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I’m planning to fit an electric fan to the Rapide and I would like to fit the fan in the place of the existing. The pulley on the water pump gets in the way of doing this – has anyone done or heard of a pulley modification to reduce the depth?
I would recommend that you speak to Guy – LR129, this has been done on his car if my memory serves me correctly.
The spare switch on the dash has been wired up for the fan. I can’t remember if he has one or two fans now.
Thanks Simon. On my TR4 this is quite a standard modification upping the power by about 10bhp. I don’t really want to add a secondary fan as to my mind this will futher reduce the air flow, also I would quite like a neat solution.
The problem with Kenlowe is the fan is very chunky and thermostat is inserted down the side of the rad pipe, the Revotec fan is much better looking and has an integral inline thermostat.
Another thought, might I also suggest that you take a good look at the AMOC forum, to see what people have done on the DB4/5/6 cars ?
I have 2 fans on my other car, the thermostat for the electric one is in the top hose and there is also a manual override switch. Personally I wouldn’t fit only an electric fan to a Rapide because it will always be on!
Thanks David, that’s helpful – I had wondered if the fan would be on all the time. I have a re-cored radiator so I’m hoping that will help too.
Heat management in the Rapide can be a real issue, especially when stationary in traffic, becasue air flow is minimal and the side wing vents are blocked by servos etc. So the under bonnet area acts as a heat accumulator. During recent trips I have driven the car with the bonnet up on the first catch which enables hot air to exit at the base of the windscreen and this does seem to make a difference. So finding an exit for the hot air is just as important as fitting an addirional fan.
Also I’ve been trying to work out how an electric fan in a TR4 can add 10bhp to the engine output, but can’t make the maths work! Given that an electric fan which draws say 30 amps is less than a half horsepower device.I would really like to avoid overheating issues, now is the time to think about it!
The TR4 has a fan connected directly to the crank pulley, so in a traffic jam it does very little to cool and at high speed (when it’s not needed so much) it cooling too much – simular to the Rapide.
At low speed the loss of bhp due to the mechanical fan is not great, at high speed the loss is greater as the fan is taking more power away for obvious reasons – it is generally thought with the TR4’s 2.2l engine to be 10 bhp worst case.
So if you remove the mechanical fan and fit an electric fan you loose that inefficiency. The electric fan only comes on when needed so the rest of the time you gain the power you would have lost of the mechnical fan.
I’m considering 4 mods to my car for reduced-stress continental touring in due course: 1. full flow oil cooler under the front valence; 2. electric fan in front of radiator; 3. small high volume extractor fans in the wing vents, or as minimum 1 on the exhaust side; 4. modified bonnet (my spare) to give it a “flip tail” vent. Or all the above!
The other modification worth thinking about is to remove the bypass hose from water pump to thermostat housing thus forcing all water to pass through the radiator – any thoughts?
You can`t move the bolting face on the pump drive pulley,the
body of the punp is about 3mm from the inside of that face.
It isn`t advisable to remove the bypass system, this is there to
prevent hoses being blown off. The pump will produce upto 45psi when the engine is reved. Are you shore the temp
gauge is wright, test it by disconectind it and imerseing in a
kettle and boil it. It should register 100c,( granny sucking eggs).
Have the rad reversed flushed. Is there anyway to increase
air flow through the engine compartment.There are many things to consider,are the bleed holes for the liners weeping,
these engines tend to silt up around the liners. Years of rad
weld to seal up leeks tends to build up at the bottom of the
liners. Fit a 72c stat, check ignition and fueling. is there a alloy
cowl bolted to the rad encircleing the fan to duct all the air through the radThanks for advice Ray, very helpful.
David, did you once mentioned something about the seal which runs around the gutter in the engine bay? I was thinking that the original seal could be swapped for a low profile finisher instead, this would create quite a large gap for the warm air to escape out of…?
Hi Christian.
I can`t see the reasom for sealing the bonnet edges, this will increase the heat soak in the motor causing vapour lock in the carbs. Remember these machines where made at a time when the roads where less congested, speeds where higher keeping air flow up. Running these engines on unleaded fuel makes them run hotter. The point about the temp gauge is somthing I found some years ago on a Aston Martin DB3S, the kettle boild and the gauge read 75c, the owner swore blind he neverraced it above 85c, hence flash over heating of the pistons.Thanks Ray, I think the slats under the bonnet are meant to keep the air flowing even with the seal in place but unleaded fuel does add an extra element to be considered.
Andy Chapman would stress that the only proper way in for air is through the radiator aperture, so the slats are for air exit, aided by the low pressure areas in the front wheel arches. Air in through the unsealed bonnet allows turbulence or static under-bonnet air which as Ray says causes heat soak; from practical experience heat soak is reduced if the bonnet is “up” on its first catch where flow is aided by the low pressure region at the base of the front windscreen, which suggests that the bonnet seal might be usefully omitted in this area. That said there is a slight lip on the underside of the bonnet here which might disable the flow when the bonnet is fully closed. It’s for these reasons that I’m sceptical about the effectiveness of the additional bonnet air inlet scoops fitted to the Australian car 110
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