The ultimate Supercharger Page For Pontiac Bonnevilles

(for more information, please visit www.pontiacbonnevilleclub.com , free to join


How they work          diagnosing problems          porting and polishing          rebuilding nosedrives          Swaps and upgrades          Adding a boost gauge         

replacing needle bearings     adding a nosedrive drain          supercharger oil change          pulley size suggestions          links, references, and sources


This page is intended as a general guide for the Eaton M62 and M90 Superchargers commonly used in the 3800 Pontiacs, Buicks, and Oldsmobiles.  Much of the information here will apply to other applications, including those that use the Eaton M45 and M112.  The author of this page, although very experienced in the procedures shown in this series of pages, accepts no liability for anything you screw up by trying to do what I do.  If you have a half a lick of common sense and mechanical experience, go for it.  You'll save yourself a ton of time and money.  The author of this page has personally rebuilt 3 superchargers.....not many, but they performed flawlessly, and the author has spent countless hours of research gathering information for the members of www.pontiacbonnevilleclub.com .

                           M62 Gen 2 Supercharger with Throttle Body

Eaton Superchargers are a 3-lobe, twin rotor design with a 60 helical twist.  Sounds mean, doesn't it?  As you go through these pages, you'll see what this description really means.  These are very durable devices that typically out-last the rest of the drivetrain they're attached to if properly cared for and maintained. 

Pontiac Bonnevilles first saw the Eaton in the form of the Gen2 M62 in 1992, and this same supercharger was used in 1993 as well, completely unchanged.  1994 and 1995 Supercharged Bonnevilles saw an upgrade with the Gen3 M62, which had epoxy coated rotors for tighter internal tolerances, and a larger inlet diameter to mate with the slightly larger throttle body.  This gained about 20 horsepower and 20 ft/lbs of torque over the 92/93, but it came at the cost of raising the horsepower and torque peaks slightly.  The 94/95 Gen3 version also had a larger EGR stovepipe, but that was largely a function of an EGR re-design by GM than it was a function of the Supercharger itself.  All Supercharged Bonnevilles from 92-95 used the same fuel pump, fuel injectors, and fuel rail, but the fuel pressure regulators were different.  Due to the 94/95 Gen3's increased VE (volumetric efficiency), the pulley in 94 and 95 was slightly larger, due to the fact that the Supercharger didn't need to spin as fast to produce the same boost or CFM.  Stock 92 and 93 L67 engines came with a 2.5" pulley on the Supercharger, and stock 94 and 95 L67 engines came from the factory with a 2.8" pulley.

M90 Gen3 supercharger with MPS pulley system

The M62 Supercharger was replaced with the M90 Supercharger in 1996 with the debut of the Series2 L67.  This engine was a near total redesign.  The M90 Supercharger displaces 90CFM per stroke as opposed to 62CFM per stroke of the M62.  Both of these Superchargers fall into the recommended range of engine displacement for the 3800, but the M90 is able to produce similar boost and CFM's as the M62, but at a much lower RPM.  The combination of the redesign of the engine and Supercharger together netted another 15hp and 20 ft/lbs of torque over the 94/95 L67, but the horsepower that the peak torque and horsepower is delivered at was raised.  Most of the reason for this was the lighter internals, allowing for a more freely rotating mass in the engine internals.  The M90 comes from the factory with a 3.8" pulley.  This design carried through to 2003, which was the last year of the Supercharged version of the FWD 3800 for the Pontiac Bonnevilles.  Two variations are common on 3800's.  From 96-2003 the M90 Gen3 was stock from the factory, but a few owners upgrade to the slightly more efficient GenV blower.  For the purposes of the information on these pages, they are essentially identical.

M90 GenV (above) and M62 Gen3 (below) for comparison.  Notice the rotors on the M62 are smaller?  This allows it to spin up to speed faster, getting into the boost quicker, and developing peak torque at a lower rpm.  The M90 also takes more horsepower to drive it, but it doesn't have to spin as fast to move as much air, so it doesn't have the heat problems hurting efficiency at the higher rpm's like the M62 does.


How they work          diagnosing problems          porting and polishing          rebuilding nosedrives          Swaps and upgrades          Adding a boost gauge         

replacing needle bearings     adding a nosedrive drain           supercharger oil change         pulley size suggestions          links, references, and sources


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All original content on this page and all subpages is 2008, 2009, 2010 www.zillamotorsports.com, and is free for public non-commercial use.  Content may not be copied without permission. 

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