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Tim D.

Fans fans fans

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Hi chaps,

been playing with cooling fans..

thought I would share my experiences.

 

Have a very recently rebuilt engine and decided (perhaps stupidly) to remove the engine driven fan..

Before rebuild I had used both engine fan only and combined with a 12 inch pusher fan (Spal). Both configurations work worked really well..

 

Then ran the new engine with just the pusher. Pretty good.. keeps the engine cool at about 95oC and turns on and off on the thermostat.

 

Then decided that I'd like a puller as they are supposed to be more efficient and would give some room for the cooler (the pusher is jamed between the rad and the oil cooler).

So had an unnamed brand 14 inch puller (aledgedly 80W motor)..

Fitted this and temp slowly climbs..

Slightly concerningly it claims that the fan is reversible.. form my basic knowledge this is not the case for the more efficient fans with proper aerofoils..

 

So have now ordered a puller 12 inch Spal (14 inch not in stock, 12 inch has a similar flow rate).

 

Just interesting to see the influence of fan quality.

 

Cheers

Tim

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Hi Tim,

My English is scholar and to avoid misunderstanding I have a question Puller vs Pusher (like on a door Push / Pull).

The one fan you tag as Pusher is a Sucker (It suck the air from the radiator), the one you call Puller is a Pusher (It push the air into the Radiator).

Am I correct ?

 

Regards

Edited by Marc R

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Yes

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Why complicate life? Electric fans, thermostats, relays and stuff all extra to go wrong.

I am not an anorak, but why all that modern stuff when its not needed.

I live in a hot climate and only have original fan live in town center so drive in traffic some days.

Just make sure your cooling system is good.

I have an oil radiator too that is by far and away the best, add on and it was an option from new, Once ran the car through town center not realising that water had leaked out of lower radiator hose during a long rest. (should have checked the radiator level before duhhh).

Well didnt blow the car up just because the oil cooler did a lot of the work the radiator would have done.

Tony

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Tony and I differ in our opinions but we both live in hot places...testament to the fact that a well sorted cooling system works whether you have the engine driven fan or a electric one.

 

Personally, Ive fitted a 14" puller, removed the engine fan and the car runs as cool as a cucumber and whilst this rebuilt engine hasnt run in the 30+ days yet as its winter here at the moment, before the rebuild (same engine) it ran just fine in stinking 35+ days without missing a beat.

 

Biggest contributor to good cooling Ive found is two things...cleaning the accumulated crud from the rear cylinders (yours is rebuilt Tim, so this shouldnt be an issue) and the fitment of the shrouding to make sure all the frontage of the grille is feeding cool air into and thru the radiator.

 

There are posts previously made on here, but make sure if you do go the electric path that your water thermostat opens before the otter switch turn off temp. That way you wont get the thermostat and the radiator/thermo fans fighting one another.

As a rough calc I was told to use 1000CFM air movement per 100HP for cooling. I have 3000 CFM in the Interceptor as it seems to do two things really well....turns fuel into noise and generates a shed load of heat. Its got ~ 350 bhp last checked.

Approx 10A per 1000CFM by the way...make sure your electrical supply is up to it!

 

Hope it helps

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Hi Tony and Andrew,

Thanks for the input. Agree that the engine driven fan is enough and I may yet go back there. Andrew your figures for the airflow match what I had from the pusher spal. The new pulley will be the same if not higher. Fan switch opens around 92 which seems to work ok. Wiring is via a relay so should be ok.

One unexpected benefit of loosing the engine fan is that I can now hear the supercharger wind up.

Cheers

Tim

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To be fair you have a supercharger so that probably makes a difference.

I have a road going F3 car and it has 4 small radiators with fans and an oil cooler but its a mid engine turbo and I get cavitation all the time so there is bound to be a lot more eat sitting around.

I think best is to get everything as free flowing as possible to start and definately an oil cooler to stop some oil breakdown.

Good luck

T

Hi Tony and Andrew,
Thanks for the input. Agree that the engine driven fan is enough and I may yet go back there. Andrew your figures for the airflow match what I had from the pusher spal. The new pulley will be the same if not higher. Fan switch opens around 92 which seems to work ok. Wiring is via a relay so should be ok.
One unexpected benefit of loosing the engine fan is that I can now hear the supercharger wind up.
Cheers
Tim

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A crank driven fan robs power when it is not needed.

That is the reason to make things more complicated.

Keep in mind that also at part throttle and high revs the

mentioned 5HP will be robbed from the fan.

If the car is at 50 Mph it might need 25HP what with high revs is to be honest a crazy

driving condition but it is possible and than 20% of engine power is used for the fan!

