Supercharger: Shoehorning in an Eaton blower
11-12-2001, 07:30 PM
#1
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Thread Starter
Supercharger: Shoehorning in an Eaton blower
I just recently got in an Eaton M90 blower for another "project"... this sucker is HUGE! For grins, I took a few shots of it in the S2k engine bay:
Full size: http://www.s2000.org/gallery/blower1.jpg
Full size: http://www.s2000.org/gallery/blower2.jpg
It looks like it would actually fit, though it would require a quite complex and convoluted new manifold. Based on this, I think it is VERY possible that an M45 or possibly M62 blower could be used in it's place, which are a fair bit smaller. While the other kit recently posted might not work LHD, I think it's entirely possible.
I'll be happy to do the development work if anyone volunteers a blower for development...
Full size: http://www.s2000.org/gallery/blower1.jpg
Full size: http://www.s2000.org/gallery/blower2.jpg
It looks like it would actually fit, though it would require a quite complex and convoluted new manifold. Based on this, I think it is VERY possible that an M45 or possibly M62 blower could be used in it's place, which are a fair bit smaller. While the other kit recently posted might not work LHD, I think it's entirely possible.
I'll be happy to do the development work if anyone volunteers a blower for development...
11-12-2001, 09:54 PM
#2
Registered User
Only one problem with using an M45 or M62. That is, they're too small - IMO.
As they arrive from Eaton, the M-series blowers don't like to be revved much above 13,000-14,000 rpm (blower speed). Their thermal efficiency, which is only average to begin with, goes to pot above that. The slower you can spin the blower, the better off you are.
An M62 displaces approximately 1.0 liters of air per revolution. That also happens to be about what the F20C displaces in normally aspirated fashion (probably about 1.1 liters per rev near the torque peak, less than 1.0 liter below 6k rpm). Thus, to make about 6-7 psi you'll need to spin an M62 somewhere near 1.5x engine speed - or about 13,500 rpm blower speed at 9,000 rpm engine speed. While you could live with that, you've basically got no headroom left.
With an M90, a 1.5 liter/rev blower, that same 7 psi would only require you to spin the blower at engine speed, which is far more efficient and leaves headroom for future upgrades if desired. I've run into the blower speed problem on my CRX, which utilizes an M45 on a 1.6 liter engine revving to 7500 rpm.
UL
As they arrive from Eaton, the M-series blowers don't like to be revved much above 13,000-14,000 rpm (blower speed). Their thermal efficiency, which is only average to begin with, goes to pot above that. The slower you can spin the blower, the better off you are.
An M62 displaces approximately 1.0 liters of air per revolution. That also happens to be about what the F20C displaces in normally aspirated fashion (probably about 1.1 liters per rev near the torque peak, less than 1.0 liter below 6k rpm). Thus, to make about 6-7 psi you'll need to spin an M62 somewhere near 1.5x engine speed - or about 13,500 rpm blower speed at 9,000 rpm engine speed. While you could live with that, you've basically got no headroom left.
With an M90, a 1.5 liter/rev blower, that same 7 psi would only require you to spin the blower at engine speed, which is far more efficient and leaves headroom for future upgrades if desired. I've run into the blower speed problem on my CRX, which utilizes an M45 on a 1.6 liter engine revving to 7500 rpm.
UL
11-13-2001, 04:30 AM
#3
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Thread Starter
Good point. I've been going through the math on my 2.6L 4 banger I'm planning to put it on. The low redline is what's saving me there (6k). At 1.5L/RPM, the M90 isn't *that* much bigger. I doubt, too that the M112 will fit!
The M90 looks like it might fit, but it will be an engineering feat. The big problem is that to line up the pulley, the inlet is crammed up against the firewall. The housing back there (which would have to be fabbed) would have to be a side-exit or U-turn shape and probably small diameter. There won't be much consideration for runner shape, either, other than being VERY short.
Depending on how my 2.6L install goes, and if I can get another of these dirt cheap (doubtful), I might try and do it on the S2.
Thanks, UL, you are always the voice of reason.
The M90 looks like it might fit, but it will be an engineering feat. The big problem is that to line up the pulley, the inlet is crammed up against the firewall. The housing back there (which would have to be fabbed) would have to be a side-exit or U-turn shape and probably small diameter. There won't be much consideration for runner shape, either, other than being VERY short.
Depending on how my 2.6L install goes, and if I can get another of these dirt cheap (doubtful), I might try and do it on the S2.
Thanks, UL, you are always the voice of reason.
11-13-2001, 05:34 AM
#5
Registered User
Thread Starter
Check out the data sheets:
http://www.eaton.com/supercharger/
It's not listed here, but according to UL the M45 will do 1.0L displacement per rev and the M90 will do 1.5L/rev (I found that on Magnusson's site). According to the flow vs. pressure charts Eaton has, the M45 will only do .5L/rev at 5 psi and .57L/rev at 10psi.
What Ul was pointing out is that the blower is only capable of moving the engine's displacement at 1x the engine speed at 0psi. That means it will only move the air the engine would normally need to run- you'd have to spin it faster to actually achieve boost. This is a bad idea since the Eatons are only designed for about 14,000 RPM. You'd therefore want to spin it at least at 1.5x or even faster. And forget an intercooler, the pressure drop would kill your boost. Blower life and efficiency would be impacted dramatically spinning faster than 1.5x.
