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MG Midget and Sprite Technical - Electric Fan query

In the hope of releasing a couple of squandered horse powers, I've been given an MX5 electric fan for my MkIV Sprite. Unfortunately the steering rack prevents it from fitting behind the radiator. It looks as though it might go in front of the radiator but I'm not keen on having it visible through the grille.

I've trawled the archive but can't see any references to MX5 fans. Has anyone managed to fit one of these to a 1275 or is my only option to ditch the MX5 fan and splash out on a Kenlowe or Revotec?

Cheers

Colin
Colin Mee

Colin,
many fans are only made to push or pull (blowing or suction) to fit in front of the radiator or behind it (in the engine bay) and to fit them opposite to their design will be a lot less effective or hardy work

is the MX-5 fan a push (blowing) fan so that it can be fitted in front of the rad?

there was a recent thread where someone had the excellent idea of using a midget 1500 rad cowling (fitted 15mm IIRC) and having a slimline 11" suction (pulling) fan fitted in place of the engine driven fan
Nigel Atkins

ETA:
>>using a Midget 1500 rad cowling (fitted 15mm - higher - IIRC)<<
Nigel Atkins

Thanks Nigel

I'm pretty sure it's a puller - which is another reason why I don't really want to put it in front of the radiator.

C
Colin Mee

I have a 'puller' fan in my 1500 but mounted in front of the radiator facing the correct direction so it's now a pusher. I tried it out spinning the wrong way and it was pretty weak so its now spinning correctly. It doesn't matter that the guard is now on the wrong side because there will be the radiator grill in front of it. So if there's not enough room behind, put it in front. I also have an oil cooler that sits in front of both so the fan will do it's job one way or another.
Nick Nakorn

A Honda prelude puller fan, the one pictured on the left with the 9 written on it, is a perfect fit size wise for the back of a midget rad, and the cowling increases it's efficiency dramatically! Just a thought if the MX5 one doesn't work out!!

David


D Prince

You shouln't see it in front of the rad as the grille obscures any view and it's sat quite far back in any case.
Jeremy Tickle

Nick's idea sounds good to me, the standard Spridget rad grille would be a good guard for the fan anyway and as put the grille and location will hide fan

you need to check if the MX-5 fan is a wire-only-one- way-motor so as not to burn it out

you'll also want to allow for the fan's electric draw on battery and/or dynamo/alternator

my electric cooling fan is controlled by a thermoswitch (without override as with all cars for the last 30+ years - and wired straight off the battery, via an in-line fuse, so that it runs on after ignition is off)
Nigel Atkins

Surely it doesn't matter which side of the rad the fan is fitted provided it's direction of rotation is not changed and the fan orientation isn't reversed. If it is designed to flow "front to back" then as long as that remains so, the air goes thro the rad after the fan rather than before.
Reversing both the fan rotation and the way it faces would seem to have the same effect but the blade profiles would be wrong.
How you physically mount it could be an issue however as the motor could impede things. And as pointed out, cowling (or lack of it) is significant.
Graeme W

to test the fan's direction and location efficiency you could do smoke tests
Nigel Atkins

hi colin look up Variable Thermostat Tempature Control Kit Radiator Cooling Fans on ebay priced at £9 and 9ins fans for £18.50 and all new at that price why fit old fans Ian. ps redline are good.
ip blain

If you're talking about the fan pictured don't waste your money, I have one, fitted it for 48hrs and removed it as it was useless for my needs! Fitted the afore mentioned Prelude fan and never looked back!! New is not always best ;) BTW if anyone wants this cheap fan I'll send it to them for the cost of postage with a fitting kit.

David


D Prince

ETA: looks like a possible answer was given before I could post my question!

I've no idea for all I know they might be wonderful but how good and long lasting are these kits(?), Colin does hill climbs so probably wants reliability (unless he trailers the car there and back)

of course there's also the issue of how much life the MX-5 has left in it but others get fans from scrap yards that last many years - I'd never risk it with my cat luck though
Nigel Atkins

On my Frog the po had fitted a fan and when I ran it the engine temperature increased!
Running the wrong way so it fought against the mechanical fan. On the other hand, I guess good for quick warm up in winter.
Graeme W

Nigel's rumbled me - yes, it's because I go hillclimbing and I want to go a bit quicker! My PB through the speed trap at Loton Park is 58mph and I'd love to break 60. Maybe, just maybe, if I can get rid of the fixed fan and have the electric one to cool things down at the top of the hill I'll have enough power to achieve 60!

