Turbo

Discussion in 'Motorcycle Technical Discussion' started by Brother-Peter, Oct 28, 2005.

  1. Is there any way of making a turbo to work on low rpm?
     
    Brother-Peter, Oct 28, 2005
    #1
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  2. Not unless the engine turning it is a diesel, no, not really.

    You need a certain amount of exhaust gases to spin a turbo properly.
     
    The Older Gentleman, Oct 28, 2005
    #2
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  3. Thanks
    1)
    what would be a minimum rpm if we take an example of
    the Suzuki Bandit which is often used as a basis
    AND
    2)
    What about mechanical chargers, belt driven?
    Has anyone ever used it on a motorcycle
     
    Brother-Peter, Oct 28, 2005
    #3
  4. God knows. What size of Bandit? 400, 600, 1200? You'd need to know the
    size of the turbo, the voume of gas flowing, and a myriad other things.
    You mean a supercharger. Yes, superchargers have been very successfully
    used on motorcycles, although (AFAIK) no manufacturer has ever made a
    production road version. I think DKW or someone did a supercharged
    two-stroke racer in the mid-to-late 1930s.
     
    The Older Gentleman, Oct 28, 2005
    #4
  5. 1200 and the smallest possible turbo
    but as I guess from the above answer, your mileage varies...
    eg. it depends on so many other things, too
    Be all free to give any possible info
    Hmmm...it might be interesting
    but I have been told by the commercial turbo-builders in Finland
    that a supercharger would be much more expensive

    Feel free to give more info on the subject
     
    Brother-Peter, Oct 28, 2005
    #5

  6. Well, in theory a turbo is simpler as it needs no mechanical drive from
    the engine. However, a supercharger delivers extra power more or less
    everywhere, whereas a turbo generally only starts working once the
    exhaust gases have spun the turbine up to a certain speed.

    There are plenty of turbo kits around, whereas supercharger kits are
    *very* rare, so I guess what you've been told is true.
     
    The Older Gentleman, Oct 28, 2005
    #6
  7. Haa!
    There is a delay in the turbo (unless it's quite small)
    :-(
    Then I think it might be better to rise the compression ratio
    (and use Euro 98E eg. "super" gasoline)
    This time I'm thinking of the Suzuki GSX-1400

    What if the timing is slightly advanced?
    I still want a have a little bit More torque (and perhaps power)
    on close to the idling rpm
    OR
    should I consider the new Kawa,
    which has 10kpm or 98Nm of torque at 2000 rpm
    and can go on from a stop "on almost any gear"
    according to the marketing text
     
    Brother-Peter, Oct 28, 2005
    #7
  8. Brother-Peter

    Dave Brown Guest

    1200 and the smallest possible turbo


    Dale Walker is reputedly the expert on Bandit performance. Check out
    www.holeshot.com.

    Good luck.
     
    Dave Brown, Oct 28, 2005
    #8
  9. The GSX1400 is in a very 'soft' state of tune, and there are many kits
    out there to increase the power.

    I'd start with a fuel injection re-chip, and a different exhaust.
     
    The Older Gentleman, Oct 28, 2005
    #9
  10. Brother-Peter

    skimmer Guest

    Select a turbo with a smaller internal volume in the scroll case. IOW
    the impeller is closer to the case, so the impeller doesn't have to
    compress the air as much before pushing it on to the intake tract.

    The air has to move on into the engine sooner.

    Also, shorten the intake tract as much as possible, by mounting the
    turbo on a manifold where the carbs would usually go, even though this
    means a long ugly exhaust middle pipe snaking up there.

    A tuned header is defeated by the turbo anyway.

    I used to have a great book on turbocharging and nitrous oxide
    injection by a guy named Innes, as I recall. I may still have it packed
    away. It was one of the series of hotrodding paperbacks by HP Books.

    Innes talked about "efficiency islands" and showed graphs of how turbos
    with smaller clearance volumes in the cases "spooled up" quicker than
    turbos with larger volumes in the impeler cases.
     
    skimmer, Oct 28, 2005
    #10
  11. Brother-Peter

    skimmer Guest

    Select a turbo with a smaller internal volume in the scroll case. IOW
    the impeller is closer to the case, so the impeller doesn't have to
    compress the air as much before pushing it on to the intake tract.