 

Designed to keep the engine temp in limits when the car is not moving

the fan produces much to much airstream on the highway.

The solution is either the electric fan to be only employed when needed

or a viscous coupling of the crank fan to limit the power taking.

 

I have both in use, a smaller viscous fan to vent the engine compartment

and two little 9" electric fans to add air in hot days, switched by the Megasquirt.

They only start under really heavy conditions.

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That was my intermediate step.

It is a STAG fan on a Rover V8 viscous coupling

fitted to the stock TR6 extension peace.

 

post-13092-0-89145700-1529053473_thumb.jpg

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This fan thing is a bit of a saga and we have been over it many times.

The best thing is a greatly efficient system.

I am not in favour of one or the other just personally dont want to complicate things more but for your info here is a copy and paste from another thread where we went all over this for the umpteenth time.

Aknowledge Waldis post.

Tony

 

Waldi, on 19 May 2018 - 6:03 PM, said:snapback.png

We lack (emperical) data, but we can still make an estimate...

Electric fan:

The electric fan which draws around 10A, has an electric power consumption of 10 A x 13V = 130 W, but the generator has an efficiency too, so the mechanical power consumption from the engine crankshaft (including the generator and fan belt losses) will be say 150W (approx. 0,2 HP). It is only needed at lower speeds (in traffic jam etc), and will run say 50% of the time only then (off course depending on engine condition, ambient air temperature), so the net required power is 0,2 * 50% / 0,1 HP for contiumuous cooling at idle.


The efficiency of an electric fan will be better than the standard fan, since it has a shroud to minimize re-circulation, and it runs at a much lower speed, which improves volumetric efficiency.



Mechanical fan:
The standard mechanical fan (driven from the crackshaft) has a (very) poor efficiency to start with :
It does not have a shroud, which increases recirculation
It is some distance from the radiator so there is even more recirculation, which costs extra power (or reduces efficiency).
Fan (volumetric) efficiency also reduces with fan speed.
Power consumption increases to the 3rd power with speed (engine RPM), this is a law of physics.

Comparison

:


Now if we know the mechanical fan is capable of cooling the engine at continuous idle speed (say 1000 rpm for this analysis), we can safely assume it will also absorb around 0,1 HP at 1000 RPM (a bit more due to its poor efficiency and a bit less since no energy conversion via the V belt and dynamo is required which also costs power) , but we lack data for a better guestimate.
As fan power increases to the 3rd power with fan speed (rpm), the power absorbed by the mechanical fan at....
3000 rpm will be around 2,75 HP (0,1 * (3000 / 1000)3 )
4000 rpm will be around 6,4 HP (0,1 * (4000 / 1000)3 )
5000 rpm will be around 12,5 HP (yes, do the math)

Regards,
Waldi

Addition to the above:
In the adapter kit I bought from Revington to replace my mechanical fan and adapter, there is a clear fitting instruction which mentions a saving of up to 6 hp.
Regards,
Waldi

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Agreed that the Supercharger as some heat into the system. Interestingly the moss kit has a bypass valve which means that the blower is only blowing into the engine when the throttle is cranked open above a certain level. This means that heat isn't being produced so much at cruise.

Whatever I added a thermostat oil cooler after seeing other tr's loose oil pressure on a run around the spa circuit.

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Just recieved the spal 13 inch fan. Pretty impressive but of kit. Trialed it on a 12v supply. Almost took off! Considerably better than the cheap job I got off eBay.

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That was my intermediate step.

It is a STAG fan on a Rover V8 viscous coupling

fitted to the stock TR6 extension peace.

 

attachicon.gifVR-Sensor.jpg

Smart solution.... Ok for the Stag Fan but for the viscous coumpling why did you used a Rover V8 one and not a TV8 viscous coupling ?

 

Regards

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I also want to keep the system simple, but a electric fan could be an interesting experiment.

Perhaps with surprising results?

 

Ciao Marco

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Fitted the Spal fan with some homemade fittings and it works way better than the cheapo 14inch fan.. brings the temp down nicely

 

Cheers

Tim

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Smart solution.... Ok for the Stag Fan but for the viscous coumpling why did you used a Rover V8 one and not a TV8 viscous coupling ?

 

Regards

The STAG fan looked nicer, white and smaller blades and was same price as TR6.

I think the viscous couplings are also very similar.

I was browsing Rimmer and checked the price and took this.

Most of these Rover/TR6/STAG/Spitfire fans fit together, we can see they

are from the same factory and stayed with the main sizes.

Actually I am on VW Passat 3B fan and coupling.

The new viscous from RImmer failed after few miles..... no good qualitiy.

Edited by TriumphV8

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