By on June 23, 2017

2017 Civic Type R (European Version), Image: Honda

The release of the Civic Type R has created a lot of buzz. The recent media launch generated plenty of opinions as to its performance, including some reviewers who believe Honda has underrated the CTR in the same manner it has done with the Accord V6 in the past.

Their speculation seemed to be proven true as a video released from a shop in Puerto Rico showed the car making 301 wheel horsepower. Many outlets reported on the dyno test and, while some showed the data with a little skepticism thrown in, others went all in and told us that the CTR has hidden horsepower.

The real truth behind the dyno test is that it is valueless. We do not have any data on its calibration or the weather, and the dyno operator could have applied any correction factor on the data to boost the results. This is not an isolated case in reporting sketchy dyno results, as I see it multiple times per month from various outlets and, in just about every case, the data and reporting are meaningless. 

We can start with the recent CTR test as an example. It was performed on a DynoJet dynamometer by a shop called DynoCenter in Puerto Rico. Their results show one of the tested cars outputting 295 wheel horsepower while another put down 301 wheel horsepower. These numbers are terribly close to the 306 horsepower as rated by Honda, which would mean the car is either underrated or has very little drivetrain loss.

A general rule of thumb many use is to estimate about 15 percent drivertrain loss for a front-wheel-drive car, which would mean the CTR should be showing about 260 wheel horsepower. So is the CTR underrated from the factory or are there some shenanigans going on? The answer is probably both. However, these tests results don’t help us get there.

Aftermarket chassis dynos are built differently than the factory dyno cells used to test engines and come in a few different flavors. Most DynoJet dynos I have encountered are inertia-style units which have a set of rollers that are fixed weight so that simple physics can be used to make a calculation. The dyno software boils down to using the formula of (Mass x Acceleration = Force) in order to calculate the result since the mass of the rollers is a known value and the acceleration can be measured by how quickly the rollers turn. That force result is then dropped into another equation which takes the distance the rollers ran and divides it by the time it took in order to get a horsepower figure. We’ll keep it simple for the purpose of our story, but MotoIQ has great deep dive showing the math behind the results here.

We now have a horsepower result which can be useful if we’re using the dyno as a tuning tool but there are many obstacles in the way that prevent us from using it to compare to an engine dyno result. The first is that the rollers on this type of dyno spin without any load; turbocharged cars that need load in order to build boost properly will show an inaccurate result. Secondly, the results change depending on elevation, temperature, and humidity, so a car tested in Bayamón, PR at an elevation of 52 feet will have wildly different results from a car tested in Denver at an elevation of 5,280 feet.

Some of these factors can be corrected for. The load issue can be resolved by using a dyno that employs an Eddy Current power absorption unit to add additional load to the rollers in order to more accurately model street driving conditions and properly load up turbocharged cars. DynoJet offers an absorption unit on models in their LC range and many others, like those made by Mustang, always come with one.

Once the load issue is (somewhat) resolved, we can focus on correcting for weather and altitude in order to calibrate the results between two different locations. There are multiple methods of correcting for these factors, ranging from preset formulas as calculated and published by the Society of Automotive Engineers all the way to some guy entering a preset multiplier based on what he thinks is best. The original formula that was released is called STD and, although it is based on the J607 standard released in 1974, some shops — including DynoCenter above — continue to use it.

STD uses a standard set of conditions for temperature, elevation, and humidity, then applies a formula to modify the uncorrected dyno result based on the difference in each. This is a somewhat stable correction factor if used exclusively to compare a single car before and after a change in tune or if used to compare cars side by side, but a more accurate correction factor called SAE was released in 1991 and updated in 2004.

