E7 versus the EM7

[03' Big Red]

here is a hypothetical question, can a E7 be turned into a EM7  ? also what is the highest HP rating for the EM7 ? seems to me ive seen a 350 hp listed some place.

seems if one had the right transmission and axle ratio the EM7 would be quite a sweet set up. My AMI 370 runs just wonderful but  i like the idea of the EM7 max torque way down at 1025 rpm versus 1250 of the AMI

i understand that the EM7 is governed at 1750 rpm and the AMI at 2150 rpm but honestly most times i can shift at 1700-1750

i am typically loaded around 72,000-73,000 lbs in a dump truck.

 

[Mack Technician]

EM7 was 250-275-300 mostly...unless someone finds a 350?

Edited July 8, 2019 by Mack Technician

[03' Big Red]

1 hour ago, Mack Technician said:

EM7 was 250-275-300 mostly...unless someone finds a 350?

so what is different on the EM7 ? is it in the pump or are other things involved  ?

Edited July 8, 2019 by 03' Big Red
n/a

[Mack Technician]

It’s all relative to what your converting to and from. Per example you wouldn’t want to deal with converting AMI to AMI.......an AMI300 to an AMI380, whole different cooling package. Otherwise, injectors, software, turbos, cam keyway offsets I’m certain years, etc... 

[JoeH]

Are you talking about mechanical or electronic e7's? I love the idea of an em7 -350 mechanical,  but I think maxidynes peak at 300 hp. 

I think it's just about all in the fuel pump. For the most part, at least on mechanicals, the injectors will put as much fuel in as the injection pump tells them to. But I think it's also important to have a lot of oil pressure so you aren't hurting crank and rod bearings by lugging it. It's critical to have a good film of oil as the the engine is making 1000-1200 ft lbs of torque at 1000rpms. That's only 350 rpms off idle. 

Would be great to get an em7-300 fuel pump and have it turned up closer to 350. You'd likely need to upgrade the transmission too. And personally I'd go Maxitorque trans.  The T310-M might be a great pairing with a maxidyne em7, you'd always be in your power band with room to spare.

[JoeH]

And you have to have a good free flowing exhaust, you'd be putting a lot of heat out. My old endt676 maxidyne engines are good for 1,125 degrees on the pyro, but my E7 is only good for 1,025 degrees.

[03' Big Red]

1 hour ago, JoeH said:

Are you talking about mechanical or electronic e7's? I love the idea of an em7 -350 mechanical,  but I think maxidynes peak at 300 hp. 

I think it's just about all in the fuel pump. For the most part, at least on mechanicals, the injectors will put as much fuel in as the injection pump tells them to. But I think it's also important to have a lot of oil pressure so you aren't hurting crank and rod bearings by lugging it. It's critical to have a good film of oil as the the engine is making 1000-1200 ft lbs of torque at 1000rpms. That's only 350 rpms off idle. 

Would be great to get an em7-300 fuel pump and have it turned up closer to 350. You'd likely need to upgrade the transmission too. And personally I'd go Maxitorque trans.  The T310-M might be a great pairing with a maxidyne em7, you'd always be in your power band with room to spare.

i am talking about a mechanical EM 7 300

seems a Eaton 8LL amd 4:42 axle ratio would be a great set up, i see how well that set up works with my AMI 370, that's rated at 1480 ftbl @1300 rpm

[Maxidyne]

IIRC Maxidynes only went to 300 HP until the 2001 models, when the top HP was finally cranked up to 370. The low RPM Maxidyne with the 1020 RPM torque peak was discontinued after 2000, I suspect they had to have the engine rev higher to pass the tighter 2001 emissions requirements.

[JoeH]

12 minutes ago, 03' Big Red said:

i am talking about a mechanical EM 7 300

seems a Eaton 8LL amd 4:42 axle ratio would be a great set up, i see how well that set up works with my AMI 370, that's rated at 1480 ftbl @1300 rpm

My 8LL on my e7-350 shifts like a POS once in a while. Sometimes when you come outa 6th gear to hit 7th the shifter goes to the neutral zone, but the trans stays in 6th for a sec.  Does it in 2nd too. It's held up, but I'd rather a maxitorque behind a maxidyne. Started on a 2 stick maxitorque, its got 560k miles of local beating and my brothers and I all learned on it and it still shifts smooth as ever, and the motor still pulls like a Mack.

The 8LL has 253k miles on it. Long way to go to catch up to that 2 stick for wear.

