Close

Page 3 of 5 FirstFirst 12345 LastLast
Results 51 to 75 of 113
  1. #51
    Join Date
    Feb 2010
    Posts
    293
    Rep Points
    226.0
    Mentioned
    0 Post(s)
    Rep Power
    3


    Yes Reputation No
    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    If they do read thigh though, why is it dynojet readings almost always correlate to the accepted 15% drivetrain loss figures for manuals for example?
    Self-selecting bias... 145 *.85 = 123

    That "accepted" 15% figure was just a guideline based on steady-state conditions. During acceleration the weight/inertia of the driveline causes additional losses
    Last edited by spdu4ea; 02-09-2011 at 11:41 PM.

  2. #52
    Join Date
    Jan 2010
    Location
    SoCal
    Posts
    119,425
    Rep Points
    32,105.3
    Mentioned
    2106 Post(s)
    Rep Power
    322


    Yes Reputation No
    Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
    Self-selecting bias... 145 *.85 = 123
    Sorry, I don't follow?

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  3. #53
    Join Date
    Feb 2010
    Posts
    293
    Rep Points
    226.0
    Mentioned
    0 Post(s)
    Rep Power
    3


    Yes Reputation No
    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Sorry, I don't follow?
    The founder of dynojet thought there should be a 15% drivetrain loss and adjusted the calculations until it read 15% lower than the manufacturer's claimed crank power. Therefore dynojets can't be used a proof of 15% loss...


    The problem is that drivetrain loss is not static during acceleration. That "widely accepted 15%" figure is a guideline based on steady-state conditions and deals primarily with energy losses due to directional changes (transmission, rear end, and axle joints) and frictional losses (drag from bearings, seals, and oil windage).


    Imagine a car with a lightweight flywheel, carbon driveshaft and axles, and lightweight wheels/tires. It will accelerate faster than stock because there is less rotational inertia even with identical crank horsepower. Therefore it has less drivetrain loss...

    That same car will have exactly the same top speed as stock, because at the top-speed's steady-state conditions, the rotational inertia does not play a factor. Therefore it has the same "15%" drivetrain loss as stock...


    So clearly drivetrain loss is not a static percentage. You'll have more drivetrain loss when accelerating quickly (say 0-100mph) than when accelerating moderately (100-150mph), which will have more loss than when accelerating slowly (150-200mph)

  4. #54
    Join Date
    Jan 2010
    Location
    SoCal
    Posts
    119,425
    Rep Points
    32,105.3
    Mentioned
    2106 Post(s)
    Rep Power
    322


    Yes Reputation No
    Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
    The founder of dynojet thought there should be a 15% drivetrain loss and adjusted the calculations until it read 15% lower than the manufacturer's claimed crank power. Therefore dynojets can't be used a proof of 15% loss...
    So the 15% drivetrain loss rule originated from the creator of the dynojet?

    Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
    The problem is that drivetrain loss is not static during acceleration. That "widely accepted 15%" figure is a guideline based on steady-state conditions and deals primarily with energy losses due to directional changes (transmission, rear end, and axle joints) and frictional losses (drag from bearings, seals, and oil windage).
    I hear you, conditions like those available during a dyno.

    Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
    So clearly drivetrain loss is not a static percentage. You'll have more drivetrain loss when accelerating quickly (say 0-100mph) than when accelerating moderately (100-150mph), which will have more loss than when accelerating slowly (150-200mph)
    This is true, but the static aspect would be the loss the transmission itself imparts which is a mechanical constant. The transmission will always take a certain % no matter the wind, uphill, etc, which you should be able to see during a dyno.

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  5. #55
    Join Date
    Feb 2010
    Posts
    293
    Rep Points
    226.0
    Mentioned
    0 Post(s)
    Rep Power
    3


    Yes Reputation No
    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    So the 15% drivetrain loss rule originated from the creator of the dynojet?
    No, its been around a long time.


