Does anyone have any knowledge of thermofan/s being used to cool the flat four instead of the pulley fan being driven off the crank.

I'm not that despirate for a few extra horse power and quite happy with the current set up but I was just curious if thermo fans have been used with any success in the past.

Questions I have-
...would one thermo fan be enough?
...would a larger alternator be needed?
...should the the fan/s be on a thermostat?
...failsafe measures in case of fan failure?
...inherent vibration / grit / moisture problems?
...too efficient causing engine to run cold.
...shroud difficulties and added noise.

Of course I'm thinking along the lines of a baja.

to be honest I don't think a thermo is capable of supplying the cooling required. If you think that the doghouse setup produces loads of CFM (sorry can't remember exactly how much)the power required to produces that cooling is reasonable large say (at a guess) 5hp That is nearly 4000watts that sure would be a big ass fan

The point of a thermatic fan on a water-cooled car was that when you are moving, the air flow through the radiator provided enough cooling, meaning the 5 hp the engine used to drive the fan was wasted. So unless you can provide the equivalent amount of cooling to that provided by a VW engine fan when the car is moving, you'd have to have your thermatic fan on all the time.

[Edited on 23-12-2002 by mnsKmobi]

do u mean an electrically powered fan? If so, its not feasible. basically the stock fan uses about 3HP or about 2kw. on a 12v electrical system thats about 166 Amps, which is an absolute S-Load of current, and this is assuming that the alternator is 100% efficient which it is far from. If you could even get an alternator to suit, it would draw a fair bit of power from the engine and put a fair bit of load on it which increases the heat produced in the first place. Not to mention that it would probably be very expensive and probably huge.


You tend to lose a lot of efficiency because u convert mechanical to electrical to mechanical again, instead of mechanical to mechanical. So basically the stock setup is very efficent and effective. Some drag racers do use electric fans but they are run off a battery and turned on after a run.


If you need more cooling in a type 1, you can try to go to a doghouse setup and/or try to get hold of a US-Spec FI Doghouse (i acquired one recently). This rare shroud has more vanes inside as well as a venturi at the fan inlet. Cools about 10% more than a stock doghouse with the same fan. It can cool a 2.3L type 1 engine. Also ensuring all the tinware is sealed and making sure the fan is getting enough cool air will keep overheating at bay.

However if u meant thermatically controlling the stock fan, yes its really interesting and feasible, its just difficult. There has been some research done by some people into this, what u can do is use some kind of clutch device on the fan to vary its speed according to head temp, and oil temp as well as load etc. This would free up some power in some situations and the cooling of the engine would be more consistent. However you would have to probably be an engineer to figure it all out and execute it properly.

Che has it about right with his answer.

The doghouse fan on the type 1 engine produces about 25cf/sec at about 5psi.

Getting 25cf/sec is not that hard - but doing it at 5psi is a BIG task, and in fact the doghouse fan absorbs about 5hp (not 3 as Che says) to get that volume at that pressure.

The thermatic fans used on watercooled cars do not work with any appreciable pressure - they just move air within the atmosphere, and are only "booster" fans to keep air moving whem the car is stopped, so are usually only about 100-200watts (roughly 1/5th hp). So your average thermatic fan has about 1/25th of the power needed to cool a VW engine!

As the air travels through the cooling fins it heats up and expands, forming a sort of mobil "plug" which resists more air moving through the fins, so you need PRESSURE to force the heated air through and allow more cooling air flow to get into the fin area. Getting that volume with the pressure needed is what take all that cooling energy.

The std fan in a vw is a centrifrugal type of fan while a thermo fan is a axial flow type. would u have to modify the inside of the tinware so as to properly disperse the air with a thermo fan?, as the std fan "throughs"the air out in the std direction. If I remeber correctly (IF) a axial type fan can flow more fluid (eg air) than a centrifrugal while centrifrugal pump can make a higher pressure.

This is a very interesting area in which I would like to do some experimenting in with differeing setups on an engine stand.

I do very much appreciate your opinions and agree with them. I understand what you mean by mechanical - electrical - mechanical and the loss as a result from on top of the alternator loss' as well.

I notice that many modern cars are running huge thermos and dual thermos and the are forcing a huge amout of air through their radators, transmissions, intercoolers, aircons etc etc attached to modern systems. If you have ever crouched down beside a commodore at idle for any length of time then you might be able to appreciate just how hot they run and the force to which there thermo fans are pumping air.

Their would be a significant amount of draw for sure but altering the revolutions on an electrical motor is certianly easier than that of a mechanical system through clutches and fluid systems.

