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Can someone exlplain to me the difference in power between water and air cooled motors?

I went to the International Motorcycle show in Long Beach last weekend.
Spoke with one of the reps at the Ducati booth about the S2R Vs my current bike, Ninja 650R.
He told me the power would be about the same but the Duc would have more torque.

Any comments would greatly be appreciated as I can't get a response on the board I post
to regularly.

Thanks! [thumbsup]
 

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it's more complicated than just water vs. air.

in the water cooled ducs, there are 4 valves per cylinder. more valves = better/ more efficient air pump/engine. the air cooled ducs have only two valves per cylinder. with similar displacements, a two valve twin cylinder engine will put out less power than a four valved twin cylinder engine.

your ninja has four cylinders. I dunno how many valves per cylinder you have, but for the sake of comparison i'll assume that they have only two (intake / exhaust).

monster 620 vs ninja 650.

ninja=8 valves
monster=4 valves.

the ninja will make higher horse power numbers, but lower torque

your ninja has 650 cc's of displacement but it is divided by 4 (number of cylinders) giving you 162.5 cc's of explosive force each cycle per cylinder. I'm going to assume that a single revolution of the crank shaft is achieved with each of the cylinders firing to complete one revolution. (if i'm wrong I'm sure someone will chime in to correct me.) smaller steps faster. the explosive force is spread out over more of the turning of the crank shaft. less torque. the four cylinder engine is better balanced and has less net rotating mass/ internal inertia, and as a result can spin faster (higher rpm's) and produce more horsepower.

the monster has 618 cc's of displacement divided by 2 giving 309cc's of explosive force per cylinder with each cylinder firiing once to complete a revolution. bigger steps slower. the explosive force is concentrated, but happens less frequently. more torque. the two cylinder engine has more net rotating mass/ internal inertia and as a result has a lower max rpm which limits max horsepower.

it would be like two runners.

one can only take little steps, but can take them very fast. will have a higher top speed but will take longer to get there.

the other can take steps twice as big, but only half as frequently. will have a lower top speed but will get there very quickly.
 

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For an equivalent displacement, water cooled bikes will always have higher output. For example, a Ducati 749 puts out ~ 100rwhp (25hp+) and has roughly equivalent torque.

In a nutshell, they have tighter tolerances, generally have higher compression, more valve area and more consistent temperature control afforded by liquid-cooling simply allows for a higher output engine.

Other factors affect torque, it is entirely possible for a water-cooled engine of the same size to have as much if not more torque. Displacement and bore/stroke have more to do with torque output than how an engine is cooled.

Good to hear the Ducati reps didn't try to pull the wool over your eyes- yep, the 800cc S2R will have roughly equivalent horsepower to a Ninja 650R but the bigger, longer stroke S2R will put out more torque and at lower rpm.
 

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CapnCrunch said:
it's more complicated than just water vs. air.

in the water cooled ducs, there are 4 valves per cylinder. more valves = better/ more efficient air pump/engine. the air cooled ducs have only two valves per cylinder. with similar displacements, a two valve twin cylinder engine will put out less power than a four valved twin cylinder engine.

your ninja has four cylinders. I dunno how many valves per cylinder you have, but for the sake of comparison i'll assume that they have only two (intake / exhaust).

monster 620 vs ninja 650.

ninja=8 valves
monster=4 valves.
The Ninja 650R is a water-cooled, dohc 4v/cylinder parallel twin.

This bike would eat a 620/695 alive. It has significantly more power and has equivalent torque. It will give an S2R 800 a good run on top end.
 

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CapnCrunch said:
in the water cooled ducs, there are 4 valves per cylinder. more valves = better/ more efficient air pump/engine. the air cooled ducs have only two valves per cylinder. with similar displacements, a two valve twin cylinder engine will put out less power than a four valved twin cylinder engine.
HP is work per unit of time. The same torque at a higher rpm will yield more HP. The 2v Ducati engines run out of air before they reach maximum piston velocity. The 4v Ducati engines breathe better and can put out their power at higher rpms. 4v heads are harder to design for air cooled engines. This is the primary reason the water cooled Ducati engines have more power.

CapnCrunch said:
your ninja has four cylinders. I dunno how many valves per cylinder you have, but for the sake of comparison i'll assume that they have only two (intake / exhaust).

monster 620 vs ninja 650.

ninja=8 valves
monster=4 valves.

the ninja will make higher horse power numbers, but lower torque
The Ninja 650 is a parallel twin with 4 valves per cylinder. But, even if it were an inline 4 with 16 valves, the number of valves would not determine which engine would have more HP or torque.

