5.9 Cummins Street vs Marine

[guldam]

I'm wondering what the differences are between the much higher horsepower Marine Cummins 5. 9 engines vs the ones we have in our trucks (mine is a 2nd gen 12v. ). I suppose our trucks were limited in horsepower because of drive train limitations. Still, 370hp versus 180hp on my Truck is pretty substantial. Gotta be more than injectors, no?



GulDam

 

[LSchulz]

Cooling is a huge factor. You can dump a lot more heat into the water than you can into the air.

 

[seafish]

Just guessing, but I'll bet that smog restrictions probably have something to do with it as well.

 

[CBlack]

I think some of the internals are different. I remember reading on one of the forums that the marine engine has different pistons which would lead to other things as well.

 

[NIsaacs]

During the 2nd. Gen. era, they also used a huge Nippondeso fuel pump. I think the Marine engines were only rated about 25% duty cycle at full power and due to the drive train it would be hard to use the torque abilities so they could rate them higher safely.



Nick

 

[JLEONARD]

I think the Marine engines were only rated about 25% duty cycle at full power

The rating is actually 1 hour at full power out of 8 which is 12%.

"Contunuous" duty rating is 200 rpm below WOT rpm.

I don't have my marine power curve handy or I could get the hp number off the chart.

The high hp engines also use sea water cooled aftercoolers and that lowers the compressed air temp by a lot in addition to the sea water cooling which was mentioned.

And they come with fuel coolers that are sea water cooled.

 

[NIsaacs]

The Marine Engine rating seems to be variable depending on use also, depending on if it is pleasure craft or commercial vessels.



The lowest rating I found was "intermittent duty" 2 hrs out of 8, "medium continuous duty" 6 hrs out of 12, "heavy duty" 8 hrs out of 10 and "continuous duty" all day.



Nick

 

[Tinman]

A lot of it is duty cycle. The "recreational" duty cycle in the CR 5. 9 goes up to 485hp..... at that 12% wot.

 

[JLEONARD]

depending on if it is pleasure craft or commercial vessels.

If you look closely at the specs I think you'll find that the commercial ratings are lower than pleasurecraft ratings, hence the ability to increase the duty cycle for commercial.