[ChrisM4]

In the end what matters is what’s to the wheels and trap speed.

The trans, differential, light forged wheels are all likely to be very efficient compared to what’s being used as the correction factor by the chassis dyno to guesstimate crank horsepower.

For example you compare the efficiency of a drag car with built TH400, 5000rpm stall non lock up converter, 9 inch rear end, 35spline axles and a heavy driveshaft against the BMW and it’s no comparison in terms of parasitic loss. (A 20-25% loss on a drag car could be 8-10% on a modern car like the G80/G82)

Either way any car trapping 122-123mph at 4100pds with driver is flying for a stock street car.

[hooked]

What if BMW/ZF have figured out a way to reduce the drivetrain losses from the crank to the wheels? Has anyone been able to measure both on the same vehicle to compare? I think most people/dyno operators assume a 15% DT loss? What if it's actually <10% putting the crank and wheel HP numbers closer together?

[MiamiFan13]

Originally Posted by ChrisM4

In the end what matters is what’s to the wheels and trap speed.

The trans, differential, light forged wheels are all likely to be very efficient compared to what’s being used as the correction factor by the chassis dyno to guesstimate crank horsepower.

For example you compare the efficiency of a drag car with built TH400, 5000rpm stall non lock up converter, 9 inch rear end, 35spline axles and a heavy driveshaft against the BMW and it’s no comparison in terms of parasitic loss. (A 20-25% loss on a drag car could be 8-10% on a modern car like the G80/G82)

Either way any car trapping 122-123mph at 4100pds with driver is flying for a stock street car.

Bingo!

[FC4]

Originally Posted by B_davis

Why do they even attempt to show BHP... it's entirely interpolation

Originally Posted by chris719

Wake me up when someone runs one on an engine dyno to get a real number, not some estimated number with huge correction factors.

Europeans are obsessed with estimating BHP, rendering all their effort completely useless.

[GOLFFRR]

nice,

[Forzanerazzurri]

Originally Posted by TJR_///M3

EU Type Approval regulations have a conformity of production requirement. This is what it says for engines:
“During the tests to verify conformity of production, the power shall be measured at two engine speeds S1 and S2, corresponding respectively to the measurement points of maximum power and maximum torque accepted for type approval. At these two engine speeds, which are subject to a tolerance of ± 5 per cent, the net power measured at least one point within the ranges S1 ± 5 per cent and S2 ± 5 per cent shall not differ by more than ± 5 per cent from the approval figure.”

Non-compliance can result in withdrawal of type approval, which precludes sale of the vehicle:
“The approval granted in respect of a drive train type pursuant to this Regulation may be withdrawn if the requirements set forth above are not met or if a drive train bearing the approval mark does not conform to the type approved.”

So… do we really think BMW is consistently producing engines that are significantly (more then 5% ) above their type approval rating?

Sorry, you think car manufacturers follow EU regulations? Did you miss the whole Dieselgate scandal?

[TJR_///M3]

Originally Posted by Forzanerazzurri

Sorry, you think car manufacturers follow EU regulations? Did you miss the whole Dieselgate scandal?

Valid comment, but I don’t think the situations are comparable.
Also, I think the $25B penalty that VW was hit with is probably a disincentive to any OEM contemplating knowlingly breaking the rules.
Additionally, I am not sure what BMW would gain by certifying at a lower power output than the engines actually deliver. If they were consistently delivering 8-10% over the certified level, they would want to use that in the marketing material…

[Forzanerazzurri]

Originally Posted by TJR_///M3

Valid comment, but I don’t think the situations are comparable.
Also, I think the $25B penalty that VW was hit with is probably a disincentive to any OEM contemplating knowlingly breaking the rules.
Additionally, I am not sure what BMW would gain by certifying at a lower power output than the engines actually deliver. If they were consistently delivering 8-10% over the certified level, they would want to use that in the marketing material…

But they commonly do certify at lower power output than the engines deliver. This has been tangibly proven over and over.

They also wouldn't be hit with anything like 25b in penalties for this because there really are no damages to consumers (ie, no misleading fuel consumption and environmental emissions figures). Like VW killed people and they still didn't care.

[TigahRouge]

I said it had to be at least 540hp the first time I drove my G82 comp two and 3/4 years ago!! Good to see the numbers verified!!

[CrownRoyal79]

Originally Posted by OUGrad05

This guy horsepowers…

r/ThisGuyThisGuys

[TJR_///M3]

Originally Posted by Forzanerazzurri

But they commonly do certify at lower power output than the engines deliver. This has been tangibly proven over and over.

They also wouldn't be hit with anything like 25b in penalties for this because there really are no damages to consumers (ie, no misleading fuel consumption and environmental emissions figures). Like VW killed people and they still didn't care.

Agree - I am sure BMW errs on the conservative side, but I remain skeptical that in truly comparable test conditions for engine alone on dyno (not backing up from WHP to crank) with the same ambient, humidity, fuel, intake and exhaust arrangement, etc. the engines are routinely giving 8-10% more power than certified.

Agree, they wouldn't be fined anything substantial.
VW cheated because with the parameters needed to meet the emission requirements the cars performance was unacceptable. So they sensed that the vehicle was on a test cycle and ran a different calibration from what the vehicles ran on the road - I seem to recall that it was steering related, when no steering input was detected on the emission chassis rolls it ran one setting, when steering input was detected on the road it ran a different one... or maybe that was a cheat used by somebody else )
This situation is different... the vehicle (engine) is performing better than they claim, so why not take credit?

