (which has a lot of the same requirements as the Class A RV industry) HP is almost irrelevant to get the job done the best way possible. Otherwise we'd all have V10 Ford gas engines turning 7000 RPM's getting 1.5 MPG making 900 HP in the back of our pushers, because they are cheaper to buy and cheaper to maintain than our diesel engines, right?

[RunningHard]

I have a 5.9 w/300 hp. I know it’s not what your asking for, but thought I would pass on my feelings. My rig is 36’, and I travel West of the Mississippi. I either pull a car or trailer with a RZR side by side. It does fine, never the first the reach the summit of large mountains, but never ever the last. It is a pre emissions engine, and have had zero problems. I would not hesitate to recommend, but am currently planning on another rig in next year in the 42-45 range. With the larger rig, will come a larger engine. Good luck!

[Flyinfish]

Originally Posted by HaRVey 74.5

The "360HP Tune" is what Cummins called the optional ECM program for our 6.7 diesels with the Allison 2100 transmission. It can be installed by any authorized Cummins service center which has the Cummins InSite diagnostic tool.
The tune increases your horsepower from 300 to 360 and torque from 640 to 800, is covered by the factory warranty and does not exceed the torque limiting features/overides of the Allison transmission (TCM).
The tune and instalation cost about $500 (I think I paid $460). If you have it installed, you'll want to keep the invoice for your records and make sure any future techs don't reflash or "update" your ECM with the stock 300hp tune but the current 360hp.

Really interested in this 360 tune. I called Cummins and was transferred several times with no answers. Im also in the LA area. Where did you have this done and who did you speak to? Thanks in advance.

[vincee]

After Memorial Day I'll be taking my new to me 2014 Cross Country 300HP & 660# torque to the local Cummins Shop, Buffalo, NY area. They quoted me $370 to upgrade to 360HP & 800# torque. They do it while I wait. Can't wait!

[EZRider800]

Originally Posted by Flyinfish

Really interested in this 360 tune. I called Cummins and was transferred several times with no answers. Im also in the LA area. Where did you have this done and who did you speak to? Thanks in advance.

Go talk to a Cummins shop locally, or maybe even a Heavy Truck Dealership that sells and services Cummins engines. They can tell you exactly what is involved. If you are calling Cummins Corporate you probably got an office guy who doesn't know what you're talking about.

[bobca1]

Originally Posted by Flyinfish

Really interested in this 360 tune. I called Cummins and was transferred several times with no answers. Im also in the LA area. Where did you have this done and who did you speak to? Thanks in advance.

Is the tune available on 340hp too? I have 2016 Forza and also in LA area. Handles grades pretty well without Toad, once I connect up my Wrangler I notice significant difference. Not sure that +20hp would make much difference though.

-edit-
Checked specs and I see my 340hp is 700lbft torque so a boost to 800 probably would be pretty noticeable.

[sinterior]

Not to change the subject but one huge advantage of electric motors, which I believe could be in the future, is 100% torque at 0 rpm.

[vincee]

Wouldn't 100% torque at 0 RPM mean the engine isn't yet turned on or yet in motion?

Also, isn't that the exact reason trains run on GE electric engines and most if not all cruise ships.