Direct drive SBC

Discussion in 'Chevy' started by Natty Bumpo, Oct 24, 2011.

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  1. Jul 24, 2014 #961

    Badwookie

    Badwookie

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    Greetings,

    This has been an interesting thread to peruse and develop ideas for my (seemingly distant) future kitplane endeavour.

    Anyway as a new member, is there much information readily available about turbo compounding an Auto V8?
    I ask as I came across the idea on Paul Lamar's site Turbo and I was wondering if it could be used to kill two birds with one stone - firstly upping the hp available at a given RPM, and secondly dependent on it's mounted position if it could help tame some TV and other harmonics?
    If you could reliably predict that the turbo and it's connecting gearbox would bear a large amount of these forces then you would have an easily removed, inspectable (is that even a word?:nervous:) and of the shelf replaceable component.

    At the moment this is an exercise in thinking out loud and I have no thoughts on implementation or nor knowledge of which actual components would fit the bill.

    Cheers.

    Tom
     
  2. Jul 24, 2014 #962

    rv6ejguy

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    Paul Lamar likes to dream about many things but actually builds very little in the flesh and makes his ideas work in real life.

    Safe to say that turbo compounding is a very complex thing to make work- far beyond the budgets and capabilities of most folks here. This would be an incredibly complex and expensive way to boost hp at low rpm when we can simply turbocharge the engine which is cheap, reliable and well proven in other DD aircraft applications. Wright, Allison and Scandia spent fortunes making TC work in real life.
     
  3. Jul 24, 2014 #963

    nerobro

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    PRT: Power Recovery Turbine ... Actual meaning? "Parts Recovery Turbine." With a PRT, nothing escapes the engine without other damage. :)
     
  4. Dec 12, 2014 #964

    popeto

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    Hi all,

    Been lurking here for a while and have been reading this and other threads about auto conversions. My question is, could you use a large displacement engine, (all aluminum. 632 cubic inch. approx. 800 HP for example) run it at 3000 RPM direct drive (and in my scenario with a drive shaft), and still end up with approx 400 HP? I have been keeping an eye out on the race car sites for used aluminum motors and there are some deals to be made. And yes it would have to have the right parts, not wore out and changed over to F.I. but it could be done. Nothings is cheap for sure. What's the consensus?
    Thanks!
     
  5. Dec 12, 2014 #965

    stol

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    With that many cubic inches, you will have no problem getting 400 hp @3000rpm..
     
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  6. Dec 12, 2014 #966

    Himat

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    Consensus?
    One thing for sure, on auto conversions there are no consensus.:gig:

    The question of power is easier. If you can find the torque curve as a function of rpm the power at 3000 rpm can be calculated.
    Actually, if you find the power at 3000 rpm for another engine of 630 cid capacity that is the first approximation of what you get.

    Edit; STOL posted as I was writing.
     
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  7. Dec 12, 2014 #967

    BBerson

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    It would depend on fuel type and boost. Without boost, most private airplane engines at 2700 rpm, develop 1/2hp per cubic inch.
     
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  8. Dec 12, 2014 #968

    popeto

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    Thanks guys! Good info to chew on. I was hoping to keep it simple but I think a turbo will be a good thing even though its another point of failure. It will help on both ends. I'm thinking about 5 to 8 lbs boost is all it would need and it would live a little better in the long run.
    Thanks
    Tom
     
  9. Dec 13, 2014 #969

    cheapracer

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    Nah, gave that up when I was a teenager.


    Flip through EPI's site ... EPI, Inc. Home Page
     
  10. Dec 13, 2014 #970

    popeto

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    Thanks Cheap, interesting read and good basic info.
    Thanks
    Tom
     
  11. Dec 13, 2014 #971

    Toobuilder

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    400 HP, 638ci at 3000 RPM = a BMEP of 165. This is right in line with a typical Lycoming. I'd say there would be no need to turbo the engine for such a modest output.

    OTOH, 400 HP requires a big prop. It's going to be tough to keep the diameter small enough to keep the tips subsonic at 3000 rpm.
     
  12. Dec 13, 2014 #972

    popeto

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    Thanks Toobuilder, I'm still learning so would I be correct that all of the higher HP planes have to go to a less efficient 3 or 4 blade prop to make the combination work?
    Thanks
    Tom
     
  13. Dec 16, 2014 #973

    MARCVINI

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    Hi, popeto!!!