Perhaps the truth is that they now have enough conformity of production data to say with certainty that the engines are consistently giving more power, hence the rumored power bump in 25MY.

I'm happy either way.

[Forzanerazzurri]

Originally Posted by TJR_///M3

Agree - I am sure BMW errs on the conservative side, but I remain skeptical that in truly comparable test conditions for engine alone on dyno (not backing up from WHP to crank) with the same ambient, humidity, fuel, intake and exhaust arrangement, etc. the engines are routinely giving 8-10% more power than certified.

Agree, they wouldn't be fined anything substantial.
VW cheated because with the parameters needed to meet the emission requirements the cars performance was unacceptable. So they sensed that the vehicle was on a test cycle and ran a different calibration from what the vehicles ran on the road - I seem to recall that it was steering related, when no steering input was detected on the emission chassis rolls it ran one setting, when steering input was detected on the road it ran a different one... or maybe that was a cheat used by somebody else )
This situation is different... the vehicle (engine) is performing better than they claim, so why not take credit?

Perhaps the truth is that they now have enough conformity of production data to say with certainty that the engines are consistently giving more power, hence the rumored power bump in 25MY.

I'm happy either way.

Bang on. What a crazy story.

[G80indy]

And don’t forget
Less loss in a manual
Vs
Automatic
😆😉

[davidmct-M3]

I think I might have said this before in another similar thread. The engines will give a range of outputs due to air pressure (altitude), ambient temperature, fuel quality etc. the DME will aim to compensate but I am not surprised that sea level and reasonable temperatures give a bit more power than quoted. Plus someone previois stated that dyno’s are only good at measuring relative power differences as they are not calibrated and comparing between machines is a fools errand.

[turbojg]

It's a matter of choosing your poison. When I had my custom/performance shop I owned an 'engine' dyno. For me the engine dyno was more convenient because I built engines and a lot of the engines went into racing boats which would make a chassis dyno impractical. I felt the engine dyno was more accurate when comparing data between dynos as it was direct drive, force is measured with calibrated load cells, and all ambient factors were compensated for in a known fashion with the exception of fuel quality. However, it wasn't real world because of the losses in the vehicle/boat it was installed in.

Chassis dynos make getting horsepower numbers easier without removing the engine from the vehicle and give a better idea as to how the engine/vehicle will perform in real life. But since there is a lot more variables due to mechanical parts and coupling the dyno to the vehicle there can be a lot more inaccuracy between dynos making them more valuable as a reference in tests performed on the same dyno.

Another factor is how the tests are performed. Energy gain or loss due to rotational mass can add or detract from the numbers depending on rate of change of speed or direction of the test. If one is trying to convert between BHP and WHP that is a crap shoot unless one has consistent data on the vehicle losses.

[bjcarls]

Originally Posted by TJR_///M3

This situation is different... the vehicle (engine) is performing better than they claim, so why not take credit?

I think they do it for competitive and marketing purposes. Isn't it fun to see a head to head competition with a ~3/4/500hp Audi, MB and BMW and for some reason the BMW is (almost always) punching above its weight class.

[perezr10]

Originally Posted by Higgs Boson

BMW rates their engines using static point dyno testing

sweep tests give higher numbers

BMW doesn't underrate their numbers, the aftermarket consistently performs the test differently giving a different result

Even so, we’ve all seen countless video drag test comparisons where the host ends with something like this:

“And so the BMW, with the worse power/weight ratio, somehow managed to win this drag test!”

[Higgs Boson]

Originally Posted by perezr10

Even so, we’ve all seen countless video drag test comparisons where the host ends with something like this:

“And so the BMW, with the worse power/weight ratio, somehow managed to win this drag test!”

That would make sense if the other manufacturers did their tests like the magazines. Doesn't change anything.

Put them all on the chassis dyno back to back and they make what they make. Put them all on the drag strip same day/time and they run what they run.

I'm not saying that the BMW making more power than BMW rates them at is a lie, I am saying the testing method is different and if you test them all like BMW does, they will all show less power.

That's not the same thing as saying a car makes 500 and it really makes 550. If you don't take the same test, you can't compare answers. I am not talking about the "what" but rather the "why."

[Tobster3]

Originally Posted by TJR_///M3

Perhaps the truth is that they now have enough conformity of production data to say with certainty that the engines are consistently giving more power, hence the rumored power bump in 25MY.

I'm happy either way.

Interesting point! Has there been anything publicly announced on what changes with the 2025 Car have resulted in more power?

[mcx7]

Hi my results on a dyno seems low? 23 Comp xdrive.
I think they didn’t even put a fan in front of the car. Just 1 run.
Mods = 300c dp + single mid pipe and a MST intake. Otherwise stock. 326wkw is 437whp I’m going backwards lol ?

[MT6]

Not skilled on how to Dyno, I would try Rwd with sport+ for engine mode yeah a fan will help

[Mapper]

Originally Posted by chris719

Exactly. It's far more likely that these chassis dynos are applying too much correction. They are good for relative numbers only IMO. It's also possible that BMW test conditions are not 25 C at sea level etc.

The turbo BMWs always perform very well in real drag races also, but this is plausibly explained by the fact that they have excellent area under the power curve. Peak torque and peak horsepower don't tell much of a story.

It is all too common to see a dyno operator apply a SAE J1349 or similar correction on a wastegate controlled turbo engine... which one isnt supposed to use. Uncorrected is best due to the nature of the air in the manifold vs ambient and if one asks the manufacturers of the dynamometer they say the same thing.