crank pulley, S/C pulley, boost, rpm
02-27-2002, 06:46 PM
#1
Burning Brakes
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crank pulley, S/C pulley, boost, rpm
i need to know what the crank pulley on a 944 n/a is...
next for my s/c pulleys a 7 and 5 psi, i have one that measures 2 3/32 and 2 3/8....my understanding is that the 7psi pulley would be the smaller one...right?
i called whipple and asked them if they had any pulleys that i can used for higher boost. i asked him about the autorotor sc i have and he said it can run 13000 RPM continuous....is it possible that i can run it at higher RPM for short stop light to stop light runs?
next, how can i get what boost is produces with what size pulley?
next, can i divided the sizes of the pulleys and muiltiply them by the rpm to get the rpm the SC is running?
thanks,
space
next for my s/c pulleys a 7 and 5 psi, i have one that measures 2 3/32 and 2 3/8....my understanding is that the 7psi pulley would be the smaller one...right?
i called whipple and asked them if they had any pulleys that i can used for higher boost. i asked him about the autorotor sc i have and he said it can run 13000 RPM continuous....is it possible that i can run it at higher RPM for short stop light to stop light runs?
next, how can i get what boost is produces with what size pulley?
next, can i divided the sizes of the pulleys and muiltiply them by the rpm to get the rpm the SC is running?
thanks,
space
02-27-2002, 07:14 PM
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i called magnuson prod. about the project that i'm doing(m90 eaton the same as huntley) and they said that it is roughly 2 times the size of the crank pulley but i think that's just a pat answer so when it comes down to the wire for my project i'll do some serious math to get what is needed
02-27-2002, 08:50 PM
#3
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[quote]Originally posted by ThE sPaCeCoWbOy:
i need to know what the crank pulley on a 944 n/a is...<hr></blockquote>Can't you just measure it
[quote]next for my s/c pulleys a 7 and 5 psi, i have one that measures 2 3/32 and 2 3/8....my understanding is that the 7psi pulley would be the smaller one...right?<hr></blockquote>Correct-a-mundo
[quote]i called whipple and asked them if they had any pulleys that i can used for higher boost. i asked him about the autorotor sc i have and he said it can run 13000 RPM continuous....is it possible that i can run it at higher RPM for short stop light to stop light runs?<hr></blockquote>Depends on how long you want your engine to last
There's a direct relationship between supercharger rpm and boost pressure. Since this is a positive displacement unit, you just can't say you want to run at 13000 rpm... you might have too much boost. It all depends on your engine size and pressure ratio desired.
[quote]next, how can i get what boost is produces with what size pulley?<hr></blockquote>Actually, you do it backwords. Based on the pressure ratio you want, you try to get the correct supercharger rpm needed.
You need to get the full load performance characteristic supercharger map from Whipple. This is a "carpet plot" of pressure ratio versus volume flow, with lines for adiabatic efficiency, discharge temperature, input rpm, and power consumption.
You need to calculate your volume flow in m^3/min, taking into account the Ve of the engine and your operating pressure ratio desired. Plot that on the X-axis and draw a line across from the Y-axis at your operating pressure ratio. Where they intersect is the supercharger rpm required. You'll note that it's nearly impossible to figure out the exact rpm from the map, but you can get close.
In other words, some trial and error is probably required. Start conservatively so you don't blow the thing sky high.
[quote]next, can i divided the sizes of the pulleys and muiltiply them by the rpm to get the rpm the SC is running?<hr></blockquote>Yes.
i need to know what the crank pulley on a 944 n/a is...<hr></blockquote>Can't you just measure it
[quote]next for my s/c pulleys a 7 and 5 psi, i have one that measures 2 3/32 and 2 3/8....my understanding is that the 7psi pulley would be the smaller one...right?<hr></blockquote>Correct-a-mundo[quote]i called whipple and asked them if they had any pulleys that i can used for higher boost. i asked him about the autorotor sc i have and he said it can run 13000 RPM continuous....is it possible that i can run it at higher RPM for short stop light to stop light runs?<hr></blockquote>Depends on how long you want your engine to last
There's a direct relationship between supercharger rpm and boost pressure. Since this is a positive displacement unit, you just can't say you want to run at 13000 rpm... you might have too much boost. It all depends on your engine size and pressure ratio desired.[quote]next, how can i get what boost is produces with what size pulley?<hr></blockquote>Actually, you do it backwords. Based on the pressure ratio you want, you try to get the correct supercharger rpm needed.
You need to get the full load performance characteristic supercharger map from Whipple. This is a "carpet plot" of pressure ratio versus volume flow, with lines for adiabatic efficiency, discharge temperature, input rpm, and power consumption.
You need to calculate your volume flow in m^3/min, taking into account the Ve of the engine and your operating pressure ratio desired. Plot that on the X-axis and draw a line across from the Y-axis at your operating pressure ratio. Where they intersect is the supercharger rpm required. You'll note that it's nearly impossible to figure out the exact rpm from the map, but you can get close.
In other words, some trial and error is probably required. Start conservatively so you don't blow the thing sky high.
[quote]next, can i divided the sizes of the pulleys and muiltiply them by the rpm to get the rpm the SC is running?<hr></blockquote>Yes.
02-27-2002, 11:17 PM
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Burning Brakes
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well i cant really measure it because me, the car and the engine are all in different places....i guess i could of called the guy but i thought maybe someone on here would know right off hand and tell me....
i understand the relationship....at idle, im not going to get the full boost since the engine doesnt idle at 6800 rpm.....i was asking this question so if i hit the 6800 rpm and the s/c is turning 13000+ rpm for a short period of time what effects can i expect....yes i know it will degrade the life of the s/c but thats why they made rebuild kit ...as for the engine, im having turbo s pistons, rods, fuel injectors, fuel pump, regulator, widefire gasket, etc....all place in...so i dont think engine life will be much of a factor as s/c life....
is there a website that has this map?
thanks,
space
i understand the relationship....at idle, im not going to get the full boost since the engine doesnt idle at 6800 rpm.....i was asking this question so if i hit the 6800 rpm and the s/c is turning 13000+ rpm for a short period of time what effects can i expect....yes i know it will degrade the life of the s/c but thats why they made rebuild kit
...as for the engine, im having turbo s pistons, rods, fuel injectors, fuel pump, regulator, widefire gasket, etc....all place in...so i dont think engine life will be much of a factor as s/c life....is there a website that has this map?
thanks,
space
