6 Cyl 280 HP and 8 Cyl 280 HP is it the same??

[will99]

Hi guys,

i always wondered, WHY is there 8 Cylinders 280 HP when some cars are available at 6 Cylinders for the same power? Is it the same power?

i was just wondering if technically there is a difference between the 2 cars..


William!

[Boondoggie]

usually it's a matter of torque.

[M3/4 LIFE]

usually it's a matter of torque.

+1 ... exactly ... which engines are you referring to????

[Qsilver7]

+2... Horsepower is not the end all to be all in regards to an internal combustion engine. Although some marketing folk write advertisements as if it were. For example, take a 4, 6, 8, 10, and 12 cylinder engine, all producing 280 HP...their comparative performance will yield different "quantitative" results even though they all share the one same variable of 280 horsepower.

More cylinders in an engine yields two potential benefits: first, the engine can have a larger displacement with smaller individual reciprocating masses (that is, the mass of each piston can be less) thus making a smoother running engine. You get a smoother running engine because...engines vibrate as a result of the pistons moving up and down within the cylinder. Second, with a greater displacement and more pistons, there are more "combustion events"...in other words... more power strokes in a set period of time...which means that engines with more cylinders can generate more torque than an engine with fewer cylinders.

Torque is another crucial variable in an engine's "performance equation". Gobs of horsepower but very little torque will not have a very exhilarating end result...it would be all go but no get up! Take note of hp-vs-torque in high performance cars like the M5...the numbers are usually very close together and sometimes the torque number is higher. Understanding what torque is and how it "feels" may help. Like, consider the engine in a tractor...it will have gobs of torque but lower horsepower. A tractor has a lot of "grunt" or pulling force at lower rpm (as in tree stump pulling force)...but is not going to win any drag strip races (in its naturally aspirated form).

I'll stop here and let you digest what's already been stated.

[xn4cer]

Typically a 6 cylinder engine will have less displacement (cubic inches), but not always. If that is true, you will have to rev a smaller engine more to get the same horsepower. Some four cylinder race engines with 2.0 liters of displacement generate 800+ horsepower while most street car engines with 2.0 liters usually generate about 150 horsepower. The race engines make their power at 10,000 to 15,000 rpm while the street engine is usually limited to 5,000 to 6,000 rpm.

Regarding 6 and 8 cylinder engines in street cars, a typical v6 with 3.8 liters of displacement that revs to 8,000 rpm might generate 280 horsepower, while a v8 with 4.4 liters of displacement might generate the same 280 horsepower, but would only rev to 6,500 rpm.

Also, and unrelated but interesting tidbit about horsepower. It only takes about 11 horsepower to keep an average sized car moving at 55 mph on a flat smooth surface (but obviously much more to get it moving from a stop).

[WILDMAN]

+2... Horsepower is not the end all to be all in regards to an internal combustion engine. Although some marketing folk write advertisements as if it were. For example, take a 4, 6, 8, 10, and 12 cylinder engine, all producing 280 HP...their comparative performance will yield different "quantitative" results even though they all share the one same variable of 280 horsepower.

More cylinders in an engine yields two potential benefits: first, the engine can have a larger displacement with smaller individual reciprocating masses (that is, the mass of each piston can be less) thus making a smoother running engine. You get a smoother running engine because...engines vibrate as a result of the pistons moving up and down within the cylinder. Second, with a greater displacement and more pistons, there are more "combustion events"...in other words... more power strokes in a set period of time...which means that engines with more cylinders can generate more torque than an engine with fewer cylinders.

Torque is another crucial variable in an engine's "performance equation". Gobs of horsepower but very little torque will not have a very exhilarating end result...it would be all go but no get up! Take note of hp-vs-torque in high performance cars like the M5...the numbers are usually very close together and sometimes the torque number is higher. Understanding what torque is and how it "feels" may help. Like, consider the engine in a tractor...it will have gobs of torque but lower horsepower. A tractor has a lot of "grunt" or pulling force at lower rpm (as in tree stump pulling force)...but is not going to when any drag strip races (in its naturally aspirated form).

I'll stop here and let you digest what's already been stated.

Great answer, are you a teacher?

If you have a 4cyl and a 12 cyl engine with the same horsepower and driven under the exact same conditions, would the 12 cyl have a longer life span?

[Qsilver7]

...are you a teacher?

no...but I do work in education.

If you have a 4cyl and a 12 cyl engine with the same horsepower and driven under the exact same conditions, would the 12 cyl have a longer life span?

hmmm, good question. I'll play it safe and say that anything is possible...why tempt fate?... a small quirk could change the entire result and the 4 cyl could possibly outlast the 12 cyl or vice versa. BUT, during the course of each engines life...all things being equal...the 12 cyl would definitely not have to work as hard as the 4cyl.

[ycis]

all depends on gearing and many other factors...hp means nothing but clever marketing.

18wheeler trucks dont make more than 2 or 300 hp....but ridiculous amounts of torque....they dont make horsepower because they dont spin more than 2000rpm.

Horsepower is only a measure of torque at a given RPM and doesnt factor in gearing.

[unirok]

265 HP 3.5 V6 Nissan Maxima smoked my 275 HP 4.6 V8 bonneville GXP

[sleepy740]

If you have a 4cyl and a 12 cyl engine with the same horsepower and driven under the exact same conditions, would the 12 cyl have a longer life span?

usually a four cylinder is going to have to be built quite a bit to achieve the same amount of hp...my talon was at around 275whp, and it was built pretty good...but the liability of the engines would differ in a four cylinder and 12 cylinder...so i have to say a 12 cylinder would be more reliable if they had the same power...