CapnCrunch said:
I'm going to assume that a single revolution of the crank shaft is achieved with each of the cylinders firing to complete one revolution. (if i'm wrong I'm sure someone will chime in to correct me.)
In a 4 stroke engine, it takes 2 revolutions of the crank for a cylinder to fire.

CapnCrunch said:
your ninja has 650 cc's of displacement but it is divided by 4 (number of cylinders) giving you 162.5 cc's of explosive force each cycle per cylinder. I'm going to assume that a single revolution of the crank shaft is achieved with each of the cylinders firing to complete one revolution. (if i'm wrong I'm sure someone will chime in to correct me.) smaller steps faster. the explosive force is spread out over more of the turning of the crank shaft. less torque. the four cylinder engine is better balanced and has less net rotating mass/ internal inertia, and as a result can spin faster (higher rpm's) and produce more horsepower.

the monster has 618 cc's of displacement divided by 2 giving 309cc's of explosive force per cylinder with each cylinder firiing once to complete a revolution. bigger steps slower. the explosive force is concentrated, but happens less frequently. more torque. the two cylinder engine has more net rotating mass/ internal inertia and as a result has a lower max rpm which limits max horsepower.
The number of cylinders firing per revolution does not determine the output characteristics of an engine.
The stroke determines the maximum piston speed an engine can handle. The maximum rpm will determine the amount of HP an engine of a given toque output can achieve. So, if 2 engines of the same displacement have the same bore/stroke ratio, then one with more cylinders will have a shorter stroke, allowing it to rev higher, producing more HP for the same amount of torque. The shorter stroke will however reduce the amount of power then engine has at lower rpms.

CapnCrunch said:
ithe four cylinder engine is better balanced and has less net rotating mass/ internal inertia, and as a result can spin faster (higher rpm's) and produce more horsepower.
The L twin is a balanced engine. The inline 4 is not and requires a counter balance shaft to help keep the vibrations down.
 

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These are some terrific responses to the question. I might add a little about the actual difference/importance of air versus liquid cooling for an internal combustion engine. I have some experience with turbos and inter-coolers for cars, and some of the most important variables for those systems come down to the exact same physics at work in any motor. The most important variable, is heat. Heat generated by the combination of friction, compression and detonation. The more heat generated by a motor, the less efficient that system will perform. The high-temperature of the intake air charge will cause the fuel/air mixture to prematurely detonate, before the piston has fully reached the ideal position, before top dead centre (BTDC). Otherwise known as "pinging" or "knocking", this causes modern, EEC-equipped engines to retard the timing, and increase the percent of fuel to the mix to help reduce the heat. All this reduces power and efficiency. One way to help counteract this on a given motor, is to use higher-octane fuel. The higher-octane fuel, in itself, does not mean more power. But the effect of the increased hydrocarbons (octane, in this case) help to resist the explosive results of pressure. The higher the octane, the higher the pressure and temperature can rise in a given motor. This will allow the motor to move more air through (as it is just a glorified air pump) in the same amount of time, hence creating more power. So adding additional ways for the cylinders to transfer heat away from the incoming air/fuel mix is the first step to promoting more efficiency in the motor. Aluminum blocks, liquid-filled jackets around said block and cylinders, and in the case of forced injection, large inter-coolers, all help modern motors control their heat FAR better than any air-cooled motor can ever hope to do. So if you compare motors with identical bore-stroke, the difference being air versus liquid cooling, the liquid one will always create more power at the same RPM.
 

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so essentially you are telling me if i put an oil cooler on my monster it will make more horsepower?
 

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nissontek said:
so essentially you are telling me if i put an oil cooler on my monster it will make more horsepower?
no
 

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i know the answer is no. i am asking if that is the statement he is making. cooler engine = more power (according to the post)
 

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If you know the answer is "no" why are you asking the question? You could always perform your own test to see if heat affects performance. Try wrapping your motor with heat wrap and go for a long ride. Then you can tell everyone how that worked out.
 

