Smoothness of V6 compared to S6 engine.

I didn't miss it, just widened the scope. There are many definitions or aspects of 'smoothness'.

I have had several cars with a v6 in either direction and one with straight 6 across the car.

straight engines are not notated as S for straight, they are L4, L6, L8 the L (I believe) standing for Line

IIRC, more commonly I for inline.

That engine was designed for the rally Metros where the 'sound' it made was totally irrelevant.

True, but car shop lists tend to show L (confused me too the first time I came across it)

Then put them right. Line is either a noun or a verb. Inline is the adjective.

In the US, it's a I6, etc. And they are famous for ignoring the rules of English. ;-)

The catalogue suppliers are not likely to alter them just for me! both are I and L are okay according to wikipedia:

Is it not down to bore/stroke ratios too? Perhaps a longer stroke is smoother?

Which is entirely down to the exhaust. Here's a clue. The exhaust on a Ferrari v12 is probably not designed to produce the same results as that on a Cadillac v12.

Y'know, it'd be a lot easier if you just accepted that you didn't actually understand the OP's question.

Complete and utter cobblers.

Or, if you're German, R for Reihen. Hence VR6 etc, but I have followed a VW Toerag with an "R5" badge. Took me a while to figure out what it meant.

The critical speed is only 5000rpm for whatever engine you heard that about.

Advanced Engine Technology by Heinz Heisler shows a graph of torsional vibration amplitude for a 6.8L six cylinder Diesel. Engine order, critical speed without damper, amplitude, critical speed with damper, amplitude. (3000rpm redline)

3rd, >3000rpm, 0.2@3000rpm, >3000rpm, 0.1@3000rpm 4 1/2, 2400rpm, 0.28, 2100rpm, 0.08 6th, 1800rpm, 0.4, 1400rpm, 0.05. 9th, 1300rpm, 0.023,

These days?

First was a long time ago. 1993 Porsche 968 turbo S. 3L, 8 valve SOHC turbo, 305bhp. Smooth as it had double balance shafts in the sump from a

1975 Mitsubishi patent. shafts parallel to crank, gear and chain drive. Lanchester's 1905 balance shafts were placed at 90° to crank and driven by skew gears. 20 years, there will be kids around that aren't even aware that Porsche made 4 pots.

Nope.

Its BANGS / minute that makes an engine sound and that is down to gearing and number of cylinders. How you feel about it depends on subjective experience.

A Corvette C5 6 speed manual in top at 70mph is running at just 1540rpm. It goes BANG 1540 x 8 / 2 times per minute = 6160 BANGS / min.

Now get a older V8 without a fuel miser top gear. It will be running

1800rpm = 7200 BANGS / min.

BMW E36 328i top 1:1, final 2.93, tyre 205/60R15

70mph = 2850rpm = 8550 BANGS / min.

An I4 running at 3080 rpm will have 6160 BANGS / min. An I4 running at 3600 rpm will have 7200 BANGS / min. An I4 running at 4275 rpm will have 8550 BANGS / min. An I4 running at 7950 rpm will have 15900 BANGS / min.

3000 rpm is fairly typical 70mph I4 SI (petrol /LPG) engine speed. 3600rpm would sound thrashy like it needs another gear. For a Diesel 4275rpm is getting close to flat out, 70mph is around 2000rpm = 4000 BANGS /min (admittedly bigger bangs).

Now a 1975 Jag XJ-S V12 with 4 speed box. Top 1:1, Final 3.07:1, tyre 235/60R15.

70mph = 2825rpm Wooo 2825rpm V12 = 16950 BANGS / min. That's about 9000 BANGS / min too many. OK they are quite lame bangs as it only needs about 3bhp/pot and not the 9bhp/pot an I4 needs to make at 70mph. To all I4 drivers it's going to sound like an I4 being driven flat out at the redline and some, the sound says change up but it's in top. No doubt you get used to it and then think it's wonderful and then won't give it up.

Same as bikers playing the gears at 12,000rpm with I4 get to like the sound of 24,000 bangs / min.

Still that's nothing (a flat fart of a noise), I've heard a Honda 500/6 at 18000 rpm = 108000 BANGS / min at full chat 10 feet away from the wall I was sat on. At that number of bangs / min it's just a sonic wail at 1800 Hz, the individual bangs can't be detected.

(to get the full IOM experience crank it up to 110db) F1 V8's and V10's are musical instruments. I like an engine to sing. I'm happy to redline an I4 daily to make it sing. I don't think I would chose the thumping 2000rpm Diesel but one may be on the way.

Me, as it happens!

You'd best get on the blower to Hyundai Heavy Industries and let them know then.

So are you suggesting that any v8 at 1500rpm will sound like a Corvette? Or that a Vauxhall Corsa at 3000rpm will? Because, unless you are, then you're agreeing with me, not saying "Nope"...

Don't be daft, man. FFS, come and have a ride in our camper, with a 25yo flat-four watercooled lump, if you really believe that.

Because there's multiple sources of vibration, the more cylinders you have, the more overlap you get between power pulses, so the smoother it sounds, after that you've got primary & secondary balance of pistons, cranks etc, and once you've got as far as a straight 6 to solve the 1st 2 orders of those the crank starts to wind up & unwind. It's all carefull art of compromise. (I've never seen a 7 cylinder engine though?)

Because there's multiple sources of vibration, the more cylinders you have, the more overlap you get between power pulses, so the smoother it sounds, after that you've got primary & secondary balance of pistons, cranks etc, and once you've got as far as a straight 6 to solve the 1st 2 orders of those the crank starts to wind up & unwind. It's all carefull art of compromise. (I've never seen a 7 cylinder engine though?)

A bit OT, but radial and rotary engines used in aircraft have an odd number of cylinders in each row. Early engines such as the Anzani had only 3 cylinders arranged as \|/. Configurations of 5, 7 and 9 cylinders were common. Adding rows gave 14, 18, and even 28 cylinders. Successive rows were offset to aid cooling (air).

Some models of the Sherman tank used radial engines.