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      09-23-2017, 01:55 PM   #23
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Quote:
Originally Posted by dkhm3 View Post
when you actually do the math and compare the m3/m4 hp per lb, vs the competition, you'll find that underrated crap to be completely false. The M3 just weighs less and has less hp. Some people love to believe internet bullshit and never actually look at the math.

per car and driver:
M3 comp 8.2 hp/lbs------> 12.2 @ 120 mph
ATS-V 8.3 hp/lbs ----->12.2 @ 117 mph
C63S 7.9 hp/lbs-------> 11.9 @ 123 mph
GUILIA 7.6 hp/lbs -------> 11.9 @ 121 mph

accounting for the better efficiency of the dct vs the autoboxes you can see all cars perform acceleration tests pretty in line with their hp/lb ratios.

http://www.caranddriver.com/comparis...e-specs-page-6

but it's more convenient to believe in a lie. BMW has magical horses!
BTW, your units are reversed and should show lb/hp
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      09-23-2017, 02:01 PM   #24
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Originally Posted by Absurdium View Post
Actually I believe you've interpreted the data wrong. They listed the units as lb per hp, not hp per lb as you've described, which means a higher number is actually worse. With that definition, the M3 has pretty much the second worst weight to power ratio. The ATS-V with roughly the same power to weight, but 20 extra hp posted a trap speed that's 3 mph lower; that is a pretty big difference. Furthermore, the M3 trapped nearly the same speed to the Giulia while being down in power by more than 10% when the Giulia has a much better weight to power ratio 7.6 vs 8.2 (lower is better). Given all this data, it actually supports the theory that BMW has underrated the S55 motor.

I do believe however, that a big part of the M3/M4's good performance numbers is from the efficiency of their turbos, not just because they're underrated. The high midrange torque means that versus an NA car of similar peak power, you're making a significant amount of power higher everywhere else other than the peak. This really matters a lot because as much as peak power is great, you gotta get through the midrange to get there
Don't only look at the data in this post. Look at all the comparative reviews where the Giulia is pitted against the M3/4, the Giulia QV trumps the M3/4 in acceleration by a significant margin, just as their respective power-to-weight ratios suggest.
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      09-23-2017, 02:09 PM   #25
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Quote:
Originally Posted by CanAutM3
Quote:
Originally Posted by Absurdium View Post
Actually I believe you've interpreted the data wrong. They listed the units as lb per hp, not hp per lb as you've described, which means a higher number is actually worse. With that definition, the M3 has pretty much the second worst weight to power ratio. The ATS-V with roughly the same power to weight, but 20 extra hp posted a trap speed that's 3 mph lower; that is a pretty big difference. Furthermore, the M3 trapped nearly the same speed to the Giulia while being down in power by more than 10% when the Giulia has a much better weight to power ratio 7.6 vs 8.2 (lower is better). Given all this data, it actually supports the theory that BMW has underrated the S55 motor.

I do believe however, that a big part of the M3/M4's good performance numbers is from the efficiency of their turbos, not just because they're underrated. The high midrange torque means that versus an NA car of similar peak power, you're making a significant amount of power higher everywhere else other than the peak. This really matters a lot because as much as peak power is great, you gotta get through the midrange to get there
Don't only look at the data in this post. Look at all the comparative reviews where the Giulia is pitted against the M3/4, the Giulia QV trumps the M3/4 in acceleration by a significant margin, just as their respective power-to-weight ratios suggest.
I do agree that the Giulia out accelerates the F8x but the margin is not as big as say versus a C63s. Imo that tells me that Giulia is not as powerful as its claims and M4 is more powerful than it claims. My main point however, was to illustrate that the fellow above me has interpreted the data incorrectly and I do believe the M4 is underrated out of the factory (compared to other manufacturers anyways, except maybe Mercedes)
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      09-23-2017, 02:33 PM   #26
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Quote:
Originally Posted by Absurdium View Post
I do agree that the Giulia out accelerates the F8x but the margin is not as big as say versus a C63s. Imo that tells me that Giulia is not as powerful as its claims and M4 is more powerful than it claims. My main point however, was to illustrate that the fellow above me has interpreted the data incorrectly and I do believe the M4 is underrated out of the factory (compared to other manufacturers anyways, except maybe Mercedes)
I, on the other hand, do not believe this "underrating" BS.

I've posted this many times before, but I'll go at it again here. Modern forced induction engine behave quite differently than engines of yore. The power rating standards used to specify that engines need to be bench tested in steady state (constant RPM) and left to stabilize at each RPM point before the power readings are taken. That remains the best method to obtain the most accurate and repeatable results and was very representative of engine perfromance. However, modern FI engines can actually produce more power in transient state (while accelerating) in the mid to high RPM compared to when they are tested in steady state. Due to this, the SAE power rating standards have been amended to allow the manufacturer to test in transient state to take advantage of those characteristics. The SAE standard however leaves it to the discretion of the manufacturer to test in whatever mode it elects (steady state or transient). This now makes it quite difficult to compare power ratings between manufactures and even more so between FI and NA engines.