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CapnCrunch said:
it's more complicated than just water vs. air.

in the water cooled ducs, there are 4 valves per cylinder. more valves = better/ more efficient air pump/engine. the air cooled ducs have only two valves per cylinder. with similar displacements, a two valve twin cylinder engine will put out less power than a four valved twin cylinder engine.

your ninja has four cylinders. I dunno how many valves per cylinder you have, but for the sake of comparison i'll assume that they have only two (intake / exhaust).

monster 620 vs ninja 650.

ninja=8 valves
monster=4 valves.

the ninja will make higher horse power numbers, but lower torque

your ninja has 650 cc's of displacement but it is divided by 4 (number of cylinders) giving you 162.5 cc's of explosive force each cycle per cylinder. I'm going to assume that a single revolution of the crank shaft is achieved with each of the cylinders firing to complete one revolution. (if i'm wrong I'm sure someone will chime in to correct me.) smaller steps faster. the explosive force is spread out over more of the turning of the crank shaft. less torque. the four cylinder engine is better balanced and has less net rotating mass/ internal inertia, and as a result can spin faster (higher rpm's) and produce more horsepower.

the monster has 618 cc's of displacement divided by 2 giving 309cc's of explosive force per cylinder with each cylinder firiing once to complete a revolution. bigger steps slower. the explosive force is concentrated, but happens less frequently. more torque. the two cylinder engine has more net rotating mass/ internal inertia and as a result has a lower max rpm which limits max horsepower.

it would be like two runners.

one can only take little steps, but can take them very fast. will have a higher top speed but will take longer to get there.

the other can take steps twice as big, but only half as frequently. will have a lower top speed but will get there very quickly.
thanks for that [thumbsup]. i finally get a glimmer of understanding as to why the motors behave so differently!
 

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Tam 212 said:
The Ninja 650R is a water-cooled, dohc 4v/cylinder parallel twin.

This bike would eat a 620/695 alive. It has significantly more power and has equivalent torque. It will give an S2R 800 a good run on top end.
Don't be so quick to make that conclusion, the 650R is "slower" and less powerful than an SV650, and the SV650 would be hard pressed to really trounce a 695 or an S2R. The 695 and the 800 both run around 70hp at the wheel, the SV around 72, the Ninja in the high-60s. Weight evens out most of the difference, and the 2v motor does have considerably more torque and useable midrange. Personally for similar horsepower I would chose the 2v motors, the powerbands are much broader.

For handling, the S2R is just as good as anything in the class. The 695 is a bit old fashioned in the chassis department. But these aren't race replicas so I wouldn't discount it on that point alone.

Yes, I am omitting the 620.
 

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Well I don't know jack!! But heat wrap and ceramic coating on header pipes show gains in power.
 

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Indeed. I was going to make that distinction but figured most people would figure it out on their own. Within reason, retained heat in the exhaust system is a good thing because it increases exhaust scavenging. But the benefits of insulating the exhaust manifold are far more pronounced under the hood of a car. The insulated exhaust pipes won't convect as much heat to the motor, and hence, cooler intake charge and more power. Add a CAI to most cars, and that further enhances the net effect. Obviously, not really applicable to a motorcycle.
 

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NeufUnSix said:
Don't be so quick to make that conclusion, the 650R is "slower" and less powerful than an SV650, and the SV650 would be hard pressed to really trounce a 695 or an S2R. The 695 and the 800 both run around 70hp at the wheel, the SV around 72, the Ninja in the high-60s. Weight evens out most of the difference, and the 2v motor does have considerably more torque and useable midrange. Personally for similar horsepower I would chose the 2v motors, the powerbands are much broader.

For handling, the S2R is just as good as anything in the class. The 695 is a bit old fashioned in the chassis department. But these aren't race replicas so I wouldn't discount it on that point alone.

Yes, I am omitting the 620.
695 with 70rwhp? The most I've seen out of a stock 695 is low 60rwhp and low 40lb-ft. torque. A `03 + (FI) SV650 turns out low 70rwhp and high 40lb-ft. torque. But, I suppose the 650R reputedly puts out low 60rwhp.

I agree regarding the quality of suspension and handling potential, especially on the S2R 800.

Desmodue power delivery vs. Japanese water-cooled twins is subjective preference. Personally, I really like the 1000DS but found the S2R 800 a bit flat.
 

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Tam 212 said:
695 with 70rwhp? The most I've seen out of a stock 695 is low 60rwhp and low 40lb-ft. torque. A `03 + (FI) SV650 turns out low 70rwhp and high 40lb-ft. torque. But, I suppose the 650R reputedly puts out low 60rwhp.

I agree regarding the quality of suspension and handling potential, especially on the S2R 800.

Desmodue power delivery vs. Japanese water-cooled twins is subjective preference. Personally, I really like the 1000DS but found the S2R 800 a bit flat.
Someone here had posted a chart for the 695 that was in the 70s, I thought it might have been reasonably accurate. 620s were high 50s-low 60s, so I would expect a gain over that. The 800 is definitely in SV territory, with more torque. The SV revs nicely but is weak until about 5K and has a nice big flat spot at 3500 to slow you down. A lot like my 916 actually.

