Just wondering....I know a marine piston is available (I think).

I called ddp about it, and no answer yet.....so I was wondering if anyone has run the marine piston with aftermarket injectors?

Can anyone answer these questions?

1. is the marine piston lighter? It looks like it since it seems to have a bigger bowl?

2. Does using the marine piston, possibly help or hinder fuel mileage?

3. Do they quieter? louder?

4. How much do they lower the compression?

5. Is the ring pack the same?

Looks like Ill be running them in .5 mm oversize.

 

Yes they are available, and if memory serves me correct.. from cheapest to most expensive; you have.. Cummins, Mahle, Ross and Arias. There may be more..

I run the Cummins marines with an enhanced type of marine injector. I chose the Cummins pistons because they were the cheapest and most readily available. The Arias' had like a 6 week wait at the time. I'm sure there are many that run a truck bowl type of injector (like off the shelf DDP stuff, etc..) with marine pistons, but I'd rather have a marine spray pattern injector going into a marine piston. That all can be varied with timing and the injector washers that are installed anyway.

I don't know if there are differences in weight.. but OEMs (truck) are cast aluminum and marines are forged aluminum. I would think that the forged are heavier.. again, sorry I have no numbers.

I can't comment on fuel milege, must have noticed very little difference.

Noise difference is quite subtle too. A trained ear might pick up that the 12 valve type pistons are a swirl type, and 24 valve and marine are a tumble type. By inherent design, a tumble type is slightly louder.. just like comparing the noise from a 24 valve ISB to an old 12 valve.

A factory uncut Cummins marine piston is 15.7 for the compression ratio. All the aftermarket suppliers can make custom whatever you are looking for.

I think the ring pack is an improved design over the truck pistons. You will also notice teflon patches on the sides of the Cummins marine pistons.
..Hope this helps

 

So...do you have to use different injectors then the standard off the shelf after market (are marine injectors that much different)? Also, recomendation on rings to use with them?

 

FWIW, DDP starts out with plain jane Bosch MARINE injectors and EDMs them to size then extrude hones them, and then they raise the pop pressure to 300bar.
This is why they DONT want you to run anymore than 20* timing.
They take a $300 set of injectors and sell them for 2-3x as much as that.

 

This is either a Mahle or std versus a marine.


Side shot of a marine piston with steel lands for compression rings and coated skirts


At one time, a marine piston was ½ the price of a Mahle piston. I don't remember the weights, but a marine piston is heavier. The Mahle piston was very light

I thought a marine piston took the C/R to the lower side 15.x
I like the sound of a marine B

A standard injector has a 145° spray pattern. A marine injector has a 155° spray pattern. I'm looking for my photo of the splatter tracking outside the bowl on a std piston using marine injectors and advanced timing.
A 370 marine (and the customized variations) has a sac tip design that produces a very pronounced and annoying idle haze.

With a marine set-up, one learns the value of the block heater.

 

After much investigation.....I ve found a couple things out.

1. If you refer to a marine piston, you need to specify cummins marine, because there are other marine style pistons not with the cummins name in front of it.

2. The cummins marine probaby is not forged. I was told , it is the same as the truck, with different rings, and steel inserts. (reminds me of turbo buick (gn) pistons. By seeing the abobe pisture of the marine (side veiw) I would aggree that they are NOT forged.

3. I was told that mahle makes the "cummins" pistons. The mahle (none) cummins pistons are being widely used, and are lighter, are not a forging, and come in standard bowl and marine style bowls. (On a side note they and made by clevite which is the oem supplier side of mahle. Mahle actually makes race pistons, and other then a custom made for you, they dont make a deisel piston at all that is off the shelf. They are all made by the clevite side.

4. Some sourses say, .5 mm and 1.0 mm over but the finishh bores are....
a. standard (if you try to stay standard..= 4.020
b. first over size= 4.040
c. second over size= 4.060

This is for all the cast pistons, bot the arais high end forgings. THey would require greater piston to wall clearence then the above bore sizes for cast pistons. The cummins marine pistons also get bored to the same above numbers , which also say they are cast (not forged like some information)

Prices, for the none "cummins" name marines or truck style bowl are in the low hundreds per piston. The "cummins" marine is in the high hundreds per piston. The none "cummins" pistons made by mahle/clevite do accept a different ring package then the "cummins" pistons. You can get total seals for the none "cummins" piston. According to total seal, they can make rings for almost anything, but I did not check on or find total seals available for "cummins" pistons, and I did find them for the none cummins pistons.

The compression is said to be 15.7 to one in the cummins marine engine. The clevite/mahle cast pistons come in two different bowls. Standard truck with 43.5 cc and a "marine " style that is 52 cc. The "marine" style is not as deep as the "cummins" marine but is opened up, in the same manner, so it has a bigger diameter bowl.

I reserve the right to be completely incorrect on any of the above, but so far, its what I got.

 

(die) Cast pistons are not necessarily a bad thing. I know a company that die casts pistons that match forged quality for grain alignment.

You are correct, the Mahle/Clevite marine pistons have a much shallower bowl than the Cummins brand. It was actually closer to a stock bowl with the swirl donut than a complete open Cummins marine. The Mahle also do not have the steel land insert as the Cummins which accounts for most of the weight difference in the pistons.

I think the bowl on the Mahle marine would work with the 155° spray pattern on a stock 370 injector.
The problem is how much the EDM process distorts the original orifice on a 370 injector.

It has been a few years since I did the pricing, but a Cummins marine piston was less than $100 each where the Mahle marine was slightly over $200 each.