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Can Anyone Tell Me Their Supercharger Crank Pulley Size


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#1 nobbycameron

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Posted 11 June 2009 - 07:21 PM

Hello, as in title, can you also please put down your engine size and boost pressure if known...

kind regards

#2 nobbycameron

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Posted 11 June 2009 - 07:32 PM

from my calculations i am getting a pulley rartio of 1:1, this seems a little slow, can anyone confirm this or if you are unable to give an exact measuement of crank pulley then just a rough comparison of the two pulleys would be good to see if im somwhere near. cheers

#3 Tomf

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Posted 11 June 2009 - 07:33 PM

Form my research all the crank pulleys that the manufacturers make are 108mm both for 998 and 1275...

#4 nobbycameron

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Posted 11 June 2009 - 07:56 PM

thanks tom, is that diameter i guess, and is that with the standard size sc pulley, cheers

#5 Tomf

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Posted 11 June 2009 - 07:59 PM

Yes thats the diameter, im prety sure the standard diameter of the pulley thats on the supercharger is 64mm

Im not sure the size of the pully on the binis...

#6 nobbycameron

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Posted 11 June 2009 - 08:37 PM

do you know whether those pulleys are for a certain boost pressure, surely if the same size pulley is used on a 998 to a 1275 then the 998 would be at a considerably higher boost?? cheers

#7 Wil_h

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Posted 12 June 2009 - 07:07 AM

Yes, if it is running the same speed on a 998 as on a 1275 in theory it is pumping enough aire for the same bhp on both engines, therefore the psi will be higher on the 998. assuming both engines have a max rpm of 7k, then the 1275 will run around 10psi (fine), but the 998 will be running nearer 17 (a bit high for an M45).

1:1 looks good for a 1275, should give maybe 130bhp at 10psi.

#8 nobbycameron

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Posted 12 June 2009 - 09:53 PM

Yes, if it is running the same speed on a 998 as on a 1275 in theory it is pumping enough aire for the same bhp on both engines, therefore the psi will be higher on the 998. assuming both engines have a max rpm of 7k, then the 1275 will run around 10psi (fine), but the 998 will be running nearer 17 (a bit high for an M45).

1:1 looks good for a 1275, should give maybe 130bhp at 10psi.

cheers wil, my calculations aslo show it to be 1:1,

the only thing i can think of which may be giving errors in the ratio is the value of 0.75 litres per rev, would this change with increasing pressure?, the m45 map from eaton shows a slightly decreasing flow with higher pressure, this may account for the fairly low sc speed we have calculated, i will have to look into it again when i have more time,

also in all the photos i have seen of the pulleys the crank pulley seems to be much larger than the sc one, much more than 1:1, as what tom has said earlier

what do you wreckon??




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