Pulley Size to Boost Calculator
10-14-2013, 07:18 PM
#1
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Pulley Size to Boost Calculator
I am aware that there are many factors that affect boost beyond SC rotation. Exhaust, heads, intake, atmospheric pressure, altitude.. air density, air temp...
But knowing where typical boost levels come in I was able to create what I believe is a pretty accurate guide.
If we just do this at sea level and exclude all other factors, the Supercharger should boost as outlined below. There is a step up which is derived from a complex algebraic calculation. I just did a liner step up given numbers I have had, and or seen as my reference points.
I did not create the original chart for Sc rotation, I just extrapolated it to indicate boost
If nothing else, this should at least give you an idea of what pulley combos do in relation from each other, and where to stop. Over 17.5, you are going to have issues (imho)
But knowing where typical boost levels come in I was able to create what I believe is a pretty accurate guide.
If we just do this at sea level and exclude all other factors, the Supercharger should boost as outlined below. There is a step up which is derived from a complex algebraic calculation. I just did a liner step up given numbers I have had, and or seen as my reference points.
I did not create the original chart for Sc rotation, I just extrapolated it to indicate boost
If nothing else, this should at least give you an idea of what pulley combos do in relation from each other, and where to stop. Over 17.5, you are going to have issues (imho)
10-14-2013, 08:03 PM
#6
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10-14-2013, 08:10 PM
#8
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10-14-2013, 08:11 PM
#9
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10-14-2013, 08:37 PM
#10
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So stock boost is the upper 11s almost 12. Imagine that. I tried to tell a few people here that last week and was told I was wrong.
10-14-2013, 09:25 PM
#12
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10-14-2013, 10:49 PM
#15
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Stock boost is 11.2 i.e with 154 (stock crank pulley) and stock upper (90mm i think ) s/c pulley
The smaller S/C pulley adds ~1-1.5 boost, now that is the one with clutch not the fixed one.
The smaller S/C pulley adds ~1-1.5 boost, now that is the one with clutch not the fixed one.
10-14-2013, 11:43 PM
#17
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10-15-2013, 01:52 AM
#19
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10-15-2013, 04:55 PM
#20
Super Member
So the table with your setup says should be boosting 16.9psi. Yet you only 14.7psi. So the table is not right as 2 psi difference is quite big. What altitude you taking your boost reading at?
10-17-2013, 02:41 PM
#21
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Now I thought that you needed to start getting a better fuel rail once you hit a 180 pulley. Is this true or not quite?
I was going to do a 175 stack w/the boost pulley, and that looks to be pushing down 15.6 pounds. Is that manageable with the stock fuel system, or am I pushing my luck?
Better yet, does anyone know what the boost limit of safety is on the stock fuel rail/injectors?
I was going to do a 175 stack w/the boost pulley, and that looks to be pushing down 15.6 pounds. Is that manageable with the stock fuel system, or am I pushing my luck?
Better yet, does anyone know what the boost limit of safety is on the stock fuel rail/injectors?
10-17-2013, 02:52 PM
#22
Super Member
Just get them for peace of mind, you can get injectors for about 350 or 400 off eBay....and add the adapters ev1-ev6 for another fifty. If the injectors go static or you're at the end of its cycle boom goes the motor.... Peace of mind four hundred bucks to save the motor.
10-17-2013, 09:58 PM
#23
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Just get them for peace of mind, you can get injectors for about 350 or 400 off eBay....and add the adapters ev1-ev6 for another fifty. If the injectors go static or you're at the end of its cycle boom goes the motor.... Peace of mind four hundred bucks to save the motor.
What have people run without any problems as is?
10-17-2013, 10:12 PM
#24
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Just get them for peace of mind, you can get injectors for about 350 or 400 off eBay....and add the adapters ev1-ev6 for another fifty. If the injectors go static or you're at the end of its cycle boom goes the motor.... Peace of mind four hundred bucks to save the motor.
The stock fuel rail starves some cylinders more than others (#8) to be precise. So even if the duty cycle overall is 80%, cylinder 8 may be going lean, and that puts a big hole in the top of the piston. Many people have run a 180 without a rail/injector combo, but it is pushing it in my opinion/
10-17-2013, 10:47 PM
#25
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If I remember correctly, people were seeing 80/90% FI duty cycle around 14.8 PSI. So that would put static around 15.5, and I think that is where we saw some motors go. I am not a EFI engineer, so all of what I am sharing is hearsay:
The stock fuel rail starves some cylinders more than others (#8) to be precise. So even if the duty cycle overall is 80%, cylinder 8 may be going lean, and that puts a big hole in the top of the piston. Many people have run a 180 without a rail/injector combo, but it is pushing it in my opinion/
The stock fuel rail starves some cylinders more than others (#8) to be precise. So even if the duty cycle overall is 80%, cylinder 8 may be going lean, and that puts a big hole in the top of the piston. Many people have run a 180 without a rail/injector combo, but it is pushing it in my opinion/
Sounds like a 168 combo might be a better choice then...
