Anyone know where to find a performance map for an Eaton M45 supercharger?

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

Thanks, that looks like a reasonable size for a 2.8L or 2.3L Quad 4

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

I have an MP45 on my 2.0l DD inline 4. It's been on the motor for a little over 210,000 miles, rebuilt once at about 70,000 miles. It is great on the 2 liter, makes it way more fun to drive, but for a 2.8l the MP62 might work out better.

quote Originally posted by Larryinkc: I have an MP45 on my 2.0l DD inline 4. It's been on the motor for a little over 210,000 miles, rebuilt once at about 70,000 miles. It is great on the 2 liter, makes it way more fun to drive, but for a 2.8l the MP62 might work out better.

I found an error in my spreadsheet so agree that the M45 is a bit on the small side. A 2.8L @ 5500 rpm with 7 psi of boost requires about 500 m3/hr of inlet air flow assuming a volumetric efficiency of 90%. The M45 can do this but the efficiency is only about 57% which makes for a higher discharge temperature. The M62 would get the flow back closer to the best efficiency point and keep the discharge temperature down.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

Can a stock 2.8L V-6 handle 7 psi of boost with 100 'F MAT (intercooler) and 94 octane pump gas?

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

Honest Don's 2.8 Fiero has been running at 16 psi (turbo):
https://www.fiero.nl/forum/...HTML/144739.html#p15

My low-compression 3.1 (mostly the same as a stock 2.8) Fiero has been hitting 15 psi (also turbo) non-intercooled at the end of last year on 91 AKI pump gas.

Depends also which 2.8 you're talking about. I think that 1988 Fiero 2.8s have improvements to their lubrication system, but I don't know the specifics.

[This message has been edited by pmbrunelle (edited 01-10-2023).]

quote Originally posted by pmbrunelle: Depends also which 2.8 you're talking about. I think that 1988 Fiero 2.8s have improvements to their lubrication system, but I don't know the specifics.

I my case it's a stock 1986 2.8L V-6 with about 110,000 miles on it. I'm still toying with the idea of an electric supercharger. I have found a 7.6 kW brushless electric motor. I could install a junkyard Eaton M62 in the trunk and provide at least 7 psi of boost from 0 to 5500 rpm. This motor and M62 might even do 10 lbs. I looked at a bin file for a 2.8L and could not believe how crappy the volumetric efficiencies numbers were - 70.3% max VE - that's ugly.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

Larry, could you please explain how to read that interesting-looking map? And use small words so I will understand

I would if I could, all I know about it is in my case a higher number on the boost gauge means more fun.

quote Originally posted by Notorio: Larry, could you please explain how to read that interesting-looking map? And use small words so I will understand

Here you go:

1) The X-axis is the volumetric flow entering the supercharger in cubic meters per hour.

2) The Y-axis is the pressure ratio i.e. the absolute pressure of the discharge (psia) divided by the absolute pressure of the suction. 0 psig is 14.7 psia. So with a pressure ratio of 1.5 the discharge pressure is 14.7 * 1.5 = 22.05 psia or 22.05-14.7 = 7.35 psi of boost.

3) The near vertical lines are the RPM that the supercharger is turning. For a belt driven supercharger that will be a ratio to the engine rpm which depends on the size of the pulleys.

4) The contour lines are the thermodynamic efficiency of the compression cycle. If there were no friction, the efficiency would be 100%. If the efficiency is 70% then 30% of the input power is being lost to friction which results in excess heating of the discharge gas. So the higher the efficiency, the lower the discharge temperature. That's a good thing because lower temperature means a denser gas which has more mass per cubic meter


Let's assume the inlet air is 14.7 psia (0 psig) and 60 'F. There are 1000 liters per cubic meter. For a 2.8L how much air flow is required? Since it is a 4-stroke engine it only ingests air every other revolution of the crank shaft. Therefore at 5500 rpm:

2.8 * 5500 / 2 * 60 / 1000 = 462 m3/hr.

That's if there was no supercharger present and the volumetric efficiency of the engine was 100%. The volumetric efficiency of the engine is a measure of how well the cylinder fills. The way to look at this is what is the maximum absolute pressure in the cylinder during the intake stroke compared to the intake manifold absolute pressure (MAP). At full throttle the MAP will be close to atmospheric pressure. That will be about 100 kPa or 14.5 psia. If the volumetric efficiency of the engine is 70%, the cylinder pressure would only be 14.5 * 0.7 = 10.15 psia.

A supercharger reduces the volume of the inlet gas by increasing the pressure. How much depends on the compression ratio and the temperature of the discharge gas. To try to keep things simple let's assume that there is an aftercooler (intercooler) on the supercharger that brings the temperature back down to 60 'F. What inlet volume is required from the supercharger to supply the engine at 5500 rpm with a pressure ratio of 1.5 (7.35 psi boost) if the engine's VE is 70%:

2.8 * 5500 / 2 * 60 /1000 * 1.5 * 0.7 = 485 cubic meters per hour.

Without the aftercooler the discharge gas is less dense and there is less inlet flow to the supercharger. Of course, this means less power since the mass flow of air to the engine is less.

Hope this helps