SAE is based on the J1394 standard which offer a few advantages over the older STD standard. It uses a more realistic set of standards for weather and altitude which work better for correction and it also uses a mechanical efficiency modifier that assumes an 85 percent mechanical efficiency at the wheels (like we discussed above). While these changes may make it seem like using the SAE correction factor would yield the higher horsepower figure, the result is actually the opposite — with SAE reading about 4 percent lower on average when compared to STD. This means a Civic Type R showing 301 wheel horsepower using the STD correction would likely come down to around 289 horsepower if the SAE correction was used.

The third method of correcting values involves doing a manual correction factor and, unfortunately, it is still common in many shops. The biggest driving force for using this type of correction factor appears to be online bench racers who want to have the highest final figure. While using a manual correction factor won’t affecting how a car is tuned as long as the same one is used in the beginning and the end, it will affect the final value. Many shops start with STD and then decided to create their own mechanical efficiency modifier through a 1.15 correction factor. In those cases, the uncorrected value is always multiplied by 1.15 to create the final “corrected” results, which could mean that a car showing an uncorrected value of 262 wheel horsepower could jump to showing a “corrected” value of 301 horsepower once this manual correction factor is applied.

Just looking at these factors, we can see there many opportunities for inaccuracy — and this is just the first layer. Naturally aspirated cars can be equalized using formulas to some point, but when we get to forced induction, several other factors come into play. Modern engine management systems are very sensitive to temperature changes, fuel type, and other factors. The systems will modify fueling and, in turn, power in order to make a car perform optimally. Since these fueling changes are being made on the fly, even small things like whether a hood is open or closed on the dyno will affect the final results. The intercoolers for these turbochargers also require proper airflow, so something like my WRX would technically need a duct mounted fan going directly into the hood scoop with some type of PWM control in order to simulate airflow at each speed.

There’s plenty more nerding out that can be done when talking about how dynos work, though the point here is that almost none of these results are comparable and there isn’t any value in using them as the basis of a story. The Civic Type R might be slightly underrated, but probably does not make 40 more horsepower than it was rated for — and that Dodge Viper that was tested on a dyno in New Jersey probably did not gain power over the years. None of these figures can be accurately compared since we do not have the rest of the data used and don’t know how the car was set up when placed on the dyno.

Because test results are exciting and awake the bench racer inside all of us, writing about them is always tempting. However, since the factors mentioned above are almost never available, it is hard to do it accurately. There is one other method that can legitimize a dyno result, something I’ve only seen once in a recent story by David Tracy at Jalopnik. That is, to use other cars that have run on the same dyno under similar conditions. While this type of reporting does not require much additional effort, it at least allows us to create a scale, based on the results of several vehicles, that shows how cars are performing compared to their factory test results.

[Image: Honda]

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34 Comments on “Spinning Your Wheels: Here’s Why Dyno Results Are Incomplete and Useless...”


  • avatar
    2drsedanman

    A lot of these dyno numbers and Nürburgring times are nothing more than dick measuring contests. Razor sharp handling and > 300 horsepower always comes in handy when I’m driving to work in traffic at 35 mph. Besides, whatever the horsepower number is, it’s never enough. There will always be someone (usually a car journalist/reviewer) throwing out the same old tired line:”What this car needs is 30 more horsepower”. This reached peak idiocy with reviews of the Mazda 6.

    • 0 avatar
      FreedMike

      I disagree completely. A better engine can completely transform a car, and I can think of no better candidate for a better engine than a Mazda 6. An extra 30 hp is EXACTLY what that car needs.

      • 0 avatar
        2drsedanman

        It may need more horsepower, but there has to be an endpoint somewhere. If it had more horsepower, then someone would complain regarding the lack of brakes. This would lead to bigger wheels to accompany the brake upgrade which would lead to ride degradation.

        The only reason I use the 6 as an example is I really, really wanted to like that car and did a lot of research and test drives. I felt the power was ok for me, but the deal breaker was the intrusion of the B-pillar. It seemed I was always hitting it getting in and out of the car and my head was too close to it once inside. It just felt claustrophobic and not something I could live with on a daily basis. Too bad, I still think it is a great looking car.

