B&M vs Procharger for 540??
10-20-2004, 04:23 PM
#11
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Re: B&M vs Procharger for 540??
Tom,them carb enclosure's ARE BEAUTIFUL!Roots blowers are definately eye candy,i'd rather not advertise that my boat rips though,Smitty
10-23-2004, 05:07 PM
#12
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Re: B&M vs Procharger for 540??
Not advertise?? Why, afraid of that pressure to back up the looks??? Tis better to have raced and lost, than to never have raced at all....
10-23-2004, 11:26 PM
#13
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Re: B&M vs Procharger for 540??
Hang time,your right,i would rather race someone and lose than not race anyone. I also would rather race another boat that run's close to mine than punks in a 65 mph boat that claim it goes 85(that used to be fun though but it gets boring),Smitty
10-24-2004, 11:43 AM
#16
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Re: B&M vs Procharger for 540??
"How much power are you looking for? With 540 ci, 700 reliable hp is obtainable without boost."
Sure, but doesn't that mean over 700" lift and new valvesprings every summer at the least??..... I can see where boosting gets you a longer life on your valve train components - motor thinks it's mild until you crack into that boost.
Sure, but doesn't that mean over 700" lift and new valvesprings every summer at the least??..... I can see where boosting gets you a longer life on your valve train components - motor thinks it's mild until you crack into that boost.
10-24-2004, 12:37 PM
#17
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Re: B&M vs Procharger for 540??
Build 650 HP with a naturally aspirated 540 using JimV's heads; valvetrain life is not an issue @ 5500 RPM. Add blower later for 1000 HP! 
Building a good base engine for supercharging later requires some thought about cam and compression. If you use a moderate hydraulic roller cam and keep compression below 9:1, you can add a centrifugal blower later with no changes to the base engine. If you wanted to add a Roots blower later that compression would be too high.
If you wanted to add a Whipple later, you might pick a cam with more duration to kill cylinder pressure a bit due to their potential for high boost at low RPM. Dustin once gave me the specs for a cam he recommended for use with the Whipplecharger on a 454. The duration was in the 250 range @ 0.050". At first that sounds like way too much, but apparently it works with the screw compressor and maybe with other positive displacement blowers since they make boost quickly. It lowers cylinder pressure and avoids detonation in the midrange, then helps the engine to breathe at higher RPM.
The approach with a centrifugal blower is completely opposite. You want the engine to make as much low RPM torque as possible on its own, but you don't need to worry about the cam running out of steam at high RPM because that's where the centrifugal blowers outperform everything else. Lower discharge air temperatures for the centrifugal and the use of intercoolers which are much larger than can fit under a Roots or Whipple keep you out of detonation longer, which ultimately means more power with a given compression ratio/cylinder pressure.
Building a good base engine for supercharging later requires some thought about cam and compression. If you use a moderate hydraulic roller cam and keep compression below 9:1, you can add a centrifugal blower later with no changes to the base engine. If you wanted to add a Roots blower later that compression would be too high.
If you wanted to add a Whipple later, you might pick a cam with more duration to kill cylinder pressure a bit due to their potential for high boost at low RPM. Dustin once gave me the specs for a cam he recommended for use with the Whipplecharger on a 454. The duration was in the 250 range @ 0.050". At first that sounds like way too much, but apparently it works with the screw compressor and maybe with other positive displacement blowers since they make boost quickly. It lowers cylinder pressure and avoids detonation in the midrange, then helps the engine to breathe at higher RPM.
The approach with a centrifugal blower is completely opposite. You want the engine to make as much low RPM torque as possible on its own, but you don't need to worry about the cam running out of steam at high RPM because that's where the centrifugal blowers outperform everything else. Lower discharge air temperatures for the centrifugal and the use of intercoolers which are much larger than can fit under a Roots or Whipple keep you out of detonation longer, which ultimately means more power with a given compression ratio/cylinder pressure.
10-24-2004, 01:09 PM
#18
Re: B&M vs Procharger for 540??
Originally Posted by Hang Time 27
"How much power are you looking for? With 540 ci, 700 reliable hp is obtainable without boost."
Sure, but doesn't that mean over 700" lift and new valvesprings every summer at the least??..... I can see where boosting gets you a longer life on your valve train components - motor thinks it's mild until you crack into that boost.
Sure, but doesn't that mean over 700" lift and new valvesprings every summer at the least??..... I can see where boosting gets you a longer life on your valve train components - motor thinks it's mild until you crack into that boost.
No way, .647 lift hydraulic roller cam. 300 hours + no valve train issues.
My new combination nets .706 lift H/roller, still testing for durability. No problems to date. I'm going faster now than when I had my blower at 850 hp. (avatar). I will admit the blower was faster accellerating but I havent blowed up the drive......yet.
Last edited by JimV; 10-24-2004 at 01:20 PM.
10-24-2004, 02:11 PM
#19
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Re: B&M vs Procharger for 540??
When it comes to blowers, bigger isn't always better. Every blower has an efficiency map plotted with air mass against boost pressure. On those plots are what are called efficiency islands, showing blower efficiency for various operating points. Also on the map are blower RPM curves. If you look at the efficiency maps, you'll see that putting an over-sized blower running at slow speed can end up running the blower in an area of reduced efficiency, resulting in higher drive horsepower to get the same amount of boost, and higher blower outlet temperatures. With a roots blower this is caused by leakage being too high as a percentage of actual flow. With a centrifugal blower, the aerodynamics are a bit more complicated, and can result in compressor surge.
Some manufacturers are reluctant to publish compressor maps, probably because their blowers are not particularly efficient. I would consider it a necessity for proper sizing, and you can often coax the maps out of them with some persistence. I would pass on anyone who refuses (but that's me - I like to know what I'm buying).
Michael
Some manufacturers are reluctant to publish compressor maps, probably because their blowers are not particularly efficient. I would consider it a necessity for proper sizing, and you can often coax the maps out of them with some persistence. I would pass on anyone who refuses (but that's me - I like to know what I'm buying).
Michael
