Fitting electric fan to P6 Rover - few simple Qs?

[mikecoombs]

The later (and all air con) P6B cars in Aus were fitted with a multiblade plastic fan and thermo coupling. however it is different to the SD1 unit. Prime differences are the number of blades and the thermo unit sits behind the fan on P6B but in front on SD1. The P6B water pump is very similar and I have used a P6B unit on my SD1 with minor modification. I forget what.
The pulley on these P6Bs is also a smaller diameter so turns a little faster too.

I used an electric fan way back in the 1980s but found while it was fine in traffic and ok for daily driving about town it couldn't cope at all with full throttle over 70 MPH like when overtaking on freeway

 

[PeterZRH]

I used an electric fan way back in the 1980s but found while it was fine in traffic and ok for daily driving about town it couldn't cope at all with full throttle over 70 MPH like when overtaking on freeway

Surely you don't need a fan at all at 70mph? No forced cooling is going to push more air through the radiator.

 

[Chips]

Surely you don't need a fan at all at 70mph? No forced cooling is going to push more air through the radiator.

Surely you don't need a fan at all at 70mph? No forced cooling is going to push more air through the radiator.

Hi Peter ZRH
I am going to fit a electric cooling fan to my car soon and like the way you have done yours . Would you be able to give me a wiring diagram of how you wired it ?
Thanks Paul.

 

[mikecoombs]

The problem I found was that the air couldn't get out of the under bonnet space quick enough. It's actually a quite common problem on racing sedans. If you look carefully you can often see the rear corners of the bonnets on such cars have been raised up to get the air out. It seldom went into the red but it boiled the petrol (first)

I should add that it usually occurred with throttle flat to the board going up long hills, which back then was the only time you got to pass anything over here.

 

[jp928]

80W is not a lot of power for a decent fan - 7A doesnt go far in my experience. The SPAL 2x11" I had pulled 30A, drove 2720 CFM. sucking.

 

[eggbert68b]

I use a Kenlowe 16" fan - high spec. I found it essential on a 3.9 automatic and slow moving heavy traffic conditions.

Typically used by the Land Rover guys who need cooling driving off road with little air flow. My in-line fuse is rated at 30 amp. The fan switch is powered via a relay, with positive feed from the starter solenoid. Also switched via a temp sensor plumbed in to the radiator (via threaded boss )

 

[PeterZRH]

80W is not a lot of power for a decent fan - 7A doesnt go far in my experience. The SPAL 2x11" I had pulled 30A, drove 2720 CFM. sucking.

I have a two- speed solution. The lower speed is effectively 80W - I've NEVER heard the higher speed engage unless I force it to - that's about 150W.

So the answer is you can quite definitely cool a P6 V8 with 80W of fan even in 35+ degree heat. Calculate the area of 2x11" fans minus the voids in the centre where the motors are and you'll find it's considerably less than a single 16".

Remember how cooling works - the rate of cooling is proportion to the excess temperature i.e. the temperature the part of the radiator you are cooling compared to the air. If you've already cooled that part of the radiator down, then forcing more and more air through that part will have a diminishing effect for two reasons, firstly the temperature gradient as stated and secondly the increase in resistance as expressed as pressure - in practice the harder you suck, the more likely is all you are doing is sucking air around the side of the fan and making a lot of noise unless you have a shrouded system with a good seal. - in reality those CFM figures are not remotely close to what you'll get as that is "free airflow". It's way, way more efficient to push modest volumes of air through the maximum area of the matrix.

 

[jp928]

Peter,
This is the Spal unit I used on the 928 - radiator is wider but less height than the P6, so it fits well.

SPAL Thermo Puller Fan - Twin 11" - 12V - 2720 CFM - 2VA06-AP70/LL-37A

The 2VA06-AP70/LL-37A (EF3580) Twin 12v 11" SPAL Puller Fans feature a Straight Blade Design which can pull up to a combined total of 2720cfm / 4610m3/h.

thermofans.com.au

It is well shrouded, and it has blow-open flaps top and bottom to maximise air flow when the fans are off and the speed provides enough air.
I dont think this observation " If you've already cooled that part of the radiator down, then forcing more and more air through that part will have a diminishing effect " is relevant as there will be coolant flowing all the time, so while there will be a temperature gradient across the radiator from coolant entry to exit, there shouldnt be localized cool spots even for short periods, assuming a steady flow of air.
Strictly speaking the most effective cooling (removing the most heat) should be concentrated on the top of the radiator - highest temperature - but this is mechanically difficult with rotating fans. In my comparatively short experience with the car I have found the std export viscous multiblade fan has no trouble keeping the temperature under control, so far up to 35C. Radiator and heater core have both been overhauled recently.

 

[jp928]

Have mentioned this before- read the article here , on testing cooling at idle on Sunbeam Tigers (Alpine with a 289cid Ford V8). Systematic testing of what changes improved cooling well documented and illustrated. In summary, increase air flow (fan changes), force all front air to go through radiator by blocking gaps around radiator, remove any opportunity for air to recirculate from behind to in front of rad when idling - block gap between rear of rad and front cross member - have done this to my car - only downside is removal of 2 screws to access the oil filter.

Cooling the Sunbeam Tiger by Tiger Tom and Chuck King – TigersEast AlpinesEast

www.teae.org

Fitting an export type cowl would be my first effort for a car in Europe, it might be enough to improve cooling. If not, go to the fully shrouded viscous fan set up . When its running there is a considerable volume of air being expelled sideways from the blades; moving a hand inwards from that tangential air there is a dead area (no discernable flow) before feeling the air flow directly behind the fan.
This is my baffle from rad to cross member - alloy visible both sides of filter. Note the shrouding of the fan, and that the blades are partly outside the shrouding, hence producing the radial air flow.