How many cylinders work best?

[Ivas]

Would one of you expert mechanic fellows explain to us why some numbers of cylinders are better suited to automotive engines than others. How many different numbers and configurations have been attempted in car motors? Which were successful, and how? Why is six better than five or seven, even when inline and not in a 'V'? How do harmonic balancers compensate in some configurations? What are their limitations? Is it weight? Why is the ten cylinder of the Viper not such a great idea?

Gear heads wanna' know the full story.

Thanks in advance to whoever picks up the challenge.

[Ajaxx]

subscribed

[swagled]

Explaining engine harmonics in a few paragraphs, without illustrations... sheez

Wikipedia does have some descriptions of every different engine combination. Basically, you're nearly always damned in same fashion. Every engine has some quirks and you have to make the right tradeoffs for a sales success.

Stroke length, the angle of separation between piston banks, the engine skirt length, the motor mounts, all play a large part for the sensations sent back to the occupants. It's not just the number of cyclinders.

Sometimes a little vibration is good. Engines can be so smooth that they do not telegraph "power" back to the driver.

[DGthe3]

Originally Posted by Ivas

Would one of you expert mechanic fellows explain to us why some numbers of cylinders are better suited to automotive engines than others. How many different numbers and configurations have been attempted in car motors? Which were successful, and how? Why is six better than five or seven, even when inline and not in a 'V'? How do harmonic balancers compensate in some configurations? What are their limitations? Is it weight? Why is the ten cylinder of the Viper not such a great idea?

Gear heads wanna' know the full story.

Thanks in advance to whoever picks up the challenge.

If you had started this general automotive discussion in General Automotive & Other Cars Discussions, I probably would have gotten to it a week ago.

How many different numbers and configurations have been attempted in car motors?
umm ... lots
To my knowledge there have been 1 cylinder, 2 cylinder, 3 cylinder, 4 cylinder, 5 cylinder, 6 cylinder, 8 cylinder, 10 cylinder, 12 cylinder, 16 cylinder, and 18cylinder engines attempted for cars. Its probable that 7, 9, and 15 cylinders have been tried too.

Configurations ... there have only really been about 5 different configurations: inline, vee, flat (boxer), W, and VV.

Which were successful, and how?
The most successful were inline 4s, flat 4s, flat 6s, V6s, V8s, inline 6s, and V12s. There has been some success with inline 5s, inline 8s (more commonly called 'straight 8s') and V10s. Their success is related to a number of factors, but the driving forces seem to be packaging and smoothness/power delivery. Packaging general favours the first 5 I mentioned, depending on the application of course. While I6s & V12s have superior vibration/smoothness characteristics compared to other types of similar displacement

Why is six better than five or seven, even when inline and not in a 'V'?
An inline 6 is inherently balanced. An inline 5 isn't balanced but it has its own advantages over both I6s and I4s (essentially being a compromise between the two). Inline 7s just seem like a real bad idea. Compared to a similarly sized inline 6, an I7 it would be unbalanced, smaller displacement, less efficient, and more expensive to build.

How do harmonic balancers compensate in some configurations?
I'll leave this to someone else

What are their limitations?
For what, harmonic balancers or engines? Because if its the former, see my previous answer. The latter, look to my next answer

Is it weight?
Yes. Some types have no real limit as to how big they could be made (any flat, I6, V12). Everything else reaches a point where the parts become so heavy that they introduce serious vibrations which can't be adequately compensated for. For 4 cylinders its usually above 2.5L. V6's is around 4.5L, V8s I think are up around 8L or 9L before it becomes too unbearable.

Why is the ten cylinder of the Viper not such a great idea?
Just as an I5 is sorta a compromise between an I4 & I6, same thing happens when you've got V8 vs V10 vs V12. It won't be as smooth as a V12 but for the same amount of space you can have a larger displacement engine. If Chrysler still had big blocks in production they probably would have used that.

[BigDan]

There's nothing wrong with the V10 in the Gallardo, send it to Underground Racing for a TT build and you will own the quickest car on the streets of planet earth. Just google search 1500hp tt Lambo to see what's possible with a V10.

There is also the VR6 engine configuration.
http://en.wikipedia.org/wiki/VR6_engine

Formula 1 racing engines
http://en.wikipedia.org/wiki/Formula_One_engines

[Mr. Wyndham]

Originally Posted by DGthe3

If you had started this general automotive discussion in General Automotive & Other Cars Discussions, I probably would have gotten to it a week ago.

How many different numbers and configurations have been attempted in car motors?
umm ... lots
To my knowledge there have been 1 cylinder, 2 cylinder, 3 cylinder, 4 cylinder, 5 cylinder, 6 cylinder, 8 cylinder, 10 cylinder, 12 cylinder, 16 cylinder, and 18cylinder engines attempted for cars. Its probable that 7, 9, and 15 cylinders have been tried too.

Configurations ... there have only really been about 5 different configurations: inline, vee, flat (boxer), W, and VV.

Which were successful, and how?
The most successful were inline 4s, flat 4s, flat 6s, V6s, V8s, inline 6s, and V12s. There has been some success with inline 5s, inline 8s (more commonly called 'straight 8s') and V10s. Their success is related to a number of factors, but the driving forces seem to be packaging and smoothness/power delivery. Packaging general favours the first 5 I mentioned, depending on the application of course. While I6s & V12s have superior vibration/smoothness characteristics compared to other types of similar displacement

Why is six better than five or seven, even when inline and not in a 'V'?
An inline 6 is inherently balanced. An inline 5 isn't balanced but it has its own advantages over both I6s and I4s (essentially being a compromise between the two). Inline 7s just seem like a real bad idea. Compared to a similarly sized inline 6, an I7 it would be unbalanced, smaller displacement, less efficient, and more expensive to build.

How do harmonic balancers compensate in some configurations?
I'll leave this to someone else

What are their limitations?
For what, harmonic balancers or engines? Because if its the former, see my previous answer. The latter, look to my next answer

Is it weight?
Yes. Some types have no real limit as to how big they could be made (any flat, I6, V12). Everything else reaches a point where the parts become so heavy that they introduce serious vibrations which can't be adequately compensated for. For 4 cylinders its usually above 2.5L. V6's is around 4.5L, V8s I think are up around 8L or 9L before it becomes too unbearable.

Why is the ten cylinder of the Viper not such a great idea?
Just as an I5 is sorta a compromise between an I4 & I6, same thing happens when you've got V8 vs V10 vs V12. It won't be as smooth as a V12 but for the same amount of space you can have a larger displacement engine. If Chrysler still had big blocks in production they probably would have used that.

Very thorough!! Interesting read!