All other things being equal (total horsepower, gearing, vehicle, etc.) would a 6 cylinder engine be preferrable to a 4 cylinder engine? More efficient? Smoother power curve (thinking that you have more powerstrokes in a given timeslice than with a 4 cylinder…just guessing)?
Or is the 4 cylinder actually superior? (less expensive to build [fewer moving parts, less complexity, less to wear out, etc.)?
Or in the end is it a toss up? Neither really being distinguishable from the other in terms of bottom line performance?
6 bangs in a given timeslice gives a smoother feel and more consistent power than 4. This can be compensated by engineering the 4 banger to operate at a higher RPM–viola, same smooveness. Of course, if you lose a cylinder on a 4 you’ll notice it a lot more readily than you would a 6 or 8!
Porsche makes pretty good use of the 4 cylinder, Jaguars can have 12 or more cute little cylinders.
When I have my mechanic hat on I titter with glee at the prospect of working on 4 cylinders all lined up nice & neat. Start thowing a V configuration in there and you’ve upped the complexity ante.
There is a reason you don’t see many 4 cylinder motors with more than 2.2 liter displacement, and why you don’t see a lot of 6 cylinder motors with less than 2.2. Prolly because yes, at some point the mechanics of adding more cylinders is a better solution than 4 humongous pistons (with proportionately humongous bangs).
My stepfather had an E type Jaguar in the 60s. It was a six. There was a twelve pot engine available as well. He told me both had identical performance, but the twelve cylinder engine was more popular with middle-aged business executives and the like because it was quiet and smooth, whilst the younger guys preferred the engine note of the six.
Far too many variables to answer the question. Four cylinders have fewer parts by definition but they aren’t suitable for every application. When Porsche built the 944 they decided that a modestly large four cylinder, 2.5l, had too much vibration at high RPM due to secondary imbalances. They corrected that with a balance shaft arrangement licensed from Mitsubishi.
I owned a BMW 325i and the 2.5l straight “baby six” was smooth as silk through the whole RPM range and actually required a rev limiter to prevent damage from overrevving. The drawback to the six is of course more parts, a longer, more expensive to manufacture crankshaft and a block that is about 50% longer than a four. It was a very tight longitudinal (front to back) fit in the BMW and would have certainly been too long for the transverse (side to side) mounting most often seen in front wheel drive cars.
There are a lot of ways to build a six other than inline. The old Chevy V-6 was a V-8 with two cylinders chopped off so it sounded like a V-8 that was only firing on six. Other GM divisions used an even firing V-6 which used a different angle between the banks. VW has had a lot of success with their V-6 which has such a narrow angle that one head covers both banks of cylinders.
All things you mentioned being equal, yes, a six is better than a four. In fact I’d contend the inline six is probably the best all-around automotive engine design. But things are not so simple in the real world. Rarely does one choose between two engines that are equal in all respects aside from cylinder configuration- of the two you mention, the six will usually produce more power and consume more fuel in the process.
So… in general, a four is better than a six in an average modern car. The two most common engine configurations in modern cars, by far, are inline fours and V-sixes, so it does not make much sense to bring other configurations into the discussion.
Nearly all modern passenger cars are front wheel drive and have the engine oriented sideways (transversely) which makes underhood packaging a primary concern. This is why there are very few cars sold with inline six engines. In order to squeeze the six cylinder engine into the front of the car with room for the transmission, steering clearances and all the accessories and modern computerized stuff, carmakers usually use a V6. Two banks of cylinders require two separate heads (very narrow Vs notwithstanding), two separate exhaust manifolds and two separate valvetrains, all of which take up a lot of space and make the engine more complex than it needs to be for the purpose of making the car go.
Repair and maintenance are generally much more of a pain in the ass with a V6 when compared to an inline four. Most fours will also give better fuel economy in real world driving. Unless your hypothetical car is very large or overpowered, the four cylinder engine is always better in the average modern car.
Wow! Hold it there! You guys forget about configuration. Are we talking about straight, opposing or V engines? The configuration can make a huge difference.
It’s quite possible for a 4-banger to have as much power as a 6-banger. The most likely reason is that the 4-cylinder is tuned to make torque at higher rpm’s. In fact, that’s how a lot of Japanese cars are tuned nowadays. However, there is an obvious cost to it. An engine that’s tuned to make most of its torque up high has little down low. How drivable is a car that you have to rev the engine up over 3000 rpm to have decent acceleration? The answer is not very. Power is good for racing on an oval track or passing people quickly, but for normal driving, low-end torque is more valuable by far.
I also strongly disagree that 4-cylinder engines are usually better, or even more practical than 6-cylinders in most cars. For tiny economy cars, sure, the 4-cylinder is probably better. However, I drive a 94 Thunderbird, which is not small, but not particularly large either. I would consider it about average. It has a 232 ci V-6 in it. It has enough torque to produce reasonable acceleration without unreasonable revving, but I wouldn’t consider it more than adequate. Thus one can conclude that a 4-cylinder would be less than adequate. Conversely, my mother used to have a Kia Sophia, which is a tiny car, and the 4-cylinder in it would hardly move it unless you spun the tachometer a bit. I always did think that engine would be good on a large go-kart or dune buggy though.
