Outer Limits 4x4 Board

I have been working in the shed heaps lately and I spied in the corner an old radiator my brother must have got from the tip and attached to it is by eye a 12 inch thermo fan. I tested it on a battery and it spins pretty fast still and looks like its in good condition.
Now my question.
Is there any HP gains to be had in getting rid of the stock 1.3 engine driven fan? There's nothing wrong with my engine fan apart from the gouge it put in my radiator in a water crossing which is a plus I guess with an electric fan conversion.
I was thinking of running it to the coil so it's on when the cars on and having a missile switch with a light that shines at me when I turn it off. So when i turn the fan off while warming the car up in the morning I remember to turn it back on (not as ideal as a thermo switch but I didn't get one of them free with the fan ). The south west of w.a. isn't the hottest place in the world but in the summer time driving on the beach the car does get hot enough I have to turn on my second blow thru thermo to help with the cooling.
So basically is there anything to gain with this free thermo or just stick with the old reliable mechanical fan?

I put on a thermo a few years ago running off a DC switch. I didn't notice any real difference in HP. Personally if it heats up already on the beach then I would stick with the engine driven one although mine has only ever struggled once when the rad was full of mud but that was simply solved by changing the switch to run full time.

You will probably find the a 12 inch thermo will pull about 15-20 amps. It will ake almost as many kilowatts to generate that sort of power out of the alternator as what you will gain by removing it.
You can't beat an engine driven fan for coolin. so if you do any sand work or lots of hills then stick to the stocky one.. of course a major benefit of the thermo is being able to turn it off for river crossings...
Dan

I reckon going to a elec water pump would be a better way to combat hp robbing inertia.

Thermo fans do save some hp but it's much of a muchness as the power to drive them is turned into from eletrical drain

A) Thermo fans, but especially their wiring and switching, can be unreliable.

B) The claims for "HP gains" only refer to when the fan isn't required - so when the motor is cool. Once the engine is up to temperature and the fan is required, for an electric fan to move as much air as the stock mechanical fan, it would use more HP, as there's another inefficiency in the system - the alternator.

that is, if the fan needs 2kw to drive it, it will basically take 2kw via the crank, but a 2KW electric fan would take 3 or more Kw from crank via the alternator. ( hope that makes sense)

However, a stock sierra runs a mechanical fan that runs all the time, even when the motor is stone cold. that's dumb. as you've found out, they also run against high load, like when they are underwater - and pull themselves into the radiator.

A sierra radiator can't take a very large thermo (14" is the biggest from memory), and most of the "off the shelf" aftermarket thermos throw nowhere near the air of the stock fan, and as you've found, the stock radiator/fan combination isn't quite big enough anyway, so you'd really need to know the new thermo was flowing plenty more air than the stock fan.

you're also going to need to switch it. you're on the right track having a "defeat" switch for water etc, but running a 20A load all the time is madness.

If I were you, I'd be trying a vitara viscous hub fan first. It offers nearly all the benefits of the thermo fan, but is also quite a bit larger so it will throw more air when required.

If you really want to try a thermo, look for a SPAL thermo. Apparently, there's no distributor in Aus, but they are available on line. from the research others have done, (mightymouse, for one) these seem to be the best available aftermarket fan. Trying a wrecker sourced fan, or a cheap/unknown aftermarket fan is going to be a trial and error exercise, I'm afraid.

I switch my thermos with a Jaycar temperature controlled switch kit, with the thermocouple JB welded to the thermostat housing.

I went through the stuff you are dealing with now. I tried a magna thermo, but also reckoned my radiator was a touch small. My solution, because I have a ute, was to rear mount the radiator, (camry) with twin primary camry fans, bosch electric water pumps, and the jaycar switch kit.

I now have zero cooling issues, no radiator to fill with mud, and a much cleaner engine bay. I was forced into this by a few unique problems (crook water pump, etc) but I'm very happy with the outcome.

I'd be trying the vitara viscous fan for sure.

Steve.

Hmmm I'll probably stay with the mechanical fan for now then unless I get bored and wanna have a play around with the thermos (just pulled one off my cruisers aircon too) Could be cheap insurance against a busted radiator from the water holes tho.
Just a senario question here that i've been wondering about.
If driving at night time which has about 9*C temps here would I be able to drive with out a fan on at all just relying on the air that's being forced through the radiator? As most my driving is at night and on the open highway could i just turn the thermo off in that situation or would I just cook the motor one day when I don't realise its off? Just trying to find ways to sit on 110 and be able to overtake

Kitika wrote: If driving at night time which has about 9*C temps here would I be able to drive with out a fan on at all just relying on the air that's being forced through the radiator? As most my driving is at night and on the open highway

I'd be very surprised if you needed the fan under those circumstances.

could i just turn the thermo off in that situation or would I just cook the motor one day when I don't realise its off? Just trying to find ways to sit on 110 and be able to overtake

you will certainly boggedybazillion% forget to turn the fan on and cook your motor. Never, ever, have a switch that controls something critical on your car. My water pumps were on a acc switch for a while, mostly because I was in a hurry when I first set them up and had a spare acc switched circuit. despite knowing how important it was to keep them switched on, I still cooked the motor more than once.

The jaycar temp switch kit is about $30. Temperature switching a thermo is the only way to get any benefit IMHO.

If you have an "off" switch, IMHO, I'd have an audible buzzer when you have the fan off so you never leave it off by accident or for more than a water crossing. A light won't be enough.

