air oil cooled versus liquid

[tog]

this being a katana board, i realize that the answers may be somewhat swayed

what are the pros and cons of each?

does living in a hot environment (Texas) change how you would look at things?

[Black_peter]

Hmmm
I think this:
A water cooled bike should have the ability to
stay at optimum tempurature all the time.
(maybe this is true, I don't know)

Air/Oil cooled bikes are at the mercy of air temp, speed and humidity..
However they are generally designed for a wide range of such..

I'm glad I don't have a all air cooled bike.. but wish I had Water cooled

[md86]

Water cooled is a little more complex , and it's one more thing you gotta worry about .

[The CyberPoet]

First, let's talk about the system Suzuki uses: Suzuki Advanced Cooling System (SACS). This system has been around for about 20 years now, and is rock solid. It uses a double-sided oil pump system to deliver low-volume, high-pressure oil to the heads (as with any motorcycle oil pump); the other side of the system delivers high-volume, relatively low-pressure oil to the oil filter, oil cooler and then sends much of it in high quantities to the underside of the pistons. The oil from both sides then runs off back into the main sump (oil pan) to be reused.

The advantages of SACS is that it permits the entire engine to heat up very evenly, since the oil being delivered to all the different areas of the engine are close in temperature, so there aren't great thermal variances in the most of the various internal engine parts (other than the actual combustion chamber). This is good for metal longevity, since there is less thermal stress. It also helps ensure that everything stays oiled well, again, good for longevity. Originally, the idea was to do it for racing purposes (since oil is lighter than water), and a system using SACS wouldn't need a water pump, water radiator, thermostat to control the coolant flow, coolant, nor an overflow tank); this also simplifies the entire engine design, reducing the possible points of failure (and the required maintenance to keep it running).

One of the major downsides to oil-air cooling is that oil doesn't transfer heat at the same rate as water/coolant-mixtures (away from the parts, and at the radiator to the air), so there is a cap on how much heat can be generated compared to a water-cooled bike. This wasn't an issue when the SACS engines were first designed, but as compression ratios and displacements rose over the years, the combustion chambers put out more and more heat, heat that simply couldn't be transferred out fast enough by the oil. Hence, high-output engines normally use water cooling instead, where the water passes through passages (a jacket) around the cylinder to suck off the heat very quickly. This is why the GSXR, which started with oil-air cooling, went to water-cooling around 93 or 94; the heat-output was getting to the point that they needed a liquid with a higher thermal transfer rate to get the excess heat out of the engine fast enough. Additionally, since the water is doing most of the heat transference work, the oil shouldn't run nearly as hot.

And there you have the primary balance between the two:
Oil-air cooling is simpler to engineer, easier on the metals, less prone to component failure.
Water (coolant-mix) cooling transfers heat faster, permitting use of higher compression levels and thus more power output from the same sized displacement.

Side notes:
Most oil-air cooled bikes have no temperature gauge or other form of thermal warning, so when they get too hot, the oil starts to break down (viscosity loss due to thermal breakdown), often without driver knowledge. By the time the bike starts acting up as a result, damages may have already been done. The viscosity breakdown also permits oils to form sludges and varnishes, which is why air-oil cooled motorcycles should use oils which are high in both detergents and viscosity-breakdown-inhibitors (and why your Kat calls for API SF/SG and why I also recommend JASO-MA spec oils for it). I sell specialized open-cockpit/all-weather oil temp gauges suitable for the Katana's and other oil-air cooled bikes at MotorcycleAnchor.com.
Given the right oil, the Kat's engine is not prone to overheating under normal use. On the other hand, run a highway speeds for a longer period of time and then suddenly find yourself in a traffic jam, and you may be asking for trouble. Ditto to anyone who has over-bored their engine with a wise-co kit, since the kits not only increase the combustion chamber size, but also up the compression levels quite a bit.
Water, and water-coolant mixtures are inherently prone to generating rust (hey, water helps rust metals, duh!), and thus water-cooled bikes need extra service to ensure that their cooling systems do not become a source of long-term problems (radiator and engine-block flushes); most water-cooled bikes have a two- to four-year recommended replacment schedule for the water pump as well.
If you have a water-cooled bike, the minerals in tap or spring water can be an added source of cooling system corrosion and mineral build-up (both of which act as thermal blankets to reduce the water's efficiency). Always use distilled water mixed with coolant in your system to minimize the possible problems (just as you would with a battery if you don't have a maintenance free battery).

Cheers
=-= The CyberPoet

[tog]

awesome

thanks for the info

[midqetsex]

CyberPoet could put HowStuffWorks out of business.

[Süsser Tod]

Side notes:
Most oil-air cooled bikes have no temperature gauge or other form of thermal warning, so when they get too hot, the oil starts to break down (viscosity loss due to thermal breakdown), often without driver knowledge. By the time the bike starts acting up as a result, damages may have already been done. The viscosity breakdown also permits oils to form sludges and varnishes, which is why air-oil cooled motorcycles should use oils which are high in both detergents and viscosity-breakdown-inhibitors (and why your Kat calls for API SF/SG and why I also recommend JASO-MA spec oils for it). I sell specialized open-cockpit/all-weather oil temp gauges suitable for the Katana's and other oil-air cooled bikes at MotorcycleAnchor.com.
Given the right oil, the Kat's engine is not prone to overheating under normal use. On the other hand, run a highway speeds for a longer period of time and then suddenly find yourself in a traffic jam, and you may be asking for trouble. Ditto to anyone who has over-bored their engine with a wise-co kit, since the kits not only increase the combustion chamber size, but also up the compression levels quite a bit.

