PSI Screw Hat Fuel ??

Discussion in 'PSI Superchargers Tech Questions' started by TOL, Sep 21, 2013.

  1. TOL

    TOL Active Member

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    For a C or D screw on methanol is the job of the hat fuel (above the rotors) primarily for cooling and sealing, or lubrication of the rotors, or all the above ???......

    If it is important as a lubricant then are there any special areas to ensure are well "lubed" and targeted? Why I ask is because I plan to go down a different road than just the 4 current nozzle holes in my "C" case. Exactly what road I will take I'm in the process of figuring out, hence my question.

    I keep hearing stories of guys at high overdrives accidentally leaning out the hat fuel, and hurting the rotors, but I am unsure as to exactly why or how or where this happens. If someone could explain this better, I would appreciate it.

    Thanks.
     
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    Last edited: Sep 21, 2013
  2. Mike Canter

    Mike Canter Top Dragster
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    It is only for cooling because there are no stripes so nothing rubs
     
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  3. tcarr

    tcarr Member

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    typicaly doesnt the engine idle on the hat nozzels as the ports are on a canister? generaly speaking of course
     
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  4. rb0804

    rb0804 Active Member

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    Depends on who or how your fuel system was setup. If you go by the psi manual, they have dribblers which are open at idle to help even things out. Some cars run them some don't. Some cars run two sets of 'run' nozzles instead of one set of runs and one set of dribblers. All in how your setup and what you are trying to accomplish. Fuel through the hat helps cool the intake charge also.
     
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  5. TOL

    TOL Active Member

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    That's what I always thought, but then what's causing the rotor damage then when the hat is leaned out too much? The rotors get hot and swell and touch ??....
     
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  6. Mike Canter

    Mike Canter Top Dragster
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    I have never seen that happen. Maybe because all the screw blowers that I am associated with have the correct fuel tuneup. The only damage I have ever seen is from banging the blower because the motor went lean. There were problems with the rotors in the first PSI blowers when they first came out but they were changed. One thing is you never run a screw blower lean because the efficiency curve is completely opposite from a Roots blower and the screw blower requires fuel down track to make power. Don't think I know anyone that makes big power that uses 16 port nozzles anymore. That is pretty well a thing of the past
     
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    Last edited: Sep 22, 2013
  7. kosky racing

    kosky racing Comp Eliminator

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    nozzles

    Mike what does the # of nozzles have to do with power? I believe all the fastest alky dragsters run 16 ports-Whitely-Demke -severance -myself- Thaker-Booher-and the list goes on. Rotors do delamenate from several reasons one bearings going bad timing pins wearing with the hi overdrives more fuel is needed in the hat than before .I have run a screw longer than anyone racing .What I am stating comes from a lot of racing blown cars.
     
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  8. overkill69

    overkill69 Member

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    lean

    In the auto promod world the fuel distribution from the screw has problems so guys tend to run the hat lean to minimize it. Plus they like to be lean in general.
    Rotors have been burned up im sure.
    I always check the rear burst panel area and make sure it's not hot.
    I think the 16 nozzle setup is extinct for cars that launch WOT but I can see advantages on a clutch car without 2 step.
     
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  9. TOL

    TOL Active Member

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    I've noticed that some guys seem to add another two nozzles pointed toward the rear of the hat opening (for a total of 4 nozzles under the hat), and I also saw one guy that had three nozzles back there. Is there a particular reason to get more fuel back there?

    Wondering if a person can spread the hat fuel all around the blower opening better, and decently atomize it at the same time, then maybe the distribution out of the screw might be better/cooler overall?
     
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    Last edited: Sep 22, 2013
  10. Mike Canter

    Mike Canter Top Dragster
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    16 port nozzle systems are almost non existant for two step cars also. I think when you are talking about being lean in the top of the screw blower then you should define how lean so we can all talk apples and apples.
     
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    Last edited: Jan 12, 2014
  11. TOL

    TOL Active Member

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    Deleted post because I can't figure out how to inserrt a picture. Will revisit this after I figure that out. Can someone PM me the condensed version of how to insert a picture these days at ITA? Thanks.
     
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    Last edited: Jan 12, 2014
  12. Mike Canter

    Mike Canter Top Dragster
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    You can't post pictures on this website unless you have paid for that level of membership. Same goes for having an avatar.
     
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  13. Torment

    Torment Member

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    Cooling the rotors, sealing the rotors and cooling the intake charge.

    Being a true compressor period of high vacuum create a great deal of heat. Create enough heat and the small rotor clearances are no longer enough.
     
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  14. TOL

    TOL Active Member

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    So is it preferable to try to spray the fuel right onto the rotors evenly front to back , or, is it better to try to get the fuel well mixed/misted with the air coming into the hat first and then let that mix mesh with the rotors?

    Just wondering whether finely misted fuel delivered say up near the throttle blades might give the air/fuel time to mix and whether that might improve things at the outlet of the compressor? Although liquid fuel directly on the rotors would be best for cooling the rotors. If I get the picture thing sorted out I'll post a pic that I found of a guy running something sort of like what is described above in that he's got 9 or 10 nozzles mounted on a deepthroat injector.
     
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  15. Torment

    Torment Member

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    I'd think with a forward facing injector you have an S pattern to the manifold going for the air already - and the fuel might have a harder time yet with that. Really don't know though... I'd spray it at the rotors. It's going to get compressed by the IC of the rotors prior to hitting the manifold.
     
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  16. Mike Canter

    Mike Canter Top Dragster
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    The only reason you are spraying fuel into the top of a screw blower is to cool the air charge. The screws are not heated by friction.
     
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  17. Dale H.

    Dale H. Member

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    Believe me, I learned the hard way that when there isn't fuel on top, the rotors heat up enough to start rubbing the case! The heat is from compression not friction. A PSI benefits from having alot of fuel going in the hat to help seal the rotors.

    Dale
     
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  18. TOL

    TOL Active Member

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    Do you make any attempt to mix the air/fuel above the rotors, or do you just wet down the rotors with liquid fuel and hope that the heat of compression flashes it off?
     
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  19. rb0804

    rb0804 Active Member

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    Walter your PM's are full, I sent you an email instead
     
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  20. Dale H.

    Dale H. Member

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    I have 4 nozzles on top (about 80 thou each) with the front 2 having, I believe 30 # checks-so that there isn't too much fuel at idle.
    You would think that the back cylinders would have alot smaller port nozzles than the fronts having all that fuel coming through the rear of the blower,but there isn't. The rotors spinning and the heat from air working must evaporate the majority of the fuel.

    Dale
     
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