24 replies to this topic

[mini.cooper998]

Evening all,

Ive just been going through some old miniworlds and stumbled across a review of a car that had converted a metro turbo unit to a supercharger he had split the charger so that the exhaust side was belt driven from (and this is the bit i dont get) the flywheel, now what would i need to do to waterpump belt drive it
also what other considerations do i need to take into acount

what dump valve can i use
will it still be ok to use a metro turbo carb
will it still be ok to use a metro turbo fuel pump
also what rpm should the turbo spin at (so i can machine a right size pulley)

also what else have i missed.

surely its less prone to heating the air up less than a roots charger

what do people recon the pros and cons are

turbos are £100 notes on ebay

supercharger kits are £1000

any ideas greatly appreciated

[Sam Walters]

that was a massive truck turbo charger on there.

made quite a nice 14psi of boost iirc.

it wont be so much a dump valve but more of a bypass valve as its constantly driven.

id use all the metro inlet stuff.

the metro turbo fuel pump should be okay.

the turbo can spin to massive speeds i think they test them to 200 thousand rpm.

daft speeds!

[Monkeh]

surely it would be impossible to get the turbo spinning fast enough on the pulley end, as the pully would need to be tiiiiny

[miRon]

it would need to be pretty small but its not too hard to work out the speed with a little math...

[mini.cooper998]

cheers all

150,000 (to be conservative) / 7,000rpm (being a little optomistic i know) = a pulley ratio of 24.128 - 1 so the pulley needs to be 1/24th the size of the crank pulley in circumference.

that will be quite small but not too bad to machine

i can see why he used the flywheel 1/24th of that is still quite large i wonder if i could drive it with a starter cog of the ring wheel that would be quite near that ratio bit loud maybe

any other suggestions or points ive missed

cheers all

[norwegianminiman]

any idea what the diameter of the flywheel is?

[mini.cooper998]

ring gear will be about 20-24" but thats diameter not circumference, the gear would need to be 1/24th the circumference for the right rpm.

[mini.cooper998]

just found this on a dodge site (strange where you find the info you need in life)

140,000 to make 12psi on a Garret turbo... thats a quote from some site, not me.

so i wasnt far off at the 150,000 which means i need a 20/1 pulley for 140,000 bit easier wont be the size od a bolt head

does anyone know if you can get a bigger crank pulley to drive the belt faster

thnks

[spikyrob]

you could use a twin belt system, i.e your current fan belt drives a shaft with a reasonably sized pulley on so it doesn't slip, then using a shaft with bearings, get a toothed pulley gear on the other end, with another on the end of the turbo (look at dodgy paint drawing lol)

That way the pulley can be fairly small but by using a toothed belt you can almost guarantee it won't slip

Attached Files

•  pulleys.jpg   22.24K   32 downloads

Edited by spikyrob, 23 October 2008 - 03:53 PM.

[norwegianminiman]

think i would have a larger pully on the "intermediate shaft", on the turbo/charger side of it.

hopefully that made sence, kind of tired atm...

[mini.cooper998]

i like both of yours thinking use a pulley system to create the desired ration.

your right a toothed belt would be best could extend the crank pulley with a toothed belt drive of a large ratio run it up to a small pinion gear with a larger pulley on the outer up to the turbo/sc all parts for this are available from www.rswww.com we use them for most parts at work so can get them on contract.

what do people think i should use as a dump valve (the new cooper s uses a recirculation flap to return the air.

thanks

andy

ps just found a saab 95 turbo unit on fleebay for 9.99

bargain

[mini.cooper998]

i agree it would have to be a large pulley on the intermediate turbo side to create the speed from the rpm

[mini13]

hmmmm,

i would be concerned about side ;oadings on the turbo shaft, rotrex make an item similar to chat you want to achive, it has an eliptical stepup gear box on the "compressor"

another thing to take into account is how the boost will come in, at say 5000 engine rpm with an efficiently sized compressor you are probably going to need to turn the compressor at around 150k (25x engine speed) to make good boost. at 2000 rpm the compressor will be spining i the region of 50k, i would not be suprised if this did not give much boost at all.

if for example youse the ebay saab 95 turbo you should see boost from under 2000 rpm.

[spikyrob]

lol i was tired myself, had just finished work lol!

norwegianminiman is correct, small pulley on the crank driven end, throught the shaft, then another large toothed pulley to the turbo/sc pulley, you could do a 12-1 step down twice or othercombinations (i'm not doing the maths, its too late lol)

as for the side loading, personally i'd machine a support to ensure the shaft stays completely square, but then again i wouldn't even consider trying this conversion lol!

having said that, toothed belts can be run a LOT more loosely than the V type belts due to the complete difference in the way the drive is transferred. therefore probably negating the side loading effect.

you could also look into using a cam belt rather than A.N other toothed belt as they are designed to withstand high(er) forces and RPM(s)?


Rotrex also charge a small fortune for their SC/turbo hybrid, probably works out cheaper to buy a jonspeen kit or stick a proper turbo on using the mirage kits lol!


Rob

[mini.cooper998]

i have toyed with the cooper s roots type charger and may go down that root afetr all to get 150,000 rpm will mean the belt will be trully charging.

may have to go with my origional plan of a blow through cooper-s charger but chears for your help all