        • 0 avatar
          FreedMike

          MOAR POWER makes up for a multitude of automotive sins.

          What did you end up buying?

        • 0 avatar
          JuniperBug

          I enjoyed Jack’s article on Road & Track about “The Hayabusa Effect.”

          You get used to whatever power level is available to you. In my early 20s I had a basketcase of a Ninja 600. The brakes were warped, suspension was worn out, but the engine pulled as-new, and the bike was rated at doing 0-60 in under 4 seconds, quarter mile in the low 12s. After a season of riding it, I felt it was a little slow.

          I later had a Suzuki TL1000S which I once *accidentally* wheelied at 60 MPH while passing a slower car in second gear. By the end, I thought it was kind of lame when I couldn’t exceed 125 MPH by the end of a highway onramp.

          Speed is like a drug; the brain gets used to it, and you’ll always need more if you’re looking for that rush. Which means to me that you can ultimately have just as much fun with 200 hp as 600. I spent yesterday bombing around Laurentian back roads in a car that struggles to keep up with a new Hyundai Accent in a straight line, and still was going a good bit faster than what would be considered reasonable, and at the limit of my skill and nerve. More power would’ve just required more restraint, and what’s the fun in that?

          • 0 avatar
            Sigivald

            “It is more fun to drive a slow car fast than a fast car slow” is wisdom for the ages.

          • 0 avatar
            NMGOM

            Sigivald – – –

            Exactly.

            I get more of a real kick out of zipping and bouncing about in my 2DR Jeep Wrangler at 40 MPH than I do in my BMW Z4 at 80 MPH. Go figure. And, I don’t collect nearly as many courtesy notes from the local gendarmes.

            =======================

    • 0 avatar
      NormSV650

      I like 60-100 mph times. Good for passing merging and with 350 lb-ft of turbo-4 torque you put a vehicle just about any place in traffic.

    • 0 avatar

      Except every person I know who has purchased a Type-R has done so through the Honda Racing program and is using theirs to race . . . . so . . . . they actually do care about razor sharp handling and 300+ hp.

  • avatar
    Detroit-Iron

    I never understood why people try to derive engine HP from WHP. WHP is what it makes at the wheel, what does it matter if it makes 20-30 more at the crank? If we are bench racing anyway, consider a hypothetical competition between two cars that weigh the exact same, however car A makes 270 WHP with 20 HP driveline loss for a theoretical 290 crank, and car B make 260 WHP, but has 40 HP driveline loss. Does anyone really think car B is better? Does anyone care at all?

  • avatar
    EAF

    Dynos are great in that they provide a safe place where you can have your car tuned. Well, they are safer than tuning and data-logging on public roads anyway.

    As a benefit, you get before & after figures on the same day, same temp, same altitude, same dyno.

    As far as the CTR goes, I think if dynos across the country continue reporting stock WHP figures this high; it would be safe to conclude that Honda underrated the CTR.

    Personally, on my FWDs, 300whp is the absolute ceiling. Beyond that the power is completely useless on the street, without slicks, not to mention the ridiculous amounts of torque steer.

    • 0 avatar

      That is exactly the way I’ve always viewed them. A dyno is a tool, much like a torque wrench that allows you to complete a task on a car. They are great for tuning and seeing changes in power or fueling over the entire rev range.

      As far as the CTR being underrated, we can take a couple of other cars that are turbocharged and in the same power range and run them all back to back on the same dyno and get a pretty good idea of how well they compare.

    • 0 avatar
      Sigivald

      Good design and electronics make torque steer not an issue, don’t they?

      (I mean, my XC70 has 300whp, per Volvo, and while I don’t think it *needs* more power, I can’t see how 350 would be “useless”, and if it has *any* torque steer I certainly don’t notice it.)