As I have a baja I certianly do not have any cooling probs. The 1300 runs at about 80 degrees oil temp most days and 90 on a really hot day. On hot sand or seal it might get near 100 until I get some speed up. With the carby kit in it will probably run cooler mabey.

I would like to know more about this so if anyone wishes to add to the above or cite an examples please do. I hope to purchase a second 1300 as a spare and get it running on a stand. I hope to fold up some tin and trial a couple of ideas. They may work, they may not. Anyway it works out will be interesting and not a total waste of time as I like tinkering and experimenting with different things.

Bronze,

Electric fan cooling for a beetle engine WILL NOT WORK....read my post above.

The cooling REQUIRES about 5hp (for the doghouse cooling system or about 4 hp for the in-shroud system) and a 5hp electric motor would be about 1/2 the weight of the complete engine! Then add the giant 4kw alternator needed to power it and you've just about doubles the weight of your engine. The mechanical system VW uses has only the weight of the fan belt and pulleys to consider, and you need those anyway for the generator/alternator, so the weight aspect of the mechnical cooling system is "free".

BiX mentioned axial fans in lieu of "drum" type fans. Makes no difference.

Porsche use the axial type fan on there aircooled engines and it's STILL the same deal - about 5hp for the 7 (I think) blade Porsche fan and about 6 hp for the 11 blade fan on the larger engines.

And if you look at the Porsche fan v the thermatic fan, you'll see that the blades on the Porsche fans almost overlap - you can't really see through between the blades. THIS is what enables that type of fan to develop the PRESSURE needed to drive the cooling air through the finning of the heads and cylinders - if you tried using a thermatic style blade (with gaps between the blades) you just will NOT get the pressure needed - the air tends to leak backwards between the blades.

Thermatic type fans only work well in an "open atmosphere" type situation, where they are just moving air, but not with any appreciable pressure differential from one side of the fan to the other.

Bronze,
Not that I'm any expert, or have a great deal of experience, but if you tinkering with electrical fans, I'd recommend looking into centrifugal, as opposed to axial fans (or normal car fans), they can generated pressure better and are available industrially, and you may be able to find one at an auction or in the trade section in the trading post, they are used for blowers, and as vacuum's.
As for the thermostat, I think you'd be best sticking with the original set-up, much easier to get working correctly,
Have fun, and let us know how you go!
Andy.

I think the only way you could get around it would be an air conditioner style clutch on the alternator/generator and a dirty big scoop to draw the air in, so that the stock fan works at idle, light driving etc, but disengages when there is enough air being forced through the scoop, say at 80-100kph.

an electric replacement fan just isnt feasable due to the volume of air required.

yeah lots of people have wanted to try the electric fan idea before... just go to the RAMVA newsgroup... its been covered a billion times and it is not at all feasible.

http://groups.google.com/groups?hl=en&group=rec.autos.makers.vw.aircooled

probably the best thing to pursue would be a variable speed fan using some kind of computer controlled clutch system.

Read this and you'll have a bit more of an idea
http://www.offroadvw.net/tech/wes/fan.html

You can't say what power or flow the fan churns out because it depends on engine speed. The power required increases as a cube of the engine speed. 5HP and above will be required for high engine speeds.
At 3,000rpm highway cruising speed the fan will be pumping around 1000cfm. Try to find a thermo fan that pumps out that much and see how you go.

I didn't say u couldn't use a axial fan only that the inside of the tinware would need to be modified as it is designed for a centrifrugal fan. Thats a great idea about the water spray, what about rust? and also what would happen to the sections of heads if they are hot and get hit by a mist, would that suddenly cool them and may cause stresses in the metal?

I have a question about heating, I run a 1776 motor, with 8.4:1 cr, it has standard oilm cooler, z9 filter in left gurad and also a secondary cooler above the gear box, The engine hasen't been run in the summer yet, but thew oil seems to run cool, yet the engine "smells hot" and the dipstick is hot to touch after a long run. could the oil be running cool and the heads hot?

misting sounds interesting, although i would guess that the water mist might not reach the entire surrounds of the head, like it might not reach the undersides as easily as air would and this might cause a problem with warpage and possible a head/cylinder leak?

good point wes, i should have said maximum of 5hp

Heads can be toasty and oil can be cooll at the same time, and they do overlap a little. Head temps are affected by engine load, how much throttle and what the engine has to push against. Oil temps are mainly from internal friction, so generally higher RPM = higher oil temp.

there is overlap as oil reaches the back of the piston and the valve stems, although its slight. Head temp goes up & down quickly (like when u climb a hill and coast back down at highish RPM) and oil takes a little longer to heat up / cool down.

