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Thread: Dyno guide and dyno variables

              
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    Dyno guide and dyno variables

    I think it's time I spent a few hours writing a complete dyno guide. Question is... will people read it??

    One variable which has not even been mentioned here is barometric pressure. This has the single biggest effect on the correction factor and therefore the end result. Also the method of applying (SAE, STD etc) also has a profound effect on the power figures.

    Let me give you a very simple example.

    Let us take the 3 main variables, barometric pressure (BP), relative humidity (RH) and atmostpheric temperature (AT).

    We can have easily 2 different days where RH and AT are extremely close but the BP changes. The lower the BP the higher the correction factor. Now, according the SAE the lower the BP the lower the power should be right and therefore that's why the correction factor increases.

    However, not all cars (especially the S65) responds to small-medium changes in BP. Therefore you can have large swings in power from day to day even with the same AT.

    Then we take a situation where BP and RH are constant. As AT rises the correction factor goes up. Now we do know the S65 is extremely temperature sensitive. SAE assumes all engines respond the same but in the case of the MSS60 engine mapping the temperature compensation and correction to ignition with respect to combustion quality is extremely aggressive. So we can have a situation where the correction factor is not enough and we have a low power for that particular day.

    Now, real world scenario, the BP and AT, which are the major contributors to the correction factor, plus RH all change in different directions.

    So of course the power will change from day to day by quite alot!

    You can have many combinations and permutations of these variables to give you a scenario where uncorrected (correction factor =1.00) is equal so SAE. However, the individual variables need to be studied in this case and an educated decision needs to be made as to how accurate the correction factor actually is. This decision making can only be done by testing and analysis of the same engine.

    Now, let's add something else to the mix!

    Tyres, Tyre pressure, contact area and wheel weight. Since we are measuring wheel power on an inertia system these have a profound effect on the power through the RPM range. I can show detailed examples of the same car with different weight wheels on the same day under controlled conditions where the wheel power changes by a huge amount.

    Want to add some more to the mix??

    ECU adaption. What are the adaptive values at the time of dyno testing? Is the knock correction per cylinder +ve or -ve? What actual ignition timing is achieved? Bare in mind the ignition timing actually achieved can change by quite alot from day to day and based on what the DME decided based on it's thousands of calculations.

    Now you appreciate how many variables there are and how they all can interact with each other and how the final result can be so massively varied.

    Oh, and one more for good measure... what is the oil, coolant and inlet air temperature as seen by the cars sensors and therefore DME at the beginning of each run? If this is different on the same day from one car to the next of a the same model (in this case, S65), the results will differ and this is a FACT.

    To top is all off, how the car is strapped down also makes a big difference.

    Shall I continue to add more and more variables into the fantastic and bombastic world of dyno testing? Or shall I give you all a chance to assimilate some of this information?

    Man I have wanted to write the above for so long now! Click here to enlarge Got it out of my system!

    Now... you will most likely all hate me and a whole load of dyno operators and tuners will send me hate mail like last time!

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    Incredibly informative post as always. Not only does it raise a sense of awareness for all of us, but it really can open up our eyes even further to how we analyze dyno data.

    As I have said in many of my posts here when ever I post a dyno, I always say to "take things with a grain of salt." The exact reasons that Sal has mentioned are exactly why. He has taught me quite a bit on analyzing dyno data and even how to properly dyno my own car. Before meeting him and getting my cars tuned by Evolve, I never once thought that dynoing a car could be so complicated.

    Just to expand and further the discussion...

    For someone like me who enjoys dyno-ing every step of the way with the progression of my car, how do I even come close to controlling these variables?

    Is it best for one to just constantly log as much data as possible with every parameter and pick and choose the "best" or "most comparable" runs?

    Keep feeding us information and facts! Thanks buddy! Click here to enlarge
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    Click here to enlarge Originally Posted by evolve Click here to enlarge
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    I think it's time I spent a few hours writing a complete dyno guide. Question is... will people read it??
    Of course we will!

    Click here to enlarge Originally Posted by flipm3 Click here to enlarge
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    Incredibly informative post as always. Not only does it raise a sense of awareness for all of us, but it really can open up our eyes even further to how we analyze dyno data.

    For someone like me who enjoys dyno-ing every step of the way with the progression of my car, how do I even come close to controlling these variables?


    Keep feeding us information and facts! Thanks buddy! Click here to enlarge
    I concur!
    As much as I agree, ive been lacking in the logging department (with his car). Not for lack of effort, but not paying attention to details.

    What I personally like to do, is back up dyno #'s with performance #'s. Those are the #s that count the most, and what Im after.

    Like I said before, if you only have HP on the dyno, and not on the road, do you really have it?

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    The biggest variable you cannot control is the way the car is strapped and your wheels / tyres.

    Oh.. I forgot to mention something else. Different final drive ratio totally screws everything up in most cases.

    Everything else you can record with simple tools. BAVTECH will a add on module will record pretty much anything you want.

