Dear gents,

Here's my situation: a few months ago I rebuilt my Gen V Eaton M112. New needle bearings, new coupler, new bearings and shaft seal in the snout, fresh oil.
It seems like it didn't go entirely smoothly — after 5,000 km a little oil is seeping past the front shaft seal.

At the same time, I currently have the opportunity to buy a ultra-low mileage used Gen IV supercharger, whose rotor pack coating is still completely intact,
My question is: is the Gen IV rotor pack compatible with the Gen V housing?

My idea is to swap the snout and rotor pack from the Gen IV supercharger into the Gen V housing, so that I can retain the advantage of the larger needle bearings from the Gen V.

Or was the rotor pack design also revised during the generation change?

Thanks and best regards, Alexander

 

I have a core gen IV I can take measurements on the tail shafts of the rotor pack. I'm not sure if there would be other changes like overall rotor length changes or tolerancing between the rotors OD and the housing to account for things like the coating on the genV.

Could you just swap the snout from the donor to your blower? I'm not sure if there's any changes in the snout design going between IV and V. They did use different bolts (etorx on genV and hex head on IV). Gen IV gears are straight cut vs helical on genV so the genIV will make more noise in general operation. Also the teflon coating on the genV is technically "better" than that of the genIV but I think that's marginal gains.

 

Good morning,

Thanks for all the input and suggestions.

In the end, I simply changed the oil in the replacement Gen IV M112 and installed it as-is — I needed the car back on the road quickly, and frankly the nice weather helped make that decision easy too.

What I found on the Gen V

Beyond the snout oil leak, I also noticed that the Gen V knocks/rattles when rotated by hand. That pretty much sealed the deal on swapping it out for now. I'll be tearing it down next week for a closer look. The noise seems to be coming from the front section of the snout, in the area of the gears — which, like the leak, I can't really explain at this point.

To recap what was done during the rebuild: both snout ball bearings (NSK), the shaft seal (SKF), and both rear needle bearings (INA) were replaced. I'm running AeroShell 500 (MIL-PRF-23699 spec) as the oil. The rear needle bearings were installed exactly as the originals were seated — press depth approximately 1.4 mm, if I recall correctly. We'll see what the teardown reveals.

Back to the Gen IV / Gen V swap question

Having now placed both housings side by side, a rotor pack swap from an older unit into a Gen V housing looks very feasible — the outer dimensions are identical, and so is the bolt pattern. More importantly, the inner diameter of the needle bearings is the same for both generations (17 mm). As long as the rotor shaft journals match, it should work.

As it happens, I'll need to get into the passenger-side injector bank within the next couple of months anyway, which will give me another opportunity to attempt the Gen IV/Gen V marriage — assuming the Gen V isn't completely beyond saving.

 

Why not just use whole genV sc? Or did I miss something?

 

Good question — the short answer is that the Gen V isn't in good enough shape to simply bolt back on. Beyond the snout oil leak, it also developed a knocking/rattle when rotated by hand, seemingly from the gear area in the front of the snout.
Until I tear it down next week I won't know what's going on, so the Gen IV went in as a quick fix to get the car back on the road.

The idea of swapping the Gen IV rotor pack into the Gen V housing came from wanting to retain the Gen V's larger needle bearings.

 

Okay.