Cummins power

[Johnofbham]

The class A's that I am like have the Cummins engine. I notice that the larger/heavier rigs have more horsepower (300hp vs. 340 to 360hp)with the 6.7 L engine (same torque). How do they get the extra horsepower and is there a mileage penalty for it.

[keepingthelight]

wny_pat wrote:

john&bet wrote:

ScottG wrote:

wny_pat wrote:

keepingthelightson wrote:
I think the 300 HP is the 5.9L (older version). The others are the 6.7L

Try 230 to 250 HP!

Actually the 5.9 was sold with ratings up to 325+ HP - mines a 305.

The 5.9 they are talking about used in MH are tuned different than your or my pick-ups. They are tuned more like mdt engines and turn slower, say governed about 2500 rpm vs 3200 rpm in pick-ups thus different hp.

My 1994 motorhome's 5.9 Cummins diesel 6BT (1989 to 98) is the same as the one that is used in the Dodge pickups during those years. It is governed at 2500 rpm. The Cummins 5.9 24 valve ISB (1998 to 2007), which was used in both motorhomes and Dodge pickups, is governed at 2900 rpm. The Cummins 6.7 ISB (2007 to present) engine is governed anywhere between 2800 to 3013 rpm depending on year. It is used in both motorhomes and pickups.

What I meant was: The 5.9L Cummins was installed in MH's, then later they made the 6.7L Cummins offering more HP and torque for MH's. :R

[okgc]

Back to OP question

Johnofbham wrote:
More info:
The Fleetwood Excursion 33A has a Cummins ISB 6.7L with 300hp and 660 ft-lbs at 1,600 rpm.
The Tippen Allegro RED 33AA has the Commins ISB 6.7L with 340hp at 2600rpm and 660 ft-lbs at 1,600 rpm.
Thus the reason for my original question.

The new Thor Palazzo also has a 300hp Cummins ISB
Thor Palazzo specs

I suspect the loss of 40hp makes it cheaper to buy.


.

[Jarlaxle]

moisheh wrote:
mcdamarell. If your company simply limited the speed to 63 then mileage had to improve. There is no argument that slowing down increases MPG. Trucking companies with 3000 or more tractors usually limit the speed and they ALL get better mileage. Proven fact!

Moisheh

My company lowered speeds from 65 to 60 a few years ago. The tractors all used MORE fuel. They were geared to run 65...and could no longer climb hills in high gear with a loaded trailer! (Also, I suspect some drivers stopped using CC and simply kept the pedal floored on the governor.)

[et2]

While it's true you can get a tuner to push the hspwr on your engine, your also pushing the limits your engine is warranted for. You break it your going to pay the repair bill. I've heard on many sites guys pushing their Cummins power and blowing heads and gaskets and pistons,etc. Not to mention the other parts of the drive train. Transmissions can get real expensive.

Pick the right MH with the right engine and you won't need to worry about it.if your the type that needs to get to the top of the hill the fastest then make sure you have the correct engine to do it. It might get you there the faster adding a tuner, but it could cost you lots of cash in the long run.

[wny_pat1]

john&bet wrote:

ScottG wrote:

wny_pat wrote:

keepingthelightson wrote:
I think the 300 HP is the 5.9L (older version). The others are the 6.7L

Try 230 to 250 HP!

Actually the 5.9 was sold with ratings up to 325+ HP - mines a 305.

The 5.9 they are talking about used in MH are tuned different than your or my pick-ups. They are tuned more like mdt engines and turn slower, say governed about 2500 rpm vs 3200 rpm in pick-ups thus different hp.

My 1994 motorhome's 5.9 Cummins diesel 6BT (1989 to 98) is the same as the one that is used in the Dodge pickups during those years. It is governed at 2500 rpm. The Cummins 5.9 24 valve ISB (1998 to 2007), which was used in both motorhomes and Dodge pickups, is governed at 2900 rpm. The Cummins 6.7 ISB (2007 to present) engine is governed anywhere between 2800 to 3013 rpm depending on year. It is used in both motorhomes and pickups.

[john_bet]

ScottG wrote:

wny_pat wrote:

keepingthelightson wrote:
I think the 300 HP is the 5.9L (older version). The others are the 6.7L

Try 230 to 250 HP!

