Mack EM9

[stutz 712]

What is the the difference between a E9 and a EM9?

[67RModel]

Well I know next to nothing about E9s. However, in E6 and E7 speak the M indicates the engine is a Maxidyne high torque rise version of the engine. 

[fjh]

16 minutes ago, 67RModel said:

Well I know next to nothing about E9s. However, in E6 and E7 speak the M indicates the engine is a Maxidyne high torque rise version of the engine. 

correct! It came as a 400 hp  usually with a trans with less gears because of its huge torque curve ! This will pull its heart  out down to 1000 RPM or lower! you could use a 6 speed trans and the engine would still perform !

[terry]

the E6 maxidyne was 237 or 285 horse the E7 maxidyne was a 250 or 300 horse i believe.    terry

[The Heinz]

1 hour ago, terry said:

the E6 maxidyne was 237 or 285 horse the E7 maxidyne was a 250 or 300 horse i believe.    terry

I have a couple of VIN's of trucks with EM6's and 300hp, I would assume that's the highest a Maxidyne would go. Have yet to run across an EM9 though. 

[cruiseliner64]

Our Cruiseliner has an EM6 300 HP.  I thought I read somewhere on BMT they went to 350HP or am I mistaken?

Paul

[Vladislav]

Just now, cruiseliner64 said:

Our Cruiseliner has an EM6 300 HP.  I thought I read somewhere on BMT they went to 350HP or am I mistaken?

Paul

Mack went up to 2 valve E6-350 indeed. But those were not Maxidynes. Low torque curve was sacrificed for higher HP. And a bit higher highway fuel efficiency. I have that kind of engine in a MH of 1984.

[stutz 712]

So if the M means maxidyne, did they use a different crank?

Edited 16 hours ago by stutz 712

[cruiseliner64]

1 hour ago, Vladislav said:

Mack went up to 2 valve E6-350 indeed. But those were not Maxidynes. Low torque curve was sacrificed for higher HP. And a bit higher highway fuel efficiency. I have that kind of engine in a MH of 1984.

Thanks for explaining the difference between an E6 and an EM6 Vlad.What changed an E6 to an EM6?......fuel pump settings?.....or was it something else?..

Paul

 

Paul

[The Heinz]

Just checked two 1987 trucks, one with an E6 350, the other with an EM6 300, and they both have the same crankshaft, camshaft, con rods, and pistons, but the injectors and even the injection pumps are different. I don't know if the EM6 being in an R686ST and the other being in a Superliner would make a difference or not. 

[Vladislav]

Mack changed the crank and other heavy loaded parts when they went to Maxidyne from ENDT673. Which was of Thermodyne family which was introduced to the market in 1938. Much higher torques produced by Maxidyne required much more strength of the engine components. I don't know when Econodyne was put on the scene, probably is was a kind of mod of Maxidyne engines but with more common fuel settings. 

The difference was mostly achieved by different governing in the injection pump. Thinking about the shapes of the governor inside parts it looked to me like the governor had ability to push fuel rack at low revs so the engine would pull. Ok, I'm not almost sure on the physics but if you want torque, actually - forse, for a vehicle to pull load you need fuel to be burned. There's no magic in the world. So that fuel must be delivered into the cylinders. And if you don't thread the gas pedal hard but the truck pulls well it means fuel is supplied in sufficient quantity some how. To me it seems the governor is making the trick while you hold the go pedal relatively steady.

The second big point (mentioned in discussions regarding Maxidyne engines) is the turbo. Definitely if you want to burn fuel you need air. More fuel - more air. So turbo must do its job. It was said Maxidynes had different turbo than Econodynes. Possibly. As of me I'd like to know what was principally different in them and how big that difference was. Since I read someone's posts from time to time when a certain common turbo was installed onto Maxi engine and against expectations of experts of the community the truck gets driving fine.

Injectors could be different (and they're different) since the combustion process goes at different revs so optimal spray pattern is different too. Which could be achieved by different crack pressure. There also could be difference in the shape of cams of the pump cam shaft. Initial plunger speed may be different in different engines and the injection stroke may be longer or shorter providing different intensity of combustion. Timing angles are items from the same basket. So when you want a certain engine to be set for a certain specific performance many aspects may be performed. 

[fjh]

2 hours ago, cruiseliner64 said:

Thanks for explaining the difference between an E6 and an EM6 Vlad.What changed an E6 to an EM6?......fuel pump settings?.....or was it something else?..

Paul

 

Paul

Fuel and air (turbo)

[cruiseliner64]

2 hours ago, fjh said:

Fuel and air (turbo)

Thanks...thought it would be something to do with that.Any differences inside, like bore or stroke?

Paul

[fjh]

Nope!