How hard should you spin a Procharger?

Discussion in 'High Tech for Old Iron' started by sailbrd, Oct 10, 2014.

  1. sailbrd

    sailbrd Well-Known Member

    My D-1 on a 455 currently shows 5psi @5000 rpm. This gives my Skylark a pretty healthy pull but nothing like what John C gets with his f-1r Procharger. The D-1 does not move the air an F-1 does.

    Currently the blower is turning at 62% of maximum at 5000 rpm. If I go to a 3.25 inch driven pulley will be running 76% of max and should see 6 psi. With a 3 inch pulley will be at 83% of maximum and 6.7 psi.

    With the 3 inch pulley blower would be at 100% max at 6000 rpm and 8 psi. All the boost numbers are math based on what setup does currently.

    Procharger does not put out any maps for their blowers. I have heard that they are very conservative on rating their blowers and many have spun them much more than recommended. The question would be as you spin up to max will the efficiency be compromised to where it is not worth it? I am working on cold air intake system and do have an intercooler.
     
  2. jake csordas

    jake csordas Well-Known Member

    I think if you spin it near max or above you will start to have issues with the charger. There was some talk on the bullet about this and possibly that was contributing to the early failures of the prochargers. Although it is a street car and not running around at that rpm all the time. Also are you figuring it out correctly? I would think there would be more boost with that pulley change than just one pound especially at the charger rpm.
     
  3. sailbrd

    sailbrd Well-Known Member

    Good question on the boost. I am using simple proportions based on what I observed at 5000 rpm. So if directly proportional it should work. But if it is a curve then need more info.
     
  4. Skyhawk

    Skyhawk Well-Known Member

    john jr here. I was never able to calculate the correct boost using the formulas. Although the charger rpm formula i would assume is correct for my setup based on what others have. My boost level always seemed lower but i do know that there are variables being the intercooler, pipe diameters, and size of the engine.
     
  5. sailbrd

    sailbrd Well-Known Member

    I know the rpm's are correct. That is pretty simple math. I have never seen anything for boost so just trying to have some ideal of what size pulley I need to get. Will have to talk to Bobb again and see what his guesses are :laugh: His best guess is that I should get an F1.

    Are you comparing to other Buicks? The Mopars and Chevy's all seem to show a lot more boost with the same blower. I know a guy that has a 440 stroker and a D-1. Claims he gets 18 psi. Then again never saw the gauge.
     
  6. pmuller9

    pmuller9 Well-Known Member

    5 lbs of boost is known as gauge pressure or what a pressure gauge would read.

    The actual pressure is the absolute pressure that includes the atmospheric pressure of 14.7 psi at sea level.

    Absolute pressure = 14.7 + 5 = 19.7 psi.

    Going from 62% to 76% drive ratio should yield an absolute pressure of 24 psi or 24 - 14.7 = 9.3 psi gauge.

    That's assuming the change in compressor pressure ratio is linear with the change in drive rpm.
     
  7. 8ad-f85

    8ad-f85 Well-Known Member

    :gp:

    Don't confuse # on gauge with actual flow through engine, or power potential. A better flowing system, in and out, will show less psi on the gauge. Likewise, a tailpipe smashed closed might contribute to a REALLY high gauge #, despite the lack of output.

    To answer your Q...yes, if you spin the charger to the max, you may reduce efficiency and likely harm the unit. If you want to pull as hard, get the F-1. Or simply try it and find out how that works.
     
  8. sailbrd

    sailbrd Well-Known Member

    Did not think about absolute pressure. That is how MAP sensors are set up.

    As I said before the 455 seems to suck up a lot of air compared to other motors. John C makes a ton of power at 5psi.

    Ok, set up formula to use absolute pressure to predict psi guage reading. Put in 6000 rpm and calculate 8.9 psi. Don't think I get that. More like 6 psi (things get really busy at 6000 rpm.)
     
    Last edited: Oct 14, 2014
  9. sailbrd

    sailbrd Well-Known Member

    Screw the math and science. Just ordered a 3.25 pulley and we will see how it works. :idea2:
     
  10. pmuller9

    pmuller9 Well-Known Member

    That's also a good way to do it.

    What is the present diameters of both pulleys?
     
  11. sailbrd

    sailbrd Well-Known Member

    Going from 4 inch to 3.25 inch. Looking to bring more boost in at lower rpm's. I think I should see 6 to 6.5 psi @5000 rpm. Waiting for new belt and will be able to drive it a few days before the snow comes.
     
  12. pmuller9

    pmuller9 Well-Known Member

    You must be running a 7.25" lower drive pulley?

    If so I'm showing the supercharger impeller rpm changing from 40,000 to 50,000 rpm. Is that what you were calculating also?

    Paul
     
  13. sailbrd

    sailbrd Well-Known Member

    That's it give or take a few rpm's.
     
  14. pmuller9

    pmuller9 Well-Known Member

    If that's the case then the supercharger's compressor pressure ratio goes from 1.34 to 1.64 and the boost should be over 9 lbs at 5000 rpm.
    It will definitely get the boost in sooner

    This will be fun to see what the actual boost is once you get the new pulley on.

    Haven't seen it done yet but I have considered using the blow off valve to control the boost at a desired limit once it is reached.
    This way you can overdrive the supercharger for early boost and control the upper limit.

    Does your BOV have an adjustment screw for spring pressure?

    Paul
     
    Last edited: Oct 22, 2014
  15. Nitro71455

    Nitro71455 Procharged 455 boost baby

    Doug,

    I was getting 12psi at 4500ft above sealevel with my D1 on the 462. I found my PSI could swing 2psi depending on how close my tune was AFR wise, It was happiest at 10.7 to 11.0 to 1. Below that boost would drop. This was both pre and post inter-cooler.

    With that being said, if you're looking to upgrade your head unit, I know where you can get a screaming deal on a F1-C unit that's basically new ;-) .

    --Rich
     
  16. sailbrd

    sailbrd Well-Known Member

    Will see if the weather is good enough this week to rejet the carb and see how it runs. Never know in November.

    Running a bypass valve now. Will see what the boost is going to be. I have thought about a simple blow off valve. Maybe in conjunction with my bypass valve.
     
  17. Nitro71455

    Nitro71455 Procharged 455 boost baby

    I have an extra "Black" procharger bypass valve I'll make you a really good deal on. I ended up running 2 of them on my D1.
     
  18. sailbrd

    sailbrd Well-Known Member

    Interested. Also interested in how and why running 2.

    Wish I had the money for the F1. Actually I am not sure I could afford a free F-1. I know about that whole law of unintended consequences. :Dou:
     
  19. Nitro71455

    Nitro71455 Procharged 455 boost baby

    It was requested by Procharger to run two of them after I had a head unit issue. They felt it the pressure wasn't evacuating fast enough when I was getting out of the throttle at higher RPM's and it was creating back pressure issues.
     
  20. Michael Evans

    Michael Evans a new project

    Theory is correct, but you have to check the varibly of the blower.

    a d-1 might give you 1% rise for every 10% increase of perpeller speed increase

    where a F-1 might give you 5% rise for every 10% increase of perpeller speed.
     

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