For thirty dollars and undoing a few bolts I think i'll give it a go. Seeing as its mostly cold down here and the amount of highway k's I do it'll probably be worthwhile in gaining a KW or so. Cheers for your insight

I've converted two 4WD's from viscous hub fans to electric thermofans (with temperature controlled switching.)

On my old Feroza the power increase felt roughly the same as when I fitted extractors- it was very noticeable.

On my current vehicle (a 2.7l V6 XL-7) there is also a noticeable improvement in power. It responds faster when overtaking and feels quicker off the line.

An added bonus is the huge reduction in engine fan noise.

Take your current fan off and just go for a short test drive- see what you think.

Few comments:

My father had a 12" fan on his Sierra, it was not adequate for cooling in the scrub. We both run 14" thermo's now, and they are heaps of cooling.

Mine is on a temperature switch (Nissan Pulsar), my fathers has a temp switch with a cutoff switch on the dash. Yes he has forgotten about the dash switch numerous times, and has overheated it at least 3 times in the last 4 or 5 years purely because he forgot about the dash switch. Mine has overheated twice, both times because my wiring was way too dodgey. I have redone my wiring since then, and it has been no problem.

Do they save horsepower? I'm sure they do.
but is it very much? Beats the carp out of me...
But if it saves my radiator from getting chewed out in water its worth it.
For what its worth, I have a Suzuki clutch fan in the shed, and it may get used on a future project of mine instead of a thermo.

Thermo fans IF sized and fitted correctly do save power, and can provide far more accurate engine temperature control.

Engine thermal management is far more important tha some think and a lot of OE work is happening on this at the monent. I've heard of figures as high as 11% fuel consumption improvement for town cycles with advanced thermal manangement ( far far more than a therm fan - uses electric water pumps, electric thermostat complex bypass strategies etc. )

However a botch job without shroud, no gasket, too small, shonky wiring etc etc etc is far worse than a mechanical fan.

If the fan has to run for longish periods to keep the temperature down then its too small and a mechanical unit would be more efficient overall.

Also be a little carefull with the airflow ratings of commonly available aftermarket thermo's. When you look at the performance curves working with a restriction ( the radiator core ) the cheap ones fall off much more quickly that the quality ones. So what is quoted in free air isn't what your going to get when fitted.

An example of this is SPAL vs Davis Craig - the DC doesn't come off too well by comparrison.

In my experiece SPAL are the best aftermarket fans around if you don't mind spending a little more and chasing a supplier.

A good thermo WILL save about 2hp, standard fans don't work over about 40kph anyway.
When I ran a thermo on my suzuki I only ever used it off road, normal driving ( unless you live in the city) never required the thermo to be on.

Bad JuJu



Joined: 29 Feb 2004

Location: Brisvagas

PostPosted: Mon Apr 03, 2006 6:47 pm Reply with quote Back to top
I have a thermatic switch from a subaru.. I don't know which model.
It says 96C on it and it screws into the radiator where the drain rooster normally is.
I bought it from Ebay for $9.50.
I also have a 3 position switch in the cab so I can set the thermofan to
ON-thermatic switch-OFF demending on my needs

Does anyone know what model the subaru is that comes with this switch? Sounds like an easy install compared to having to weld a fitting into the system.

thermo switches are under $30 from repco and the on temp is adjustable.

If you decide to revert to a mechanical fan , an early Corolla steel fan is the same bolt pattern as the Zuki one---no more lunched radiators!!

Kitika wrote:

Bad JuJu



Joined: 29 Feb 2004

Location: Brisvagas

PostPosted: Mon Apr 03, 2006 6:47 pm Reply with quote Back to top
I have a thermatic switch from a subaru.. I don't know which model.
It says 96C on it and it screws into the radiator where the drain rooster normally is.
I bought it from Ebay for $9.50.
I also have a 3 position switch in the cab so I can set the thermofan to
ON-thermatic switch-OFF demending on my needs

Does anyone know what model the subaru is that comes with this switch? Sounds like an easy install compared to having to weld a fitting into the system.

Have a browse of the Thermo Fan info sticky in the Electrical section

Alrighty I've got it all fitted and took me roughly an hour I used a Tridon TFS 111 which turns on at 95*C and off at 90*C which cost me $40 and it bolts into the thermo stat housing where some heat operated vacuum switch used to be.(not helpful for people running stock carbies) The switch is usually out of a Daihatsu charade 1L if anyone wants to go look for one at the wreckers. I think the 12inch thermo won't be enough to keep the zook cool during summer but I'll see when it comes around, I've still got the backup blowthru thermo if it does gets too hot but i'll keep my eye out for a 14 or 16 inch replacement. Donno bout more HP but I know the fan's not on when driving at speed so there is probably some gain.

i run a 12" thermo on my 97 sierra and i travel aprrox 130ks a day to and from work, in winter the fan is not needed at all as my water temp does not go above 85dg however 80% of that travel is done on the freeway at or over 100kph, during summer the fan would cut in for a most of the time whilst city driving however it is not really needed over 40kph unless i am on the beach or in the scrub. As for hp i had a noticeable gain in response when it came to overtaking and acceleration while the fan is off but it is virtually the same when the fan is on. The combination of thermo, extractors and snorkel however made a noticable positive difference to my power and economy.

twitchy wrote:A good thermo WILL save about 2hp, standard fans don't work over about 40kph anyway.
When I ran a thermo on my suzuki I only ever used it off road, normal driving ( unless you live in the city) never required the thermo to be on.

2hp, seems like a worthwhile modification, though I do think that alloy checkerplate door skins might provide a better power to weight ratio.