    The air has to move on into the engine sooner.

    Also, shorten the intake tract as much as possible, by mounting the
    turbo on a manifold where the carbs would usually go, even though this
    means a long ugly exhaust middle pipe snaking up there.

    A tuned header is defeated by the turbo anyway.

    I used to have a great book on turbocharging and nitrous oxide
    injection by a guy named Innes, as I recall. I may still have it packed
    away. It was one of the series of hotrodding paperbacks by HP Books.

    Innes talked about "efficiency islands" and showed graphs of how turbos
    with smaller clearance volumes in the cases "spooled up" quicker than
    turbos with larger volumes in the impeler cases.
     
    skimmer, Oct 28, 2005
    #11
  12. a low rpm turbo? I suppose you could make one but I am afraid that the size
    would be rather large. If you want something to move air at low rpm you need
    to make it really big.

    pierce
     
    R. Pierce Butler, Oct 29, 2005
    #12
  13. Brother-Peter

    John Johnson Guest

    My impression is the guy wants more "grunt" at low _engine_ rpm. The
    previous suggestion of a smaller-vaned turbo combined with a greater
    restriction in the exhaust pipe would do it: less volume in the vanes
    means lower volume of exhaust gas necessary to spin it up to speed. More
    restriction means higher pressure differential between the high- and
    low-pressure sides of the turbo, and it's the pressure differential
    that's doing the work.

    However, it's not going to provide as much boost as a larger turbo.
    Two-stage turbochargers get around this problem by having both a small
    turbo (for quicker response right off idle) and a larger turbo (for high
    volumes of air at WOT). That's probably more than the OP wants to mess
    with, though.

    This is, of course, where the supercharger is superior: it provides
    boost from idle upwards, without lag. As the OP has found, they are
    somewhat more expensive than turbochargers for these applications.
    There's also other means of increasing torque at low engine rpm, without
    moving to forced induction (e.g. higher compression pistons and/or
    head), but gains are more modest.

    --
    Later,
    John



    'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.
     
    John Johnson, Oct 29, 2005
    #13
  14. EXACTLY, John-John! <top-posting>

    No, no 2-turbo, the small one is all I need,
    I don't want much more horsepower at the high end
    There is a spacer or some kind of seal between the upper part of the
    cylinder block
    and the lower part where most of the engine is
    Using 1mm thinner seal would give more compression out of the GSX-1400
    This can be reversed and it's cheaper than new parts
    <bottom-posting>
    to please you all ;-)
     
    Brother-Peter, Oct 29, 2005
    #14
  15. Brother-Peter

    skimmer Guest

    Day-ummm! You done *exposed* yerrself in public! You just made a idjit
    outta yerrself in front of the whole forum, Brother-Peter! "There is a
    spacer or some kind of seal..." ;-)

    Well, maybe Nomen Nescio wouldn't understand that you're calling the
    *head gasket* a "spacer or some kind of seal". ;-)

    But, no matter. We all have to learn some way.

    The basic procedures of hotrodding are to increase engine displacement
    (if the rules allow), supercharge or turbocharge (if allowed), use
    oxygen-bearing fuels, or if the engine builder is stuck with engine
    size limits, he improves upon the cams, carburetors, and compression
    ratio, in order to make the engine operate at a higher RPM and gain the
    extra horsepower that way.

    Cams. Carburetors. Compression. They *all* work together.

    With higher compression, you can use a camshaft with longer duration.
    Many newbies forget that the opposite is true. With a wilder camshaft,
    you NEED higher compression to maintain low RPM torque at a level that
    will get the car off the line without using a lot of RPM, which would
    make the car hard to drive on the street.

    And then there is camshaft degreeing. Have you ever degreed a camshaft?
    You can get the engine to "dig" better if you advance the intake valve
    closing point in terms of "lobe center" degrees, or you can make the
    engine produce more top end power by retarding the intake valve closing
    point.