Of course with fettling an SV can make some serious power that will rival 900-1000 2Vs, but I have a buggered up bottom end and some knackered barrels in my closet that shows the results of that. Not a superb design, it can't handle much strain.
 

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For what it is, the SV650 is a pretty decent design... unless you start trying to make it into something it wasn't. You're right, it doesn't that much overhead. A friend blew two motors that were fairly heavily modded- first motor was 750cc and the second was a bit milder at 700cc. Both suffered bottom end failures.

My practically stock`00 has 35K+ miles and over 20 trackdays without skipping a beat. Traxxion Dynamics front end and Penske 8900 shock (no remote reservoir) upgrade the bargain bin suspension.

INever noticed a flat spot at 3500... don't really ride the SV at that rpm. I run desnorkeled air filter, rejetted with 175 mains and a full M4 system, there is a dip at ~ 6K but the surge from 7K to 10K is satisfactory. Decent enough for cruising on the street from 4K up.

The SV650 won't outdrive or outrun a S2R 800 but it will give it a good run and it will definitely walk away from any stock desmodue that displaces less than 750cc.
 

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Tam 212 said:
For what it is, the SV650 is a pretty decent design... unless you start trying to make it into something it wasn't. You're right, it doesn't that much overhead. A friend blew two motors that were fairly heavily modded- first motor was 750cc and the second was a bit milder at 700cc. Both suffered bottom end failures.

My practically stock`00 has 35K+ miles and over 20 trackdays without skipping a beat. Traxxion Dynamics front end and Penske 8900 shock (no remote reservoir) upgrade the bargain bin suspension.

INever noticed a flat spot at 3500... don't really ride the SV at that rpm. I run desnorkeled air filter, rejetted with 175 mains and a full M4 system, there is a dip at ~ 6K but the surge from 7K to 10K is satisfactory. Decent enough for cruising on the street from 4K up.

The SV650 won't outdrive or outrun a S2R 800 but it will give it a good run and it will definitely walk away from any stock desmodue that displaces less than 750cc.
I had an 04, they had a flat spot right before the secondary fuel injectors kicked in. Cam timing is different from 99-02 models too. You could fix it with some TPS tuning and a TRE mod, but there again, you are twiddling with things. Mine was heavily tuned, I had run a 700 kit briefly but it wasn't overbored to the right tolerances and it nearly self-destructed. The bottom end I have was off a spare race motor run with the stock bore, the rear conrod is stretched about 3mm and the thrust washers on the cam drive had gone south. 99-02s had bottom end oiling problems too.

With my 700 kit, ported and polished heads, radius valves, quad intake cams, K&N, and a full Hindle system, plus 40lbs off stock, it was on par with a lightly modded M900Sie that I rode a while ago. Without the 700 hi comps it wasn't nearly as potent, but it sure as hell had more chance of surviving the season.
 

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sneather said:
If you know the answer is "no" why are you asking the question? You could always perform your own test to see if heat affects performance. Try wrapping your motor with heat wrap and go for a long ride. Then you can tell everyone how that worked out.
wow, i know heat affects performance. i figured we were discussing normal operating temperatures. of course an over-heated engine will suffer greatly. you were describing the difference between naturally aspirated engines vs. forced induction. that doesn't apply to this discussion. we are talking air cooled vs. water cooled. i believe my question is pertinent to your response. if i cooled my engine by installing an oil cooler will it create more horsepower? you stated a liquid cooled engine will create more horse power than an air cooled engine at the same rpm. if i took a 620 stock and a 620 with an oil cooler the oil cooled engine should create more power at the same rpms. i am certain telling me to wrap my engine with exhaust tape has absolutely nothing to do with this discussion.
 

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I gave you that kind of response because you were being obtuse. You already stated that you knew the answer to your question was "no".

The only reason that I even mentioned forced induction was that anyone who delves into that subject will likely learn quite a bit about the adverse effects of compression and heat. Those dynamics are absolute regardless of whether a motor is turbo-charged, super-charged, ram-fed, or naturally aspirated. The more one can do to lower the internal temperature of a motor and therefore the intake charge, the better. Liquid cooling, and if need be, oil cooling, all make for a more efficient motor - everything else being equal.

Air-cooled motors are less-complicated, lighter, but more important, less expensive to build. Other than Harley Davidson (and the other chopper guys), there aren't too many other manufacturers making air-cooled motors for production bikes/cars. I do believe that Porsche and Vee-Dub kind of put that technology out to pasture years ago.
 
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