    What airframe do you have in mind to instal on such an engine?

    Marcvini

    PS: Altough belonging to a BBC 572, this dyno chart from Smeding Performance can give you a clue of what you can expect from a 638 ci engine:
    Smedding 572.jpg
     
    Last edited: Dec 16, 2014
  14. Dec 16, 2014 #974

    popeto

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    Marcvini,
    Thanks for the graph. Every little bit of info helps. This combo, if I decide to go that way will be in a one off pusher aircraft.
    Thanks
    Tom
     
  15. Dec 16, 2014 #975

    MARCVINI

    MARCVINI

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    Speaking of pusher aircraft with v8 engines, this is a silly sketch of mine, one of a Velocity XL with an inverted BBC on the back:
    XLRG full rudder.jpg
     
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  16. Oct 8, 2015 #976

    MARCVINI

    MARCVINI

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    This is how a DD LSXV8 RV7 would seem like:

    Vans RV7 LSX for Homebuiltairplanes.jpg

    Notes:
    a. simple aluminum 4 inch prop extension;
    b. a conventional spider like intake manifold would be use, in order to allow a better streamlined lower cowling;
    c. only the lower cowling would have to be changed, in order to accomodate the intake and cylinder heads and covers;
    d. radiators would be placed inside the cowling, two of them, one on each side of the engine;

    Tailwinds.
     
  17. Aug 9, 2018 #977

    dsigned

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    Yes, but this is almost certainly unnecessary. Automotive engines run cams that are designed to make peak power at their rated RPM, and make it gradually for a nice linear powerband. A racing cam can be used, with much higher and longer lift profiles, but tends to make the engine FAR thirstier (obviously), and makes it much harder to tune the engine for a wide powerband. Some automakers partially got around this by having (in effect) two cam profiles: a "small" one for low RPM and a "big" one for high RPM. So you're not sucking gas if you stay out of the powerband, and the car runs fine. But when the VTEC kicks in (yo), the engine is using a lot more fuel. With modern EFI, swapping a cam and setting up the timing to produce a lot of power low in the powerband (e.g. below 5000 rpm) isn't "hard" (it is hard, just because doing fuel mapping is apparently a pain), it's just not a terribly common request. But AFAIK, this is exactly what EPI does.
     
  18. Aug 9, 2018 #978

    Doggzilla

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    Its also possible to put the radiator behind the engine to avoid making modifications to the power train, as they can cause vibration and bearing issues by changing the torque on the bearings.

    Also dont forget that radiators can be fit in sideways and fed from a duct sticking out the side and feeding the rad at a 90 degree angle like the cold air intakes for superchargers on muscle cars. They dont have to be inline with one another.

    In fact, it could even be attached horizontally to the belly of the crank case in that manner, fed with a chin intake like a Typhoon.
     
  19. Oct 30, 2019 #979

    Erik Snyman

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    Hello All
    Early morning idea:
    We have a problem with a DD V8 sitting upright in the cowl, as the prop thrust-line is too low. Right?
    How about this: NOTE-this is just an idea. No details have been worked out yet
    1. Remove intake.
    2. Mount a shaft in the valley, supported by pillow blocks on the ends, parallel to the crank shaft.
    3. Another bearing in the center of the shaft to counter the shaft bending.
    4. Decide which end of the engine you want to face the air stream.
    5. Fit a prop hub to one end of the shaft, a belt pulley to the other.
    6. Fit same size pulley (1:1 ratio) to the corresponding end of the engine. If you want reduction, vary the size of this pulley for the desired ratio.
    7. Get creative with the intake.
    8. Result: You can run either side of the engine to the front.
    You can have a reduction ratio if you so wish.
    The prop thrust line is now above the crank line, so there is more prop-to-ground clearance, and improved looks.
    You can have the drive belt on either side: rear or front.
    The engine is right-side-up, no oiling and cooling mods needed.
    9. As I said, just an idea. No details worked out yet.

    Erik in Oz.
     
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  20. Oct 31, 2019 #980

    pictsidhe

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    That will have all the difficulties of a redrive and lack it's primary benefit: lower revs.
    But it's basically what I'm doing with a Briggs V twin, with reduction. It suits my application and engine. It may not work as well for a V8.
     

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