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Dynoed.. finally!

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  • #46

    Re: Dynoed.. finally!

    Re: Dynoed.. finally!

    Thanks a heap Jay. :D

    So why do dyno operators use the 600rpm/sec rate if it tends to be less accurate.. or do some feel it's more suitable to the drag race application?

    I did ask the operator at the time because I thought 300 was the standard, and he said something about engine inertia exaggerating results with the slower rates.
    There are also 50 and 25 RPM/sec settings available on my dyno. Like I'm ever going to try one of those; can you imagine a 2 minute dyno pull?? :D
    Ya right, who would run an engine at WOT for that long... :P our passes at Bonneville ONLY last for 90 seconds or so.... :o
    LOL

    Hey Jay, glad you posted that data but what most folks forget is with a street engine were not tuning for every last hp so if you look at the curves they are roughly the same.
    I start out testing @ 600 then when I'm sure the tune is close I'll slow the last couple of runs down to get a nice data line. Race motors I'm more inclined to do 100/sec or 500 step. Try a 250 step test some time, start at 4500 and run to 8500 :o That's how we tested some of our SCCA Trans Am engines in the 80's & early 90's.
    There are very few people in this world who's opinion I value, you are not one of them.

    300 in 1999

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    • #47

      Re: Dynoed.. finally!

      Re: Dynoed.. finally!

      "Engine inertia sounds like BS to me."

      Really? Ever have a small engine with an aluminum flywheel?

      Run out to the garage and do a DEceleration dyno sweep and tell me what you see.

      Meanwhile, I'll argue that a step test is not the most accurate. I'm sure it is the best way to tell me how the engine operates at each individual rpm point with the engine stabilized, and I'll even agree that the dyno can capture the data more accurately and you can adjust the water more easily. However, engines don't operate at a steady state. 'd rather see a sweep, even if the numbers are not the same as what you'd see in a step test (they'll be lower). You're looking for trends that I don't think a step test will show. A good example would be oil dynamics (return, windage, etc).

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      • #48

        Re: Dynoed.. finally!

        Re: Dynoed.. finally!

        I really just want to know an accurate number of my dyno run so I can order my converter.
        Will the 600rpm/sec results be accurate enough?

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        • #49

          Re: Dynoed.. finally!

          Re: Dynoed.. finally!

          E-mail them what you have, 25 foot pounds of TQ either way is not going to matter for what your doing
          2007 SBN/A Drag Week Winner & First only SBN/A Car in the 9's Till 2012
          First to run in the .90s .80s and .70's in SBN/A
          2012 SSBN/A Drag Week Winner First in the 9.60's/ 9.67 @ 139 1.42 60'
          2013 SSBN/A Drag Week, Lets quit sand bagging, and let it rip!

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          • #50

            Re: Dynoed.. finally!

            Re: Dynoed.. finally!


            "Ya right, who would run an engine at WOT for that long... :P our passes at Bonneville ONLY last for 90 seconds or so.... :o
            LOL"

            Yikes! I never thought about Bonneville :o

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            • #51

              Re: Dynoed.. finally!

              Re: Dynoed.. finally!

              I was on the nitrous for 110 seconds one time.

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              • #52

                Re: Dynoed.. finally!

                Re: Dynoed.. finally!

                "Engine inertia sounds like BS to me."

                Really? Ever have a small engine with an aluminum flywheel?

                Run out to the garage and do a DEceleration dyno sweep and tell me what you see.

                Meanwhile, I'll argue that a step test is not the most accurate. I'm sure it is the best way to tell me how the engine operates at each individual rpm point with the engine stabilized, and I'll even agree that the dyno can capture the data more accurately and you can adjust the water more easily. However, engines don't operate at a steady state. 'd rather see a sweep, even if the numbers are not the same as what you'd see in a step test (they'll be lower). You're looking for trends that I don't think a step test will show. A good example would be oil dynamics (return, windage, etc).
                Sorry, my mistake, I'm confusing momentum and inertia. Momentum is mass times velocity, so the momentum of the reciprocating assembly at any given engine speed will be the same, regardless of the acceleration rate. Regarding, inertia, which I just looked up and found is the resistance of a mass to acceleration, I think I see your point. You are saying that at the faster acceleration rates, more power is required to overcome the engine's inertia, so less will show up at the torque link? I haven't thought of it that way before, and that makes sense. Hmmm....

                I don't have a decelleration test available on my dyno, or I'd give that a try. But of course I've noticed that at the end of the pull, when the servo valve starts to close again and the engine speed drops, there is a big overshoot from the torque link.

                Comment


                • #53

                  Re: Dynoed.. finally!

                  Re: Dynoed.. finally!


                  I don't have a decelleration test available on my dyno, or I'd give that a try. But of course I've noticed that at the end of the pull, when the servo valve starts to close again and the engine speed drops, there is a big overshoot from the torque link.
                  [/quote]

                  If you look through the Superflow instruction book you will see that you can let the engine pull all the way back down to the starting rpm. ;)
                  There is a spike but just like the data you posted above the #'s get bigger on the way down.
                  There are very few people in this world who's opinion I value, you are not one of them.

                  300 in 1999

                  Comment


                  • #54

                    Re: Dynoed.. finally!

                    Re: Dynoed.. finally!


                    I don't have a decelleration test available on my dyno, or I'd give that a try. But of course I've noticed that at the end of the pull, when the servo valve starts to close again and the engine speed drops, there is a big overshoot from the torque link.
                    If you look through the Superflow instruction book you will see that you can let the engine pull all the way back down to the starting rpm. ;)
                    There is a spike but just like the data you posted above the #'s get bigger on the way down.
                    [/quote]

                    Right, but the dyno quits collecting data at the upper RPM speed, so you're stuck with trying to see the numbers and speed as they flash by on the screen. Or, is there a way to keep it collecting the data?

                    For example, can I set the engine starting speed at 6000 RPM, and the upper test speed at 3000 RPM, and run the pull "backwards" like that?

                    Comment


                    • #55

                      Re: Dynoed.. finally!

                      Re: Dynoed.. finally!

                      It should not stop collecting the data. I'm not good enough to know how to set up the program, but I know it can be done. We've used that feature to compare engines with recipricators of differing weights.

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