Relationship between pulley size and Boost
03-21-2009, 09:12 AM
#1
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Relationship between pulley size and Boost
This question seems to always come up. I wanted to post my measurements and information so people can refer to it and not ask in every pulley thread---"whats the differance between pulley X and Pulley Y"
Here you go....These are the delta numbers you need to use....
1mm=0.2psi
1psi=14rwhp
That's it. From measurements taken; that is the delta for boost. So the difference between a Kleeman 168mm pulley and a 182mm pulley is 14mm=42rwhp.
PLEASE NOTE=>HP is a result of boost,timing, AIt's....ALL of which are controlled by the ecu. So unless all the parameters in the engine are perfect the numbers stated above will not be real. For example, a car with a 168mm pulley in 40 degree weather will have MUCH more horsepower than a car with a 182mm pulley in 85degree weather. This is because the 182mm car will have much higher AIT's and the computer will pull timing and boost via the bypass valve.
But GENERALLY....the above numbers are true. Hope this helps.
Here you go....These are the delta numbers you need to use....
1mm=0.2psi
1psi=14rwhp
That's it. From measurements taken; that is the delta for boost. So the difference between a Kleeman 168mm pulley and a 182mm pulley is 14mm=42rwhp.
PLEASE NOTE=>HP is a result of boost,timing, AIt's....ALL of which are controlled by the ecu. So unless all the parameters in the engine are perfect the numbers stated above will not be real. For example, a car with a 168mm pulley in 40 degree weather will have MUCH more horsepower than a car with a 182mm pulley in 85degree weather. This is because the 182mm car will have much higher AIT's and the computer will pull timing and boost via the bypass valve.
But GENERALLY....the above numbers are true. Hope this helps.
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maw1124 (05-17-2019)
03-21-2009, 10:36 AM
#3
This question seems to always come up. I wanted to post my measurements and information so people can refer to it and not ask in every pulley thread---"whats the differance between pulley X and Pulley Y"
Here you go....These are the delta numbers you need to use....
1mm=0.2psi
1psi=14rwhp
That's it. From measurements taken; that is the delta for boost. So the difference between a Kleeman 168mm pulley and a 182mm pulley is 14mm=42rwhp.
Here you go....These are the delta numbers you need to use....
1mm=0.2psi
1psi=14rwhp
That's it. From measurements taken; that is the delta for boost. So the difference between a Kleeman 168mm pulley and a 182mm pulley is 14mm=42rwhp.
03-21-2009, 10:39 AM
#4
That's a really hard one, you have to add variables like Density Altitude, Quality of fuel, is the car going downhill or up hill (That's part of the load calc) Aero drag at the time of the torque request. How fast you got into the throttle. How much pre throttle body pressure drop you have.
03-21-2009, 11:18 AM
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Eurocharged Performance ML63 and TT lambo
This question seems to always come up. I wanted to post my measurements and information so people can refer to it and not ask in every pulley thread---"whats the differance between pulley X and Pulley Y"
Here you go....These are the delta numbers you need to use....
1mm=0.2psi
1psi=14rwhp
That's it. From measurements taken; that is the delta for boost. So the difference between a Kleeman 168mm pulley and a 182mm pulley is 14mm=42rwhp.
PLEASE NOTE=>HP is a result of boost,timing, AIt's....ALL of which are controlled by the ecu. So unless all the parameters in the engine are perfect the numbers stated above will not be real. For example, a car with a 168mm pulley in 40 degree weather will have MUCH more horsepower than a car with a 182mm pulley in 85degree weather. This is because the 182mm car will have much higher AIT's and the computer will pull timing and boost via the bypass valve.
But GENERALLY....the above numbers are true. Hope this helps.
Here you go....These are the delta numbers you need to use....
1mm=0.2psi
1psi=14rwhp
That's it. From measurements taken; that is the delta for boost. So the difference between a Kleeman 168mm pulley and a 182mm pulley is 14mm=42rwhp.