[Oxford740IL]

Torque is another crucial variable in an engine's "performance equation". Gobs of horsepower but very little torque will not have a very exhilarating end result...it would be all go but no get up! Take note of hp-vs-torque in high performance cars like the M5...the numbers are usually very close together and sometimes the torque number is higher. Understanding what torque is and how it "feels" may help. Like, consider the engine in a tractor...it will have gobs of torque but lower horsepower. A tractor has a lot of "grunt" or pulling force at lower rpm (as in tree stump pulling force)...but is not going to win any drag strip races (in its naturally aspirated form).

Interesting,

So, the opposite would hold true for an INDYcar that weighs less than a ton makes 850+bhp but only 150 lbs of tourque?

[Qsilver7]

Interesting,

So, the opposite would hold true for an INDYcar that weighs less than a ton makes 850+bhp but only 150 lbs of tourque?

This is simple when comparing apples to apples or apples to oranges. When taking into account a race engine (compared to a normally aspirated street automobile, the engines are designed differently...the race engine uses a very short stroke with a much wider diameter piston. This brings us back to displacement and reciprocating mass (which the Indy race car will have more of) and is creating more "combustion events"...and at the same time it is reaching its peak power at 15000 rpm instead of 3500-6000 rpm.

I'm trying to think of an analogy that would make sense...I'm not sure if what I'm about to write is totally accurate but I hope you get the gist. An Indy race car engine with its short stroke and wide diameter pistons which will peak at 15000k rpm...is like using a breaker bar on your wrench. Your normal 8" handle will use a certain amount of torque to loosen a bolt vs the power it will take to exert on the handle....then compare that to what would happen if you used the same amount of power exerted on that handle when using a breaker bar. It will take much less torque to loosen that bolt.

[Boston Killer]

On a side note: Japanese seems to make the smallest horses...

[unirok]

On a side note: Japanese seems to make the smallest horses...

Huh...............

[greene08]

It looks as if we are straying a bit from the original question. The bottom line is that the number of cylinders has NO universal effect on horsepower or torque. What DOES have an effect is the size of the pistons and bore of the combustion chamber along with the length of the stroke of the engine, all other things being equal.

An example is the old Jaguar XJC's (1985 or so) with the 12-cylinder 5.3L engines. To get 12 cylinders into their 5.3L package the pistons had to be very small with little individual displacement. Make those bigger and you have more torque, make the stroke shorter and you gain more horsepower in proportion to torque.

Same idea for a 4-cylinder engine. If you have massive pistons and a short stroke you will have torque and horsepower and depending on size and stroke can easily equal that of a 6, 8, 12-cylinder engine and vise versa.

Again all things being equal, the more pistons you have the smoother and quieter the engine will be. Hence why supreme luxury cars use mainly 8-cylinder or 12-cylinder V configurations for their cars because they are smooth and quiet. BMW could certainly have opted for a short stroke big bore 4-cylinder but you would clank down the road and barely be able to keep your espresso in your hand.

A last for instance is my 1982 SeaRay 192 Shorerunner with the old MerCruiser 470 sterndrive. The engine is basically just 1/2 of a Ford 360 big block and produces 180 horsepower and 260 ft lbs of torque out of a 1982 4-cylinder engine! The pistons are enormous with a relatively moderate stroke but the thing is loud and rattles your mind.

Hope this long explanation helps, basically just remember cylinder count has little to nothing to do with horsepower or torque it just affects how smooth that power is delivered.

[greene08]

Oh yeah, and in regards to INDY cars the above explanation was correct by Qsilver. Those engines are nothing like street engines. They are like an oversized superbike motorcycle engine. They have a short stroke allowing high RPMs thus allowing for high horsepower and small pistons that allow the car to get to those high RPMs but give it little torque. Torque isn't as important in those cars because they rarely drop below 80mph and weigh nearly nothing when racing and torque is most important when starting from low speeds or a stop. As they say, horsepower is king on the freeway.

[unirok]

. As they say, horsepower is king on the freeway.

Who says that?

[sirtiger]

nice write up Qsilver7

[greene08]

Who says that?

Haha, the royal WE.

[WILDMAN]

So, though a 7 series 8cyl and a 7 series 12 cyl have basically the same performance, the 12 cyl would run smoother?

[will99]

Thank you guys for the explanations. Very detailed sometimes and very technical .

I asked this question cause the Acura 3.2 TL 2006 and i had really hard time keeping up at short distance.


William!

[greene08]

So, though a 7 series 8cyl and a 7 series 12 cyl have basically the same performance, the 12 cyl would run smoother?

Yes, in theory less vibration. The difference is minimal at that point when considering other factors such as weight of the engine, weight of the car, vibration dampening and sound deadening features.

[greene08]

Thank you guys for the explanations. Very detailed sometimes and very technical .

I asked this question cause the Acura 3.2 TL 2006 and i had really hard time keeping up at short distance.


William!

It's also important to keep in mind the differences in engine design such as intake, OEM exhaust construction, and other goodies such as VVT-i, VANOS, suspension management systems, gearing, LSDs the good ol' tranny!

[Strahan]

It's also important to keep in mind the differences in engine design such as intake, OEM exhaust construction, and other goodies such as VVT-i, VANOS, suspension management systems, gearing, LSDs the good ol' tranny!

Yea, it's funny, if you visit a car chat room there is almost always a bunch of kids who simply use HP as a ruler to measure who can beat who heh.

[greene08]

No kidding... drives me nuts. When I rode in the F430 F1 the other day it was nice to have 483hp but the 343 ft lbs of torque was a bit upsetting. Ferrari's have always been that way because they are so high-revving but if that thing just had 400 ft lbs or so it would be more than the rocket it is it would be a bullet. I realize why it doesn't have more but I oh-so-wish it did.