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    • The difference between Mustang vs. Dynojet dynamometer runs, drivetrain losses, and how dyno plots can vary wildly

      A recent article about a Mustang dyno run for the Alfa Romeo Giulia Quadrifoglio exposed a large flaw in traditional dyno thinking. On this website most readers know that you can not just grab a graph from one type of dyno and compare it to another dyno and expect the numbers to be uniform.


      Unfortunately, the average person does not understand this which is what led to someone putting out an article stating the Giulia Quadrifoglio is not making its stated output which sets understanding of dyno runs back instead of helping educate.

      Let's start with the idea that cars suffer from 15% drivetrain losses. Where did this idea start? Why is it 15%? It originated with the Dynojet and became a rule of thumb on automotive forums for manual transmission cars. The percentage changes based on if the car is automatic (20%) or even all wheel drive and automatic (25%).

      The problem here is that while the conversion factor works well to extrapolate crank horsepower from peak Dynojet figures at the wheels that is not the way drivetrain losses work. First of all, losses are not static. There is no one set figure for losses.

      What does this mean? It means that your losses in 5th gear at 8000 rpm will be different from 2nd gear at 2000 rpm. The loss figure will change based on rpm, load, and even what accessories are running. Stating all manual cars suffer from a single set figure is flawed for this reason.

      Not to mention that figure only works on the Dynojet which is inertia based. BMW M cars used to follow the number exactly back when they were naturally aspirated:

      E46 M3 S54
      Displacement: 3.2 liter
      Horsepower: 343
      Torque: 269 lb-ft
      Wheel Horsepower: 280
      Wheel Torque: 235


      E92 M4 S65
      Displacement: 4.0 liter
      Horsepower: 414
      Torque: 300 lb-ft
      Wheel Horsepower: 350
      Wheel Torque: 254 lb-ft


      85% of 414 horsepower is 351.9. Notice the E92 M3 is almost exactly at 15%. DCT models would actually dyno slightly less than manual examples due to the wet clutch dual clutch having higher losses.

      For the E46 M3 85% of 333 horsepower is 283.05. Again, the E46 M3 is almost perfectly at 15% losses on the Dynojet. It's almost scary how consistently close BMW was to this figure.

      Now, in comes the turbo era. Let's see what happens when we get to the F80 M3.

      F80 M3 S55
      Horsepower: 425
      Torque: 406 lb-ft
      Wheel horsepower: 427
      Wheel torque: 429


      How is the S55 engine producing more horsepower at the wheels than it is rated at the crank by BMW? Does the F80 M3 have a magical transmission with negative losses that somehow adds power?

      Of course not. The DCT transmission in the F80 M3 works the same way as the DCT transmission in the E92 M3. What happened was the 15% Dynojet loss rule went out the window when the turbo power war started. BMW is able to claim a lower number to not push an output war on paper yet delivers far more where it matters, to the tires.

      The drivetrain losses are still about the same for the transmission and rear wheel drive layout as the previous generation despite it no longer lining up with the crank horsepower figure which is practically meaningless.

      How does this all look on a Mustang load bearing or eddy current variant? Well, very different. While the Dynojet is spinning a drum of a set weight and calculating the result based on how quickly that weight is spun the Mustang dyno creates load.

      Why is this important? Because it simulates real world conditions which is great for tuning. A tuner can provide all kinds of different scenarios. The spool on the Mustang for a turbo motor will look different than on a Dynojet. Often time real world spool is much quicker than what is shown on a Dynojet graph due to load which generates exhaust gases more quickly for the turbochargers.

      Note: Dynojet operators can optionally eddy current load control as well which muddies comparisons further.

      The other day BimmerBoost posted an article on VF-Engineering's F87 M2 ECU flash software and provided Dynojet runs. Let's take a look at the same M2 running the same Stage I software on a Mustang:


      Now the Dynojet:


      269 rear wheel horsepower for the Mustang and 331 rear wheel horsepower for the Dynojet on the baseline figure. That is a difference of 62 horsepower at the wheels or 18.7 %.

      If you take that 18.7% difference and apply it to the tuned run on the Mustang which shows 287 to the wheels you get 354 horsepower. Almost exactly what the Dynojet tuned run shows.

      This is not an exact science as you can see. However, if you were to dyno cars all day on the Dynojet and on this Mustang you would see the runs follow very closely to the ~18% difference between the two.

      So is that it? Just convert Mustang runs by 18.7% to get a Dynojet number? No. Things actually get very muddied due to the games tuners play.

      Here is an example. The new Porsche 991.2 Carrera S on a Dynojet:


      380 horsepower to the wheels. Now here is a 991.2 Carrera S on a Mustang from AWE-Tuning:


      Why does the Mustang dyno show more power now? Because it is being corrected to read higher. People do not like low numbers and high numbers are better for marketing. BoostAddict asked AWE-Tuning what their correction factor is but they would not share it with us. You can see it is reading VERY high and higher than a Dynojet though.