[03' Big Red]

21 hours ago, JoeH said:

Are you talking about mechanical or electronic e7's? I love the idea of an em7 -350 mechanical,  but I think maxidynes peak at 300 hp. 

I think it's just about all in the fuel pump. For the most part, at least on mechanicals, the injectors will put as much fuel in as the injection pump tells them to. But I think it's also important to have a lot of oil pressure so you aren't hurting crank and rod bearings by lugging it. It's critical to have a good film of oil as the the engine is making 1000-1200 ft lbs of torque at 1000rpms. That's only 350 rpms off idle. 

Would be great to get an em7-300 fuel pump and have it turned up closer to 350. You'd likely need to upgrade the transmission too. And personally I'd go Maxitorque trans.  The T310-M might be a great pairing with a maxidyne em7, you'd always be in your power band with room to spare.

 

it seems the differences are in the  pump,turbo and injectors on a mechanical EM7 300.

I'm not completely sold on the Mack trans over the Eaton, although I have never run the newer Mack trans, only the ones found in a 83 R model.

i don't want to lose the ease of shifting and the gear spread i have in my 8LL, maybe i just need educated but from what i hear the T2080 type trans has big jumps between gears especially going into OD, that seems like one could get fatigued after a long day on the job. i would appreciate someone who has real world experience driving one of these  to educate me

Edited July 9, 2019 by 03' Big Red
N/A

[JoeH]

My first 6 years driving were on a maxidyne 285hp with 5 gears, top speed of 62 mph. The tall jumps are what make the maxidyne excel. Mine had a Jake brake, which makes a huge difference for shifting. Up until these new automatic transmissions, I could outpull most trucks on the road. You are making 90%+ torque from 11-1200 rpms up. You don't need more gears, because you're always in you're powerband.

The T310M maxitorque gears look like they match an 8LL pretty close, with the added benefit of having 6 (yes, six) reverse gears. You can shift through all 6 gears backing up. Mack transmissions have 3 countershafts which make them near bulletproof. Eaton's have 2. I haven't driven an em7, but I have a lot of seat time driving concrete trucks with maxidynes and maxitorques.

[03' Big Red]

i like that the EM 7 has  peak torque way down at 1020 rpm, if my AMI made torque that low it would a game changer.

[JoeH]

Yea the original maxidynes made torque from 1200 to the gov at 2100.  For the EM6 they dumbed the gov down to around 1750? but the powerband kicks in lower too, around 1050 or 1100. I think they did it for fuel economy and driver fatigue. Nothing like screaming along at 62 mph and 2100rpms for hours, but they'll do it all day long. My EM6-300L we bought in January says gov is at 1750? but not to exceed 2300 rpms.  We haven't finished the truck body yet so it's just sitting, I have no hard experience with the EM6 yet.  The old endt676 maxidynes were gov'd at 2100, but you could go towards 2300  according to the visor for you shifts, but I never liked that nor needed to. The EM6 uses the same block as the endt676.

[Maxidyne]

On the original 237 HP Maxidyne the longest gearing offered was around 3.90 which gave 63 MPH at 2100 RPM on 10.00x20 tires, that was pretty buzzy but just about every big diesel truck of the time cruised at the same buzzy 2100 RPM. Mack upgraded to the 285 HP Maxidyne and offered 3.70 gears around the time the speed limits dropped to 55, so we crawled along at a more comfortable 1700 to 1800 RPM. The Low RPM Maxidyne typically was geared to cruise at 1500 or so RPM at 55, and when that wretched "double nickel" limit was raised to 65 the cruising RPMs were still pretty reasonable. I put a lot of miles on UPS MHs with the low RPM Maxidyne and it was a sweet ride... Probably the best Mack ever built!

[03' Big Red]

Ok

I’ll ask this question another way, can a E7 be turned into a EM7 ?

what would have to be changed ?

[JoeH]

I would guess just the fuel pump. Maybe the turbo. Maybe the camshaft too if the maxidynes use different valve durations.

Personally I would want higher oil pressure. My 79 maxidyne makes 60 psi at idle, 90+ for the powerband. Higher oil pressure helps ensure the crank bearings have a good film they're floating in so the bearing surfaces can't contact. You really need it IMHO when you're pulling with 90%+ of your peak torque at 1000 rpms.

Look through used truck ads for a truck with an em7 and run the VIN through your dealer to see what camshaft/turbo part numbers are used. See if it compares to yours.