1991 R100 GS/PD dyno run

Discussion in 'Airheads' started by midlman, Feb 27, 2011.

  1. Lornce

    Lornce Lost In Place

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    WM, If you've got the time, click on "Rebuilding a 92 R100GSPD" in my sig line.

    Venolia 1050 pistons mated to modded '77 R100S "squish band" heads at approx 12:1 (measured pressures, not cc'd). Torque, mid range power and fuel efficiency are all up by significant margins.

    Now if only I could find a way to control distorting cylinders that have been bored too thin to maintain dimensional stability... :scratch

    It never ends.

    :thumb
    #81
  2. supershaft

    supershaft because I can

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    Oops! I didn't mean that larryboy was being a bonehead. I was making fun of all kinds that just can't get past the numbers.
    #82
  3. larryboy

    larryboy Chopper Rider

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    I got it, been a good topic to read on. The initial poster doesn't seem aware that a Dynojet factors in 20% more which should read about 39 HP at the wheel, not the inflated 'factored' dyno sheet. An 85,000 mile twin isn't putting 48 HP to the ground...since we're talking numbers. :D
    #83
  4. round the block don

    round the block don soreass

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  5. midlman

    midlman Adventurer

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    I'm fully aware of differences between the various dyno numbers. I've not seen anything that suggests a dynojet factors in 20% over factory crank numbers..... I know that there is usually a 10% diff between a SAE number and the dynojet number.. and have seen 15% differences between a dyno dynamics unit and the dynojet number. What engine dyno did BMW use to figure out their numbers ? Maybe my drivetrain losses are less than others because I use the magical super synth lube :D LOL... (just kidding btw)

    either way..maybe not correct to compare to the factory crank numbers..but this was a baseline..from which I hope to optimize a few parameters...and then at some point..go back on the same dynojet dyno...to see how it did...
    #85
  6. supershaft

    supershaft because I can

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    So are you saying that all Dynojets read high or just their inertia dynos? I have always thought that their inertia dynos read high. Where did you get the 20% number from?
    #86
  7. anotherguy

    anotherguy unsympathetic

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    It's a small bore with a wide included valve angle that needs a big dome to get even moderate compression that benefits the most from long rods.The flame front has to travel far more than the bore radius leading to some serious advance to get peak cylinder pressure at the right time. Lots of shrouding going on in that hole.Harley,BMW,Guzzi and the like. Check the rod length on an R1,GSXR ect. Mostly pushrod stuff,why would you waste a DOHC on a narrow bore? Dual pugging is cheaper and less costly in the long run and achieves the desired result.

    And a calibrated DynoJet will give good HP numbers. I've run SuperFlow SF-901,FactoryPro EC997 and Dynojet from 100 to 250i. Favorite is the EC997. The SuperFlow is an awesome tool but difficult to use for motorcycles. Harleys are the easiest to mount to the 901 but not close to easy. When all is said and done the numbers only matter at the bar. Results speak far louder than numbers. The proper use of the tool is what you seek. As I alluded to earlier it's the area under the curve that gets the job done and the only way to see that is a dyno printout no matter where it comes from.
    #87
  8. larryboy

    larryboy Chopper Rider

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    Didn't say that, they're measuring power at the wheel and their software gives you back 20% for parasitic losses. If you're on a Dynojet you need to take away 20% from what they tell you. Look around the 'net, it's pretty common knowledge.
    #88
  9. midlman

    midlman Adventurer

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    ok.not 20% over factory..but still..I've not seen anything that says a dynojet gives back 20%.... I'll go look around the internetz to see..but what you are saying is that dynojet numbers should in theory be close to or greater than the factory crank numbers? (assuming drivetrain loss is 20%)..(in a non-locking automatic..for sure....manual..maybe 15% losses).
    #89
  10. larryboy

    larryboy Chopper Rider

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    Yes, they get you back to a crank reading...a little misleading, but the whole tune on the same dyno still works and is a great tool. Do you really want to go looking for power with 85,000 on the clock?
    #90
  11. midlman

    midlman Adventurer

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    Funny you ask...the bike runs great, but I always tinker...so why not fix it till it's broken LOL :D I've even tossed around the idea of dual plugging/40mm bings/exhaust etc.. :rofl
    #91
  12. Lornce

    Lornce Lost In Place

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    Sure.

