set back blowers

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by NITROBANDIT1, Nov 17, 2009.

  1. badbird

    badbird New Member

    Joined:
    Jun 16, 2008
    Messages:
    373
    Likes Received:
    1
    if as mike says the air exits the blower at 45 degrees forward surly having the pie in the exacy middle isnt optimum by quiet some way, the pie would almost have to be at the back of the blower opening needing more set back like a fuel car, or more which isnt practicable in a door car,


    anyone have any pics of a shoe to make a stock location hh work??
     
    #21
  2. SoDak

    SoDak Active Member

    Joined:
    Dec 29, 2006
    Messages:
    1,492
    Likes Received:
    1
    On our Frt discharge LF's we used to have and these SSI's, the chunk of aluminum right in the front of the rotors has been machined to take the angled air coming out of the rotors and directing it more towards straight down.

    Is the shoe you guys are talking about down in the corner of the manifold where the front wall meets the plenum floor?
     
    #22
  3. Mike Canter

    Mike Canter Top Dragster

    Joined:
    Mar 10, 2004
    Messages:
    3,987
    Likes Received:
    53
    Since we are on the setback subject. If anyone is interested in making your supercharger blow some skirts up;). I happen to know where there are two brand new extended snouts for setting the blower back. Both of them are 11.25" snouts. The snout is billet and has bosses for the belt guard and lower snout support all part of the billet assembly, also has webbing at the base running lengthwise for strength. The snout are complete with snout drive and such. They fit all Kobelco blowers and most every other 12 bolt blower out there. They are brand new and only going for $900 each. Email me at mike.c@mindspring.com if interested. I do have a picture. Check the length of your snout now and subtract that from 11.25" and that is how much this snout will set that blower back. Tell your wife you want a snout for Christmas and see what happens (lol):D







    In case you run across someone wanting to go down the road of the converasation i just read.
    I made them on a custom order and made two more than i needed. would sell for 900 each complete assembly. send u a photo if your interested.
    Darren
     
    #23
  4. NITROBANDIT1

    NITROBANDIT1 LOST IN SPACE

    Joined:
    Apr 18, 2005
    Messages:
    634
    Likes Received:
    2
    set me back

    so, from what ive gathering here, sounds like a little setback doesnt do much as you would think, and to do it right and really set it back will cost a lot of money and would make the engine a little better with a more equal air distribution. but, the question of how much hp difference are we really talking here? is this another case of monkey see, monkey doo doo, or unless your really looking for a few more hp on a really sorted out combo, its not worth the expense? i understand the psi is a rear discharge blower, and doesnt need the setback, so why dont they make the discharge outlet at the rear of the roots case instead of the front? :confused:
     
    #24
  5. Mike Canter

    Mike Canter Top Dragster

    Joined:
    Mar 10, 2004
    Messages:
    3,987
    Likes Received:
    53
    A Rootes blower is like one of the sausage machines with two corkscrews. Because of the roatation and twist in the rotors the air is pulled to the back of the blower on the inlet side and pushed to the front on the bottom exit side. The longer the air is kept in the rotors the more boost you are going to get so that is why the pie opening way up forward but the longer you keep the air in the rotors the steeper the exit angle is. Because of the physics of the design it is impossible to exit the air in the back on a Rootes blower. You ask if it is worth it. Well what is a pound of boost worth? An average a pound of boost is about 150 hp. So if you can get 3 to 4 lbs of boost increase and bring up those low boost cylinders then the answer is yes it is worth it. If you never want to win then you are wasting your money.
     
    #25
  6. LeWhite

    LeWhite BB/Alt

    Joined:
    Jan 23, 2008
    Messages:
    167
    Likes Received:
    0
    So then Mike wouldn't it stand to reason that the blower should open with a backwards delta in the rear? That's where the rotor capture begans.
     
    #26
  7. Mike Canter

    Mike Canter Top Dragster

    Joined:
    Mar 10, 2004
    Messages:
    3,987
    Likes Received:
    53
    The more time the air stays in the rotors the better it is. Remember which way the rotors are turning. The air is going in and down the outside of the rotors and drawn to the back ontop then on the bottom it is pushed foward. The longer the air can be pushed the better it is so if you had the opening at the back in the bottom it wouldn't be very efficient. With the pie opening all the way up front allows the air to be pushed and compressed longer. I might add at this point that the purpose of the white stripes is to stop that compressed air from going back up through the middle of the two rotors as it is pushed forward.
     
    #27
  8. NITROBANDIT1

    NITROBANDIT1 LOST IN SPACE

    Joined:
    Apr 18, 2005
    Messages:
    634
    Likes Received:
    2
    screw comp

    so mike, what is the principals of air compression that a screw compressor uses, and why is it so much better than a roots, and why doesnt it need restripped as often as a roots blower? ive seen these things banged off the tops of motors many times, and they act like nothing ever happened. are they that overbuilt for their use on alch fc/dragsters?
     