    I hear you, conditions like those available during a dyno.
    Not really. A dynojet is the worst at this -- look how fast a 600rwhp pull is over. The entire drivetrain has to be spun up way faster than it could ever be accelerated in the real world (which is why the original dynojet calculated only 90rwhp for a 145hp bike). Load-based dynos spin up much more slowly -- closer to real-world driving -- so the drivetrain's inertia plays a smaller part. This is why other dyno manufacturers haven't had to include a fudge factor (although operators still sometimes incorporate one to stroke egos/match dynojets)



    This is true, but the static aspect would be the loss the transmission itself imparts which is a mechanical constant. The transmission will always take a certain % no matter the wind, uphill, etc, which you should be able to see during a dyno.
    Different gears may be more efficient than others and oiling losses are not linear, but you're right that there will be a minimum drivetrain loss that you will see on a properly calibrated dyno. The input and output shafts, gears, etc within the transmission all have inertia though -- so even just the transmission itself will show additional losses under acceleration.

  6. #56
    Join Date
    Jan 2010
    Location
    SoCal
    Posts
    119,425
    Rep Points
    32,105.3
    Mentioned
    2106 Post(s)
    Rep Power
    322


    Yes Reputation No
    Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
    No, its been around a long time.
    Ok, and the dynojet was built around this? If so, that is a pretty good thing I imagine.

    Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
    Not really. A dynojet is the worst at this -- look how fast a 600rwhp pull is over. The entire drivetrain has to be spun up way faster than it could ever be accelerated in the real world (which is why the original dynojet calculated only 90rwhp for a 145hp bike). Load-based dynos spin up much more slowly -- closer to real-world driving -- so the drivetrain's inertia plays a smaller part. This is why other dyno manufacturers haven't had to include a fudge factor (although operators still sometimes incorporate one to stroke egos/match dynojets)
    Interesting, so you are saying having load affects the numbers? Well, the dynojet is still consistent in this regard even though the pull is over so fast.

    Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
    Different gears may be more efficient than others and oiling losses are not linear, but you're right that there will be a minimum drivetrain loss that you will see on a properly calibrated dyno. The input and output shafts, gears, etc within the transmission all have inertia though -- so even just the transmission itself will show additional losses under acceleration.
    Yes, different gears may be more efficient or change the numbers since they are affecting the torque multiplication but the power sapped by the trans should still be a mechanical constant. There are other variables that play in, but that one is static.

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  7. #57
    Join Date
    Sep 2010
    Posts
    289
    Rep Points
    1,038.2
    Mentioned
    225 Post(s)
    Rep Power
    11


    Yes Reputation No
    All of these dyno's are very very good. There is no question in that.

    I used a Dynojet out in Dubai when I was tuning a V10 and it's just so so easy to use with such little variables. Gained excellent power but that's another story.

    It doesn't really matter which dyno reads higher than the other. The issue here is consistency and abuse.

    Dynojet everything is plain in your face with the winpep files. Dyno dynamics - much more control is required.

    I would just like to point out that this is not the first time I have put lots of information out there. Last time I plainly got ignored.

  8. #58
    Join Date
    Jan 2010
    Location
    SoCal
    Posts
    119,425
    Rep Points
    32,105.3
    Mentioned
    2106 Post(s)
    Rep Power
    322


    Yes Reputation No
    Click here to enlarge Originally Posted by evolve Click here to enlarge
    I would just like to point out that this is not the first time I have put lots of information out there. Last time I plainly got ignored.
    What do you mean?

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  9. #59
    Join Date
    Sep 2010
    Posts
    289
    Rep Points
    1,038.2
    Mentioned
    225 Post(s)
    Rep Power
    11


    Yes Reputation No
    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    What do you mean?
    I mean I have put up information about dyno's before and talking about correction factors being shown.

  10. #60
    Join Date
    Jan 2010
    Location
    SoCal
    Posts
    119,425
    Rep Points
    32,105.3
    Mentioned
    2106 Post(s)
    Rep Power
    322


    Yes Reputation No
    Click here to enlarge Originally Posted by evolve Click here to enlarge
    I mean I have put up information about dyno's before and talking about correction factors being shown.
    Yes, we discussed some aspects before and it was good information as I recall.

