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EJ6
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Discussion Starter #1
...and its not necessarily a good one.

We got shafted; the hole is too small.

I was browsing CAPA, an Aussie site that still has relevant data on the 3rd gen Eaton blowers and I noticed something peculiar. If you look at the 3rd gen blowers (M45,M62,M90) you'll notice that the bigger the blower, the larger the discharge port. This is makes sense. If you follow the 4th gen numbers you'll see similar increases.

The interesting tidbit is when you compare the MP45 to the M45. The MP's discharge port issignificantly bigger compared to the 3rd gen M. So what does that have to do with anything? Now compare the MP45 to the M62.

Do you see it? At first I thought the two were identical, but as it turns out the MP45 has a slightly bigger discharge port than the older M62, its close but it's bigger! The two superchargers flow roughly within 50-75 cfm of each other! Therefore, M45 + M62 discharge port = MP45. M62+M90 DP=MP62 and so on.

Therefore, I can safely say looking at the published numbers the problem with our JRSC is not the size of the blower but rather the case.
 

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Yes, and thats why the M45 sucks.

I still stand by that a roots blower is not nearly as bad as everyone thinks, as much of the negative experience comes from the awful JRSC kits that were so popular.
If they had at the time sold the kit with an MP62 you would see much more love for roots blowers and superchargers in general.
Better yet, if twin screws had become popular in the import world, you would probably see just as many people running them as turbos, and they would be just as fast (for the most part).
 

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1988 Honda CRX
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If someone ran one of the TVS style, I am sure the opinions would also change to significantly more favorable.

TVS Roots-Type Superchargers
 

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Meat Popsicle
91 CRX Si
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I wish it was that simple...to say M45 + M62 discharge port = MP45 is pretty far off.

The M62 and MP45 have longer cases and longer rotors.

Funny thing is that the MP45 flows almost identically to a M45 at hotter temps. Only real advantage is that it was designed to spin faster than the M45
 

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1988 Honda CRX
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One limitation to discharge port design and size is that no part of the rotor tip can uncover any part of the outlet until that tip has already has no part of the inlet port uncovered. The higher the helix angle on the rotor and the longer the rotor, the more restrictive it becomes, so take care when porting Eaton blowers.
 

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If someone ran one of the TVS style, I am sure the opinions would also change to significantly more favorable.

TVS Roots-Type Superchargers
Indeed. I was surprised when the zr1 was announced to have a roots until I learned of the improvements of the 4 lobe design over the old 2 lobe designs. The efficiency rivals a twin screw with less cost. Plus it's positive displacement
 

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1988 Honda CRX
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From what I hear, the TVS is used on some factory supercharged Jet Skis.
 

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EJ6
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Discussion Starter #12
I wish it was that simple...to say M45 + M62 discharge port = MP45 is pretty far off.

The M62 and MP45 have longer cases and longer rotors.

Funny thing is that the MP45 flows almost identically to a M45 at hotter temps. Only real advantage is that it was designed to spin faster than the M45
The MP45 case may be longer but it is narrower. I double checked the flow data and the MP outflows the M by 100 cfm nearly equaling the M62.






 

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Meat Popsicle
91 CRX Si
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Like I said above, the MP45 graphs show data all the way up to 16000RPM where the M45 shows data up to 14000RPM.

Forget the last 2000RPM and compare the graphs from a M45 to a MP45 and you'll see that the flow characteristics are nearly identical and the MP45 actually gets a litter hotter than the M45.

The M62 flows the way it does because it has longer rotors, a larger outlet, and displaces more air per revolution.
 
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