    You can simulate a camshaft of a different duration by degreeing it. I
    didn't understand why hotrodders were dicking around with dial
    indicators and degree wheels after building their engines. For years I
    thought that the cam timing marks were good enough to "get 'er done".
    Then a hotrodder convinced me to degree the cams on my GS-1100,
    advancing the timing about 2.5 degrees on both intake and exhaust cams.

    Oh. My. Gawd. It works. The engine digs so much better. I get into 5th
    gear by 60 mph, short shifting. The motorbike is much more fun to ride
    in the lower RPM ranges, I don't need to ride at 120 mph to feel the
    torque. And it still revs up to 9K, which was the stock redline anyway.

    Would-be hotrodders always got the impression that there was some
    magical increase in power to be gained from "milling the head" and
    doing nothing else.

    And others figured that there was some horsepower advantage from the
    thinner stamped metal head gaskets with formed ridges instead of a
    metal/asbestos sandwich. They figured that the engineers in Detroit
    were just hotrodders at heart, which wasn't untrue.

    Back when gasoline was very low octane, 4:1 or 5:1 compression was all
    that could be used. When reformed and leaded gasoline became available
    it was possible to use 7:1 or 8:1 compression and improve the
    efficiency of the engine. If you can raise the compression ratio from
    5:1 to 10:1 and burn the mixture at a higher temperature, you get
    almost 13% increase in air standard efficiency.

    But, when compression ratios were raised in the late 1940's (a trend
    that continued in high performace cars in the USA until some cars has
    12:1 compression)the old fashioned head gaskets *leaked*, so thinner
    ridged gaskets were installed to make a better compression seal.

    Thinner gaskets were part of the improvements necessary to use higher
    compression ratios.

    And, while higher compression ratios will increase low end torque and
    make the engine "dig out" better from a dead stop, the engine will
    reach its top RPM and stop revving.

    It's a simple fact that if you increase the operating RPM by 50%,
    you'll get 50% more power out of the engine. Yamaha has been a world
    leader in advanced engine technology for years. When Toyota wanted an
    advanced engine for a sports car they never actually produced, they
    went to Yamaha for engineering expertise.

    Yamaha discovered that they had two choices with the selection of
    compression ratio in their 1980's cutting-edge technology 20-valve
    Genesis motor. Yamaha's selection of 12:1 compression ratio initially
    put me off on that design. I didn't realize that with all those valves
    they had a lot of valve area at very low lift and they *needed* the
    higher compression ratio. And the Genesis motor runs on regular
    gasoline with 12:1...

    Yamaha tested the genesis concept with 5, 7, and 9 valves per cylinder,
    using single cylinder test engines to study the concept. They settled
    on 5 valve per cylinder, 3 intakes, 2 exhausts.

    Yamaha found they could run higher compression and have an engine that
    accelerated well but wouldn't rev freely at the top end, or they could
    use a slower-accelerating, lower compression ratio and enjoy the
    benefit of more power at higher RPM *and* have an engine which could be
    over-revved in a lower gear without the rider needing to shift gears.

    That's why motorbikes like the Yamaha YZF-R6 have such stratospheric
    redlines. The latest version has a 17.5K redline so the rider can use
    2nd gear for most corners. What compression ratio does it have? I
    dunno, and could care less. The R6 has just enough compression ratio to
    avoid problems with *too much compression*!!!!!

    The high RPM doesn't matter because the stroke is so short the engine
    doesn't experience high piston speed and the rings are so thin (around
    0.025") they have very little mass and are almost immune from ring
    flutter as they experience plus and minus 4000 g's at the ends of the
    stroke.

    Back to your thinner head gasket notion. The deck height and connecting
    rod stretch is critical on modern Suzuki engines. There is only about
    0.010 squish clearance between the piston at TDC and the cylinder head.

    Early SRAD GSXR's had problems with the pistons hitting the cylinder
    head.

    Suppose you did find a way to increase cranking compression and get a
    big motor with a lot of "dig". What's it going to do to the rod
    bearings, when you apply a lot of pressure on top of the pistons at low
    RPM when the oil pump isn't making a lot of pressure?

    Did you ever drive a car in the wrong gear and "lug" the engine?
    Lugging is not the same as "bogging". The latter is when you operate
    the engine at too low an RPM for the carburetion to work correctly.
    Lugging is when you run the engine so slow the oil pump doesn't produce
    enough pressure to float the crankshaft off the bearings. You hear a
    buzzing sound and a vibration throughout the car.