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  11. #61
    Join Date
    Sep 2010
    Posts
    289
    Rep Points
    1,038.2
    Mentioned
    225 Post(s)
    Rep Power
    11


    Yes Reputation No
    So.... what's the outcome of this?

    Are you going to implement something where tuners have to post their correction factors up and show they are running the cars consistently.

  12. #62
    Join Date
    Jan 2010
    Location
    SoCal
    Posts
    119,425
    Rep Points
    32,105.3
    Mentioned
    2106 Post(s)
    Rep Power
    322


    Yes Reputation No
    Click here to enlarge Originally Posted by evolve Click here to enlarge
    Are you going to implement something where tuners have to post their correction factors up and show they are running the cars consistently.
    I would truly like to but getting tuners to adhere to it is almost impossible.

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

  13. #63
    Join Date
    Mar 2010
    Posts
    56
    Rep Points
    35.0
    Mentioned
    0 Post(s)
    Rep Power
    0



    1 out of 1 members liked this post. Yes Reputation No
    So I got a leak down and compression tests done this past weekend. All number looked good. For compression my numbers were all between 125-130. For leak down all were in the 5-10% range.

    Next up SC! =)

  14. #64
    Join Date
    Feb 2010
    Posts
    293
    Rep Points
    226.0
    Mentioned
    0 Post(s)
    Rep Power
    3


    Yes Reputation No
    Click here to enlarge Originally Posted by gixxer_kidd Click here to enlarge
    So I got a leak down and compression tests done this past weekend. All number looked good. For compression my numbers were all between 125-130. For leak down all were in the 5-10% range.

    Next up SC! =)
    Are those #s normal for the S65? How many miles do you have?

  15. #65
    Join Date
    Nov 2010
    Location
    le Paris
    Posts
    6,648
    Rep Points
    -168.0
    Mentioned
    48 Post(s)
    Rep Power
    0


    Yes Reputation No
    Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
    Are those #s normal for the S65? How many miles do you have?
    depends on how you treat your engine. mine was about 5% but i have seen 15% or more

  16. #66
    Join Date
    Feb 2010
    Posts
    293
    Rep Points
    226.0
    Mentioned
    0 Post(s)
    Rep Power
    3


    Yes Reputation No
    5% leakdown is what I'd expect on a newer quality engine -- 10% would seem like its long in the tooth (or maybe just not broken in). But its the 125psi compression that seems awfully low for 12:1 compression ratio -- I'd expect 170+

  17. #67
    Join Date
    Mar 2010
    Posts
    56
    Rep Points
    35.0
    Mentioned
    0 Post(s)
    Rep Power
    0



    Yes Reputation No
    Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
    Are those #s normal for the S65? How many miles do you have?
    for the leak down, the meter reading was well inside the green area (which is where you want to be). i believe anything under 20% is good.

    Click here to enlarge Originally Posted by Sorena Click here to enlarge
    depends on how you treat your engine. mine was about 5% but i have seen 15% or more
    thanks for sharing. i was trying to find these numbers everywhere and no one seem to post it anywhere.

  18. #68
    Join Date
    Mar 2010
    Posts
    56
    Rep Points
    35.0
    Mentioned
    0 Post(s)
    Rep Power
    0



    Yes Reputation No
    to be honest it could of been 5%. i just quickly glanced at the meter, but since it was in the green, I didn't pay too much attention to it.

    as for compression i'm still confused. is the absolute matter what you want to look at or that they are all within the same range? i believe we were well under 125psi. i'll ask again what pressure we used.

    but my BMW tech friend said everything appears to be normal.

    my odometer is about to hit 20k miles.

  19. #69
    Join Date
    Feb 2010
    Posts
    293
    Rep Points
    226.0
    Mentioned
    0 Post(s)
    Rep Power
    3


    Yes Reputation No
    For comparison, a stock S54 is normally 160-180psi, 3-10% leakdown.

