I'm waiting for the 5 L to be dropped into the G

 

Seriously? Horsepower is simply a mathematical calculation. A close approximation is P=(Txw)/5252 where P = horsepower in hp, T = Torque in ft lbs, w = rpm in r/min and 5252 is a rounded constant. Without a figure for torque, there'd be no way to measure hp. Torque is the actual turning force that moves a vehicle. HP doesn't "physically" exist.

The reason for offering two engine options with similar output ratings is a simple one really. Just because both engines make close to the same peak hp, they don't necessarily make it at the same rpm. The 2.5L turbo 4 is a more peaky and "sporty feeling" motor while the 3.0L flat 6 has a more linear and smooth power delivery. While their peak hp figures differ only by 2hp, their torque curves probably differ from one another quite a bit more.

the turbo 4 will be for the enthusiast driver who likes to keep his motor on the boil. The NA 6 will be for the guy who intends for his car to be more of a highway cruiser.

 

Let's not open up this can of worms. They are both important as HP can demonstrate sustained torque at high rpm. A lonely torque figure at one rpm cannot. Higher rpm vehicles can take advantage of more aggressive gearing, which leads to torque multiplication, and better performance. So, I think you need all the info to understand the overall performance of a vehicle.

I agree that the 6 cylinder (in this case at least) is most likely the smoother engine, and power may be better distributed but the numbers say this:

1. Subaru 3.0 L makes 245 HP and 215 lb-ft or torque (at 4,200 rpm - not low at all)
2. The new WRX engine makes 265 HP and 244 lb-ft of torque. So, the 4-cylinder turbo makes more power and more torque.
3. As far as I know, the new 265 HP 4-cylinder turbo does not have an rpm for that peak torque announced yet, but in the previous 226 lb-ft version, the torque peaked at 2,800 rpm. If the same remains true (and it should as the engines are similar), the turbo 4 makes more power, more torque, and more torque at a lower RPM. Odd indeed.

Not all turbos have to be harsh engines. The 3.0 twin-turbo in my 335 is very smooth, and max torque is on tap at 1,500 rpm, and stays pretty flat for the whole mid-range. The amount of torque on tap is pretty amazing. I can stay in 6th and cruise at highway speeds, and then just quickly move through traffic without ever downshifting.

Anyway, in general I agree with you on the power delivery advantages of a 6-cylinder over a 4 turbo, but I still think Subaru and Infiniti need to upgrade their larger engines to keep up with their smaller counterparts (which Infiniti has).

 

I would want no part of the V8 in the G, too heavy and gas guzzler for ME, if 5L V8 is really wanted then M should have it in about a year or so. As for keeping up with the competition put in TT in the G37 and you have more than a compelling case considering the new GT-R 3.8TT, just my $0.02

 

simply put a v8 with slightly less hp than a v6 will typically have more power "under the curve" ie more avg or usable power and thus perform better despite its lower peak rating. hp numbers are very deceiving and while important not reliable when judging performance between vehicles.

edit: also hp (or tq) requires gas + air + ignition and as a result regardless of engine size like power output generally requires like amounts of fuel. there are exceptions to this based on efficiency of said engine.

 

displacement = torque, revs = hp.

A low output V8 and a high output V6 will have similar "area under the curve" if the torque output is the same and they have the same redline. Alternatively, if the v8 makes more torque, but the V6 makes the same hp with a higher redline, and gearing makes it so the gears are equal length (in terms of speed), then the area is STILL the same.

Take the old 4.6 v8 out of the previous generation mustang, and the 2.0 i4 out of the 1st generation S2000.

260 hp vs 240 hp. The area under the curve is almost the same. The mustang generates a hell of a lot more torque, but the s2000 makes up for it with a much higher redline, and much more agressive gearing. Remember, gearing is mechanical torque multiplication, which isn't reflected in the output of the engine itself, but is reflected in the power put to the wheels. (This is why a ratio is required on many dynos)

 

There's alot of physics and math that goes into the outcome of power & acceleration, and I definately won't get into that here. But I just want to point out that the 335i makes about the same peak RWHP as the VQ37VHR. But it has a beefier powerband, which is one of the main reasons that its quicker. Beefier powerband = more average hp throughout the RPM's. (And to add on top of this, its still slightly lighter than the G37).

FI Power curve > NA Power curve

(Yet, I still favor the linear feel of NA power given they make the same peak HP ).

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M37/M50 should be right around the corner.

Yep. Then people wonder why I hate 0-60 bench racing

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very well stated. i was grossly over-simplifying things to be perfectly honest. so many factors come into play when dealing with a topic such as this and without starting a battle which i very well could lose lol that same s2000 engine while having similar area under the curve would be a dog in the heavier mustang chassis.

please do school me if i'm wrong

 

If the s2000 engine had the mustang's gearing, then it would be terrible to drive, especially given the engine's particular characteristics...

The mustang in the s2000's chassis would have insanely short gears and have a top speed of about 110 (gear limited)

 

Wow, this is always a fun discussion but I certainly didn't mean to open the torque/hp Pandora's box when I started the thread. I've seen this argument so many times on so many boards it's not even funny. It's a complicated matter and one that is difficult to express/teach in the forum environment. Most of the time there are those that already get it, those that refuse to get it, and those struggling to get it. I'm impressed that most of this group leans towards getting it. The best tool I ever saw for explaining it was a graph showing propulsion force (in lbs) by gear and rpm for a given vehicle. Very enlightening stuff.

I mean really, at the end of the day, it's all about Newton's 1st law (Force = Mass * Acceleration). We all have a mass, we all want acceleration, so we need more force. Force is so much easier for most people to understand than hp & torque.

IMO, power delivery is a product of the SHAPE of the torque curve, not the area under it. After that, it's about driver preference.

- Some people love the feeling of a VTEC engine kicking in at 6000-7000 rpm. Others seldom drive their car into that rev range and that high-end power would be totally lost on them.
- Others love instant off the line torque for a quick kick in the pants but don't care about wringing the engine out. These folks prefer pushrod V8s and muscle cars.
- Some people want the same torque on tap all the time. This is suited by modern turbos like the VW/Audi 2.0T and BMW 335 that have long flat torque curves that peak below 2000 rpm and hold steady through most of the rev range.
- Personally, I prefer good DOHC NA engine with decent torque down low and decent hp up high that provides a steady build in power that makes runs to redline rewarding but not required.

Just like suspension settings, there is no right answer. There are only compromises. If it were all about torque we'd all be lusting after diesels. If it were all about high-rpm hp we'd all want cars powered by something along the lines of modern sportbike engines that make almost 200hp at the crank from normally aspirated 1.0L 4-cyl engines spinning to 15,000rpm.

 

All this just proves how awesome foreign technology is. In a span of just five years, they can produce V6's with more power and with much more efficiency than the outgoing V8's.