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.

[ScottG]

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.

[wny_pat1]

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

Try 230 to 250 HP!

[ScottG]

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.

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

[Johnofbham]

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.

[Passin_Thru]

I agree with mdamerell and Scottg. We had a 435 CAT and turned it up to 500 HP. It got better mileage and was actually easier on the engine when running east of the Ms. river. By the time you were to the top of a small hill it had'nt reached full manifold pressure of 40 inches. You can barely tell the difference in mileage in the Cummins 350 inline 6 and 400 inline six in motorhomes. BTW/a 435 CAT has 1250 ft lb and a 500 CAT has 1450 ft lb at 2100 RPM so there is no difference in RPMs, it is the torque. The newer ones were turned back to 1800 RPM.

[ScottG]

Ivylog wrote:
HP = Torque x RPM so more RPMs.

The torque is whats higher in this case, not the RPM's.

[Ivylog]

HP = Torque x RPM so more RPMs.

[ScottG]

There isn't really much (if any) fuel mileage penalty because the HP is derived in part from injector matching technology, more boost and fuel pressure and newer variable geometry turbos. So the power comes in great deal form increased efficiency.
Any cost in FE is negligible.

[mdamerell]

The new engines are all computer controlled. They can dial in a range of horsepower settings and torque. Often times turning these engines down reduces their fuel economy.

When my company turned our truck engines down and limited them to 63 mph they lost fuel mileage. When they complained to Detroit Diesel they were told it was their fault for turning the engines down. A castrated engine has to work harder and thus the mpg suffers.

That may explain part of your question.

[keepingthelight]

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