      In this instance it is better to focus on the delta which you will often hear tuners say. That means the difference between the two runs as comparing the peak figures to other runs on other dynos is pointless due to the unknown correction factor.

      Good for marketing, bad for those who want relevant figures to compare with. It can also be very bad for consumers. Why is that you ask? Because some people will dyno without a correction factor and then change the correction factor to show larger gains.

      A good example of someone who plays with the numbers is Vivid Racing: http://www.bimmerboost.com/content.p...a-Mustang-dyno


      They claim 407 wheel horsepower for an exhaust and canned tune on a Mustang dyno for the E92 M3. Anyone who has an E92 M3 (like me) and has had these modifications and dyno'd the car knows this is impossible. It looks good for someone who doesn't know that though and wants to buy parts thinking they make a ton of power, right?

      Always keep in mind when you see figures from a company or tuner you should question them. Independent runs are the best to go by as the person usually isn't trying to sell you anything but just share their results. Also remember the Mustang can be configured like most dynamometers to read whatever the operator wants it to read.

      If vendors and tuners did not play with dyno runs for sales we would have a great resource to work with for comparisons and so forth. You can not trust all tuners to do so. Fortunately, VF-Engineering has no dog in the fight and provided us with a variety of runs showing the difference between their Mustang and their Dynojet.

      Yes, they have both. That is the proper way to do it. One dyno for tuning and one for marketing. Rather than correcting figures with whatever percentage generates the most sales they show the uncorrected runs on both machines so people can learn from and reference the pulls.

      BMW 335i (N55) Stage TWO

      Dynojet:


      Mustang:


      An 18.2% difference between the peak horsepower on the tuned figures. There will be variance from run to run, day to day, fuel to fuel, gear to gear, etc.

      Ultimately, remember, while dyno runs can tell you a lot about a motor or modifications they can also mislead people. Even worse, people can read them incorrectly and spread misinformation or manipulate them to sell parts.

      A dyno is just one, albeit important, piece of the performance puzzle.

      This article was originally published in forum thread: The difference between Mustang vs. Dynojet dynamometer runs, drivetrain losses, and how dyno plots can vary wildly started by Sticky View original post
      Comments 20 Comments
      1. Forced_Downunder's Avatar
        Forced_Downunder -
        Great article.
      1. Duckmann's Avatar
        Duckmann -
        Very informative.!
      1. Sticky's Avatar
        Sticky -
        Appreciated, thanks.
      1. RobNyc's Avatar
        RobNyc -
        Well done sticky!

        Do you prefer Mustang or Dynocom (load-bearing) or Dynojet ?
      1. Sticky2's Avatar
        Sticky2 -
        Click here to enlarge Originally Posted by RobNyc Click here to enlarge
        Well done sticky!

        Do you prefer Mustang or Dynocom (load-bearing) or Dynojet ?
        I prefer winpep and Dynojets for all power measurements posted to forums. If you want to claim a record or have the largest point of reference, Dynojet. The graphs look better, the numbers make more sense, it's just better all around.

        I'm not a tuner but if I was I'd prefer a Mustang or Dyno Dynamics.
      1. BuraQ's Avatar
        BuraQ -
        I had to tag this as reference.....lol

        However wouldn't it make more sense to have any dyno whp backed up with some sort of vBox reference ?
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by BuraQ Click here to enlarge
        However wouldn't it make more sense to have any dyno whp backed up with some sort of vBox reference ?
        It makes sense to back up any dyno with a 1/4 mile run, 60-130, 60-160, 1/2 mile, etc. There will be variance there to depending on conditions, temps, elevation, etc.

        The more data, the more useful. As stated in the article the dyno is just one (important) part of the whole picture.
      1. F16HTON's Avatar
        F16HTON -
        This is absolutely correct.

        I had one instance in which I failed to make a significant power increase (pre and post calibration update) on the dyno, but then immediately backed it up with a Pbox measured improvement of of over .7 seconds in the quarter mile, this result was repeated three times in a row.

        Does this mean the dyno was bad? Probably not, but it did show that for one reason or another, the measured dyno result was not reliable.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by F16HTON Click here to enlarge
        This is absolutely correct.

        I had one instance in which I failed to make a significant power increase (pre and post calibration update) on the dyno, but then immediately backed it up with a Pbox measured improvement of of over .7 seconds in the quarter mile, this result was repeated three times in a row.

        Does this mean the dyno was bad? Probably not, but it did show that for one reason or another, the measured dyno result was not reliable.
        That's very odd. What type of dyno was this?

