ESE's works engine tuner

[Buddha#81:Me]

I wouldn't bother with a vaccum cleaner. Get 2 or 3 high rpm 120mm or 200mm 12v computer cooling fans. Can get some pretty good airflow and will run of a smallish battery ok.

Why not try riding really fast and using the air flow to do all that?

[Yow Ling]

I wouldn't bother with a vaccum cleaner. Get 2 or 3 high rpm 120mm or 200mm 12v computer cooling fans. Can get some pretty good airflow and will run of a smallish battery ok.

I think that you guys are thinking cooling fans are good because they are used for cooling, they are great on computers for removing say 50w of heat. put your hand out the car window at 100kph, now put your hand behind one of these powerfull computer fans, see the difference? remember you are trying to remove about 7 or 8kW of heat from the head you need a mighty airstream to do this . Buddha is right onto it

[Buddha#81:Me]

Buddha is right onto it

Thanks big guy......and at 12.30 last night when I was drunk.......go figure.

[TZ350]

Why not try riding really fast and using the air flow to do all that?

I have found the problem with riding really fast, its that there is always a corner at the end of the fast bit and corner bits are confusing.

A motorcycle pulling out of a slow corner is like an aircraft climbing out, they are both making max power and thats when they both need the most cooling. Because of the motorcycles slow speed and the aircrafts angle of attack their engines are getting the least airflow when they need it the most. I think supplementary cooling is required if I am going to make some real power.

Its just how to do it and stay air cooled?

[koba]

Just an idea for inspiration:

Look at a Volkswagen Beetle engine.
The cooling system is an amazing piece of engineering, tuners have been trying to improve it over the years and there is very little that can be done to make it better.

More oil cooling is the only way to do it But strangley if you take the oil cooler out of the fan shroud it cocks the whole thing up because it was so carefully designed.

These engines began life pumping out about 30 horsepower from 1100cc, the ones with the most advance cooling systems were good for 50 horse from 1600cc but the cooling system on it routinely puts up with 150+ hp on modified engines, the craze is centred in California so I guess they can probably handle it on a hot day too.

One reason for the fan and tin shrouding is that it is all jammed in the back of a car and way out of the airflow.
They cool better the slower you go!

There is some good infor here

They also have pics of the fan shrouds cut in half.

[TZ350]

Thanks Koba, for the the V-Dub info. That is a very informative article. I did not know it takes eight times the power to double the fan speed and the heat transfer is not linear with velocity but roughly 0.73 of the difference in velocity.

Its probably no surprise that linear air is better than turbulent air for cooling.

Forced air cooling and ducting for the bike in some way has got to be the go.

I have allways known about cavitation but did not know that:-

"The fan cavitates - wrong, cavitation is only a liquid phenomena, it is boiling of a liquid due to a localised pressure drop below the vapour pressure of the liquid, you cannot boil a gas.

The fan chokes - wrong, you need to be approaching blade tip speeds near the speed of sound for that one to happen, trust me the VW fan isn't going to mechanically survive speeds anywhere near that.

The fan stalls - This is an interesting one. People say it aerodynamically stalls and cannot pass anymore air, this is wrong and is basically the fan chokes argument. However the fan stalling is partly correct, but it is not aerodynamically stalling, it is the fan belt slipping and preventing the fan from spinning any faster. This has to do with the VW fan belt being very small and not capable of transmitting enough power to continue accelerating the fan forever."

Quoted from the artical in Koba's post.

[TZ350]

I think that you guys are thinking cooling fans are good because they are used for cooling, they are great on computers for removing say 50w of heat. put your hand out the car window at 100kph, now put your hand behind one of these powerfull computer fans, see the difference? remember you are trying to remove about 7 or 8kW of heat from the head you need a mighty airstream to do this . Buddha is right onto it

Thanks Yow Ling, its a good point you make, do you know the ratings in degrees C per watt of any CPU fan assisted heat sinks?

I am hoping there could be some scrubbing action by the small fans air stream shifting the hot boundary layer air from between the fins and then that hot air being swept away by the main air stream.

I measured the fin area of one I have and the small heat sink (80X80 fan) had 1/3 the fin area of my GP125 cylinder head.

I suspect although there is plenty of area the thin fins of the CPU cooler offer a higher thermal resistance to heat flow than the thicker fins on the GP125's head.

Or they are thick because the die cast metal used in the head is not so great a heat conductor as pure aluminum and well spaced so that when stationary or going slow there is some heat dissipation by convection.

Enlightenment about this would be welcome.

I am also concerned the plastic CPU fan will melt as from what I'v read typically an air cooled head runs at 250-350 degrees C and a water cooled head is about 80-100 degrees C. So the fan could easily melt on the air cooled head.

I tried a duct with an air scoop on the GP at Taupo but the results were inconclusive. Mainly because I had not done any before and after measurements.

I don't know a lot about cooling systems but now I have a reason to find out and being a bucket its affordable to apply to my bike. This is what I enjoy about buckets, the challenge and afford-ability.