PLEASE NOTE=>HP is a result of boost,timing, AIt's....ALL of which are controlled by the ecu. So unless all the parameters in the engine are perfect the numbers stated above will not be real. For example, a car with a 168mm pulley in 40 degree weather will have MUCH more horsepower than a car with a 182mm pulley in 85degree weather. This is because the 182mm car will have much higher AIT's and the computer will pull timing and boost via the bypass valve.
But GENERALLY....the above numbers are true. Hope this helps.
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03-21-2009, 12:22 PM
#8
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Thread Starter
That's a really hard one, you have to add variables like Density Altitude, Quality of fuel, is the car going downhill or up hill (That's part of the load calc) Aero drag at the time of the torque request. How fast you got into the throttle. How much pre throttle body pressure drop you have.
I recall Finny was seeing high boost on his car with a tranny that had a sensor loose. He rebuilt the tranny to better than stock and replaced the sensor and saw a reduction in boost and HP. (whatever happened with that Finny??)
Anyhow....the point is....when the car is cool......with very good gas and an ecu that raised the torque limits of the TCU.......and no Intercooler issues....In other words on a dyno.......each 1mm increase in pulley size=0.2psi
stock==========154mm=10psi(number depends on gear and rpm)
Rentech/kleeman=168mm=12.8psi=+42rwhp
Various========172mm=13.6psi=+54rwhp
VRP===========175mm=14.2psi=+63rwhp
Various========178mm=14.8psi=+72rwhp
Evosport=======180mm=15.2psi=+78rwhp
Actual numbers can vary...but the delta(change) should be pretty accurate.
03-21-2009, 11:44 PM
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2006 E55
Thanks for taking the time to put the post together. Looks like a good sticky item. If we had compressor maps we could show the exit temps of the supercharger for the various pulley sizes.
03-21-2009, 11:59 PM
#10
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wow! great info!
thanks for sharing!
i guess it is worth it to go from 168 to 180mm (with custom tune and cooling upgrade of course)
if u do upgrade the cooling system and use a 180mm can the car consistently stay at its hp potential or will it get heat soak and cut power easily?
thanks for sharing!
i guess it is worth it to go from 168 to 180mm (with custom tune and cooling upgrade of course)
if u do upgrade the cooling system and use a 180mm can the car consistently stay at its hp potential or will it get heat soak and cut power easily?
Last edited by jikjak; 03-22-2009 at 12:10 AM.
03-22-2009, 12:20 AM
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2006 E55
Fair evaluation is research how many people are disapointed with the 180mm pulley. If you are willing to make the investment to do cooloing mods the 180mm seems like a no brainer.
03-22-2009, 12:54 AM
#12
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im definitely going to upgrade my cooling and unfortunately theres no autobahn here so i guess it will work for me if i got to 180mm.
what is the approximate time frame needed to cool down?
will i be able to do 2-3 1/4 mile runs consecutively?
what is the approximate time frame needed to cool down?
will i be able to do 2-3 1/4 mile runs consecutively?
03-22-2009, 05:02 AM
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03-22-2009, 05:54 AM
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C55,SL55,C63
I've had a few (alot) beers tonight. Can some one do some math for me? I have a 101.6 mm (4 inch) custom stacked pulley on my SC setup that puts out 5psi of boost. I need to get a new one made to get to 8spi. what size pulley would i need?
Note: I'm running a stacked crank pulley like you 55k folks, but my stacked crank pulley that runs the blower is smaller then your stock size (101.6mm)
Note: I'm running a stacked crank pulley like you 55k folks, but my stacked crank pulley that runs the blower is smaller then your stock size (101.6mm)
03-22-2009, 06:40 PM
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03-23-2009, 05:16 PM
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2004 E55 AMG
The question to ask is at what psi does the stock supercharger max out. also, who does the 180 affect reliability. it would suck to add the pully only to kill the supercharger a few months later.
03-23-2009, 07:17 PM
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2006 E55 (white); 2016 GL 550 (white)
03-23-2009, 07:22 PM
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E55 211
Hi,
what do you think about this .. :
Pulley P RPM1 CAT
154mm=10psi 0,69 9913 96°C
168mm=12.8psi=+42rwhp 0,88 10956 115°C
172mm=13.6psi=+54rwhp 0,93 11200 118°C
175mm=14.2psi=+63rwhp 0.98 11413 122°C
178mm=14.8psi=+72rwhp 1,02 11600 125°C
180mm=15.2psi=+78rwhp 1,05 11740 128°C
CAT befor IC
RPM1 = CompressorRPM at 6000 RPM engine ... ?