    #28
  9. Mike Canter

    Mike Canter Top Dragster

    Joined:
    Mar 10, 2004
    Messages:
    3,987
    Likes Received:
    53
    You need to look inside the top of a screw blower to really see the difference in the rotors. The description of screw really describes in well. It looks like two large threaded screws mated together. Because of the rotor design it doesn't require contact stripes between the rotors as with a Rootes. This means no heat generated by friction and less power required to turn it. The screw only requires around 150 hp to spin it but the Rootes requires around 450 hp to spin it. The efficiency of the Rootes goes down as you spin it up because of the heat generated and the hp required to turn it so you have to lean it out going down the track. The screw is totally opposite and need just a little less fuel to start until the boost comes up then needs fuel to go down the track. More fuel means more horsepower. Keeping that air charge cool is the same as lowering the density altitude. As you increase the OD on a Rootes then the more horsepower required to drive and the hotter the air charge from friction into the motor. So on a Rootes there is a point at which nothing is gained by spinning it faster and that is not so on a screw blower.
     
    #29
  10. Policy Peddler

    Joined:
    Oct 12, 2005
    Messages:
    188
    Likes Received:
    0
    I I added photo's to the tag below, showing more of veney manifold and snout.

    BBC changing from a standard blower intake to a 4 barrel single plane manifold with the blower on top, netted 100hp. all the runner will use the same nozzle size.

    I have a 10" snout from Littlefield and then turned my top pulley around backwards.

    the Indy BBC manifold also improves the stagger a lot and the more you set back the blower the better you are!

    Hemi: look at a veney manifold they are very close to a 4 barrel manifold, that is the blower is set way back, with long runners to the front.

    [​IMG]

    obviously i did not know how to insert this image so here is the url!
    http://picasaweb.google.com/lh/sred...sRgCKvbkLqUzJHu4wE&invite=CMnuv_oJ&feat=email


    want a longer snout, use the one you have and make a spacer between it and the blower & a spacer between the coupler and the front blower gear.
    if you only want to go 2 inches put a spacer behind the blower pulley.

    all this said, all you guys who know me know I am not interested in going fast anyways, so maybe you want to reconsider what I am saying! :)
     
    #30
    Last edited: Nov 28, 2009
  11. cudacustoms

    cudacustoms New Member

    Joined:
    Jan 13, 2007
    Messages:
    87
    Likes Received:
    0
    set back

    Has anyone else ever tryed turning the manifold around backwards? We have did it on a blown weadge chrysler and it gave us 3 5/8 set back. We were haveing trouble getting heat in back clyinders and when we changed it helped.The snout was a LF 8". Has anyone ever tryed this on a hemi. We have now switched to a BAE fathead. The manifold for theBAE looks like you could do the same thing.
     
    #31
  12. Mike Canter

    Mike Canter Top Dragster

    Joined:
    Mar 10, 2004
    Messages:
    3,987
    Likes Received:
    53
    Normally manifolds are designed to help even out flow. Some of ridges on the floor and other things. I can't see how turning a manifold around backwards ould help unless it was a badly designed manifold to start with,
     
    #32
  13. M Tigges

    M Tigges TAFC

    Joined:
    Jun 11, 2003
    Messages:
    643
    Likes Received:
    0
    Anybody ever tried swaping the rotors left to right and put the opening in the rear of the case! We use to talk about it.
     
    #33
  14. SoDak

    SoDak Active Member

    Joined:
    Dec 29, 2006
    Messages:
    1,492
    Likes Received:
    1
    Our stuff is BBC and our Indy manifold is made assuming the blower outlet will be close to the front wall of the plenum, for this we were real happy with it. The hemi manifolds that I've seen for setback blowers do remind me of our Indy manifold if it were put on backawards. I do see this concept working if the blower is moved way back.
     
    #34
  15. SoDak

    SoDak Active Member

    Joined:
    Dec 29, 2006
    Messages:
    1,492
    Likes Received:
    1
    SSI is making some that is for reverse rotation engines (for use in the 4engine pulling classes), the inlet/outlet is in the rear of the blower.
     
    #35
  16. ta455

    ta455 Member

    Joined:
    Nov 26, 2003
    Messages:
    195
    Likes Received:
    2
  17. shawn davis

    shawn davis Member

    Joined:
    Feb 27, 2004
    Messages:
    658
    Likes Received:
    0
    I have seen a big chief dominator intake modded with a plate, and the opening centered over that. Worked really well on Harold Lairds pro mod, went low low 6's couple years ago
     
    #37
  18. craig moss

    craig moss Member

    Joined:
    Sep 29, 2006
    Messages:
    572
    Likes Received:
    5
    #38
  19. john348

    john348 Top Alcohol

    Joined:
    May 29, 2003
    Messages:
    1,347
    Likes Received:
    2
    we did one the year IHRA pulled the plug on us so we didnt finish getting to where we needed to be
    built the car just for this , firewall back and all
     
    #39
  20. WIZBANG

    WIZBANG Member

    Joined:
    Nov 8, 2004
    Messages:
    748
    Likes Received:
    1
    #40

Share This Page