That being said, since the Giulia QV, C63, RS5 and M3/4 are all EU manufacturers with FI engines, it is very likely they all obtained their ratings using the traditional steady state method. Now, why does the C63S outpace the Giulia QV? The answer is simple: area under the curve. With 38% more displacement the C63S makes (28%) more torque sooner in the RPM range for a beefier powerband.
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Last edited by CanAutM3; 09-23-2017 at 02:53 PM..
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      09-23-2017, 03:06 PM   #27
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Quote:
Originally Posted by CanAutM3 View Post
I, on the other hand, do not believe this "underrating" BS.

I've posted this many times before, but I'll go at it again here. Modern forced induction engine behave quite differently than engines of yore. The power rating standards used to specify that engines need to be tested in steady state (constant RPM) and left to stabilize at each RPM point before the power reading is taken. That remains the best method to obtain the most accurate and repeatable results and was very representative of engine perfromance. However, modern FI engines can actually produce more power in transient state (while accelerating) in the mid to high RPM compared to when they are tested in steady state. Due to this, the SAE power rating standards have been amended to allow the manufacturer to test in transient state to take advantage of those characteristics. The SAE standard however leaves it to the discretion of the manufacturer to test in whatever mode it elects (steady state or transient). This now makes it quite difficult to compare power ratings between manufactures and even more so between FI and NA engines.

That being said, since the Giulia QV, C63, RS5 and M3/4 are all EU manufacturers with FI engines, it is very likely they all obtained their ratings using the traditional steady state method. Now why does the C63S outpace the Giulia QV? The answer is simple: area under the curve. With 38% more displacement the C63S makes (28%) more torque sooner in the RPM range for a beefier powerband.
The power rating test method is information that I have not been exposed to before; thank you for that explanation. Given this information, I believe perhaps that the problem of our discussion should be more directed at the nomenclature of what is overrated and what is underrated. If say manufacturer A measures their car in the steady state while manufacturer B measures their car in the transient state, and they both produce a car that on paper produces the same amount of HP/TQ. Assuming both cars are forced induction, given the information you've provided, it is likely that manufacturer A's vehicle is faster in real world performance as its measured reading was at the steady state. At this point, do we say manufacturer A's car is underrated or do we say manufacturer B's car is overrated?

But I do understand what you are getting at so perhaps a more appropriate definition would be to say that, BMW, specifically the F8X used a measuring method that is more favorable in terms of producing real world performance than other car makers.

As for the area under the curve concept, I understand that quite well as I've mentioned in my previous post; I've just got it worded differently.

"I do believe however, that a big part of the M3/M4's good performance numbers is from the efficiency of their turbos, not just because they're underrated. The high midrange torque means that versus an NA car of similar peak power, you're making a significant amount of power higher everywhere else other than the peak. This really matters a lot because as much as peak power is great, you gotta get through the midrange to get there."

The higher torque of the C63s does sound like a good explanation for that difference. Considering the weight difference however, the difference between its performance in comparison to the Giulia still impresses me.

Good discussion all in all. Always enjoyable to discuss these awesome vehicles with a fellow enthusiast
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      09-23-2017, 07:04 PM   #28
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Quote:
Originally Posted by Absurdium View Post
I do agree that the Giulia out accelerates the F8x but the margin is not as big as say versus a C63s. Imo that tells me that Giulia is not as powerful as its claims and M4 is more powerful than it claims. My main point however, was to illustrate that the fellow above me has interpreted the data incorrectly and I do believe the M4 is underrated out of the factory (compared to other manufacturers anyways, except maybe Mercedes)
My hastiness, I had the units labelled in reverse, lbs per hp.

The information and the data is the same, because lbs per hp is what I meant to say.

The M3 shows slightly better times vs the weight because of the dct, the power from the engine to the wheels is transferred more efficiently than a conventional torque converter or multi plate wet clutch mct.
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      09-23-2017, 08:02 PM   #29
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Quote:
Originally Posted by dkhm3 View Post
when you actually do the math and compare the m3/m4 hp per lb, vs the competition, you'll find that underrated crap to be completely false. The M3 just weighs less and has less hp. Some people love to believe internet bullshit and never actually look at the math.

per car and driver:
M3 comp 8.2 hp/lbs------> 12.2 @ 120 mph
ATS-V 8.3 hp/lbs ----->12.2 @ 117 mph
C63S 7.9 hp/lbs-------> 11.9 @ 123 mph
GUILIA 7.6 hp/lbs -------> 11.9 @ 121 mph

accounting for the better efficiency of the dct vs the autoboxes you can see all cars perform acceleration tests pretty in line with their hp/lb
ratios.



http://www.caranddriver.com/comparis...e-specs-page-6

but it's more convenient to believe in a lie. BMW has magical horses!

