# Truth in Horsepower



## LDV330i (May 24, 2003)

Many of us have always wondered how a 330i could keep and best the acceleration of cars like the G35, Acura TL, etc. which had motors rated at 30 to 50 HP higher than the BMW. SAE has last year updated its procedures for testing motors for horsepower. A third party witness is now required at the tests. It appears the biggest losers in the new horsepower rating are the japanese brands. The Acura TL is now rated at 258 HP, it was previously rated at 270 HP. Acura acknowledges this drop on their website. American cars made some modest gains when retested. 

Car and Driver has article on this issue here.


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## hawk2100n (Sep 19, 2005)

Finally some truth in the ratings that they post on these cars. I like the designs of acuras, but who wants a 270, or 258hp front driver. Not me.


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## hugh1850 (Jun 20, 2003)

LDV330i said:


> Many of us have always wondered how a 330i could keep and best the acceleration of cars like the G35, Acura TL, etc. which had motors rated at 30 to 50 HP higher than the BMW. SAE has last year updated its procedures for testing motors for horsepower. A third party witness is now required at the tests. It appears the biggest losers in the new horsepower rating are the japanese brands. The Acura TL is now rated at 258 HP, it was previously rated at 270 HP. Acura acknowledges this drop on their website. American cars made some modest gains when retested.
> 
> Car and Driver has article on this issue here.


I figured that the BMW was geared higher than the G, hence the similar performance. :dunno: I would be curious to know if the changes will affect the G's stated HP.


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## SpeedFreak! (May 1, 2005)

Holy crap... :yikes: as if the Scion wasn't already bad enough... no wonder my lap times are so bad.. :eeps:


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## iateyourcheese (Sep 9, 2004)

SpeedFreak! said:


> Holy crap... :yikes: as if the Scion wasn't already bad enough... no wonder my lap times are so bad.. :eeps:


People that make graphs like that should be shot. It looks like the Scion has 1/8th the hp of the other cars. Well comparing things, use 0 as the origin.


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## Test_Engineer (Sep 11, 2004)

LDV330i said:


> Many of us have always wondered how a 330i could keep and best the acceleration of cars like the G35, Acura TL, etc. which had motors rated at 30 to 50 HP higher than the BMW.


I think the biggest reason is the differences in the motor configuration. An Inline 6 has a much broader and flatter torque curve, than a V6 which tends to be more peaky. It's all about the area under the curve and how well it is matched to the transmission ratios.


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## MR325iT (Feb 21, 2002)

hugh1850 said:


> I figured that the BMW was geared higher than the G, hence the similar performance. :dunno: I would be curious to know if the changes will affect the G's stated HP.


Me too. That comparison test in C/D recently included both the TL and G35. Both cars went 0-60 in 5.9. Both were manuals, and IIRC their weights weren't far off. I didn't look at gearing, but if the TL was only making 258HP, and the G was making a "claimed" 298, how did they wind up so close?

I'll be interested to see if Infiniti restates their numbers, however I think it's purely voluntary.


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## 99flhr (Apr 12, 2005)

Test_Engineer said:


> I think the biggest reason is the differences in the motor configuration. An Inline 6 has a much broader and flatter torque curve, than a V6 which tends to be more peaky. It's all about the area under the curve and how well it is matched to the transmission ratios.


 Any configuration of engine can be designed for high or low power peaks. A flat six Porsche is a revver but a Lycoming aircraft flat six makes max power at @2500 rpm.
GM used to build large V-6`s for commercial trucks that were all about torque and an Acura NSX V-6 is obviously a "peaky" motor. A 327 Chevy was offered as a truck torque monster OR a solid lifter revver in a Vette. I don`t dispute that the engine in question may be tuned for high rpm power but it`s not a question of configuration.


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## Test_Engineer (Sep 11, 2004)

99flhr said:


> ....but it`s not a question of configuration.


The inline 3.0l BMW motor produces a torque curve that is "flat" for a little more than 1000-1500 RPMS wider than say a Nissan 3.0l VQ!

BMW has a power band of about 4000 RPMS, while the VQ has about 3000 RPMS! :dunno:

PS...Honda and Toyota are worse than the Nissan VQ!

It's all about the area under the curve, and inline motors typically have more area.


