Why would BMW ever under rate their horse power on an engine especially an M3/4

[JS919]

Originally Posted by mkoesel

One reason would be to establish a proper hierarchical relationship among products with respect to their position in the lineup. For example, perhaps BMW has good reason to want the M3/M4 to sit below the 550i/650i (especially the latter) when you compare the horsepower on their spec-sheets. It may be that research tells them that a 650i buyer values this. Remember, marketing is not about being forthright or forthcoming, its about telling people what they want to hear. On a side-note, I would make a terrible marketer.

This explanation doesn't make sense to me. If BMW is underrating all their engines that would mean the 550i/650i is underrated as well. So if the idea was to keep a sizable HP gap between the M3/M4 and 550i/650i because the 550i/650i buyers value it, why not just rate both engines at their correct values and there still will be a substantial gap.

Not to mention an M3 and 550i are nearly the same price and the M4 and 650i are not to far apart either.

[mkoesel]

Originally Posted by coloradoe92m3

If it were from other reasons listed like keeping hierarchy in check, then the NA motors would have also been "underrates"

Some were. And by no means should my explanation have been taken as a blanket statement.

it is solely due to turbos extreme variance and susceptibility to heavy soak, fuel quality etc.

Another plausibility among the others given in this thread. Note that the OP asked for possible explanations. Opinions (and these are all opinions, after all) are naturally going to vary.

[M3ryder55]

how about this, lets say, bmw of late, has been issuing "conservative numbers" ; )

[tisme]

Originally Posted by ZGM3

Can someone from Europe chime in on this.
I often thought that due the extremely high cost of insurance in Europe (especially the UK) that rates have a correlation to the HP of the vehicle.
I could be wrong, but if you talk to anyone from the UK and ask them what their insurance on their car is compared to the US, you will see that we have it extremely good and cheap.

In the UK, rates are a direct correlation to the car's "Insurance Group" which gets assigned to each model of each car. The insurance group is set based on value, top speed, acceleration etc, so the M3 will be fairly high and is 43 (Ferrari F430 is 50, the top and a Toyota IQ is 3, near the bottom).

I was quoted £350 fully comprehensive insurance per year on an M3 6 months ago; but I expect I'll have to pay more when mine arrives

[tomwac]

Originally Posted by aus

Because if you state you make X HP but really only man x HP, you get sued and have to pay owners a boat load of money or buy the car back.
It also helps insurance premuims to have a lower listed HP reading.

.

Not exactly... I took my E92M3 LCI to the dyno (at a very reputable tuner) and it showed 385hp at the crank iso 420hp (EU specs). I went to the dealer and explained the situation, they all started to scratch their heads and asked me to leave the car for a few days. They put it on their own dyno several times and the best result was 384hp at the crank (torque was down to, but I don't remember by how much). I said that this is unacceptable and after a few calls back and forth with Munich they just showed me a paper where BMW states that a 10% 'variation' is normal to them and I just have to live with that fact...

[ss134]

I remember reading an interview from someone at BMW M ( can't remember the name) a couple of months ago that stated that the S55 will achieve it's stated HP in all conditions at all times. This would suggest that 425hp will be the absolute minimum this engine will produce in the worst conditions ie altitude, heat, poor fuel etc.

I personally don't care for hp outputs but I do care about the performance stats and from what I've seen this car is going to be considerably faster than E92. Whether the engine is underrated or not doesn't matter 0-1000m in 21.9 is fast!!

[Kadema]

0-1000 km in 21.9s is indeed fast. Very fast.

[swamp2]

Originally Posted by JoeFromPA

First off, haven't you ever heard you can't compare dynos across different machines? A normal dyno to dyno comparison may be 10% different.

Now we are comparing expected wheel dyno output to BMW benchmarked engine dyno? This is getting ridiculous.

Turbo engines are very volatile to external factors. Heat soak, fuel grade, air flow to the engine. They are more likely to have larger swings on a dyno.