Poet, I have a couple of questions.

a) Are SJ/SL and I think the newers are SM oils good for the Kat??? What about Mobil 1 that is now SM??? What about a plain SL synthetic?

b) What do you mean about getting into trouble after riding @ highway speeds and then getting stuck on a traffic jam?

[Anonymous]

i dont know ive had both types of bikes and i prefer the oil air cooled ones ive sat on the las vegas strip in mid summer at 132 air temps in the noraml traffic jams the asphalt being around 165 to 180 with my kat idleing for 45 mins and nothing happened yet my cbr which is water cooled can do the same thing but it happenes to puke out a lil coolant every now and then so its a 50/50 deal but alot of the water cooled bike run water thru the oil filter area to help absorb some of that heat but tis not near enough im thinking about a second cooling fan and adding a small oil cooler from a small oil cooled bike if space allows

[The CyberPoet]

a) Are SJ/SL and I think the newers are SM oils good for the Kat??? What about Mobil 1 that is now SM??? What about a plain SL synthetic?

No, SJ/SL/SM oils are not good for the Katana. Your Katana wants SF/SG and can live on SH (or even SH+SJ if needed). SJ/SL/SM are all "energy conserving", contain way too little ZDDP (zinc + phosphate), and your engine is not made to run these -- PERIOD. If you look at the API oil guide, it specifically says next to SJ/SL/SM "for automobiles built after..." while previous ratings say for "all 4-stroke gasoline engines built after..."
This is also why Mobil 1 offers specific motorcycle oils (Mobil 1 MX4T 10w40 and Mobil 1 VTwin 20w50); their motorcycle oil formulation is API SG/SH and JASO-MA rated.
You can find all your questions on motorcycle motor oil here:
CyberPoet's "Guide to how to understand and choose motorcycle motor oils, including additives, wet-clutches, formulations, etc." at MotorcycleAnchor.com, now offering 400 degree F oil temp gauges for GSX600F, GSX750F and other oil-air cooled motorcycles!

b) What do you mean about getting into trouble after riding @ highway speeds and then getting stuck on a traffic jam?

As long as you are moving forward, the oil cooler is doing it's job, and the oil in the sump is staying fairly cool, although the metal in the engine is fairly hot at this point from continuously running. As you come to a halt and the air stops moving through the cooler, the oil temps start to rise very rapidly, because the engine is still full of heat and creating more (especially problematic with the ignition advancer, which causes the bike to run hotter). Stay in stop-n-go traffic for 15 to 20 minutes, and the oil temps may reach a level where two things start happening:
- the oil in the heads starts hitting it's flash-point (various by brand of oil, from as low as 360 degrees F for some car oils to as high as 470 for a few; most are between 405 and 415) and resulting vapor starts forming heavy varnish build-up;
- while the oil in the sump can shoot up into the 375 - 400 degree range, breaking down the viscosity very rapidly.

Example: coming back from the KR rally a few weeks ago, I was tooling along at 85 - 90 mph for hours on end (except for gas stops). Outside Valdosta (about 95 degrees, 90% humidity), I hit a 10 mile patch of stop-n-walking speed traffic due to a semi-trailer that had broken (the cops had sealed all but one lane of highway). Slowly, the oil temp gauge started climbing... when it hit 350 and was bouncing violently towards 400, I got off the highway for a few minutes at the next available exit, rode a couple miles to drop the temp again, then came back and got in traffic -- this time with the engine off. If I had just sat there, the oil temp would have easily hit a temp that it couldn't readily cope with without breaking down, etc.

i dont know ive had both types of bikes and i prefer the oil air cooled ones ive sat on the las vegas strip in mid summer at 132 air temps in the noraml traffic jams the asphalt being around 165 to 180 with my kat idleing for 45 mins and nothing happened...

My guess is that nothing happened that you noticed; I doubt nothing happened at all (oil hitting certain temp ceilings and breaking down, vaporizing, etc). A high detergent oil would do a good job of scouring out the varnishes after the fact, and leave your engine nice and pretty again.

Cheers
=-= The CyberPoet

[Mr Nice Guy]

Hey Cyber I was stuck in that same traffic Jam on my way back from the rally. I never saw a trailer broken in the middle like that. Crazy lookin'. If you saw a Blue Frontier with a Kat and a SV650S squeezed in the back that was us. Just thought it was strange that we were in the same traffic jam....Later

[KAT6]

That is why I think that in the southern states in the summer we should use the mobil one synthetics for V twin it is a 20-50 and can handle more heat than 10-40.

Joe

[The CyberPoet]

Hey Cyber I was stuck in that same traffic Jam on my way back from the rally. I never saw a trailer broken in the middle like that. Crazy lookin'. If you saw a Blue Frontier with a Kat and a SV650S squeezed in the back that was us. Just thought it was strange that we were in the same traffic jam....Later

You would have spotted me -- I was on the bike
[EIDT] Blue Kat, Givi hardsided saddle bags, black perforated leather jacket, red-black helmet. I think I recall seeing the SV...

Cheers
=-= The CyberPoet

[Mr Nice Guy]

I mean I had never seen a trailer broken like that before. It was off to the side by the time we got to it. It was really crazy looking snapped in the middle. I shoulda taken a pick but it was too late and we were past it by the time I saw it.

[WildKat]

Countless 95 degree plus days, hot as all hell, bumper to bumper traffic and the Kat never misses a beat.

[SweetLou]

Of the water cooled bikes I have been on, I haven't really cared for them much. Seemed to really blow back a lot of hot air as I was just sitting. I didn't like that.