    This will give you a huge amount of data to use.

    A good example:

    Two cars with everything equal dyno at two different peak numbers with slight differences in the power graph shape. You can analyse the VANOS and igniton timing and you will most likely see one car achieves higher ignition than the other (hence different power) and even the VANOS actual position of inlet and exhaust is different giving you ultimately different valve overlap which will obviously again effect the power (not as much as ignition as the tolerances are smaller for deviation from request).

    The problem here is how many of you can discuss this on multiple forums in a calm and structured manner such that people don't get upset and actually begin to understand these variables and why things happen?

    Try your best gentlemen. I will be more than happy to tutor you to the best of my knowledge (which is weak compared to some out there...X) in the background.

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    Thanks for clarifying a bit more! I need to buy a BAVTECH before we tune my E46 M3...haha...

    How does final drive ratio effect power output on a dyno? For instance on an E46 M3, who would be putting down more power recorded on a dyno; 3.62, 3.91, 4.10?

    If there's any message forum where we can have a civil discussion about proper dyno protocol and analysis...BimmerBoost/GermanBoost is the one!

    If I may kind of deviate away from dyno graphs specifically and pick your brain a bit more about how different cars can achieve higher ignition and VANOS targets than others. Would you say this is a by product of how the car is driven? For example, a car that's driven conservatively and reasonably versus a car that is pounded on track or brought to redline on a daily basis on the highway?

    The reason I ask is because I got a ride in an E46 M3 this past weekend that only had catless headers and 3.91 gears. Stock tune. His car felt like an ABSOLUTE monster. He said that he can't explain it but his car keeps up with a lot of further modified E46 M3s and is just so much faster than it should be based off his modifications. He does admit that he drives his car very hard on a daily basis and does constant full pulls through the gears...of course in safe conditions. So maybe it has to do with adaptations? Hitting higher ignition targets?
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    Click here to enlarge Originally Posted by flipm3 Click here to enlarge
    This quote is hidden because you are ignoring this member. Show Quote
    Thanks for clarifying a bit more! I need to buy a BAVTECH before we tune my E46 M3...haha...

    How does final drive ratio effect power output on a dyno? For instance on an E46 M3, who would be putting down more power recorded on a dyno; 3.62, 3.91, 4.10?

    If there's any message forum where we can have a civil discussion about proper dyno protocol and analysis...BimmerBoost/GermanBoost is the one!

    If I may kind of deviate away from dyno graphs specifically and pick your brain a bit more about how different cars can achieve higher ignition and VANOS targets than others. Would you say this is a by product of how the car is driven? For example, a car that's driven conservatively and reasonably versus a car that is pounded on track or brought to redline on a daily basis on the highway?

    The reason I ask is because I got a ride in an E46 M3 this past weekend that only had catless headers and 3.91 gears. Stock tune. His car felt like an ABSOLUTE monster. He said that he can't explain it but his car keeps up with a lot of further modified E46 M3s and is just so much faster than it should be based off his modifications. He does admit that he drives his car very hard on a daily basis and does constant full pulls through the gears...of course in safe conditions. So maybe it has to do with adaptations? Hitting higher ignition targets?
    Good questions

    What exactly do we want to log from a bavtech?

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    Click here to enlarge Originally Posted by LostMarine Click here to enlarge
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    Good questions

    What exactly do we want to log from a bavtech?
    Thanks! I am always the curious one....

    In regards to stuff I would personally like to log and graph:

    RPM
    IAT
    Ignition
    Knock
    Knock Retard
    AFR
    I think these would be very valuable tools to provide to Sal to remotely tune my E46 M3 AlphaN to the max! Click here to enlarge
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    Moved to advanced tech
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    Click here to enlarge Originally Posted by evolve Click here to enlarge
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    Oh, and one more for good measure... what is the oil, coolant and inlet air temperature as seen by the cars sensors and therefore DME at the beginning of each run? If this is different on the same day from one car to the next of a the same model (in this case, S65), the results will differ and this is a FACT.

    To top is all off, how the car is strapped down also makes a big difference.
    No hate mail from me, that's just a peek into the real world of instrumented testing.

    I love how people look for boost pressure and AFR on dyno graphs, when timing advance, and engine temps can effect the outcome more.

    If you really want to have fun, you can start digging into sensor variation and latency.....just because the DME thinks the sensor is showing 82 degrees doesn't mean that the fluid is actually 82 degrees! Oh...and sensor noise...that's always a fun one that nobody really sees because most ECUs or data loggers buffer the variation.

    Last....those peak power #s quoted on many un-smoothed graphs are silly. You can play with the smoothing values and see deviations of up to 10% in some cases. In my experience, it's the smoothed...or averaged values that are more meaningful. Also, a vehicle with slightly lower peak power value with a smoother dyno trace can be faster than a vehicle with a jagged dyno graph but high peak values.

    Seems you got me all excited....no wonder why I'm designing a dyno room into my new shop at my house. (Seriously)
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    Certainly no hate from you.