BMW MAY not be under-rating, but instead be producing an engine dyno rating that can be consistently achieved using lower quality fuel, some heat soak, and non-ideal air flow or air density (i.e. providing a dyno that's accurate at 4000 feet elevation)

But hey, let's all ignore the actual science and possibilities here and claim "under-rating compared to my sea level, Joe's mustang dyno + massive fans dyno which measured the output at a completely different part of the car and applied an unscientific adjustment for parasitic loss!"

You miss a key point I've already made here in this thread. I fully agree that one can get just about any result from a dyno that they want to. However, we can judge a car being under-rated or not from its performance. We can also judge it by simulation. Yes losses in simulation are a bit of an imprecise science but such an objection is fully covered by a simple "bracketing" exercise. When dyno, testing and simulation all conclude under-rating I believe under-rated it is.

Also, the point about tubro charging is good and producing a given amount of minimum power under a broad range of conditions seems like a darn reasonable explanation. If you have a better density altitude, expect more power.

[CanAutM3]

Originally Posted by tomwac

Not exactly... I took my E92M3 LCI to the dyno (at a very reputable tuner) and it showed 385hp at the crank iso 420hp (EU specs). I went to the dealer and explained the situation, they all started to scratch their heads and asked me to leave the car for a few days. They put it on their own dyno several times and the best result was 384hp at the crank (torque was down to, but I don't remember by how much). I said that this is unacceptable and after a few calls back and forth with Munich they just showed me a paper where BMW states that a 10% 'variation' is normal to them and I just have to live with that fact...

Sorry, but I call on this story.

[imserious]

The only time I can remember auto manufacturers purposely underrating cars were the japanese in the 90s when every car strangely had 298 hp, when in reality it was more. That was due to some sort of regulatory HP limit that has since been lifted.

BMW has nothing to gain from underrating HP, but a lot to lose from overrating HP. As many mentioned, turbo engine performance varies due to environmental conditions so they choose a conservative number that is not going to be challenged. I think other manufacturers are more aggressive in their "avg" therefore there is less a sense of underrating. This is a non-issue in N/A engines.

This is nothing but a good thing for people who actually like driving their cars and paying less insurance money while doing it.

[aus]

Originally Posted by tomwac

Not exactly... I took my E92M3 LCI to the dyno (at a very reputable tuner) and it showed 385hp at the crank iso 420hp (EU specs). I went to the dealer and explained the situation, they all started to scratch their heads and asked me to leave the car for a few days. They put it on their own dyno several times and the best result was 384hp at the crank (torque was down to, but I don't remember by how much). I said that this is unacceptable and after a few calls back and forth with Munich they just showed me a paper where BMW states that a 10% 'variation' is normal to them and I just have to live with that fact...

If you go find 20-30 cars with the same low out put, then get a class action lawsuit, it'll work. Mazda got nailed and I think Ford got nailed too in the US.

.

[Falafel Combo]

The quality of pump gas also varies, which may influence HP measurements.


Besides, It's always good business to under promise and over deliver.

[ss134]

Originally Posted by alpinweiss 335i

The quality of pump gas also varies, which may influence HP measurements.


Besides, It's always good business to under promise and over deliver.

Plus when the comparison tests begin and the ///M with ' only 425hp' beats RS and AMG competitors with more claimed Hp it just adds to that M car mystique- 'how did the M with 40hp less ( just a guess ) beat the higher powered cars?!?!'

[tomwac]

Originally Posted by CanAutM3

Sorry, but I call on this story.

Care to explain why?

[tomwac]

Originally Posted by aus

If you go find 20-30 cars with the same low out put, then get a class action lawsuit, it'll work. Mazda got nailed and I think Ford got nailed too in the US.

.

Not in EU... you just need to bend over here...

[CanAutM3]

Originally Posted by tomwac

Care to explain why?

Can you elaborate which tuner shop took the engine out of the car and installed it on a bench dyno to measure 385hp crank?

Can you also tell us which BMW dealer has a bench dyno on which to test engines to get crank power and actually take the engine out of your car to test it? I seriously doubt any dealer would have even have a chassis dyno much less a bench dyno.

