Diesel vs gas......................

Madhatter1 wrote:

OhhWell wrote:

Madhatter1 wrote:

Hannibal wrote:
You need to put it into perspective. A 350 hp tractor engine running at it's peak hp rpm of 1800~ is at it's peak hp rpm. A 350 hp SB gas V8 in a pickup truck running 1800 rpm is almost 4k rpm under it's peak hp rpm and is likely making less than 120 hp.

If you think those 350HP enines are equal for moving a big load you are way off. The tractor is over 1000 lbs torque at 1800 and the gas is at 300 lbs at 4K (using your example numbers). Another BIG factor is the tractor is makeing big HP numbers at lower RPM's and the peak torque is going to be much higher than 1K. You guys are doing a dis-service to posters looking for info on gas vs Diesel. Even if us Diesel guys post they are not as fuel efficient, as reliable, or as cost effective as they used to be the gas fans still neeed to say "mine can pull the same load through gearing". Might be able to do the job (which is an inportant fact for those that need a truck more for a daily driver than towing) but a low RPM Diesel has a big advantage pulling a load. Get off your high horse and talk facts to help out posters looking for some real world info. I drive a 4X4 3500 Dually Diesel but can recognize that is not what everyone else needs. I pull a 14.5K to 15K trailer all over. Off road a lot. Still not gonna tell someone who pulls the same load 100 miles to a paved campground they need the rig I went with. And you "engineer math guys" need to drive a truck with a load on it. Your calc's do not work out in the real world. If they did a pair of 260HP 350CI gas engines could equal the 260HP Cummins 360CI in my boat. They would never be expected by any marine designer to even get the boat to plane off. What??? I thought HP was HP. 350 HP at 1800 RPM in a whole different animal than 350HP at 4K or 5K. Flame away.

Opps, sorry. Missed that part. Despite bringing a boat to a truck fight, I will address this. A high torque engine in a boat amkes a much better direct drive powerplant than a low torque engine obviously. That's why gas inboard engines often have transmisions. No way a low torque gas engine is going to turn a large prop easily at low RPM. That's what a high torque rating is for.

Big heavy boats and big heavy trucks are well served by high torque slow turning diesel engines. If you want speed, that's more the realm of gas and horsepower, especially in boats.

Umm...., My Diesels have transmisions. Same 3 gears as a gas marine engine. Forward, nuetral, and reverse. I bring my boat to a truck fight (if ya wanna call it that) because so many like to break out a formula to show how a gas and a Diesel making equal HP can do the same job as well as each other. 260HP small blocks- not even considered for use in a boat my size and weight. 330HP big blocks used in a boat my size. 260HP Cummins 5.9 Diesels that replaced the modern, not tired, properly geared and wheeled, lighter, 330HP gas engines which reached top RPM took cruise speed from 19 MPH to 27 MPH and top speed went up a little too. Fuel consumtion went from.7 mpg to 1.25 mpg. How can this be possible if HP is HP. And as far as using a boat for example it is a good one since it is uphill everywhere it goes and you can actually hold it against a constant load at any RPM.

You replaced a 330HP engine with a (Heavier?) 260HP engine and wound up with a gain in top speed. Do you really think that the 330HP engine was geared properly?

I'm not on stable footing (hahahah) when it comes to discussing marine applications so I will not argue with you too much about the boats. As I do understand it though, the transmission has just one foreward gearing. That foreward gearing and the propeller size/type then have to be matched for the engine? If the engine has to turn fast to make top HP, then the prop just slips a whole lot until the boat finally gets moving fast enough to "catch" and propell at max efficiency. That might take entirely too long on a large boat to gear the shaft properly for a high reving boat.

I think I did mention that diesel is a better solution usually for large heavy boats and trucks.