how much hp can you make with a cummins 8.3 with mech fi?
03-26-2014, 11:23 AM
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how much hp can you make with a cummins 8.3 with mech fi?
i like to price and parts availability on the cummins 8.3. how much reliable hp can you make with a mech fi 8.3 cummins. thx, rm
03-26-2014, 03:28 PM
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P pump engine? I'm not sure how fast you can spin those. Horsepower is the rate at which work is done. Probably stupid amounts of torque though. I think they are like 250hp stock, slip of the fuel plate and turn of the pre boost screw, probably almost double it. I'm not sure if a 5.9 governor spring kit will work will work in the 8.3 pump, but then you could turn upwards of 3200-4000 rpm. If they are the same, there is even 5k gsk's. I have no idea if the lower end will even hold 4k stock. There are tons of companies out there to edm the nozzles on the injectors. Timing I think is similar to the 5.9. So that's fairly simple to do.
03-26-2014, 04:02 PM
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http://youtu.be/DevOp3Fx02c
Here's a good video of one turned up. I'm not quite sure how to do that in a boat, but someone more resourceful than me can tell you the ins and outs of water cooling everything.
03-26-2014, 09:17 PM
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8.3's right from Cummins are 600hp marine; the early mechanical engines were up to 450hp direct from Cummins. With a Nippendso pump off an old style 300B the 8.3 can make 450-500hp with the addition of a higher pressure lift pump and no mods other than turbo and bigger after-cooler. There are bigger plungers and barrels for that pump to make all kinds of HP but that opens up other problems (see below)
The 8.3 are so long and heavy you need a big engine bay to carry them in, are far as how fast they will spin stock not much over 3,500 rpm without problems, the pistons and pins, rocker arms, push rods weight too much and you’ll stretch the rods, bang valves or heads and go boom!
I have said before the rpm is limited by the time it takes for fuel to fill the barrel on a P style pump. It has nothing to do with governors, springs or anything other than fluid dynamics, you can take the governor off and control the rack by hand if you want to and the engine under load will still not go 1 rpm faster and here’s why but there is one way around it somewhat – if you had bigger enough plungers and barrels that when starved still can flow enough fuel to make the HP you want to go the rpm you want, the engine could turn faster BUT the you would over fuel at low and midrange RPM’s sooo much it would look like those tractor pull engines with all the BLACK SMOKE pouring out. We all know those engines don’t last, they can’t make power more than a few seconds at a time and if you add up all the seconds in-between rebuilds it would not even 1 lap around the course in Key West!
It takes X seconds for fuel to go through the fill port and fill the barrel, as the engine goes faster the time available that the port if uncovered for fuel to go in gets less than X, the faster it spins the less time (–)X we have. As we have less time, less fuel will get into the barrel the less fuel in the barrel the less HP the engine can produce. At some point there is not enough fuel to make enough HP to keep accelerating, the engine goes flat. The greater the HP you are trying to achieve the lower the RPM the engine will go flat at, simply because time to put enough fuel in the barrel is lessened.
As you increase fuel galley pressure from higher PSI lift pumps so that you can try to fill the barrel quicker while it is uncovered as soon as the plunger raises enough the cover the fill port the pressure exerted through the fill hole against the plunger will push it to one side and it will start to score. There is a lot of work to make plungers and barrels operate at high speeds – making an engine do a few tractor pulls or a 500cui engine burning nitro get down the track is much simpler than trying to make almost 2hp/cui and have it run for hundreds of hours.
The 8.3 are so long and heavy you need a big engine bay to carry them in, are far as how fast they will spin stock not much over 3,500 rpm without problems, the pistons and pins, rocker arms, push rods weight too much and you’ll stretch the rods, bang valves or heads and go boom!
I have said before the rpm is limited by the time it takes for fuel to fill the barrel on a P style pump. It has nothing to do with governors, springs or anything other than fluid dynamics, you can take the governor off and control the rack by hand if you want to and the engine under load will still not go 1 rpm faster and here’s why but there is one way around it somewhat – if you had bigger enough plungers and barrels that when starved still can flow enough fuel to make the HP you want to go the rpm you want, the engine could turn faster BUT the you would over fuel at low and midrange RPM’s sooo much it would look like those tractor pull engines with all the BLACK SMOKE pouring out. We all know those engines don’t last, they can’t make power more than a few seconds at a time and if you add up all the seconds in-between rebuilds it would not even 1 lap around the course in Key West!
It takes X seconds for fuel to go through the fill port and fill the barrel, as the engine goes faster the time available that the port if uncovered for fuel to go in gets less than X, the faster it spins the less time (–)X we have. As we have less time, less fuel will get into the barrel the less fuel in the barrel the less HP the engine can produce. At some point there is not enough fuel to make enough HP to keep accelerating, the engine goes flat. The greater the HP you are trying to achieve the lower the RPM the engine will go flat at, simply because time to put enough fuel in the barrel is lessened.
As you increase fuel galley pressure from higher PSI lift pumps so that you can try to fill the barrel quicker while it is uncovered as soon as the plunger raises enough the cover the fill port the pressure exerted through the fill hole against the plunger will push it to one side and it will start to score. There is a lot of work to make plungers and barrels operate at high speeds – making an engine do a few tractor pulls or a 500cui engine burning nitro get down the track is much simpler than trying to make almost 2hp/cui and have it run for hundreds of hours.