I don't believe in Internet Bullshit, But that is a good one , I read emperical data that which includes Rear Wheel Dynos of my Stock M3 vs. other vehicles such as a stock C7 on the same dyno, same day I dynoed much higher. However, Since you such as smart guy tell me how how did you account for the R-comps in your Insightful analysis above on the GULIA ??? Oh wait you did not Put all cars on the same drag strip, SAME TIRES, same day, same ambient temps, and maybe you have something. BTW Stock M3/M4 have run in the 11's but that doesn't really mean anthing.. A wheel dnyo is a much better measuring devise IMO. I would love to see a GULIA VS M4 same day Dyno
And Yes I have read CAnAutM3's Steady State Explanation as he is quick to remind us every single time this debate arises

Last edited by kitesurfer; 09-23-2017 at 08:11 PM..
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      09-23-2017, 10:36 PM   #30
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Quote:
Originally Posted by kitesurfer View Post
I don't believe in Internet Bullshit, But that is a good one , I read emperical data that which includes Rear Wheel Dynos of my Stock M3 vs. other vehicles such as a stock C7 on the same dyno, same day I dynoed much higher. However, Since you such as smart guy tell me how how did you account for the R-comps in your Insightful analysis above on the GULIA ??? Oh wait you did not Put all cars on the same drag strip, SAME TIRES, same day, same ambient temps, and maybe you have something. BTW Stock M3/M4 have run in the 11's but that doesn't really mean anthing.. A wheel dnyo is a much better measuring devise IMO. I would love to see a GULIA VS M4 same day Dyno
And Yes I have read CAnAutM3's Steady State Explanation as he is quick to remind us every single time this debate arises
Formulate your answers into a question.
Post data from same dynos from same day of stock cars you are discussing.
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      09-23-2017, 11:27 PM   #31
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Originally Posted by dkhm3 View Post

The M3 shows slightly better times vs the weight because of the dct, the power from the engine to the wheels is transferred more efficiently than a conventional torque converter or multi plate wet clutch mct.
WOW how do you have have all the explanations....you must be a powertrain engineer with intimate efficiency knowledge of not only one but of 3 performance transmissions from 3 different manufactures ......or did you just stay at a Holiday Inn Express last night
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      09-23-2017, 11:35 PM   #32
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Originally Posted by kitesurfer View Post
WOW how do you have have all the explanations....you must be a powertrain engineer with intimate efficiency knowledge of not only one but of 3 performance transmissions from 3 different manufactures ......or did you just stay at a Holiday Inn Express last night
Nope, but I did retire at 39, which is much better than staying at Holiday Inn's.
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      09-24-2017, 11:50 AM   #33
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M3/M4 Dynos on 91 octane and some discussion:
http://f80.bimmerpost.com/forums/sho....php?t=1266343

http://jalopnik.com/the-true-power-o...run-1603070524

Alpha Dyno:
http://jalopnik.com/heres-how-much-p...lio-1792840088

Granted these are NOT apples to applea comparison Dynos (dynojet 91 oct vs. Mustang xxoct?) between the Alpha & BMW but it is some food for Thought regarding the kind of power these cars are producing.
It would be nice to see what the Alpha puts down on a dynojet wiht the same fuel.

With all that said....... I would not be surprised if the Alpha that ran the Ring in 7:32 was"Specially Tuned" buy Alpha Engineers before its glory run....I would like to see what Sport Auto time would be with a regular press car.
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      09-24-2017, 02:05 PM   #34
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Quote:
Originally Posted by kitesurfer View Post
M3/M4 Dynos on 91 octane and some discussion:
http://f80.bimmerpost.com/forums/sho....php?t=1266343

http://jalopnik.com/the-true-power-o...run-1603070524

Alpha Dyno:
http://jalopnik.com/heres-how-much-p...lio-1792840088

Granted these are NOT apples to applea comparison Dynos (dynojet 91 oct vs. Mustang xxoct?) between the Alpha & BMW but it is some food for Thought regarding the kind of power these cars are producing.
It would be nice to see what the Alpha puts down on a dynojet wiht the same fuel.

With all that said....... I would not be surprised if the Alpha that ran the Ring in 7:32 was"Specially Tuned" buy Alpha Engineers before its glory run....I would like to see what Sport Auto time would be with a regular press car.
There is no food for thought. Mustangs are know to read lower than Dynojets
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      09-24-2017, 10:30 PM   #35
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Don't worry guys - I'm sure mcc3456 has an explanation for this!!!
Don’t need to explain anything because y’all are BMW circle jerking each other fine on your own.
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      09-25-2017, 07:57 AM   #36
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Quote:
Originally Posted by Powerslide View Post
Don't worry guys - I'm sure mcc3456 has an explanation for this!!!
Don’t need to explain anything because y’all are BMW circle jerking each other fine on your own.
Great comeback!!
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