    You guys keep discussing. Rather than spoon feed you it's better you have a think.

    If you need me to come and clarify anything then just email me and I will come back on.

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    Click here to enlarge Originally Posted by flipm3 Click here to enlarge
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    Thanks! I am always the curious one....

    In regards to stuff I would personally like to log and graph:

    RPM
    IAT
    Ignition
    Knock
    Knock Retard
    AFR
    I think these would be very valuable tools to provide to Sal to remotely tune my E46 M3 AlphaN to the max! Click here to enlarge

    anything about vanos?

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    Logging Vanos - unless you want to see if your VANOS is hitting the set targets. Usually it does.

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    Excellent thread. I'd like to know on an inertia based dyno how power is affected with changing final drive ratios and tire size/pressure/contact patch
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    Thank you evolve for clarifying this. I didn't know that the S65 was in particular more sensitive to AT then BP, I think purely the fact that not all engines react the same to the 3 properties of air (humidity, pressure and temperature) should be an eye opener to anyone who pounds their chest to dyno numbers. There are lots of other variables as you pointed out, the engine itself is a computer.
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    Click here to enlarge Originally Posted by dzenno@ProTUNING Freaks Click here to enlarge
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    Excellent thread. I'd like to know on an inertia based dyno how power is affected with changing final drive ratios and tire size/pressure/contact patch
    An excellent question. This will vary from dyno to dyno from what I have seen. You would really need to put that to the test.
    As far as the dynojet is concerned, dyno testing in different gears is not so different to using a different final drive ratio. There is a difference going from 3rd > 4th > 5th gears. I will need to dig up the dyno graphs.
    Sometimes the lower gears produce less power even though more torque is being applied. However, the load on the engine may not be enough to allow it to produce maximum power. So it kind of swings in roundabouts.

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    Click here to enlarge Originally Posted by DBFIU Click here to enlarge
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    Thank you evolve for clarifying this. I didn't know that the S65 was in particular more sensitive to AT then BP, I think purely the fact that not all engines react the same to the 3 properties of air (humidity, pressure and temperature) should be an eye opener to anyone who pounds their chest to dyno numbers. There are lots of other variables as you pointed out, the engine itself is a computer.
    No problem. There is actually no clarification at all. Just that a whole load of variables give a whole load of different results.

    It is very interesting how the BP does not effect some engines (therefore SAE playing havoc) and on some it does.

    I should put up some of the previous results we have had on S65's and S62's where the same car, same fuel has come in on two different days. Dyno tested in exactly the same way. SAE calculates a 7% difference in correction factor... the difference in power through entire rpm range is almost exactly 7%! Telling you that SAE (which is being adjusted in these cases primarily by BP) is not actually working properly on these engines because they are not reacting to BP like SAE thinks. Infact, they are not reacting at all almost!

    I drive these engines almost every day alternating. The BP is measured at our shop everyday and I for one cannot tell the difference from one day to another. Only when the humidity is real high and the BP is real low do you feel the engines a little lacking.

    SAE works much better with respect to ambient temperature.

    Dyno numbers are very very important but the conditions need to be analysed aswell as many other factors for getting a good estimation of what is real.. and what is not.

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    Jeez...my mind is exploding right now with the wealth of information I just learned in the past 30 minutes or so...haha
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    It will melt soon.

    Mine did years ago.

    Feels good.

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    Click here to enlarge Originally Posted by evolve Click here to enlarge
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    It will melt soon.

    Mine did years ago.

    Feels good.
    Yipes....I might have to stop...I have to save the rest of my brain for learning how to save people's lives...hahaha
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    Click here to enlarge Originally Posted by evolve Click here to enlarge
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    I think it's time I spent a few hours writing a complete dyno guide. Question is... will people read it??

    Now, let's add something else to the mix!

    Tyres, Tyre pressure, contact area and wheel weight. Since we are measuring wheel power on an inertia system these have a profound effect on the power through the RPM range. I can show detailed examples of the same car with different weight wheels on the same day under controlled conditions where the wheel power changes by a huge amount.
    Thank you @evolve for the informative post. Just a question here about wheels!

    so lets say, you got the same car with same tires and same tire pressure dynoed once and then dynoed another time with lighter wheels (keeping the same conditions in AT RH BP), should the numbers be higher or lower?

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    Nice tutorial, Sal, thanks for this! It's really just more fodder for the fact that dyno's are TUNING tools, not bragging rights... and frankly each dyno session needs to be viewed on it's own as much as possible. If you need to move to the next day, then you need to establish a new baseline to level the two dyno sessions. (experimental protocol and all...). It's really sad we get kids (and men and unscrupulous companies) with ego's and no brains posting dyno numbers like they're a badge of honor or something.

    If you want to show me something show me vbox60-130 times or 1/4mile trap speeds. these are the true real world test of how powerful a car is and you can't fake it... Physics FTW!

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