2015 Ford F-350 0-60 MPH Test
Man this thing is strong... Some comments made that compared this F350 to a RAM 2500. 0-60 Times: Ford F350 DRW - 8.17 sec RAM 2500 SRW - 8.9 sec Link
Forum Discussion
Lessmore wrote:blofgren wrote:
The inline 6 cylinder design of the Cummins is not designed to make RPM's fast; it is designed to pull a heavy load with massive torque which it does extremely well. I
.
I know many say that, but I do question whether an inline six is not designed to make rpm's fast. BMW after all has a long tradition of making high performance inline sixes. The Jaguar inline six was well regarded both as a high performance street engine and a racing engine for decades. The inline six design is known to be inherently smooth...and as far as it's ability to rev quickly through it's range, I don't think it is at a disadvantage, when compared to V type engines.
...snipped...
I think there is some mis-understanding here. It isn't the I-6 design of the Cummins that make it such a lazy revver, it's the fact that it has a huge stroke and a very heavy lower end (due to accomodating that huge stroke) that makes it lazy to rev. Compared to the Duramax or Powerstroke, the Cummins motor has a 124 mm stroke. The Powerstroke has a 107 mm stroke, Duramax is 99mm. Doesn't sound like much difference, but when you factor the leverage from the center moment of the crank to what that translates in piston speed, the Cummins motor has the pistons moving pretty fast and it still takes a while to fully complete that stroke. This is why, relatively speaking, the Powerstroke and Duramax motors are rev happy and seem more responsive.
Now if you build a shorter stroke engine, you lower peak piston velocity so you can rev higher and lighter. You also have much more of the combustion force acting throughout the whole stroke. Chances are, if you're really oversquare, you're still burning fuel and spitting it out the exhaust as it's still expanding at a good clip. This is why F-1 cars and Lamborghini's spit fire through the mufflers when they're flooring it around a race track. So there's give and take on a design when deciding bore and stroke. Having a longer stroke (within reason) tends to make more use of the energy in a given charge of air and be more efficient.