  • avatar
    VW4motion

    The goal to have more HP will never end. Ford and Chevy been competing in the HP championship for years. More is better for men with lack of genital girth. This theory can be used for the rolling coal boys. For these type, More smoke and more chemicals into the air equals more HP which makes up for lack of penis size.
    So dyno testing is the only real measure for HP in turn helping out men that lack length in other attributes in their lives.

    Having said the above statement. I’m shopping for a 1 ton pickup with as much HP as possible.

    • 0 avatar
      OzCop

      …as has Mopar…Max Wedges and Hemi’s of the 60’s and 70’s, and the current 707 and 808 hp Chargers and Challengers…

      • 0 avatar
        VW4motion

        Absolutely, Mopar is actually king of the HP wars.

        Asian market is in that HP war now and we get articles like this one that dyno testing doesn’t matter anymore.

    • 0 avatar
      mike9o

      Lightweight. I’m getting a 14.8L diesel semi with 1,850 lb-ft of torque that will blanket the west coast while rolling coal.

    • 0 avatar
      Sigivald

      I find it amusing that my 2007 SuperDuty has less horsepower and torque than three of the five* F-150 engine options this year.

      And that it weighs about a ton more, but *still* gets out of its own way pretty well (I credit the 4.10 rear end for that).

      (* And the 2.7L EB has more horsepower and barely less torque; the only true loser in comparison is the NA 3.5.

      I suspect the F-150 EB engines all have a better torque curve than my 5.4, as well as *not possibly being more prone to failure* than the farkin’ Modular.)

      • 0 avatar
        iNeon

        I’m not sure what to make of this.

        Should we all be 5.5″ers in Accords to make you more comfortable– or might we just drive to work without you thinking about our peens?

  • avatar
    BigOldChryslers

    Thanks for summarizing the issues with chassis dyno setup. I knew that it was easy to generate fancifully high chassis dyno results, but didn’t know the rationale that the operators used to justify their setups.

    Some bigger car shows will have a portable chassis dyno on-hand which you can pay to use. Sounds like it would be helpful to know not only what method the operators used to calculate correction factors, but also the specs of the other cars running on the same day for comparison purposes.

  • avatar
    Menar Fromarz

    Regardless of the numbers, it’s too bad the damn thing looks so hideous. Jesus Murphy. Do they give you a bag to wear on your head while driving it?

    • 0 avatar
      redmondjp

      Nobody’s going to see you driving it, as they are all too busy checking their phones to even notice what your car looks like ;)

      • 0 avatar
        Pesky Varmint

        “Nobody’s going to see you driving it, as they are all too busy checking their phones to even notice what your car looks like ;)”

        Don’t bother me, I’m on the phone!

  • avatar
    LazyJK

    For me a dyno is a tool to either tune a car or check engine health. It’s way too easy to either screw up or doctor the results.
    I did take my current car to the dyno since it was ECU tuned by some unknown person for the previous owner. Everything thankfully looked OK, apart from slightly wavy curves – possibly the car could benefit from higher octane fuel, but not in a noticeable way and the tune was very safe in general.

  • avatar
    06M3S54B32

    “Personally, on my FWDs, 300whp is the absolute ceiling.”
    Horsepower doesn’t cause torque-steer. . Torque does.

    • 0 avatar
      JuniperBug

      Unless your engine is making its torque at zero RPM (in which case it’s not going to get a lot of work done), horsepower is a byproduct of torque.

  • avatar
    Heino

    Elvis Perezly is alive, he was hiding in PR.

  • avatar

    Mustang dynos have been breaking hearts and crushing egos since their inception – I don’t trust any other dyno.

  • avatar
    thornmark

    >>including some reviewers who believe Honda has underrated the CTR in the same manner it has done with the Accord V6 in the past.<<

    Accord 4 cylinder, current gen – C&D pointed that out.

  • avatar
    Andy

    Somebody got their paper racing heart broken by a dyno and wrote an article to poo poo on dynos…. lol My mildly modified F150 ecoboost dyno’s at 366hp and 484ft/lbs tq.


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