Conversion to 12V thermo fan?

[murcod]

Pics,

So much space with the shroud and viscous fan removed!



A frame was made that mounted onto factory bolt holes (eg. power steering reservoir mount, lower radiator support bolts...) Studs were welded onto it to bolt the fan assy onto







And, the finished product





A big thankyou to my father inlaw who did all the welding/ cutting/ and a lot of the design for mounting them. I'm sure he could have done other more enjoyable things with around 9hrs of his time!

He also machined up on his lathe a piece to bolt onto the water pump to provide strength where the viscous hub used to bolt on

[murcod]

Oh yeah, I didn't get a chance to buy new belts while it was all bare, but I'm pleased to say access is still 1000% better than having the old shroud/ fan in place.

I've also got detailed fuel consumption figures for the last 14mths/ 11000km, so can post up the changes after I've driven it for a while.

[murcod]

The conversion had a "baptism of fire" today with the temperature reaching 43.6 degrees C just as I was driving home. That's the official temp recorded by the weather station about 2km from where I work- it's the highest temp recorded in 5yrs.

Comparing the monitored ECU temp sensor voltage the engine was running significantly cooler than the 41 degree day I mentioned a week or so back with the viscous fan . Even on the long hill I go up (with the A/C on) the voltage only dropped (lower = hotter coolant) to the same voltage as it did with the viscous fan on the 41 degree day. At the traffic lights the electric fans are a clear winner, my only concern is the alternator/ battery keeping up (voltage drops to 12.4V)

I've also got a gap either side of the fans that needs sealing (approx 20mm either side) which will improve their performance even further. So, I'm happy to say that the electric conversion seems very successful from a coolant temp point of view.

Some other points:
- the engine has noticeably more power off the lights on extremely hot days
- the engine runs whisper quiet, it's amazing how quiet it is now (especially when first started.) Even my father inlaw commented how he could hardly hear it now.
- on the way to work this morning (23 degrees C) the fans only came on once briefly for around 10 seconds on low speed. Basically it appears if you're moving then the fans aren't needed for these conditions.
- I'm hopeful of decent economy gains, but will have to wait and see.

[murcod]

I just drove home in 46 degree C heat (115 degrees F) !!!

Needless to say the fans were operating for a lot of the trip home, but the temps were good with the A/C on all the way home.

[XL7Limited]

looks like a success David!! way to go

[murcod]

I've done some wiring revisions which will hopefully help cure (or minimise) the false triggering issues I was getting with the electronic side of the circuit.

Basically, I've gone from using a body bolt inside the cabin for an earth to wiring them directly to the battery negative terminal. The previous earth point is now used to exclusively earth out the heavy duty relays that turn the fans one. Previously the same earth was used for both the circuit and relays- and I was finding I was getting around 100mV depending on the electrical load.

It mightn't sound like much voltage (and it isn't), but that's the difference between the engine sensor running at normal temp and starting to get too hot. (The earth "floating high" was changing the switching point for the control circuits.)

I'll drive it like that this week and see how it goes. I'm not expecting huge fuel economy gains at the moment due to the fans running more often than they need to, and we're experiencing 40 degree C plus days constantly at the moment . That's not the "norm" and not a fair comparison to my previous logged consumption.

[murcod]

This article is worth a read: A comparison of viscous drives and on/off fan drives for diesel engine cooling | Diesel Progress North American Edition | Find Articles at BNET

Although a few years old and about diesel trucks it shows clear gains in economy from a change to an electric fan vs a viscous hub. In a higher revving petrol engine the change should be even more noticeable (diesels economy doesn't change as much as a petrol when under load .)

A quote from the article on how viscous fans operate:

Viscous Fan Drives

Viscous fan drives are used to reduce the fan load when cooling is not required, and thereby lessen power requirements and related fuel demands. A viscous fan drive offers an improvement in efficiency over direct drive fan cooling. This hub-mounted, fluid-coupled device contains a hydraulic turbine using a viscous silicone fluid to transfer energy from driving element to driven element.

Typically, a bi-metallic element on the front of the viscous drive senses the temperature of air passing through the radiator and operates a valve to control the silicone transfer fluid, thus effecting fan engagement and disengagement. The fan drive is not controlled directly by engine temperature but indirectly by sensing the temperature of cooling air passing through the radiator.

The hydraulic nature of a viscous drive prevents it from achieving fully on or fully off operation. Consequently, in the disengaged mode, the fan continues to operate at speeds as high as 45 percent of the fully engaged rate, usually between 650 to 1000 rpm.

In the engaged mode the slippage (fluid shear) common to the viscous drive's liquid coupling restricts fan speed and associated cooling capacity by approximately 5 to 10 percent. Figure 1 shows the typical operating range of a viscous drive compared to the wider range of engine speeds, taking into account both parasitic drag (partial engagement) and fluid shear (slippage).

The partial engagement or parasitic drag of a viscous drive can contribute to engine overcooling, resulting in unnecessary fuel consumption. For example, with a truck engine speed of 1400 rpm, an average vehicle speed of 50 mph and yearly travel distance of 30,000 miles, a viscous drive consuming 0.5 hp (0.4 kW) in the off mode burns approximately 48 gal. of fuel per year.

The physical properties of the hydraulic fluid in a viscous fan drive may also change over time, and lead to decreased performance and further degradation in cooling performance.

Driving today the electrical stability has improved from re routing the earths. I also sealed up the 15mm gaps either side of the fan shroud on the weekend- high speed was pulling the temps down very quickly today and it was 39degrees.

[murcod]

I've done just over 1000km since the install. Comparing the 1000km travelled just before the conversion the economy is a whopping 0.2l/100km better. Massive I tell you!

It's worthwhile for the power increase and engine quietness. Interestingly the economy for the first 1000km when we bought it was 0.6l/100km better than what I'm getting now- might be time for some new spark plugs?

[*Kiwi]

My first tank running free-wheeling hubs has yielded an impressive 0.22 L/100km better than my average up to the change

Of course that was city driving only, still looking forward to testing with a proper road trip at highway speeds.

The little things add up though...

[murcod]

Too true. A lot of those 1000km have been in 40degree heat with the A/C on. I was also experimenting with the turn on voltage and had the fans running more than necessary.

I'm at the stage now where I just need to make some more permanent circuit mods to the Voltage Switches (to allow finer voltage setting to be done) and then I'll permanently mount them under the dash. The acceleration off the light now is impressive and in gear it has more urge.