The M90 will only do .9L/rev at 10psi, and 1.06 at 5psi. This is a "better" match, allowing for a 1x pulley, 5psi boost across the board, and a sub-10k RPM blower speed. Keeps the blower efficient. You could step up to a 1.2-1.4x pulley to add boost or overcome the effects of an intercooler and still keep the blower thermally efficient.
http://www.eaton.com/supercharger/
It's not listed here, but according to UL the M45 will do 1.0L displacement per rev and the M90 will do 1.5L/rev (I found that on Magnusson's site). According to the flow vs. pressure charts Eaton has, the M45 will only do .5L/rev at 5 psi and .57L/rev at 10psi.
What Ul was pointing out is that the blower is only capable of moving the engine's displacement at 1x the engine speed at 0psi. That means it will only move the air the engine would normally need to run- you'd have to spin it faster to actually achieve boost. This is a bad idea since the Eatons are only designed for about 14,000 RPM. You'd therefore want to spin it at least at 1.5x or even faster. And forget an intercooler, the pressure drop would kill your boost. Blower life and efficiency would be impacted dramatically spinning faster than 1.5x.
The M90 will only do .9L/rev at 10psi, and 1.06 at 5psi. This is a "better" match, allowing for a 1x pulley, 5psi boost across the board, and a sub-10k RPM blower speed. Keeps the blower efficient. You could step up to a 1.2-1.4x pulley to add boost or overcome the effects of an intercooler and still keep the blower thermally efficient.
11-13-2001, 07:50 AM
#7
Registered User
marcucci,
Check the stat sheets again. You'll see the M45 displaces 0.75 liters (the model number is the displacement in cubic inches). On the inlet flow vs. pressure numbers, since they are pressurized CFM its harder to work with there. For example, at 6000 rpm the M90 should displace 318 cfm, but it only rates 250 cfm at 5 psi on the spec sheet. The pressure/volume relationship seems to account for the diff pretty well. Or maybe you were trying to communicate that and I just missed it :-)
What I like to look at are the delta T's and the power requirement. For example, let's compare our M62 at 12,000 rpm (7 psi at 8,000 rpm engine speed) vs. the M90 at 8,000 rpm for the same boost. Use the 5 psi curve so you don't have to extrapolate. The M90 consumes 14 hp and adds about 88F of temp to the intake charge. By comparison, the M62 needs 18 hp and adds 100F. Go to higher rpms where the M62 really gets non-linear and the temp diffs become larger. Even at the numbers I posted, the M62 requires 4 more hp to drive and you'll lose 1-1.5% hp due to temp rises.
UL
Check the stat sheets again. You'll see the M45 displaces 0.75 liters (the model number is the displacement in cubic inches). On the inlet flow vs. pressure numbers, since they are pressurized CFM its harder to work with there. For example, at 6000 rpm the M90 should displace 318 cfm, but it only rates 250 cfm at 5 psi on the spec sheet. The pressure/volume relationship seems to account for the diff pretty well. Or maybe you were trying to communicate that and I just missed it :-)
What I like to look at are the delta T's and the power requirement. For example, let's compare our M62 at 12,000 rpm (7 psi at 8,000 rpm engine speed) vs. the M90 at 8,000 rpm for the same boost. Use the 5 psi curve so you don't have to extrapolate. The M90 consumes 14 hp and adds about 88F of temp to the intake charge. By comparison, the M62 needs 18 hp and adds 100F. Go to higher rpms where the M62 really gets non-linear and the temp diffs become larger. Even at the numbers I posted, the M62 requires 4 more hp to drive and you'll lose 1-1.5% hp due to temp rises.
UL
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11-13-2001, 08:06 AM
#9
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Thread Starter
Sorry... and it was even on the link I posted! I misread and was looking at the M62 (1L/rev). You're right, I was trying to communicate that the L/rev is at 0psi, or just straight flow- no boost. To get the boost I just used the chart to determine 90CFM/4000Rev at 5psi and so forth. The M45 numbers I have in that post should otherwise be correct.
I understand the need to operate the blower where it's most efficient- one reason I selected the M90 over the M62 for my truck. Well, that, and I couldn't have asked for a better deal on the blower ($350, new). I love eBay!
I understand the need to operate the blower where it's most efficient- one reason I selected the M90 over the M62 for my truck. Well, that, and I couldn't have asked for a better deal on the blower ($350, new). I love eBay!
11-13-2001, 11:38 AM
#10
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Hmm... positive displacement FI...
I looked at this at one point, and came away disappointed. turns out that w/ the terrible VE and AE on the roots-type, you'd need a significant intercooler, and have mounting/belt routing/space issues to boot. Plus, there's still the issue of parasitic loss due to driving the SC.
Although, a twin-screw blower has nearly the same VE and AE as a turbo, and provides nearly instant boost. All the other issues (space, belt, drag, etc.) still remain, tho.
In the end, I think a small turbo is going to work better. No loss, fantastic VE and AE, _incredible_ powerband improvements; it's just a better solution. Yah, it's more expensive, and requires a bit more care, but in the end, it's the right choice, and I doubt(given derryck's and ChrisD's results) that SCs will ever match the performance.
I looked at this at one point, and came away disappointed. turns out that w/ the terrible VE and AE on the roots-type, you'd need a significant intercooler, and have mounting/belt routing/space issues to boot. Plus, there's still the issue of parasitic loss due to driving the SC.
Although, a twin-screw blower has nearly the same VE and AE as a turbo, and provides nearly instant boost. All the other issues (space, belt, drag, etc.) still remain, tho.
In the end, I think a small turbo is going to work better. No loss, fantastic VE and AE, _incredible_ powerband improvements; it's just a better solution. Yah, it's more expensive, and requires a bit more care, but in the end, it's the right choice, and I doubt(given derryck's and ChrisD's results) that SCs will ever match the performance.