Reveresing Blower direction

I think MannySC tested that long ago and found that the answer was, "Hmm, yeah, kind of." What I understood was that it will build boost, but it's not as efficient as it could be because the port configuration is meant to work the other way. Still, I think it will build boost.

Is this Honda related?
 
If using same orientation and just rotating the rotors backwards it will not work, no way to compress the air.
 
If using same orientation and just rotating the rotors backwards it will not work, no way to compress the air.

I think you might be surprised.

Would you believe Tom Morana sells a kit to spin one backwards for use with a carburetor?

http://www.moranav6racing.com/category.html?CategoryID=47#155

http://www.moranav6racing.com/downloads/DSCF1997.JPG

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2e2pipt.jpg

Remember, a M90 is not a compressor. It's just a blower. It just pulls air from the inlet and forces it to the outlet side. As long as the air can't slip back past the rotors, it will build pressure.
 
No, this is air compressor related. Working with a local shop to make the M90 into a air compressor or at the very least use it to make a multistage compressor.

A top inlet and back outlet make things a lot easier, but if standard configuration is better I may still go that way.

IF Morana is doing it I may continue on my current course.
 
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That Tom Morana tried something does not mean it works. Using the blower backwards is horribly inefficient. Not to mention you'd have to run it off the back side of the belt since you can't spin the blower backwards just by bolting things on opposite. You can't run a poly rib belt in a way to make the blower spin backwards. The whole idea is just silly.
 
That Tom Morana tried something does not mean it works. Using the blower backwards is horribly inefficient. Not to mention you'd have to run it off the back side of the belt since you can't spin the blower backwards just by bolting things on opposite. You can't run a poly rib belt in a way to make the blower spin backwards. The whole idea is just silly.

I see that something with the drive is amiss in Morana's pictures. I doubt he really meant for it to run off the back side of the belt.

I know it's less efficient, that's for sure.

I am just saying, from Morana's site, Manny's tests (not fully documented, I know), and other examples I have seen on the web where they were used on reverse-rotation Hondas, it can work. Not saying it's a great idea, just that it works to a point.
 
The rotors in the m90 are designed to spin the way they were indented from the factory, they actually catch and compress the air through the through the top to bottom of the unit.
Running to rotors backwards would almost be like sucking air out of the unit vs forcing air down through it.
Now if the rotors were manufactured with a reverse screw then it would not be a issue.
 
No, this is air compressor related. Working with a local shop to make the M90 into a air compressor or at the very least use it to make a multistage compressor.

A top inlet and back outlet make things a lot easier, but if standard configuration is better I may still go that way.

IF Morana is doing it I may continue on my current course.

What is meant by air compressor related?
 
The rotors in the m90 are designed to spin the way they were indented from the factory, they actually catch and compress the air through the through the top to bottom of the unit.
Running to rotors backwards would almost be like sucking air out of the unit vs forcing air down through it.
Now if the rotors were manufactured with a reverse screw then it would not be a issue.

This is correct. Charles has created a reverse rotation gear box for the M90 for the Honda guys so they can use it backwards but spin it forward. Some guys will try anything because they lack the understanding to realize that what they are trying isn't going to work, but from an engineering standpoint, it is fallacy.

Also, just so you all know, the M90 (and all roots blowers) do not compress air. They only pump air. This is important to understand as it is what separates the Roots design from a twin screw. A twin screw is a hybrid, part compressor, part pump. This is evidenced (proven) by the fact that you can submerge an M90 in a tank of water and it will pump water. If it were compressing anything then it would not be able to turn in a liquid.

Roots blowers and twin screws are used to compress air though. They are used in industry and science when clean, oil-less air is needed at high volumes. For example, in production applications, a typical compressor that you would find in a large shop for compressed air is typically a piston design which is loud and if overused will have issues with cooling/overheating. For shops that use massive amounts of compressed air, a couple specially designed twin screw blowers typically used in series will create a continuous high volume of relatively cool compressed air continuously all day long, for years on end when a typical piston compressor would have required continual service and replacement. Because the roots blower works off of a pressure ratio inlet to outlet, running them in series is a great way to get a high volume of air to higher pressures quickly and efficiently.
 