  20. #70
    Join Date
    Feb 2010
    Posts
    293
    Rep Points
    226.0
    Mentioned
    0 Post(s)
    Rep Power
    3


    1 out of 1 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by gixxer_kidd Click here to enlarge
    to be honest it could of been 5%. i just quickly glanced at the meter, but since it was in the green, I didn't pay too much attention to it.
    Most of the gauges will have green up to 20% or so -- which is fine for an engine from Detroit, but its unusual for a newer German or Japanese engine to be over 10. Either way, you were under 10 so that part is ok

    as for compression i'm still confused. is the absolute matter what you want to look at or that they are all within the same range? i believe we were well under 125psi. i'll ask again what pressure we used.
    Both. A large variance tells you there is a problem with the low cylinders. Consistent low #s in general suggest the rings are worn or not properly seating.

    There can be quite a bit of variance from gauge to gauge so if this was a S54 and you said you have 140psi all across the board, I wouldn't think much of it (same as if you said you had 200psi across the board). But 125psi just seems awfully low. Did you hold the throttle open during testing?

  21. #71
    Join Date
    Nov 2010
    Location
    le Paris
    Posts
    6,648
    Rep Points
    -168.0
    Mentioned
    48 Post(s)
    Rep Power
    0


    Yes Reputation No
    to be honest it could of been 5%. i just quickly glanced at the meter, but since it was in the green, I didn't pay too much attention to it.
    I did the same too , but since i had an engine failure the pro guy came and did it himself. I say this time be more precise
    but 5-10% isn't bad at all , untill 20% it's ok.
    as for compression i'm still confused. is the absolute matter what you want to look at or that they are all within the same range? i believe we were well under 125psi. i'll ask again what pressure we used.
    Don't bother yourself , it's normal. if it was in the green range it's ok

  22. #72
    Join Date
    Nov 2010
    Location
    le Paris
    Posts
    6,648
    Rep Points
    -168.0
    Mentioned
    48 Post(s)
    Rep Power
    0


    Yes Reputation No
    Spd4ua , I assume he has some modifactions on his car , can mods effect on the pressure?

  23. #73
    Join Date
    Mar 2010
    Posts
    56
    Rep Points
    35.0
    Mentioned
    0 Post(s)
    Rep Power
    0



    Yes Reputation No
    Click here to enlarge Originally Posted by spdu4ea Click here to enlarge
    There can be quite a bit of variance from gauge to gauge so if this was a S54 and you said you have 140psi all across the board, I wouldn't think much of it (same as if you said you had 200psi across the board). But 125psi just seems awfully low. Did you hold the throttle open during testing?
    I know for sure the throttle wasn't held open because he was standing right next to me. Should it be? My friend who did the same tests at a different shop resulted in the range of 145-150.


    Click here to enlarge Originally Posted by Sorena Click here to enlarge
    Spd4ua , I assume he has some modifctions on his car , can mods effect on the pressure?
    No mods except for my rear muffler.

    But we took out all the plugs before we started testing. Is this how it's suppose to be done or only 1 plug should be removed at a time?

  24. #74
    Join Date
    Feb 2010
    Posts
    293
    Rep Points
    226.0
    Mentioned
    0 Post(s)
    Rep Power
    3


    Yes Reputation No
    Click here to enlarge Originally Posted by gixxer_kidd Click here to enlarge
    I know for sure the throttle wasn't held open because he was standing right next to me. Should it be?
    Yeah, it'll read higher with throttle held open. The other thing that will make the readings jump up is if you remove all of the spark plugs rather than one at a time (engine cranks faster, but with a slight risk of dirt getting sucked in). Here's the bentley manual for S54:

    Click here to enlarge
    Click here to enlarge
    Click here to enlarge

  25. #75
    Join Date
    Mar 2010
    Posts
    56
    Rep Points
    35.0
    Mentioned
    0 Post(s)
    Rep Power
    0



    Yes Reputation No
    Thanks for posting that. I was reading the roundel this morning and in the tech section one of the writers talked about how every BMW owner should own a Bentley manual. I'm going to order one now!

    Also I'm getting compression/leak down confused. For the compression we removed all the plugs then tested each. He cranked the engine for 10 seconds (not sure if he held the throttle open). The highest reading I saw was around 130. Again since he said it was normal I didn't bother writing it down or take a closer look to see the exact number.

Page 3 of 5 FirstFirst 12345 LastLast

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
  •