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## 99flhr (Apr 12, 2005)

Test_Engineer said:


> The inline 3.0l BMW motor produces a torque curve that is "flat" for a little more than 1000-1500 RPMS wider than say a Nissan 3.0l VQ!
> 
> BMW has a power band of about 4000 RPMS, while the VQ has about 3000 RPMS! :dunno:
> 
> ...


 Don`t disagree with your 1st 3 statements nor the first part of #4. But inline sixes can and have been designed with either objective in mind. Please reread where I did not dispute the specific examples cited. Many factors ( intake length/shape & cam profile for instance) decide the curve. I`ll stick with my assertion, the configuration of the cylinders is not the deciding factor. As for "inline" motors, many straight 8`s were built for torque (Buick & Packard) others were built for rpm (Alfa & Mercedes GP units) the power curve was decided by intended usage NOT the inline design


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## Test_Engineer (Sep 11, 2004)

99flhr said:


> Please reread where I did not dispute the specific examples cited. Many factors ( intake length/shape & cam profile for instance) decide the curve. I`ll stick with my assertion, the configuration of the cylinders is not the deciding factor


OK...you design a V6 and I'll design an inline 6....Same displacement...Goal: Largest area under the torque curve wins. The winner gets $10M. Are you so sure that you would go ahead and take that bet. I don't think so. It's much more than just cam profiles and intake runner length. The basic design of an inline motor allows for 1 connecting rod per crank journal....and that is more efficient when making seamless, flat torque curves. Because if that is not the case, why wouldn't Nissan, Honda, and Toyota simply reshape the intake runners and cams and get 1000 more RPMs in the power band. :dunno: Because they can't. They are limited by the physics involved with a V. it's the same reason why GM can make that 4.2l I5 torque monster....V6 can't do it.


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## 99flhr (Apr 12, 2005)

Test_Engineer said:


> OK...you design a V6 and I'll design an inline 6....Same displacement...Goal: Largest area under the torque curve wins. The winner gets $10M. Are you so sure that you would go ahead and take that bet. I don't think so. It's much more than just cam profiles and intake runner length. The basic design of an inline motor allows for 1 connecting rod per crank journal....and that is more efficient when making seamless, flat torque curves. Because if that is not the case, why wouldn't Nissan, Honda, and Toyota simply reshape the intake runners and cams and get 1000 more RPMs in the power band. :dunno: Because they can't. They are limited by the physics involved with a V. it's the same reason why GM can make that 4.2l I5 torque monster....V6 can't do it.


Neither one of us is capable of designing either one. I gave cam & intake as just two of many variables, please reread. I could continue to cite real world examples of same configuration engines being developed for different end results but obviously that won`t help. As to why the Asians shoot for high peak hp, I assume they believe that it helps "sell" cars. Should they learn that total under the curve yields better performance? Yes, by all means. Could they obtain it with a V6? Absolutely. "limited by the physics involved with a V" have you ever heard of V-8 torque? Gee, not many examples of that, are there?


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## DaKine (Aug 17, 2005)

iateyourcheese said:


> People that make graphs like that should be shot. It looks like the Scion has 1/8th the hp of the other cars. Well comparing things, use 0 as the origin.


I agree.... someone should photoshop the graphs withe "0" as the refrence point. It would make them LOOK a whole lot more accurate and thruthful


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## chuck92103 (Oct 9, 2005)

You want true horsepower,

have your car dyno'd to measure HP at the rear wheels,

I think BMW's HP specs will be closed to the truth than some cars, i.e. vtech where you run the squirl all the way to the end of the tach to realize the HP. :dunno:


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## Test_Engineer (Sep 11, 2004)

99flhr said:


> Neither one of us is capable of designing either one. I gave cam & intake as just two of many variables, please reread. I could continue to cite real world examples of same configuration engines being developed for different end results but obviously that won`t help. As to why the Asians shoot for high peak hp, I assume they believe that it helps "sell" cars. Should they learn that total under the curve yields better performance? Yes, by all means. Could they obtain it with a V6? Absolutely. "limited by the physics involved with a V" have you ever heard of V-8 torque? Gee, not many examples of that, are there?