Manny inverted the blower upside down if I remember correctly similar to a GTP, not running the belt backwards.
 
What is meant by air compressor related?

Just that, use a M90 for a compress or secondary stage instead of a piston pump. Honestly I'm only expecting 20PSI (running small HP motor ~3HP at ~8kRPM). Test motor is much bigger so we will see if/what it stalls at.
 
IIRC, these two brothers who raced an AMC Marlin out of Denver in the 24 Hours of Lemons (Speed Holes Racing) decided a while back to attempt twin supercharging it. They used M90s because those and Toyota Previa SCs are the only ones commonly available at junkyards...

One of them sold me a 3.73 gear set for cheap (which BTW, you can bring on as a carry-on through the Denver Airport) and I recall him telling me that his brothers reversed the impellers inside the M90 SC to work for his application
I don't think it lasted very long but it was apparently glorious to behold (and was setup to run w/o the SCs if needed). According to this posting on TTAC, the setup pushed 5psi so I'm not sure if the lower than stock # was because of tuning (aka pulley diameter) or loss of efficiency.

http://www.thetruthaboutcars.com/20...ugh-amc-marlin-racer-gets-twin-superchargers/

MarlinBlowerHell-03-550x412.jpg


-g
 
An M90 case is asymmetrical in terms of flow, right? Wouldn't it just be a matter of reverse-installing the rotor pack?
 
Those guys aren't turning them backwards, they are just attempting to drive the opposing rotor because as you know, the rotors turn in opposite directions. They are still blowing air out of the outlet like Eaton intended. This is what Charles did already as I mentioned above for the Honda guys. You can't just flip the snout around and put it on backwards because it is not symmetrical and this is why Charles made a new snout. Yes, you put the rotor pack in backwards, but that doesn't change airflow through the case, it just moves the drive side from right to left which allows you to drive it from the opposite side if you have a snout that will fit. OP was asking about moving air backwards through the blower which is something that would have very poor efficiency.
 
IIRC, these two brothers who raced an AMC Marlin out of Denver in the 24 Hours of Lemons (Speed Holes Racing) decided a while back to attempt twin supercharging it. They used M90s because those and Toyota Previa SCs are the only ones commonly available at junkyards...

One of them sold me a 3.73 gear set for cheap (which BTW, you can bring on as a carry-on through the Denver Airport) and I recall him telling me that his brothers reversed the impellers inside the M90 SC to work for his application
I don't think it lasted very long but it was apparently glorious to behold (and was setup to run w/o the SCs if needed). According to this posting on TTAC, the setup pushed 5psi so I'm not sure if the lower than stock # was because of tuning (aka pulley diameter) or loss of efficiency.

http://www.thetruthaboutcars.com/20...ugh-amc-marlin-racer-gets-twin-superchargers/

MarlinBlowerHell-03-550x412.jpg


-g


like the dryer hose to the left thats a real good addition to the mix
 
You could use a 2 sided ribbed belt and route the belt like you would the water pump so it turns the correct direction. If you can find a 2 sided belt. It would take a hell of a idler pulley to get enough wrap. ( I am not speaking from experience here just throwing out ideas lol )
 
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Just that, use a M90 for a compress or secondary stage instead of a piston pump. Honestly I'm only expecting 20PSI (running small HP motor ~3HP at ~8kRPM). Test motor is much bigger so we will see if/what it stalls at.

Does it not take like 30 or so hp to turn this blower to get that type of pressure?
 
Does it not take like 30 or so hp to turn this blower to get that type of pressure?
It will depend on what blower rpm he intends to spin and what CFM is required. In our application where 20psi generally requires 15-18K rpm, it would take over 100hp to generate that pressure. However, assuming CFM requirements are much lower, he may be able to underdrive the blower. If drive HP is 3hp @ 8000rpm, by turning 1/2 that rpm torque will be doubled, and so on. It all depends on cfm requirements. If cfm requirements are low enough though, the blower will end up out of it's efficiency range and may not perform well (ie. 2000rpm). They will just have to try it.
 
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