More cylinders/V-engine = longer engine life than fewer cylinders/Inline?

[Huntsman]

Originally Posted by SirWilliam

The advantage of a V12 from my perspective is that the engine is much smoother than a V8 I6 etc...because each cylinder has to deal with less power.
No. A V-12 is smoother than a V8 for two reasons, and smoother than an I6 for one. 1) Perfect primary and secondary harmonic balance, as already noted, will make it smoother than a V8, or, in fact, any engine that does not share that characteristic. 2) A V-12 is smoother than any engine with fewer cylinders not because each cylinder has to deal with less power, but rather more power strokes are delivered to the crank per unit time than in any engine with fewer cylinders. If you think of the mixture detonation and that force imparted to the crankshaft as, say, and audible bang, there will of course be a series of bangs for a given amount of crankshaft rotation ( or period of time). The more cylinders you have, the more bangs will occur in that period of crank rotation, which is equivalent to smoother overall power delivery. the less cylinders, the greater the gaps between the bangs and the more ragged-feeling is the power delivery. ~ H

 

[dtmt]

Also, if this more cylinders = better idea was really true, you'd see I-4s being replaced by similar sized engines with more cylinders, like the 1.8L V6 from the Mazda MX-3, or the 2.5L-2.6L V8s that BMW and Daimler made in the 60's.

 

[Bird's One View]

The number of parts scales nearly linearly with the number of cylinders ... This is why small cars (and RC airplanes, and lawn mowers) are not made with tiny eight and twelve cylinder engines. I4 engines are not "just as good" as 6, 8, or 12 cylinder engines with the same displacement, but they can be nearly as good while costing much less to manufacture.

Furthermore at some point materials science issues take over and you can't scale the parts down any further. The only way to lower the displacement beyond this is to use fewer cylinders.

Aside: it made me a little sad when Mercedes switched from I6 to V6 engines in the 90s.

I have seen claims that most of the carmakers dropped I6s so that they could shorten their engine compartments (back when longitudinal engines and rear wheel drive were ubiquitous ... I6s obviously can be a tight fit transversely as well although it is occasionally done).

 

[crazyquik]

Originally Posted by Bird's One View

I have seen claims that most of the carmakers dropped I6s so that they could shorten their engine compartments (back when longitudinal engines and rear wheel drive were ubiquitous ... I6s obviously can be a tight fit transversely as well although it is occasionally done).

Definently. At least the VW VR6 cuts the baby in half, so to speak. Longer than a V6, but still short enough to be transversely mounted. Narrow-enough angle (15*) to approach the smoothness of an inline 6.

 

[Tck13]

Originally Posted by Southern-Nupe

GM has both an inline-6, and a 5-cyl truck motor in their arsenal. I've heard good things about the 6 cylinder, not so good about the 5.
5 cyl? I never heard that from GM. (I'm not disagreeing, I just never heard it). I thought the old Ford Explorers had an I6? Isn't Mazda's rotary engine really a 5 cyl engine? Also, why has the boxer engine in Subaru's always been so slow? Is it because of the i4? It's not bad now but IMO it's always been very slow compared to other cars.

 

[zippyh]

Originally Posted by Tck13

5 cyl? I never heard that from GM. (I'm not disagreeing, I just never heard it). I thought the old Ford Explorers had an I6?

Isn't Mazda's rotary engine really a 5 cyl engine?

Also, why has the boxer engine in Subaru's always been so slow? Is it because of the i4? It's not bad now but IMO it's always been very slow compared to other cars.

GM inline 5.
http://en.wikipedia.org/wiki/GM_Atlas_engine#L52

A rotary is quite different from a piston engine regardless of the number of cylinders.

I suspect the relative slowness of Subarus has more to do with other design choices (cost/awd/etc) than engine configuration.

 

[A Y]

There are some seriously fast (modified) Subarus out there. It's not the engine config.

--Andre

 

[dtmt]

13.3 @102.3 mph = slow ?

Also, it is not an inline 4... google boxer engine

 

[Tck13]

Originally Posted by dtmt

13.3 @102.3 mph = slow ?

Also, it is not an inline 4... google boxer engine

I wasn't talking about a brand new Subaru (or turbo). The newer engines are nice but a long standing complaint about Subarus is that they've always been slow. And I meant flat 4 (as mentioned by Huntsman).

 

[nicad2000]

Originally Posted by A Y

It's an interesting question, considered in the abstract, all-else-being-equal situation, but in real life, so many other things can affect an engine's longevity. For example, even for the same engine architecture (say an I-6), different manufacturers will do things differently in the implementation of the engine which will affect its longevity.

Speaking of high mileage, in the early 90s, Mobil did a marketing campaign where they ran an E30 BMW 325i for 1 million miles on a treadmill, following just the recommended service intervals, using Mobil 1 oil, and simulating varying speeds, but mostly at highway speeds. Except for servicing, the car ran 24/7 during the 4-year period it took to get to 1 million miles. They took the engine apart after 1 million miles, and found that the tolerances were still like new or well within spec.

When the Lexus IS first came out, it had an inline-6. Those guys shamelessly copied BMW.

--Andre

I'm not saying they didn't copy BMW, but Toyota ran an I6 version of what became the IS engine in the Supra in the early 90's, if not before. That configuration seemed to be quite popular in rear-drive foreign cars 15-20 years ago. Sadly enough, I can't think of anyone besides BMW that still uses it.

 

[zippyh]

^^^ Volvo still makes an inline 6.

 

[visionology]

There are too many other variables in an engine to judge a lifespan on the number of cylinders. In a perfect world where each engine offered the exact same build quality and received the same maintenance schedule perhaps you could judge it this way but that isn't happening any time soon.

 

[visionology]

Originally Posted by dtmt

13.3 @102.3 mph = slow ?

Also, it is not an inline 4... google boxer engine
I know right... 1995 Lamborghini Diablo VT 0-60: 4.7 1/4 Mile: 13.2 1989 Ferrari Testarossa 0-60: 6.2 1/4 Mile: 14.2 1989 Porsche 911 Turbo 0-60: 5.1 1/4 Mile: 13.6 1996 Dodge Viper RT/10 0-60: 5.0 1/4 Mile: 13.2

 

[dtmt]

Originally Posted by Tck13

I wasn't talking about a brand new Subaru (or turbo). The newer engines are nice but a long standing complaint about Subarus is that they've always been slow. And I meant flat 4 (as mentioned by Huntsman).

That makes no sense. The cheapest models have lower power and are slower, the more expensive ones have more power and are faster. How is this different from Chevy or BMW or any other car company?

 

[Tck13]

Originally Posted by dtmt

That makes no sense. The cheapest models have lower power and are slower, the more expensive ones have more power and are faster. How is this different from Chevy or BMW or any other car company?

I'm talking about ALL models of Subaru before the latest engine. Anyone know what Im talking about or is it just me?

I've mentioned it in passing on the Subaru's forums and I was told that the latest engine was adequate (which I test drove and liked) but others agreed that the older engines were very slow... I didn't ask why...