        If power is showing in the 1/4 mile it should also show on the dyno. Maybe there was ecu adaptation involved?
      1. F16HTON's Avatar
        F16HTON -
        Click here to enlarge Originally Posted by Sticky Click here to enlarge
        That's very odd. What type of dyno was this?

        If power is showing in the 1/4 mile it should also show on the dyno. Maybe there was ecu adaptation involved?
        Mustang AWD dyno, could be ECU adaptation, could be IAT, could be many other variables. Dyno's are only one piece of the puzzle when it comes to determining the true performance of a vehicle.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by F16HTON Click here to enlarge
        Dyno's are only one piece of the puzzle when it comes to determining the true performance of a vehicle.
        That is what I want people to take away from this.

        Also, hopefully, a better understanding of drivetrain losses and how dynos can vary.
      1. RobNyc's Avatar
        RobNyc -
        Click here to enlarge Originally Posted by Sticky2 Click here to enlarge
        I prefer winpep and Dynojets for all power measurements posted to forums. If you want to claim a record or have the largest point of reference, Dynojet. The graphs look better, the numbers make more sense, it's just better all around.
        I'm not a tuner but if I was I'd prefer a Mustang or Dyno Dynamics.
        I know the Mustang is preferred for Tuning, although know a personal friend who was on Dyno Dynamics and now has a huge issue 5-6k rpm this should of been caught IMO.
        Dynocom also suppose to be good "load dyno" but seen cars that start misfiring and crapping out once its off the dyno why wasn't this caught ?

        Then there's Mainline, seen a lot of cars come out of this solid after some tuning session.
        I do hear that a car tuned on mustang will usually run the same way once its on the street.
        424xLC Dynojet will be the one for me.
        Click here to enlarge Originally Posted by F16HTON Click here to enlarge
        Mustang AWD dyno, could be ECU adaptation, could be IAT, could be many other variables. Dyno's are only one piece of the puzzle when it comes to determining the true performance of a vehicle.
        True, It's hard to justify the Mustang these days, so many ppl have them (Dyno operators not tuners) and screw up the Load-Profile and the reading/calibration. One place down the block will tell you it reads 18-25% lower than DJ, the other place in the other town will say it will read 10-15% lower. PITA
      1. rezin23's Avatar
        rezin23 -
        This is why I mostly care about 60-130 and 1/4 mile. It tells more than what a dyno does.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by RobNyc Click here to enlarge
        although know a personal friend who was on Dyno Dynamics and now has a huge issue 5-6k rpm this should of been caught IMO.
        I'd blame that more on the tuner than the dyno though.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by RobNyc Click here to enlarge
        424xLC Dynojet will be the one for me.
        I've thought about buying one and seeing if I could make money on it renting out dyno time.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by rezin23 Click here to enlarge
        This is why I mostly care about 60-130 and 1/4 mile. It tells more than what a dyno does.
        That's not true. First of all, people manipulate slope and I've even seen people edit Vbox files.

        Secondly, 1/4 mile times very with density altitude significantly. Then there is the launch, driver skill, etc.

        This article isn't discounting dyno runs it is explaining them. You ideally want a dyno, 60-130, and a timeslip. No matter how well you run on the dragstrip it isn't going to show you your torque curve, boost readout, timing, etc. on the timeslip.
      1. Sticky's Avatar
        Sticky -
        AWE-Tuning got back to me regarding their dyno procedures and correction. We were having some e-mail issues before:

        Click here to enlarge Originally Posted by AWE-Tuning Click here to enlarge
        Back in 2002, we changed multiple settings to get our Mustang AWD-500-SE to read more like a Dynojet, including settings that offset the curves higher than as-delivered, to settings that also change the weighting of the curves (shape) to mimic the Dynojet better. If you want all those figures, we're more than happy to share.

        We're happy to share because, to be perfectly honest, we'd prefer to see *all* Mustang operators using these settings so publicly published results look more consistent dyno to dyno, reducing possibility of confusion and mistrust in the consumers' minds. Back in the day, all the Mustang dynos in our "tuning network" (GIAC, Streetwerke, ESE) were all running identical settings in an attempt to standardize.

        For the record, we have kept these settings ever since establishing them in 2002, when we took delivery of our AWD Mustang dyno. We do not change settings car to car or when results are not expected. The only time we change is when switching between AWD and 2WD mode.

        Also for the record, the reason why we felt the need to change the factory settings is because, when we took delivery of our first Mustang dyno in 1998, a single roller model, Dynojet was the king, and market expectations were set by the numbers that would come off of that brand dyno. Mustangs read considerably lower as delivered, and we were having a lot of trouble getting the enthusiast markets to take our numbers seriously.

        As you know, chassis dyno results are not absolute, they are relative, so there was no intrinsic value in being handicapped with lower than expected numbers from our Mustang. We actually worked *with* Mustang techs to learn how to adjust the offsets and curve shapes on our original dyno in order to remove this, very impactful, perceived handicap. We did the same and worked with them when our AWD model was delivered in 2002.

