Engine and Transmission Tech

I want a simple comparison test. In other words, like to test the output of a popular oem blower, like the Eaton M90. I want to know what size/diameter of a restricting plate,( like used on a flow bench), to quantify boost pressure at a given blower speed. For instance on an oem application this M90 might max at 12,00 rpm ? Say on a 3.8L Buick V6 might produce XX of boost ? I have a totally of-the-wall design, I want to compare with an M90 or M112.
Thanks, Art.

The M90 is a good choice for a 3.5L engine, the M112 works fairly well on a 5.7L

Jim

X2 with what Jim said above.

Max efficiency RPM limit of a stock GM M90 is about 12,000 RPM. (blower speed) That being said, that limit can be increased to 14,000 RPM with proper housing porting. Generally speaking the gains from porting start to kick in at around 10,000 RPM. To fully utilize the porting you would want to overdrive the blower more by going to a smaller driven pulley, as well as cylinder head and manifold porting.

For M90 performance parts I have used ZZperformance [zzperformance.com]

Also there is some additional info here at [www.3800supercharger.net]

Bill



Edited 1 time(s). Last edit at 10/23/2018 02:29AM by MG four six eight.

So much for that comparison test. ;)

Yes, thanks but not the question. About what diameter hole/restricting orfice to equal real world boost, with M90 on say a 3.8L Buick @ 12k. max blower speed ? Example is to compare output to my design. art.

Art, you don't typically use any sort of a restricter plate, instead you size the blower pulley to get the output pressure you are looking for. Magnuson sells various sized blower pulleys and other accessories. Use a puller to remove it.

To the best of my recollection I used a 2" pulley with a 6-1/2" crank pulley on my M90 and had over 16psi of boost on the 215 at full-tilt-n-boogie, but that was with Olds heads and a stock cam. Every engine is different so a certain amount of trial and error is unavoidable. On the 340 the top pulley is about 2-1/2" and I'm running 5 psi of boost with the M112.

Note that it isn't uncommon for boost pressure to rise somewhat with engine speed. This is especially true at lower rpms but can also hold true all the way to redline.

Jim

Jim, ok Eaton M90, 6.5"/2" pullies,5,000 engine = 16,250 on blower= " blower retaining straps please". Last call here. Eaton M90, 12k. blower rpm. I put it to a 2" restricting orifice,(test only). How much boost ? Do I need a 1.75" ? Like a flow bench, in reverse, I can easily test performance of various blower sizes/designs. art.

Art
This is the best I could come up with for air flow data on the M90 [www.mscperformance.com]

If you fabricating a flow bench with the blower driven by an electric motor, your probably going to have to do some math calculations based off of published M90 flow ratings in order to figure out what size restrictor plate you'll need.

Also at 10 psi the blower can require over 40 horsepower to drive it. So your going to need one heck of an electric motor! (if that's what your doing)
Bill

Art, the blower rotors are symmetrical and have no unbalanced loads so spinning them above the conservatively rated 12K limit has no downside other than possibly reduced aerodynamic efficiency. I was making over 16psi in the 5-6K range of engine speed and never had any issues with contact between the rotors and the housing. The 3 lobe twisted shape is very rigid.

Jim