[speedpro]

You need lots of heat sinking ability as close to the combustion chamber as possible. Water cooling is the obvious choice if you are allowed but if not then I reckon lots of thin(ish) fins bolted tightly to the combustion chamber with heat sink compound, and then a shroud/duct to make sure plenty of air goes through the fins. Years ago, Frank (Paul Francois) bolted a stack of thin aluminium pieces to his AC50 head and then bent the ends up progressive amounts to form his own radial fin head. Until I watercooled mine it was obvious that mine faded lots more than his in a race.

[gav]

One of the popular mods for a VFR800 is to use a computer cooling fan to cool the regulator/rectifier. Somehow I don't see the same unit able to cool a 125cc cylinder head.

[TZ350]

You need lots of heat sinking ability as close to the combustion chamber as possible. Water cooling is the obvious choice if you are allowed but if not then I reckon lots of thin(ish) fins bolted tightly to the combustion chamber with heat sink compound, and then a shroud/duct to make sure plenty of air goes through the fins. Years ago, Frank (Paul Francois) bolted a stack of thin aluminium pieces to his AC50 head and then bent the ends up progressive amounts to form his own radial fin head. Until I watercooled mine it was obvious that mine faded lots more than his in a race.

That's a really good idea. As pure copper is a much better thermal conductor than pure aluminum. Then the strength of an alloy block for the combustion chamber and the fins made from copper sheet could be the go.

[TZ350]

Look at a Volkswagen Beetle engine.

These engines began life pumping out about 30 horsepower from 1100cc, the ones with the most advance cooling systems were good for 50 horse from 1600cc but the cooling system on it routinely puts up with 150+ hp on modified engines, the craze is centred in California so I guess they can probably handle it on a hot day too. More oil cooling is the only way to do it.

Looking at a hot V-Dubs 150hp from 1600cc thats 94hp per liter.

If I can get 22hp from my GP125 then thats 176hp per liter.

A significantly greater cooling load, so increased oil cooling for the gear box might be an option too.

[koba]

If you want to fight about rules you could make an oil cooled head.
But then it would be oil cooled and I think the 125 rule specifically says "aircooled".

[koba]

Looking at a hot V-Dubs 150hp from 1600cc thats 94hp per liter.

If I can get 22hp from my GP125 then thats 176hp per liter.

A significantly greater cooling load, so increased oil cooling for the gear box might be an option too.

Plus it doesn't have the extra stroke to unload the heat from the piston...

[TZ350]

From Koba,s post, and Goggle I have found some interesting info on air cooled motors. Before the "War" in some circles water cooling was considered inefficient, unreliable and expensive. This is the era V-Dubs come from.

Before the "War" Hitler had the Autobahns built, this was before there were fast cars. Then he encouraged the car makers to build Autobahn cars. They were often air cooled and very aerodynamic. There was an air cooled 3.8l V8.

In the 80's when large wind tunnels became available some of these old cars were tested and their drag coefficients (and fuel consumption) were lower than modern cars.

A quick intro to Mackerle. Julius Mackerle was the chief engineer at Tatra motorworks for many years. Tatra make a lot of air cooled vehicles and trucks. Mackerle published a huge amount of interesting air cooled engine information in a book of his called Air-Cooled Engines.

The interesting thing is that the air cooling was effected in different ways.

There was the V-Dub style cooling fan

Another device like a turbo charger that was spun by the exhaust gas and the fan compressor sucked or blew the air through the cooling fin ducts.

And a ventuire ejector system that also used the energy of the exhaust gas to sucke the air through the cooling fin ducts.

I am not sure about the difference between a venturie and a venturie ejector. But I think a venturie is like a motorcycle carb's needle-jet/choke arrangement. Where a small pipe leads into the middle of the venturie's choke and a venturie ejector is more like the old vaccume cleaner spray paint gun?

A venturie ejector is used where shifting bulk is the aim.

Here is an abstract from a US Patent.

Venturi exhaust cooler Document Type and Number: United States Patent 3875745

"The kinetic energy of the exhaust gas from an internal combustion engine is utilized as a driving fluid to aspirate a large volume of quiescent ambient air as a driven fluid for cooling the exhaust gas quickly in a very short path of travel. This mode of operation is to be distinguished from conventional injector and ejector devices utilizing a current of air as the driving fluid. The present device utilizes the Coanda effect to introduce the exhaust gas around a lip on one end of a venturi tube, causing the gas to flow in a high velocity film adherent to the inner surface of the tube. This laminar flow draws in a large volume flow of air through the center of the venturi, cooling 1000°F. exhaust gas down almost to ambient temperature in a distance of a few inches."

I have seen on some modern expansion chamber designs, that the stinger has changed to a restricter that looks like a venture with a tail pipe, makes me think this could be made into a venture ejector.

The good thing about using the energy in the exhaust gas to do some work, is that it quietens it like a muffler does.

A ventuire ejector might have possibilities.

.

[Yow Ling]

the norton rotary race bikes used a venturi ejector to draw cooling air through the rotor internals, the road bike version drew fuel air mixture through the engine to cool it, which wouldnt be helpfull on the race bike as it would reduce the charge density. this vid shows the ejector input at the start of the muffler http://video.google.com/videoplay?do...55775237376823 Maybe worth a google