Making more HP in a Cummins M11

**xkmail** · 04.26.2007

I am looking at a freightliner with Cummins M11 rated at 330hp for local work.
Can I bump this up to 370 or 400HP and what is involved?
thanks

**PackRatTDI** · 04.26.2007

Pretty sure all that's required in bumping a M11 330 to an M11 400 is a simple reprogramming of the ECM. Sould be able to get that done at any Cummins shop or somebody with access to Cummins software.

**Burky** · 04.26.2007

I could be mistaken, but I think that you can probably go up to 370 hp okay with just a software change, but the versions in an on highway truck rated above that used a different cylinder head. The 370-426 hp versions use a 4 valve cylinder head. There are ratings for fire service that go above that in a 2 valve engine, but those trucks run very short miles and producs their max hp under stationary pumping loads, so the running cycles are different.

I have spent some time in 370 hp m-11's, and they are still a pretty stout motor if they are geared appropriately. Set them up so they run out no higher than about 68 or so at peak rpm and they will boogie down the road just fine.

When the time comes to buy a truck of my own, an M-11 in that rating is very high on my list of desirable engines.

**vegetto** · 04.27.2007

all m-11 cylinder heads are 4 valve per cyl. the only upgrade needed is a block stiffner plate for the higher horse engines. without it, block fretting will happen.

**MACK E-6** · 04.27.2007

370 or 400 is a little much for an M-11, isn't it? I was always told that when you modify engines and try to get to much of one thing, such as horsepower, you lose some of another thing, usually life.

**PackRatTDI** · 04.28.2007

Originally Posted by MACK E-6

370 or 400 is a little much for an M-11, isn't it? I was always told that when you modify engines and try to get to much of one thing, such as horsepower, you lose some of another thing, usually life.

I don't see why it would be too much power, the M11 was available with 400hp from the factory. Now if you were trying to squeeze 500hp or more out of it, then yeah, you'd probably burn a piston or blow a turbo, lol.

**1989 Pete** · 03.17.2008

all m-11 cylinder heads are 4 valve per cyl.

**Sportster2000** · 03.17.2008

You can get 500hp out of a M11 without emission equipment on there and it is reliable. Now I am not saying that they can all do that but we do have a truck at our shop that does have a 500hp test engine (M11) in it with an allision 6 speed auto behind it. In my opion if you want to go above 400 hp just get an isx.

**Thronapple** · 04.20.2008

I'm looking at a International 9800 COE that has a M11 in it. This one is a baby cause it's a 280 hp version. Some of you say that all M11's have 4 valve heads, so could the baby of the bunch be turned up to 300 to 400 without any mod's internally? Just a software change?
Do you loose MPG when you do that?
this one has 3:90 rears witha Super 10 with OD.
What kind of mileage should I expect? I've been told 8 - 10.
Planing to pull a short trailer (28 - 34) usually mostly empty. 3000 - 12000 lbs.
Thanks.

**kah68** · 11.26.2009

Thronapple

I uprated my 97' 280/1050 to 330/1250. It was done at an international dealership and I was told the CPL (Critical Parts List?) only allowed the 1250 rating and it wouldn't be safe to exceed that. I'm running a 9 speed O.D. (.73), 22.5's, with 4:11's and average 9-10 mpg grossing between 16 -30 ton cruising low 60's mph. Of course I deliver my own product so I'm only loaded one way, but I also travel in hilly conditions.

Does anyone know where you can buy the Cummins engine software and the plug to fit in the cab, I would like to be able to change my settings with taking it to the dealer and costing me $1-200 each time.