Air-cooled vs liquid-cooled.

**Oakie** · 26th December 2007, 15:14

There's an outside chance that I may be buying a new GS500F K7 at $7790. The GS is air cooled and I guess the conventional wisdom is that liquid-cooled bikes are better than air-cooled. Any comments/explanations on this would be welcome.

In case it makes a difference, it is a fairly un-exciting bike for a fairly un-exciting rider so the engine wouldn't be thrashed. Use would be the daily commute (18km each way) and weekend cruising.

Also, any comments on the GS500F from people who have owned one would be welcome.

**James Deuce** · 26th December 2007, 15:19

I've yet to see a compelling argument for why air-cooled is worse than liquid-cooled, especially for general road use. For the high constant revs required by racing, water cooling makes sure things with different expansion rates maintain tolerances to avoid things hitting each other.

The GS500 engine will do 200,000kms before you'd look at doing anything to it.

The only reason air-cooled engines are falling out of favour rapidly is noise regulation. No water jacket to help muffle the sound of explosions.

**Grinner** · 26th December 2007, 15:23

Temperature wise liquid cooled motors are more stable so the tolerances (distance) between parts can be closer leading eventually to higher compression ratios etc, ie a means of gaining more horse power and reliability.
Nothing wrong with air cooled, if anything they are simpler machine with less to go wrong, ie no water pump, water radiator, hoseing etc
As for the Suzi 500

**Speedo-cop** · 26th December 2007, 16:39

The key is packaging - water-cooling allows a more compact unit, while air-cooling has some surface area requirements. This is most beneficial when using 2+ cylinders.

It's fair comment to suggest that a water cooled system would have less extreme temperature fluctuations - but when pushed hard, both air and water cooled systems will stress.

All in all, water cooling allows a tighter package - sometimes this is good - sometimes is doesn't matter - apart from that it will moderate temperature fluctuation up to a point.

Remember, though, at the end, it's all air-cooled anyway.

And think checks and balances.

**Ocean1** · 26th December 2007, 18:02

All true. Personally I like a minimum of bits, makes for reliability and, usually, a lighter machine.

I think a lot of the growth in sophistication of bikes can be attributed to marketing, the need for newfangledbling in the battle for sales. Particularly the need to match or better power outputs against the competition's comparable models. And it's true that more revs and more HP can be wrung from a water-cooled beastie than an air cooled, (actually more oil cooled) mill.

The competition's compareable models are, of course, always defined primarily by engine capacity, hence the magic HP/Litre number race. An important consideration, to be sure, if you're constrained in capacity by law or racing regulations. Otherwise it matters not a jot, I'd rather have 100HP from an air cooled thou than a water-cooled 600 for any purpose I'd put a bike to.

Personally I couldn't give a flying fuck what capacity a bike engine is, as long as it produces sufficient useable and reliable power while not compromising overall bike design intent I'm happy. For the moment I'm particularly happy with a relatively unsophisticated and reasonably bulletproof air-cooled 1200, which makes about as much HP as an 800 tourer, or a 600 sprotbike, (if rather a lot more torque).

**Oakie** · 26th December 2007, 18:13

All good info thanks.
How about this then? If I had a couple of similar cc bikes, one liquid-cooled and the other air-cooled, and treated them in the same manner (not thrashed, serviced regularly), would you expect them to have about the same lifespan?

**Ocean1** · 26th December 2007, 18:21

Originally Posted by Oakie

All good info thanks.
How about this then? If I had a couple of similar cc bikes, one liquid-cooled and the other air-cooled, and treated them in the same manner (not thrashed, serviced regularly), would you expect them to have about the same lifespan?

I think whether a bike's air or water cooled would make less difference to engine life than other variables. Probably true that if both were making similar (moderately high) HP the water cooled one would last longer, simply less amplitude in the expansion cycles. Having said that it's going to be more expensive to maintain, and rebuild.

**dipshit** · 26th December 2007, 18:26

Originally Posted by Ocean1

I think a lot of the growth in sophistication of bikes can be attributed to marketing,

You'll probably find that a lot of it has to do with stricter emission controls. Fuel injection, tighter tolerances from water cooling etc help engineers overcome problems like cold start emission.

**James Deuce** · 26th December 2007, 18:33

Originally Posted by dipshit

You'll probably find that a lot of it has to do with stricter emission controls. Fuel injection, tighter tolerances from water cooling etc help engineers overcome problems like cold start emission.

Nah, improvements in metallurgy have sorted that. It's purely about noise.

**Edbear** · 26th December 2007, 18:45

Way back when, I had a T500 Suzuki, a 500cc two-stroke twin with a solid and deserved reputation for reliability. It developed 45hp and was considered quick for its time, though the RD350 Yamaha and the 350 Kawasaki triple could match it and they were both air-cooled two-strokes.

The main issue is the stage of tune, and an unstressed air-cooled engine will be very reliable and long lasting. Water cooling has two advantages and influenced my choice of current bike. Water, (more correctly, liquid), cooling allows tighter tolerances for the reasons others here have given, and a higher state of tune, read -(more hp) for a given engine size.

The other advantage today, is idling in traffic. My previous bike, the '89 GSX-F600 was what Suzuki termed air-oil cooling and for the most part was great, however it could overheat in stop-start, slow traffic conditions whereas the C50T with fuel-injection and liquid-cooling can idle all day and plod along at walking pace with the only consequence a bit of fan-noise at times.

Having said that, I have never heard of a problem with the GS500 and they've been around long enough that if there were any issues they'd be well known. I'd say for what you want, it would be pretty much ideal.

**HornetBoy** · 26th December 2007, 18:58

Originally Posted by Edbear

The other advantage today, is idling in traffic. My previous bike, the '89 GSX-F600 was what Suzuki termed air-oil cooling and for the most part was great, however it could overheat in stop-start, slow traffic conditions whereas the C50T with fuel-injection and liquid-cooling can idle all day and plod along at walking pace with the only consequence a bit of fan-noise at times.

yea my katana 600 is an 04 model and air/oil cooled, and i feel my pants getting a little hot at highway speeds ,and i do notice it gets alot hotter than my previous bike,which was a liquid cooled 900 hornet, it really is noticeable when in traffic and around town,sometimes worrying but if suzuki kept it this way it must be alright i figure.

**Bonez** · 26th December 2007, 19:27

Originally Posted by Hornet250Boy

yea my katana 600

Its a tea pot!!

**HornetBoy** · 26th December 2007, 19:37

Originally Posted by Bonez

Its a tea pot!!

yes well in that respect i guess it is lol,ah well tried and true technology non the less

**James Deuce** · 26th December 2007, 19:59

Originally Posted by Edbear

My previous bike, the '89 GSX-F600 was what Suzuki termed air-oil cooling and for the most part was great, however it could overheat in stop-start, slow traffic conditions

My '99 GSX600F didn't. The worst bike I've ridden in traffic for heat is an Aprilia RSV-R. Which of course is liquid cooled.