Actually the 5.9 was sold with ratings up to 325+ HP - mines a 305.

The 5.9 they are talking about used in MH are tuned different than your or my pick-ups. They are tuned more like mdt engines and turn slower, say governed about 2500 rpm vs 3200 rpm in pick-ups thus different hp.

[mdamerell]

moisheh wrote:
mcdamarell. If your company simply limited the speed to 63 then mileage had to improve. There is no argument that slowing down increases MPG. Trucking companies with 3000 or more tractors usually limit the speed and they ALL get better mileage. Proven fact!

Moisheh

More too it than just reducing speed to save fuel and yes I drive my pickup based on the sweet spot of the engine torque curve which is around 2,000 rpm or 60 mph with a 4.1:1 rear.

Depends upon the gears and the sweet spot of the engine. If the truck was originally spec'd with tall gears to run at peak torque (around 1,400 rpm in 10th) and then you turn it down mpg will drop. At 62 mph the rpms want to be at 1,300 rpm and fall out the bottom of the torque band. At 65 mph they sit right around 1,400 and the truck runs fine. Not to mention the local speed limit is 65 and now we are a rolling road block. The company acknowledges this but they say the loss of mpg is offset by insurance costs. Since we lease most of our trucks they were geared to run 70 mph. The new 14 speed Volvo's are properly geared and are doing better. In the Detroit engine's program when they limit the speed it limits torque as well. Likewise you can also have two different torque settings (one on cruise and one on the foot) so much depends upon the engines program.

I've driven engines that were turned up and driven the same engines after they were turned down. Mpg has always dropped when the engine is turned down. Just because the engine is turned up does not mean you always have to use it, but when it's limited, it takes longer to climb and longer to accelerate so you end up using more fuel in the long run. That's my 19 years experience.

[moisheh]

duplicate post

[moisheh]

mcdamarell. If your company simply limited the speed to 63 then mileage had to improve. There is no argument that slowing down increases MPG. Trucking companies with 3000 or more tractors usually limit the speed and they ALL get better mileage. Proven fact!

Moisheh

[wny_pat1]

ScottG wrote:

wny_pat wrote:

keepingthelightson wrote:
I think the 300 HP is the 5.9L (older version). The others are the 6.7L

Try 230 to 250 HP!

Actually the 5.9 was sold with ratings up to 325+ HP - mines a 305.

He said older version. i.e., the 12 valve 6BT. That was the older version. It is rated at 160 to 215 HP, but was up rated to 230/250 HP in the motorhome/firetruck version. The run was thru 1998 when it was replaced by the 24 valve 5.9L ISB. The newer 5.9L ISB was sold with ratings up to 325+ HP.

[BobandShaz]

ScottG wrote:


I have never heard of a 6.7 with 300/660 and I'm thinking this is may be a mistake in their literature. It could be a 300/620. Cummins 6.7 300 HP

We have seen many issues with literature MANY

[Hjudge49]

NO matter what engine you have, the more horsepower it actually makes, the more fuel it burns to make it. That said, a more efficeint engine that has a higher horsepower rating may be more fuel efficeint that a lower rated engine to push the vehicle at a set speed. Diesel engine today are very easy to turn up for more horsepower, if you give it more fuel and let it breathe easier, you will get more power. For instance, a Ford 6.0 Power Stroke in 2005 came out of the box with a rated 300 HP. International, which made the engine, rated their same truck engine at about 250. By adding a bigger exhaust system and a "chip", I turned mine up to 435hp,without any modifications to the intake system, turbo or block. Computers are great.

[Jarlaxle]

The Cummins 6.7 is available in ratings as low as 200HP and as high as 360HP. Anything over 320HP is RV and emergency vehicle only.

[mhepburn]

If you are specifically referring to Cummins..........follow the Cummins engine designation for the displacement ISM, ISL, ISX etc. The horsepower differs considerably based on the engines ECM (electronic control module). We have an ISX, which is a 15 litre engine. Ours is a 525 HP, however the same engine is rated up to and over 600HP. The only difference is ECM programing. We get 7MPG prairies or mountains....no difference. I have discussed the higher HP with Cummins, the consensus is more HP = more fuel for the same displacement. So, understand the engine model of Cummins you want or have and choose the HP you need. Hope this helps interpret the info you're working to understand.....Malcolm