Why so many new MINI superchargers on ebay
Discussion
Went to a chap at Thruxton to try and sort the Audi out this week.He has an aftermarket kit he designed with a larger supercharger,Brembo brakes,different springs etc.Some cars have only 6 miles on them befroe being ripped out.He says they get a 240bhp upgrade!!!! The disc brakes are huge.I said why so big on a road car and his answer was because the get to 150 mph pretty quick.........Some conversions are 10k cost!!!
greenv8s said:
I guess they're all from cars that have had aftermarket go-faster versions fitted. Do seem very common, shame they'too small to do much good on a proper size engine unless you fit two or three ...
what's their limit then peter? .. and is there a downside to using two apart from space and weight?
Space and complexity. I've seen a V8 with a pair of M90s before the M112s were commonly available, but given the complexity, cost and relatively small difference in physical size between the different capacity blowers it's hard to justify using two blowers when its so much easier just to use one bigger one. A single M112 can flow roughly the equivalent of 8.5 liters normally aspirated, that should be enough for most applications!
GreenV8S said:
Space and complexity. I've seen a V8 with a pair of M90s before the M112s were commonly available, but given the complexity, cost and relatively small difference in physical size between the different capacity blowers it's hard to justify using two blowers when its so much easier just to use one bigger one. A single M112 can flow roughly the equivalent of 8.5 liters normally aspirated, that should be enough for most applications!
yup yup .. what's the limit of the cheaper m90 version? .. for a non - tvr application of 2.5 litres and approx 220 bhp .. would one of these ex mini cheapo units be up to that do you think? .. sounds to me like it's just the ticket for summink I might get involved in ..
Hmmm... supercharged Esprit...
The efficiency of the Eaton blowers drops off quite dramatically at higher pressure ratios, it isn’t worth going over about 1.5:1. As the pressure ratio rises the reduced efficiency means the blower takes more and more power off the crank and puts it into the charge as heat – a double whammy because this promotes detonation so you have to back off the ignition and lose even more power. If you go too far this can cost you more than you are gaining from the supercharger, you can actually end up with less power than the normally aspirated engine! You can combat the heat with a charge cooler or water injection but this is only a partial solution. However, if your base engine puts out 160 BHP or so in normally aspirated form, then 220 BHP doesn’t seem an unrealistic target running a pressure ratio of about 1.5:1.
An M45 could just about supply this but it would be outside its most efficient operating range, you would be better off going for one of the larger units with lower gearing. The M60 would be adequate but they’re very rare. If you can find space for it, I would suggest an M90. These aren’t as common as the M45s but they do come up from time to time, £300 should get you a good one. Not my money but IMO the cost of the blower is not an issue (compared to the other costs and work involved in the overall conversion) and certainly not important when deciding which size blower to use – you can get any of them for £300 if you shop around.
An M45 could just about supply this but it would be outside its most efficient operating range, you would be better off going for one of the larger units with lower gearing. The M60 would be adequate but they’re very rare. If you can find space for it, I would suggest an M90. These aren’t as common as the M45s but they do come up from time to time, £300 should get you a good one. Not my money but IMO the cost of the blower is not an issue (compared to the other costs and work involved in the overall conversion) and certainly not important when deciding which size blower to use – you can get any of them for £300 if you shop around.
cptsideways said:
Fuel injected onto the rotors improves efficiency at the higher pressure's by improving sealing and reducing friction, also helps reduce charge temps.
Little known outside of drag racing but definately very effective.
Eaton say that the bearing seals are not petrol friendly so unfortunately this isn't viable for a road car. OK for a dragster where you aren't too worried about durability. Upstream water injection works almost as well though.
kenmorton said:
The problem with the eaton/roots supercharger is its efficiency. Its the least efficient supercharger so it is limited to lower boost levels.
Its only advantage is that it is cheap to manufacture.
You sure it's a Rootes blower? These pics:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=61308&item=7903579758&rd=1&ssPageName=WD2V
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=33597&item=7903532931&rd=1&ssPageName=WD2V
seem to show part of the actual rotors, which look more like Lysholm screw rotors. These are pretty good on efficiency.
kenmorton said:
The problem with the eaton/roots supercharger is its efficiency. Its the least efficient supercharger so it is limited to lower boost levels.
Its only advantage is that it is cheap to manufacture.
Why do all the top fueld dragsters run rootes blowers then? Is it just that they're the only blowers made big enough, as I can't imagine it's a cost thing?
Just curious.
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