    Motorcycle oil pumps are intended to produce oil pressure at high RPM
    and to get the oil up to the camshafts. Some drag racers would actually
    install restrictors in the main oil gallery to redirect oil to the
    camshafts, while risking oil starvation to the main bearings. My
    GS-1100 has different oil pump drive gears to spin the oil pump faster
    and produce oil pressure earlier.

    If you're going to try to get more "dig", you need to think about what
    you need to do with the oil pump. Will the turbo be running off of
    engine oil pressure, at the expense of the camshafts and bearings?

    You really need to think out what you're doing and why you're doing it
    and understand the misconceptions of ignorant shade tree tuners before
    you commit you time and money to a modification project. You could
    avoid winding up with a pile of crap in your garage that resulted from
    an ill-conceived modification project.
     
    skimmer, Oct 29, 2005
    #15
  16. X
    "Hmmm...it might be interesting
    but I have been told by the commercial turbo-builders in Finland
    that a supercharger would be much more expensive"

    As you can see from my earlier post I live in Finland
    My dictionary book is not in close reach
    I'm not native English speaker,
    so my technical vocubilarity is limited
    that doesn't make me an idiot,
    neither does your post with spelling errors make you an idiot
    B-P
    PS: thank you for understanding
    what I explained with my limited English skills
     
    Brother-Peter, Oct 29, 2005
    #16
  17. Brother-Peter

    skimmer Guest

    I don't think you are really an "idiot". That was just a joke. And my
    "spelling errors" weren't errors, they were an attempt to emulate the
    regional dialect of the southern United States, where a lot of shade
    tree mechanics build some very fast cars to race on dirt oval tracks.

    But you won't gain any significant power by fitting a thinner head
    gasket, you might just have the pistons hit the cylinder head, or the
    valves will hit the piston and you have a badly damaged engine.

    Modern Suzukis have too little clearance between the piston head and
    the
    combustion chamber to use the thinner gasket approach.

    I've been hotrodding for over 40 years, and I learned the basics from
    working around hotrodders that also worked on aircraft engines as well
    as sportscars and motorcycles and "Detroit Iron", IOW, American V-8's.

    Whether it's a 2-stroke, or a 4-stroke, the compression ratio is
    selected to compensate for valve timing or port timing. The more
    radical the valve or port timing, the more compression is needed to
    compensate for it.

    Slightly increasing the compression ratio by itself does very little
    for an engine. Increasing the compression ratio radically reduces peak
    power because the engine cannot breathe in fresh mixture at some
    critical RPM.

    I once milled 1/8th of an inch off of a Suzuki GT-750 3-cylinder
    2-stroke engine's head in order to compensate for a wild port job. It
    turned out that the available aftermarket pistons wouldn't work with
    the crankshaft I had, so I wound up using the high compression head on
    an engine with a far less radical port job.

    All that happened was the engine had more low end power, but it
    wouldn't rev up as high a the stock engine would rev. I sold that
    motorbike to a guy who collected 2-stroke race bikes and he told me
    that the head had far too much compression for the port job. I told him
    that I knew that already.
     
    skimmer, Oct 29, 2005
    #17
  18. X
    Very informative, like your last post, thank you!

    I think that it's better put my money on the new Kawa 1352cc
    rather than boost up any other engines up to it's level
    I is already designed have good torque at low rpm
    [if one can believe the marketing]
    while at the same time give enough horse power at high rpm
    Brother-Peter
    PS: My real name is Veli-Pekka
    which is translated as Frere-Pierre [this time in French]
     
    Brother-Peter, Oct 29, 2005
    #18
  19. Brother-Peter

    Learner Guest

    Peugeot JetForce Compressor - scooter with a supercharger. Power output
    boosted from 12BHP to around 19BHP.

    www.planetbikes.co.uk/peugeot_jet_forcecomp05.shtml
     
    Learner, Oct 30, 2005
    #19
  20. Cool!!!!
     
    The Older Gentleman, Oct 30, 2005
    #20
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