Further, I also seriously doubt that BMW says a 20% variance (+/-10%) on engine output is normal.

[tomwac]

Originally Posted by CanAutM3

Can you elaborate which tuner shop took the engine out of the car and installed it on a bench dyno to measure 385hp crank?

In the EU nobody measures at the wheels but the dyno takes into account the rolling resistance or something like that (I'm not an expert)

Originally Posted by CanAutM3

Can you also tell us which BMW dealer has a dyno on which to test engines?

see above...if the dealer comes back with the same numbers as the tuner, I would guess it's a close call

Originally Posted by CanAutM3

Further, I also seriously doubt that BMW says a 20% variance (+/-10%) on engine output is normal.

Whatever dude, didn't know you were standing next to me when they were explaining it to me

Carry on...

[M4TW]

Originally Posted by ss134

Plus when the comparison tests begin and the ///M with ' only 425hp' beats RS and AMG competitors with more claimed Hp it just adds to that M car mystique- 'how did the M with 40hp less ( just a guess ) beat the higher powered cars?!?!'

Exactly. Most of BMW's cars are benchmarks in their respective classes and hence targets for their competition - especially the M3. Cars take a while to develop so BMW would have every reason to understate the performance metrics of their cars slightly so that their competitors adjust their engines and drivetrains accordingly. Then when the comparisons start, their competition discovers that they've been sandbagged once again.

Best play in poker is when someone believes that they have a better hand than you.

[CanAutM3]

Originally Posted by tomwac

In the EU nobody measures at the wheels but the dyno takes into account the rolling resistance or something like that (I'm not an expert)

see above...if the dealer comes back with the same numbers as the tuner, I would guess it's a close call

Whatever dude, didn't know you were standing next to me when they were explaining it to me

Carry on...

No answers to my question?

Then the call remains

[Alpine F31]

Originally Posted by aus

If you go find 20-30 cars with the same low out put, then get a class action lawsuit, it'll work. Mazda got nailed and I think Ford got nailed too in the US.

Hyundai did too. My wife got a check from a class action suit against Hyundai because of overrating horsepower numbers.

"Hyundai Motor America, the United States arm of the automaker, admitted in September 2002 that it overstated the horsepower on the Santa Fe, Sonata, Tiburon and other models sold in the United States."


http://www.nytimes.com/2004/06/22/bu...ower-suit.html

[tomwac]

Originally Posted by CanAutM3

No answers to my question?

Then the call remains

You need to learn how to read iso acting like God-knows-all

And btw, the fact alone that you directly assume that people have nothing else to do with their lives than making up stories just to post them on some forum, says a lot about you and your life ...

Like I said: whatever dude, I give zero f*cks what you think, just shared my story on how (recent, starting with about E46, excluding the blown engines) BMW's are notorious with delivering less power than promised...(except for the M550d which never delivers 380hp)...okay, raise your BS flag again and call it quits... But then, how can I argue with someone who has all the inside memo's from BMW on power trains and even writes statements on behalf on Munich to Belgian dealers about engines not delivering...how else can you know that I'm making it all up... Get a life, I'm done with this conversation...

[CanAutM3]

Originally Posted by tomwac

You need to learn how to read iso acting like God-knows-all

And btw, the fact alone that you directly assume that people have nothing else to do with their lives than making up stories just to post them on some forum, says a lot about you and your life ...

Like I said: whatever dude, I give zero f*cks what you think, just shared my story on how (recent, starting with about E46, excluding the blown engines) BMW's are notorious with delivering less power than promised...(except for the M550d which never delivers 380hp)...okay, raise your BS flag again and call it quits... But then, how can I argue with someone who has all the inside memo's from BMW on power trains and even writes statements on behalf on Munich to Belgian dealers about engines not delivering...how else can you know that I'm making it all up... Get a life, I'm done with this conversation...

You come on an internet forum with an improbable story to attempt to justify your claim that BMW defrauds its customers with engines that are overrated. You then get upset because somebody calls you out

You're right about about one thing, time to move on