Why do they sound different to water cooled ones?
I ask the question because I know beetle engines are that way inclined and I heard an advert on the radio that had a big air cooled Harley in the background, similar sound.

Do they have to have a different firing sequence or something?

less sound insulation around the crankcase, cylinder heads etc was always my thoughts.

Might be the fins vibrate and work as a sound source.

Which water cooled engines are you comparing them to?

Beetle used a flat four (boxer engine) – the same layout used by subaru, which have a similar exhaust sound.

The Harleys run a large capacity undersquare (stroke > piston bore) v-twin. Most cruisers which run a similar layout sound the same.

Beetles are boxer engine configuration which gives them their sound. Not sure for reason of air-cooled engines in general sounding different.

i can spot a beetle/aircooled vw van by the noise. i always assumed it was the limited exhaust run/loose bearings/noisy tappets/general impending calamity that created the whole noise effect.

love it. too many good memories associated with the noise.

As stated above, the aircooling itself isn;t responsible for the sound – it’s the engine configuration. It so happens two well known aircooled engines have a distinctive note.

Last aircooler I drove was a Pinzgauer which sounded lovely and smooth.

Air-cooled engines in cars usually have a dirty great fan – that makes quite a contribution to the distinctive noise.

Design of the engine & the fact that there isn’t a water jacket around the engine muffling any sound!

less insulation (to allow air passage)

Which water cooled engines are you comparing them to?

Say, a standard Focus and a Japanese sports bike. I know they’re not really like for like comparison but the two engines mentioned do have a fairly similar sound. i’m happy to accept that not all air cooled engines sound like that though.

There’s a ‘tuned’ (actually probably detuned with the state of the UK tuning scnene) Imprezza (water cooled) near my mums that sounds exactly like an old air-cooled VW camper van.

Say, a standard Focus and a Japanese sports bike

Well, comparing an aircooled VW engine to a Focus is like comparing an abacus to a PC, for a start! Totally different! 60 Years + of development and different cyclinder layout
Compare, say an older air/oil cooled GSXR 750 engine to a moderen GSXR 750 engine and they’ll be very much the same as the layout is the same

Had aircooled VWs and now have wasserboxers – the sound is a little less brash but that is due to better exhaust systems, but the underlying burble is the same.

Near to me a (frickin’ awesum!) family has a T1 transporter and a t25 which recently-ish had a subaru boxer fitted. To my ears, at parking/pulling-off-up-the-road speeds, all three engines sound more like each other than they do to water-cooled ‘inline’ 4 cyl petrol engines (tht ‘burble’ as above). But again as mentioned above, there is also the exhast to consider: I am sure the subaru boxer would have sounded different in the front of its donor car with a longer exhaust system too.

FWIW, for the same reasons of timing/clylinder layout rather than cooling arrangments, my VW van-salesman-and-petrolhead mate swears that a 5 cylinder T4 tdi engine at high revs sounds quite a lot like the original 80’s 5cyl(petrol of course) quattro that shares the same engine block (but nothing else of course). I have never been in a quattro so I’d have no idea, but my t4 does has rather a fun growl (for a diesel!) at 3000+ rpm…

A harley crank is offset so the 2 cylinders are out of phase, the Buell version has a crank that is in the same plane. (iirc)I believe the tuned versions use this design of crank too.

This has a 2.2 Scooby lump in and it sounds not unlike the 2.1 it replaced:

Not sure for reason of air-cooled engines in general sounding differen

to prevent over heating aircooled engines have fewer, bigger, slower revving cylinders, hence a deeper boomier sound? just a thought

*dribbles a bit at rogerthecat’s synchro* 😳

don’t scoobys fire like a pair of twins? e.g. where 2 cyclinders fire on the same stroke leaving 2 power free strokes from each 4.

or do the fire as per a straight 4? e.g. one cyclinder fires on each of the 4 strokes. I remember reabing some WSB stuff a few years back that the twins could put their power down better with 2 more powerful blips of power that the 4 closer spaced. might be the same for scoobys in WRC.

if so than that’d explain the twin like burble as per Harleys

+1 on short exhausts and less insulation from water jackets too though

the aircooled engine in my old Beetle was pretty silent most of the time, sometimes it sounded like a screaming starter motor, other times it made loud banging noises when the cylinder heads cracked.

but when it was working the stainless exhaust made is properly loud.

Water jacket can silence an engine a bit (when a mate’s SV650 lost most of its coolant, I noticed because when we next stopped it sounded a bit louder and sharper.

What, farty noises?
Like this air cooled Double Wasp…

[video]http://www.youtube.com/watch?v=FQxb-V-rZqA&feature[/video]

Compared to this liquid cooled V12?
[video]http://www.youtube.com/watch?v=e2AS1rW5GwU[/video]