As for configuration, that’s subject to debate. I think it really depends on the displacement. For a really small engine, inline would be good for ease of repair and fewer parts. However, I’d like to see you make a 460 ci inline engine that fits nicely in any reasonable engine bay.
No, configuration is very important. It has to to with balancing and vibrations and such. There was a website explaining the differences, I wish I could find it again.
You need to be more specific about what you mean by “better”.
better gas milage?
better power & acceleration?
better running (smoother engine firing)?
better reliability (fewer parts to break)?
better economy (cheaper to build)?
…etc.
There are lots of ways one design can be “better” than another. And many of them involve trade-offs that you have to decide (like how much gas milage will you give up to have faster acceleration?).
The Porsche 4 cylinder was an in-line 4. 3.0 litres for the normally aspirated. 2.5 l for the turbo. Way back there were horizontally opposed 4s.
These days the better manufacturers make 4 cylinder engines that are all you could want. Balancer shafts, forced induction, electronic management.
Personal favourites are the Honda 2.4 sedan (Acura in the US) and 2.2 diesel and the Mercedes Benz supercharged 4s. So if you are like to go hi-tech a 4 is the right choice.
If you prefer low-tech a 6 OK is but why bother? Even the Koreans make decent twin-cam 4s nowadays.
Smoothness is the advantage of a 6. A balancer shaft 4 will be as good, like my adorable Honda 2.4.
A 4 will use less fuel unless you drive near the limit of the cars’ peformance, constantly. As mentioned there are substantial packaging and handling advantages to a 4. LIkewise price. For example, Mercedes Benz makes 2 cars of identical size and performance. 1 a supercharged 4 the other a 6. There is a huge price difference for a small benefit in the smoothness.
Just some of the the rear engine cars. The 356 and 912 used a flat four that has some common ancestry with the VW type 1 engine. The 914 used the same engine as type IV VWs. 911s and other rear engine cars use a flat 6. 944 and 924 use an inline four in the front.
A former co-worker bought a Jeep Wrangler. He opted for the 4-cyl. engine because he wanted better gas mileage than the six. As it turned out, my heavier Jeep Cherokee with an in-line six got better mileage. Why? Because we both used our cars primarily on the freeway. At 70 mph the co-worker was flogging his four-banger, while my six was just “loafing”. He never took his Wrangler offroad, but I can tell you I appreciated the “grunt” of the six on steep, slippery, muddy trails.
I’m big on “mission”. I feel that a person should choose a car that suits the mission. For ecample, I had a Chevy Sprint Metro. The mission was to get from Point A to Point B using the least amount of fuel, and to handle well in city traffic. The Sprint did get great mileage. It was also easy to park in small, often hard-to-find, parking places. As a bonus, it seemed to have been built as a tesseract. It had a surprising amount of room inside for such a tiny car.
I had a Porsche 911SC. I wanted superior handling and accelleration. But I also needed something that could carry “stuff”. (My movie camera case would not fit in it.) So I sold it and got the Cherokee. The Cherokee gave me the carrying capacity I needed, towing ability that I needed, and it gets marginally good fuel efficiency if driven carefully. Now my mission has changed. While I still need towing capacity, I don’t need as much as the Cherokee offers. Fuel efficiency is needed now. Unfortunately I can’t afford to replace it yet.
What I’m getting at is this: Four-cylinder engines are better for some applications, and sixes are better for others. If you’re doing a lot of fast freeway driving, you should either get a six or get a four that was designed for sustained high speeds. See the co-worker’s Wrangler anecdote. Most people seem not to take the mission into account though. It seems that people buy cars for cosmetic reasons instead of getting the ones that most closely suits their needs.
I had a similar to Johnnie L.A.'s co-worker. I leased a brand new Ranger pickup at the same time as having a Bonneville. The Bonny had a good sized V6, but I opted for the 4-banger on the Ranger to save gas. Of course it was all highway mileage, so that poor little enginer wined and wasted a lot of gas at 70 to 80 mph. The Bonny – even at higher speeds (cars handle better than trucks, remember that you wreckless truck a**holes) got absolutely great mileage, and that was even while beating the hell out of it.
I guess it kind of continues – I now have a Continental with a V8 that I beat the hell out of, too. It weighs a bit more than the Bonny, has more HP, is faster off the line, and yet I get the exact same mileage (yes, I know this to be true; they both had/have on-board gadgets to tell me the mileage, although I miss the oil change gadget on the Bonny).
Like the Audi 5 cylinder (“four is too small, six is too bulky”), or the 3-cylinders that the Suzuki used to have.
An even wierder one: SAAB used to have a V-4 engine…that thing was tiny!
And, Iused to have an OSSA 1 cylinder dirt bike…could you power a car with a 1-cylinder engine?