Best to use gauges (something i have to get off my arse to install someday ) for both head temp and oil temp.

Thanks guys for all your input. This is good food for thought. I do agree that the original VW set up would of course be the best. Why change it, why alter it? Why not? What have I got to lose?

I eventually want to set up a volkswagen motor in a two person hovercraft just forward of the fan assembly. The working revolution would be similar to an aircraft at 4-4500rpm and occasionally down to idle. I was hoping to incorperate the engine cooling from air that is drawn into the prop. The use of a suitable oil cooler can do this but that address the problem of head temp.

Rotary, Subaru, Volks and inline engines are common in hovercrafts, it's just that hovercraft are not common to find and design off.

It will be a year before I can start building one but that dosen't mean I can't start developing an understanding of the physics of aircooling from an earlier date.

I understand fully your point it not being feasable to cool using thrmo fans because the air needs to be pumped past the heads. I don't plan to install a hybred cooling system into the Dog-O-War as the current one cools just fine and I don't want to be caught between Dubbo and Newcastle because a broken wire cooked my heads. But I did want to know why thermofans wern't being used on aircooled engines and why I hadn't seen at least one with a thermofan instead of the usual setup. Well now I know.

I think misting is a fairly common setup for turbo motors to cool intake air. I don't know much about it but did read a little in a car mag while at the doctors a few months ago.

Thanks all for you knowledge and understandings of this topic.

Happr new year and all the best to you and yours.

The point about misting water into the cooling air is an interesting one, and as many suggest it has come up often before. It came up a while ago on a US user list (type2.com), where a couple of people has used it with very limited success.
The first problem is it is of most use in hot air (high ambient temp), were the water will evaporate into the air cooling it down (before it gets to the heads/cyls), so some sort of thermostat needs to turn it on and off depending on the incoming air temp. It also means you get no additional cooling if the air is already reasonably cool and you have an engine pumping out heaps of HP. They also found it difficult to get a fine enough mist so that it fully evaporated before getting to the heads/cyls and giving an even cooling to the incoming air.
The other biggest problem was carrying enough water. Unless your racing most VW's, especially Kombi's get used for reasonably long trips, and carrying enough water becomes impractical.
I might need to tow a trailer of water for my up coming trip to Adelaide!!!!
Just my thoughts.
Andy.
:thumb

Bronze thats called a water to air intercooler, as air is compressed by the turbo it heats up. Autospeed did an entire article on water to air intercooling
http://www.autospeed.com/A_0090/page1.html
good read!

something I came across which may be of interest here, is the Lexus GS300, or Aristo as they are in japan, uses a hydraulic pump off the water pump to drive the fan via a small hydraulic motor (for reasons only the japs will ever know).

this may well be adapted to drive the VW fan, and as it is regulated by a bypass restrictor elctronically, you could set it to rotate at a set max speed, and even disable the fan rotation at say full throttle.

lets face it, the amount of time at full throttle is nowhere near the amount of time spent on back off, part throttle or idle. it'd be a lot more reliable than the air con clutch concept, as with much more load on them they fry pretty quick.


just fuelling ideas

For the sake of 5hp I say why bother but then when I stop to think for a while when filling up and the bowser read over a dollar a litre for standard unleaded then I guess it's good to squeeze ever drop of economy out of the flat four I suppose.

Running such big rubber, carrying so many tools and crap for the kids efficency went out the window when I put the roof rack on. I have a 34 pict 4 sitting on the tp1300 which was the original setup when I got it. I'm sure the carb is two big as the Baja chews as much fuel as my 2 litre telstar with the aircon on over the same K's around town.

Although the 1300 is very very good on the freeway. It's efficiency is unbelieveable. At first I though it was the trucks I was sitting up the ass of - then I thought about them blowing a tyre so I didn't do that on the way home and still the Dog-O-War gave an excellent mileage. I didn't do the maths yet at all but of course heaps heaps better than around town. The trip out to Dubbo shouldn't be all that expensive.

Thanks for the link to the misting. A very interesting read. Has anyone had any dealings with those electric turbo chargers that look like little cpu fans? They go between the carb and the manifold and force induct to a small degree and creat an advantagious spin on the mix before combustion? Only read the adds which are of course best case scenarios!

yeah ur right a clutch wouldn't be that good.... although something like a Continuously variable transmission could be used for that purpose? Maybe a pulley that can change diameter with speed (centrifugal weights)? mmm

yeah the electric turbo charger thing is something similar in vein to the electric cooling fan, its so inefficient its impractical. I thought it was a joke at first when people started selling them on ebay

Different head stud pattern between type1 and wasserboxer.