Does anyone have an Eaton M112 sitting on a running 4.6?

[akadeutsch]

Im considering a blower instead of the turbo. I think the M90 is a little small. Im looking for experience with or trying an M112 supercharger on a Jeep 4.6 stroker. Pro's and Con's

[duck454ss]

i will in a few months...... what you got for questions?


Pros:

Similar efficiency to the M90/rpm (if not better). Translates to same air flow and potential boost without having to max out the blower and create a ton of heat.
Allows for 2-3psi boost right off idle with 10-12psi above 3500rpm (depending on pulley size to Crank pulley ratio)
Internal Bypass reduces the amount of parasitic drag during low load/idle.
looks big and mean as F***
easy to install water meth to compensate for no intercooler


Cons:
tis big and long.... it will dominate the intake side of your engine bay covering the entire manifold and is long enough to reach nearly the entire length of the block....
pulley set up will be custom.
heavily modify the intake manifold
will have to problem solve the IAC and TPS
hood clearance might be an issue

[akadeutsch]

You had me at, "Big and Long." TJ hoods are still a dime a dozen so I don't mind cutting one up. Im thinking of something like corvette summer, butt on my HelL J. When I built my 4.6 I bumped the compression up a full point from ~8.5 to ~9.5 What would the extra boost do to my compression ratio? Can I achieve 8-10 psi boost with cooler IAT and at lower rpm with the M-90, for which there is an off the shelf kit? Or is the better choice with the same goal in mind the M112? BTW, This jeep has never seen 5,000 rpms. The only time it ever saw 4,000 was during the break in period. I don't drive it everyday. I want low torque. Its an auto because Im missing my right leg, but I still want power before 1,000 rpms.

[duck454ss]

You had me at, "Big and Long." TJ hoods are still a dime a dozen so I don't mind cutting one up. Im thinking of something like corvette summer, butt on my HelL J. When I built my 4.6 I bumped the compression up a full point from ~8.5 to ~9.5 What would the extra boost do to my compression ratio? Can I achieve 8-10 psi boost with cooler IAT and at lower rpm with the M-90, for which there is an off the shelf kit? Or is the better choice with the same goal in mind the M112? BTW, This jeep has never seen 5,000 rpms. The only time it ever saw 4,000 was during the break in period. I don't drive it everyday. I want low torque. Its an auto because Im missing my right leg, but I still want power before 1,000 rpms.

really comes down to what you want to spend to make it work and what you're content with for power. A big concern from my side of the fence is your compression ratio. if we have the same crank pulley diameter (with stock 3" blower pulley)... at 2100rpm with WOT an M112 (spinning at 5000rpm) can add about 5psi of boost with ~70% VE efficiency . At this point your DCR will hit the 10:1 ish mark. Once at that point you need to be considering premium fuel or something to cool your IAT. Now if you roll into it and you get to 3500rpm when passing you can expect the efficiency of the blower to get into the 80's and boost will hit ~8psi. That bumps you DCR to 13.1:1.... by this point you will most definitely need to address fuel quality and chances of issues in the combustion chamber......

now a potential solution... swap out the blower pulley to a 3.5" pulley.... at 1200rpm you could be close to building boost. by 2100rpm you'll be scratching on the 2-3psi boost mark, a 9.7DCR, and low blower rpm (4000rpm). this would make for ok bottom end torque and better then N/A cyliinder efficiency but nothing mind shattering in the power realm. you could say that this would be good for daily driving and mileage.... where you will see things really come together is when you make the motor spin.By 3500rpm you will get to 5psi boost with the blower in a sweet spot for efficiency and minimal heat generation. great for wheeling/passing...by 4500rpm you'll hit 6.5psi and near peak VE of the blower and your DCR might hit the 12:1 mark where you'll need to consider everything i already mentioned.......

all in all it seems like a pretty simple fix to make the M112 work on your motor.... but in reality you're getting marginal gains compared to a M90 with a small pulley spinning faster. if you're truly keeping the rpms relatively low you wont have much concern with the m90 being a big heat pump........ and if you're concerned about it run a water meth kit that's boost referenced with the money you save not "making a M112 work"..

long story short i wouldn't do an M112 unless you are building a motor specifically to take advantage of it.. like the engine i'm building. but i have a problem with going too far with my projects..... lol..