Thermo Fans

[cj!]

I need to look at my fan setup on the Vit. To be able to mount the winch back as far as possible I really need to remove the A/C fan on the condenser. Now as I'm a bit soft I also need to keep my A/C functional so the idea is to replace the existing engine cooling fan with a thermo that can also be used as a pull through fan for the A/C condenser as well as being the engine cooling fan. As I understand it this is done on some vehicles by manufacturers so it should be achievable. I would need a thermo switch for the engine and a switch for when the A/C is used and also a switch to shut it down for water crossings. Obviously it is ideal to have a shroud for optimum efficiency and as there is already one there for the Factory engine fan it would make sense to use that if possible. The hole in the shroud for the fan is 475mm or 18.7" in dia. and the Factory cooling fan has a dia. of 420mm or 16.5". The depth of the shroud is 75mm. Now it seems that 16" thermo fans are a fairly common size and I have seen some that supposedly flow around the 2750cfm mark. Here are a couple on ebay http://cgi.ebay.com.au/HIGH-PERFORMANCE ... otohosting

http://cgi.ebay.com.au/ws/eBayISAPI.dll ... :IT&ih=010
The Factory cooling fan has a clutch arrangement that has the fan doing about 500-800rpm when the temp is below 50deg. As the temp starts to rise and reaches between 50-70 deg. the fan starts to increase speed gradually. Once the temp reaches 70 deg the fan clutch turns on and the fan increases speed in proportion to engine rpm. Once the engine reaches 4000rpm the fan speed remains constant at 2250-2550rpm.

So the big question is will something like one of the thermo fans on ebay do the job?

[cj!]

Here are pics of the Factory setup.

[christover1]

It can be worth fitting a manual switch on also, for those times that you know better than thermostat switches.
(Switch would be 3 positions - on/auto/off)
I've seen many thermos fail thru wiring and thermo switches, so it can be handy to overide them when needed.
Keeping an engine cool is easier than cooling down a hot engine, so ability to manual switch when you know extra cooling could help is handy.
I have seen a few thermo fans fail due to poor connections where wires go into fan motor, so keep an eye on the quality of that area.

[mightymouse]

Thermo fans worry me - I am using one as theres no room for an engine fan - but its an ongoing challenge and hasnt ben a happy relationship.

Issues IMO are :

1/ do they move enough air ?
2/ they arn't progressive - some electronics on the control side would be great
3/ large ones can impose a significant drain on the electrical system to the point of stalling a car if its hasn't got idle speed control
4/ reliabilty, havnt had one fail but the viscous couplings are very reliable.
5/ manual overides eventually get forgotten

[gwagensteve]

I'm not generally a fan of thermo setups that aren't factory engineered.

case in point- Greg's green car.

This car was running a 14" thermo (same width as the radiator) of high quality, fully shrouded. It was controlled via the stock ECU as per the cappuccino. It didn't like hot weather or long periods of full load - it would get warm. Not actually overheat, but there was a noticable swing.

Piggles runs the stock mechanical fan and shroud. Fan is about the same diameter, car runs about the same hp, same intercooler, exhaust, and just wont heat up beyond 1/2 at all - the needle just doesn't move.

Another example- A fellow G wagen owner spent $$$$$$$$ on his cooling system - twin 14" thermos, radiator strip and clean fan controller etc, and hig G would still get hot. replaced the silicone in his factory viscous fan clutch - never, ever needed to turn the thermo's on again.

Personally, I'd investigate the following ideas -

A) an electronic clutch fan (mercs use these, to name one) that can be switched constantly on when the A/C is running (these are like an A/C clutch)
B) can you shorten the fan hub and move the radiator back?
C) if you must go thermo, maybe a whole radiator/fan arrangment from a donor car (like muggin's AU falcon) so you at least get factory engineering.

Just some ideas.

[robsjimny]

Another thing to think about is noise. Using a large fan with enough flow will be loud. I played with electric fans but when you pull up to a set of lights and hear it. I went back to normal


Rob

[cj!]

Noise is an issue although as I understand it, the "S" shaped blades are quieter.

I'll have a closer look at the elctromagnetic clutch fans, I like the idea. I think BMW have used them as well as Mercedes and probably others.

I know what you are saying about keeping things Factory and that would be my preference but I would also like to keep my approach angle reasonable and not have too much weight hanging way out the front if possible.

Moving the radiator back may be an option. I'll have a look.

Using a Factory setup off another vehicle is a possibility but it is a matter of trying to fit it in the space. Could work.

[mightymouse]

As the electrical load created by a decent size thermo fan system can be significant, you need to consider what's going to happen to engine idle with everything electrical turned on.

Current factory EFI systems have active ( proportional ) idle speed control and can dynamically adjust for idle variations caused by load, the fans are sometimes also electronically controlled and soft start - but if its an older system it may simply have an idle up solenoid thats sized to maintain idle with lights on and A/C. so a bit of extra plumbing / wiring might be necessary.

The Feroza's currently suffering from this, the thermofan is "rossbuilt" and isn't currently hooked into the ECU idle up system, so with every electrical load on, and the thermo fan, it stalls when in gear. If fact I think a second idle up solenoid might be necessary as the original one looks a bit small.

Good EFI systems solve soooo many problems.

[mightymouse]

Some of the best thermofans available..... PWR sell locally.

also of interest is the FAN-PWM controller which has some desirable features - two speed, staged dual fans, AC input...

its not perfect... but its the best commercial aftermarket unit that I have seen and its not badly priced

http://www.spalusa.com/

[mightymouse]

OK - having been doing some serious research on thermo's, coupled with some interesting discussions with the guys who did the ford twin setup and others

Their advice on thermo's is...

1/ pull is the preferred option
2/ any brand that says its pushes or pulls equally, simply by reversing the blades is fill of #$%^ - the blade profile is very different on a pull fan to push.
3/ any brand that doesn't publish flow vs pressure drop vs current draw is a risk.
4/ the special "very high performance" units sacrifice motor life for flow - once again a reputable supplier will identify this in their documentation.
5/ thick cores or multi layers pose special problems - their are special fans for these applications - once again a reputable supplier will identify this.
6/ "S" shaped blades are quieter but often don't flow as well - so its a trade off.
7/ speed control is a great asset - a bit of air flow when the temperature is just over target beats a heap after its got hot. Having said that - they hadn't seen a "fantastic" aftermarket fan controller.