        As Mustang gained market share over the years, and other dyno brands arrived on the US tuning scene, of course this result differential as compared to Dynojet became less confusing in the market, but back in the late 90s and early 2000s, it was a real, and an undeserved obstacle to overcome in gaining market acceptance of our product design. We felt justified in removing it, as long as we rigorously adhered to the new settings we established.

        Also, for years, especially as compared to our peers in the European car tuning space, we were the only ones to disclose our actual chassis dyno graphs. Most others were only publishing enhanced spreadsheet graphs, "corrected" to the crank. It took us several years to finally acquiesce and start doing the same, because, similar to the Dynojet situation, there was still confusion in the market when trying to compare graphs, and the higher (crank number in this case) result always wins.

        Once we decided to start producing crank graphs, we had the obvious challenge of choosing a "correction factor" for driveline loss. Since every car varies in its parasitic drag, we've decided to establish correction factors for each model we test based on first dynoing stock and then comparing against factory published stock crank power. The multiplier is then applied linearly across the wheel power results to come up with a "crank" curve, in the attempt, again, to keep us on par with our competition. We opted, however, to always publish *both* chassis and crank results, in the interest of full transparency (we're one of the few that does that to this day).

        Lastly, as you are fully aware and wrote about, base settings on a load dyno can dramatically alter graphed results. However, operator errors in dyno protocol have as much impact on results as these keyed-in settings. Cooling fan air velocity (not volume) capacity, fan placement, cooldown interim procedure, applying barometric SAE correction to forced inducted engines, tire slippage, tire pressures, and unfamiliarity of how to put certain cars in "dyno test mode" all inadvertently contribute to inconsistencies across the industry.

        In the end, all that matters is the skill and honesty of the source of the results.
      1. Flinchy's Avatar
        Flinchy -
        Click here to enlarge Originally Posted by Sticky2 Click here to enlarge
        I prefer winpep and Dynojets for all power measurements posted to forums. If you want to claim a record or have the largest point of reference, Dynojet. The graphs look better, the numbers make more sense, it's just better all around.

        I'm not a tuner but if I was I'd prefer a Mustang or Dyno Dynamics.
        Why would you prefer mustang or dynamics? Not like they're cheaper or have any clear advantage that I can see?

        Why not simply have a dynojet with the load cell.. load off for power runs, on for tuning. Seems like it should be the best of both worlds no?

        Something you didn't mention (that I read at least) is that load bearing dynos need routine calibration, which can vary wildly. Hence from one mustang (or any other model) to another of the exact same brand and spec etc. You can get wildly different numbers.

        I've been at dyno days where they start going out of calibration midway through the day, and absolutely absurd figures start to show (low, not high, mostly - like <100hp where it should be 200+ lol)

        A dynojet has the calibration stamped to the specific roller which is locked in the software. Every dynojet will be comparable as such, as long as the correct value is entered.
      1. Sticky's Avatar
        Sticky -
        Click here to enlarge Originally Posted by Flinchy Click here to enlarge
        Why would you prefer mustang or dynamics? Not like they're cheaper or have any clear advantage that I can see?
        Based on what tuners tell me. You would have to talk to them but many tell me they love the Dyno Dynamics for tuning. I'm sure tuners each have their preferences.

        Click here to enlarge Originally Posted by Flinchy Click here to enlarge
        Why not simply have a dynojet with the load cell.. load off for power runs, on for tuning. Seems like it should be the best of both worlds no?
        This option is mentioned in the article. I don't have any experience with these types of Dynojets but you can get the eddy current option from Dynojet.

        Click here to enlarge Originally Posted by Flinchy Click here to enlarge
        Something you didn't mention (that I read at least) is that load bearing dynos need routine calibration, which can vary wildly. Hence from one mustang (or any other model) to another of the exact same brand and spec etc. You can get wildly different numbers.
        I did not, you're right. All dynos require software and hardware maintenance. This is yet another reason I prefer the Dynojet for comparisons though.

        Click here to enlarge Originally Posted by Flinchy Click here to enlarge
        I've been at dyno days where they start going out of calibration midway through the day, and absolutely absurd figures start to show (low, not high, mostly - like <100hp where it should be 200+ lol)
        Never personally experienced this at a dyno day.

        Click here to enlarge Originally Posted by Flinchy Click here to enlarge
        A dynojet has the calibration stamped to the specific roller which is locked in the software. Every dynojet will be comparable as such, as long as the correct value is entered.
        Yep. One reason to love them Click here to enlarge
      1. Flinchy's Avatar
        Flinchy -
        Mm I'm guessing what you're used to and maybe some advantages in the software finer control etc, given they've always been that type of dyno

        Wish I could get hands on with a variety of them..