If the RPM1 is correct, the CAT is 10° higher at 180mm than 172 mm ?!
what do you think about this .. :
Pulley P RPM1 CAT
154mm=10psi 0,69 9913 96°C
168mm=12.8psi=+42rwhp 0,88 10956 115°C
172mm=13.6psi=+54rwhp 0,93 11200 118°C
175mm=14.2psi=+63rwhp 0.98 11413 122°C
178mm=14.8psi=+72rwhp 1,02 11600 125°C
180mm=15.2psi=+78rwhp 1,05 11740 128°C
CAT befor IC
RPM1 = CompressorRPM at 6000 RPM engine ... ?
If the RPM1 is correct, the CAT is 10° higher at 180mm than 172 mm ?!
03-23-2009, 07:44 PM
#20
MBWorld Fanatic!
Hi,
what do you think about this .. :
Pulley P RPM1 CAT
154mm=10psi 0,69 9913 96°C
168mm=12.8psi=+42rwhp 0,88 10956 115°C
172mm=13.6psi=+54rwhp 0,93 11200 118°C
175mm=14.2psi=+63rwhp 0.98 11413 122°C
178mm=14.8psi=+72rwhp 1,02 11600 125°C
180mm=15.2psi=+78rwhp 1,05 11740 128°C
CAT befor IC
RPM1 = CompressorRPM at 6000 RPM engine ... ?
If the RPM1 is correct, the CAT is 10° higher at 180mm than 172 mm ?!
what do you think about this .. :
Pulley P RPM1 CAT
154mm=10psi 0,69 9913 96°C
168mm=12.8psi=+42rwhp 0,88 10956 115°C
172mm=13.6psi=+54rwhp 0,93 11200 118°C
175mm=14.2psi=+63rwhp 0.98 11413 122°C
178mm=14.8psi=+72rwhp 1,02 11600 125°C
180mm=15.2psi=+78rwhp 1,05 11740 128°C
CAT befor IC
RPM1 = CompressorRPM at 6000 RPM engine ... ?
If the RPM1 is correct, the CAT is 10° higher at 180mm than 172 mm ?!
03-23-2009, 07:57 PM
#21
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E55 211
But if the gear oft the compessormap is the same like in the M113ML so it is ok...
I think 10°C over the 172 and 32°C over stock will be no problem....
the temperature in the map is witout IC.
03-23-2009, 09:08 PM
#22
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10-14-2011, 07:05 PM
#24
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I know this is an old thread, but with people going bigger all the time, the data is very relevant. I refer to these calculations often
One thing to take into consideration:
As engine airflow is optimized (Throttle Body / Intake) and Back Pressure is reduced (Headers / Race cats), the boost levels shown will drop.
It is also possible to make more horsepower with less boost due to the effect of the combustion cycle. If you add headers and exhaust, you might lose .5 psi of boost, but make more power (when properly tuned).
Theoretically, you could then up your boost (bigger pulley) to get back to the previous boost level and make more power than is shown in the examples. AITs will be primarily affected by compression of air, however I suspect some heat is also generated from the actual mechanics of the supercharger. Anything spinning at 14K is going to radiate some heat (I think)
One thing to take into consideration:
As engine airflow is optimized (Throttle Body / Intake) and Back Pressure is reduced (Headers / Race cats), the boost levels shown will drop.
It is also possible to make more horsepower with less boost due to the effect of the combustion cycle. If you add headers and exhaust, you might lose .5 psi of boost, but make more power (when properly tuned).
Theoretically, you could then up your boost (bigger pulley) to get back to the previous boost level and make more power than is shown in the examples. AITs will be primarily affected by compression of air, however I suspect some heat is also generated from the actual mechanics of the supercharger. Anything spinning at 14K is going to radiate some heat (I think)
