Stocious
Active Member
Can anyone tell me if the Eaton m65 supercharger used on the M271 is a screw type or roots, Eaton make both and I have not had one on the bench yet, 
M271 supercharger type, screw or roots
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Stocious
Active Member
Also what capacity is the supercharger, .65 liter ??
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Stocious
Active Member
Screw type so, anybody ever bought a used one? What do they go for?
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Stocious
Active Member
Capacity: 65 cubic inches or 1.065 liters 
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Stocious
Active Member
Correction, it is a roots type with twisted rotors, the 3 lobes should of made it apparent
Don't know what the supercharger designation number means in terms of capacity, I thought they used pulley size to differentiate the various power outputs. Also many of the M271 engines used an M45 rather than an M65.
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Stocious
Active Member
There capacity is measured in cubic inches per rotation, or liters per rotation, in the case of Eaton it’s the number after the M which is its capacity in cubic inches, learned a lot since I touched on this topic, I presume the 45 cubic inch charger is for the lesser rated engines , mine is 163hp , The roots and screw type develop full boost and hold it from about 2000/6000 rpm, if there’s a taper off towards redline the charger is undersized, I’d love to fit a discreet boost gauge where my ashtray is, I don’t use it, a STACK gauge would be nice, also comming from turbo land and it’s methods, it’s a different approach, if you were to seek more power, it’s the valve, porting, boost drops significantly with less restriction, THEN you change pulley size to bring back boost to same level, and in turn I THINK achieve this with less heat generated, also there is almost a 1:1 with exhaust back pressure and manifold pressure, if you free up the exhaust boost drops again, same thing as freeing up the intake side just the exhaust, giving you more scope on pulley size, to me all this makes the after market stuff make sense, headers, exhaust, and mostly that pulley kit, and remapping once done, inter cooling is also important but not for air density but that’s another topic, but to keep detonation at bay, there is leeway with the higher compression lower horsepower M271’s if you keep charge temp down and use octane booster, if I buy an engine stand, it’s started again
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Stocious
Active Member
Any info is welcome, especially interested in empty case photos, I need to get my hands on a used M65 and rebuild it but better, and that’s hard with an Eaton , there around a long time
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Stocious
Active Member
If any of the above is incorrect tell me please, I think I’ll buy a book on the charger thing it’s interesting,
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Stocious
Active Member
I was initially a little bemused at those graphs starting at 4000 rpm and finishing at 12,000 rpm but of course the supercharger typically runs 2.5 times faster than the engine. No wonder they consume a lot of power.
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Stocious
Active Member
Yes and a screw type charger is less parasitic than a roots which I have, also a screw produces less heat, there both positive displacement chargers as they reach full boost and hold it throughout the rev range, unlike centrifugal which raises boost or capacity per rotation as the revs rise, the biggest revelation to me was the inter cooling facts, the cooler you can get the charge the more timing you can run = more power, not more dense air, example, if you fill a ballon with air the density of the air does not change according to temperature, it can not make oxygen just because it’s colder, I’m not sure how fuel tables tie in to that fact but thinking about it, adding more charge, cool charge, allows for more fuel, fuel is a charge coolant also, win win
Bellow
Hardcore MB Enthusiast
You're welcome.Thank you
Yes and a screw type charger is less parasitic than a roots which I have, also a screw produces less heat, there both positive displacement chargers as they reach full boost and hold it throughout the rev range, unlike centrifugal which raises boost or capacity per rotation as the revs rise, the biggest revelation to me was the inter cooling facts, the cooler you can get the charge the more timing you can run = more power, not more dense air, example, if you fill a ballon with air the density of the air does not change according to temperature, it can not make oxygen just because it’s colder, I’m not sure how fuel tables tie in to that fact but thinking about it, adding more charge, cool charge, allows for more fuel, fuel is a charge coolant also, win win
Density is important and the cooler the charge the more dense it will be hence a greater mass of air. More air enables more fuel to be burned and more torque and power as a consequence. Boost isn't everything - if it's just air queuing up. Mass air flow is all.
Remember, the cylinder has rigid boundaries - the balloon does not.
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Stocious
Active Member
Thanks I know about boost is only a measurement of restriction, still leaving the balloon theory alone, air cannot generate oxygen once cooled once already in the inlet tract past the charger, what was pointed out and I forgot to mention it’s pre charge temps effect oxygen density, what you do achieve is more air in the rigid cylinder, so in a way more oxygen, but post charger air does not become more oxygen rich when cooled, does that make sense, at the side of the road typing sorry, thanks, if I’m wrong tell me
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Stocious
Active Member
Would I be right in saying that someone has tried a bigger cooler on the M271 without HP gains??
I think I read that on here maybe not, interesting tho all the same
I think I read that on here maybe not, interesting tho all the same
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Stocious
Active Member
Ok back on topic, superchargers and boost plus heat management, I can come back to heat management later, it is important with a roots type blower, in post 9 if modifications are made in the right order, reducing restrictions on both intake tract and exhaust, boost lowers, would it not be ok to fit the larger charger off the -/+ 200 HP 230?
This may achieve the same result as a pulley chane with the original charger to bring boost back to original level, but with the benefit of not pushing the charger out of efficiency and just generating heat, you can over speed a charger, , another topic,
This may achieve the same result as a pulley chane with the original charger to bring boost back to original level, but with the benefit of not pushing the charger out of efficiency and just generating heat, you can over speed a charger, , another topic,
Bellow
Hardcore MB Enthusiast
Thanks I know about boost is only a measurement of restriction, still leaving the balloon theory alone, air cannot generate oxygen once cooled once already in the inlet tract past the charger, what was pointed out and I forgot to mention it’s pre charge temps effect oxygen density, what you do achieve is more air in the rigid cylinder, so in a way more oxygen, but post charger air does not become more oxygen rich when cooled, does that make sense, at the side of the road typing sorry, thanks, if I’m wrong tell me
Back to basics.
Increased air density is the aim. Any volume of air will contain the same amount of oxygen as a percentage (circa 20%). For any given cylinder volume to say, double the quantity (mass) of air the density must be doubled. The cylinder volume is as it was before so increasing the density of the air to enable twice as much in the same volume is the only possibility.
That in cylinder density should be a reflection of the 'boost' pressure. If boost pressure is a consequence of any restriction before the cylinder, there will be a pressure drop which will deny the cylinder full pressure and thus the desired density and mass of air in the cylinder. Therefore, removal of restrictions are valid (for any manifold pressure - NA to heavily boosted) but the age old compromises of achieving good torque over the entire rev range rear their heads. This can be exacerbated if the chosen charger operates over a narrower speed range or the CR is reduced.
Controlling inlet temps serves three purposes.
Firstly it serves to increase the air density so a greater mass of air can be ingested.
Secondly, as alluded, it helps in raising the detonation threshold.
Thirdly, as the temperature at any point in the (thermodynamic) cycle is dependent on the initial temperature (eg, air entering the cylinder 20 degrees hotter will mean that the temperature at any point in the following cycle will likewise be 20 degrees hotter) any reduction in inlet temp will reduce combustion temperature by the same amount and reduce heat loss to the cylinder walls to the benefit of efficiency.
Improving exhaust flow in a mechanically driven supercharged engine is beneficial as there is a greater amount of exhaust product to exhale and if the exhaust system (valve and its opening duration included) are restrictive then it will create an increase in pressure on the piston crown during the exhaust stroke which is work taken from the crankshaft - work that would otherwise appear as power at the flywheel. Emptying the cylinder quickly also helps reduce internal engine temps (detonation threshold). ('Lakers' use expansion cones to ''suck the heat out''!)