    Why not?


    :dunno
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  13. supershaft

    supershaft because I can

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    What model Dynojet is suppose to get you back to a crank reading? Is it an option an the printout? I think their inertia dynos read high but not 20% high. Does their software have an at the crank button? No one has ever showed it to me. Is it a new feature? Where did you get the 20% figure. What about Dynojet brake dynos? They don't just make inertia dynos. Some don't even consider an inertia dyno as being a real dyno. Torque isn't really measured on an inertia dyno. It is estimated by a computer.
    #93
  14. anotherguy

    anotherguy unsympathetic

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    Any of you guys experienced operators? 'Cause some of that stuff is just plain wrong.

    You can do a negative run on a DynoJet and figure parasitic drag but it's not part of a roll on run. You must go into the software and select it. On some bikes it's a bad idea to do. Like a 2 stroke.

    [​IMG]

    The DynoJet uses drum weight/diameter,gear ratio,RPM and time to calculate HP.
    #94
  15. supershaft

    supershaft because I can

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    I'm not! I have helped with many a dyno run but I have never actually run the dyno.

    Oops! Does Dynojet ONLY make inertia dynos? I thought their brake dynos were eddy current dynos? I don't understand how an inertia dyno brake works? I guess it is a combo electric/enertia that still depends on a computer model reading?

    Back in the early seventies, our shop's dyno had a torque meter and a tach. No computer. No printer. Of course, it wasn't an inertia dyno. They hadn't been invented yet? If I understand it right, inertia dynos HAVE to have a computer?
    #95
  16. Lornce

    Lornce Lost In Place

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    As far as I understand it, the Dynojet dynos work with a speed sensor tracking speed/acceleration of the drum, which is a known weight.

    All power and torque figures are derived by the dyno's computer from that collected acceleration data and monitored engine RPM.


    Anyone know different?

    :dunno
    #96
  17. anotherguy

    anotherguy unsympathetic

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    You have the gist of it. The load control DynoJets are hybrids. It's an eddy current brake used to load the engine for writing maps but isn't capable of steady state torque readings. It has a load cell that needs to be calibrated via an arm and weights. So it's physically capable of it. Not sure why they didn't go all the way.

    It really doesn't matter (within reason) how accurate the numbers are as long as they're consistent. I don't consider it done until I get 3 consecutive runs with the same result. It's use is as a comparator so you can see the results of changes. An increase/decrease will give evidence of the path your on being right..................or not.

    The DynoJet uses RPM,gearing and the acceleration rate from A to B to calculate the numbers. The RPM comes from an inductive sensor attached to a plug wire. Gearing is calculated by RPM vs. drum speed rate that is read via Hall Effect sensors. On set up it asks how often spark occurs,i.e. 180/360/720 degrees to help determine gearing. The software is calibrated for each machine via the drum serial number that allows them to determine the exact weight and diameter via records from manufacturing. The DynoJet dyno is better than it's detractor would have you believe. It's a solid tool that in the right hands allows the best to be extracted from and engine. The operator is the standard that makes it right. A good operator takes care of his machine and knows how to use it.

    That being said notice the Factory Pro EC997 is my favorite. It's faster,lighter and easier to get consistent results from. It uses a far more reliable 5 gas analyzer vs. the DynoJet O2 sensor which has serious shortcomings. However those standards come with a price. A very steep price.
    #97
  18. supershaft

    supershaft because I can

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    I am guessing the Pro Flow is an eddy current? Does anybody still use hydraulic? I would think hydraulic dynos would be the most consistent?

    It baffles me why Dynojet didn't go all the way with their brake dyno's. I would think steady state would occasionally be handy.
    #98
  19. supershaft

    supershaft because I can

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    I have had people tell me that they thought their dyno itself changed more than a little when it warmed up and then got hot. It seems to me that hydraulic would do that the least.
    #99
  20. anotherguy

    anotherguy unsympathetic

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    It's the engine that makes the difference. As the insides heat sink it reaches an equilibrium. That's accounted for in the engineering/design phase of development. Ever held a Harley TC88 cylinder head? Massive. Designed to hold the heat for emissions reasons. Takes 3-4 WFO runs after a 5 minute warm up to reach true operating temperature.