Ultimately, the inline-6 engine is more efficient yet smoother. V6 has more energy loss because it duplicates valve gears and camshafts (which increase frictional loss), while the use of 2 cylinder banks leads to more heat loss. The crankshaft of the inline engine does not have to share the same space on the crank, so the acceleration of the other con-rod is not an issue. I don't care who you get to build an engine....you will NEVER build a V6 that has more area under the curve than an inline-6, as a result, the inline-6 will always have a smoother and broader power delivery.....AND that is the answer to the original question in this thread! Toyota and Nissan BOTH made inline-6 in the Supra and the Skyline GTR respectively, BUT they BOTH caved in to the designers and gave up on the inline motor for a smaller V-6 package to make the rest of the design team happier. BMW has not come to that compromise.

V-8's are a completely different animal. You have more choices! Well, you have 2, cross-plane(American Muscle) and flat-plane(European screamers) crankshaft configurations....this is way OT, because the initial topic was a question about 6's, but I can elaborate if you like.


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## LDV330i (May 24, 2003)

Test_Engineer said:


> Ultimately, the inline-6 engine is more efficient yet smoother. V6 has more energy loss because it duplicates valve gears and camshafts (which increase frictional loss), while the use of 2 cylinder banks leads to more heat loss.


I have yet to figure out what was in Ford of Germany's mind when it marketed a 1.7 liter V4 engine in the 60's. They also had a 2.0 liter V6. These motors were available in the Ford Taunus 17m and 20m. The V4's were later dumped and the tooling sold to Saab who then offered in their cars.

I would have the same question for the Mazda engineers who came up with a 2 liter V6 for the MX-3 hatchback. Though there I could see the need for a compact tranverse engine in a front wheel drive, which is the same reason VW came up with the VR6. The german Fords were rear wheel drive.


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## Technic (Jun 24, 2002)

LDV330i said:


> I have yet to figure out what was in Ford of Germany's mind when it marketed a 1.7 liter V4 engine in the 60's. They also had a 2.0 liter V6. These motors were available in the Ford Taunus 17m and 20m. The V4's were later dumped and the tooling sold to Saab who then offered in their cars.
> 
> *I would have the same question for the Mazda engineers who came up with a 2 liter V6 for the MX-3 hatchback.* Though there I could see the need for a compact tranverse engine in a front wheel drive, which is the same reason VW came up with the VR6. The german Fords were rear wheel drive.


I asked the same question 13 years ago, when I saw the specs of that MX-3 V6 (it was in fact a 1.8 liter V6, not 2.0) and compared it with the 1.8 I4 in my Protegé of that time: _5 horses and 3 pound feet of torque at a higher rpm peak more._

I did understand that in those early 90's every manufacturer thought that the big next thing was the CRX class, so Nissan, Mazda and Toyota came with their offerings (NX2000, MX3, Paseo), so Mazda tried to be in a class by itself with the only V6 in the class. But it ended up being a real waste... even the CRX disappeared after 1991.


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## Chris90 (Apr 7, 2003)

In defense of the Japanese (yikes), there is more to performance than 0-60 times. On a race track, you don't use the lower end of your rev range, so that broad torque curve is useless. The G35 is a fast track car, if not particularly fast 0-60. The Japanese do a lot of track development for their cars. 

But I suspect manufacturing and development cost is the bigger factor in why some engines outperform others.


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## Pinecone (Apr 3, 2002)

Not quite right. SAE changed the testing methods to reduce some loopholes in the testing method. The old method allowed you to use specific modesl for somet hings, new test requires you use the actual parts (things like power steering pumps, exhasut systems, etc). Kicker was, if you used the same engine in the car that had been tested under the old method, you didn't have to change to the new method right away. So no direct comparisions of HP are possible for a few years.

Many Japanese comapnies decided to retest under the new setup for all engines.

The other thing is BMW specs their engines to be +x%, -0% of the rated HP. IOW, the rated HP is the lowest you should find in any engine coming off the line. Virtually every other company reports the highest HP result they ever got for that engine. So it is most likely that NO engine you buy will make the HP reported.

And lastly, the curve and the gearing have a LOT to do with it. More area under the curve means more acceleration throughout the range, maybe the peak is lower, but overall it is better. And BMW engiens are know for revving, which allows better gearing for acceleration.


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## fm_illuminatus (Jun 13, 2005)

LDV330i said:


> American cars made some modest gains when retested.


Um... weird. How did they make gains I wonder... ( :stupid:  )


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