Thanks for all the advice. The MX5 fan has a plastic shroud with it but that is designed to fit behind the radiator. If I manage to fit it I'll certainly be making sure it spins the right way.

As Nigel has described, I'm intending to wire it (fused) straight off the battery and with a manual override switch.

David, thanks for the Honda Prelude suggestion - I'll look into it if the MX5 route doesn't work.

My overall strategy is to get the chassis sorted before I start looking to doing anything to uprate the engine but, in the meantime, I will try to reclaim some of the horsepower that gets swallowed by ancilliaries. I started by replacing the blowing two box exhaust with a Maniflow single box system that definitely helps the car breathe better. The budget for the winter is allocated to things like polybushes and negative camber trunnions and I can't really justify the expense of a new Kenlowe or Revotec fan.

Thanks

Colin
Colin Mee

Gday Colin
My fan (12 inch from a Toyota)is in front and has an extra intake as shown. You can just see the fan nestled in front of the rad, oil cooler below and in front. Works well. On a 1500 in OZ you need an over-ride switch.
cheers
Rod


R W Bowers

Colin,
the thermoswitch is very easily adjustable, you could set it not to power the fan until the end of your run

if the fan cuts in during the run it might reduce the power available slightly - I have an oversized, heavy, alternator and can easily tell when it's providing for the cooling fan (motor driven fan is removed)

personally I've never seen the point of an override or manual switch as it's like having a dog and barking yourself - you can adjust the thermoswitch before every run if you want and a thermoswitch won't forget to turn on or turn on too soon or too late if set correctly

if you must have a manual switch then you'll need it with a warning light to remind you when it's on and off (you could forget unlike the thermoswitch)

just a last thought are you allowed to install an electric cooling fan in your class of hill-climbing
Nigel Atkins

It seems to me that if you wanted to minimize the drag on the engine, you would use the electric fan, and put the over ride switch on the generator/alternator.

Then, if the cooling system needed the fan during the climb, the fan would run off of the battery and not add load to the gen/alt. I'm no electric wiz, but I think the gen/alt would need to be cut out before turning the key on to avoid the exciter power to the gen/alt coils.

Charley
C R Huff

Running an alternator without load is a sure-fire way of seeing off the regulator inside.

Also, the much derided cheap fans off eBay need mounting directly pressed against the core to be effective. Any gap and the bigger the gap and the less effective the fan will be.

Modern fans pull air from the engine bay and push it forward. This may seem counter-intuitive but it lowers the engine bay temp when driving slowly. In traffic, instead of blowing hot air from the radiator into a hot engine bay, it draws hot air out of the engine bay so allowing colder air in to lower the temperature.

Rob
Rob aka MG Moneypit

That's interesting Rob.

I don't have any cooling problems on the move. Even after a quick dual carriageway run the temp gauge only goes up to N.

The hillclimbs I do are only short sprints and even I manage them in less than a minute and a half, so running the fan on the move isn't really an issue.

In addition to the presumed extra power available, an electric fan would come into its own in two ways. One, I wouldn't have to run the engine for so long in the paddock to get up to temperature before a timed run,
Two, I could run it if there is a hold-up in the queue for the start - in which case a fan that pushes forward and draws hot air out of the engine bay might be preferable.

A bit more research required I think!

Thanks for all the suggestions and advice so far.

Colin
Colin Mee

Colin,
do you mean >>Even after a quick dual carriageway run the temp gauge only goes up to N<< when stationery or as you go along - if when stationery fine, if when still going along then you might (only might) have a cooling or running weak issue at higher speeds/revs unless you mean running at sustained very high speeds for a long time
Nigel Atkins

As Nigel mentioned, the 1500 radiator support bolts right in an earlier Midget and gives you enough room to put use a slim puller fan and remove the stock fan. You will need to use different hoses as the originals will be an inch or two short. I did this with a Spal fan (the Kenlowes and Revotecs aren't as available over here). The more I looked at it, I don't see why (except for the cost) you can't have a custom radiator made with mounting flanges that bolt right to the supports and do away with the original surround altogether. Would give you another couple of inches to work with for a larger (deeper) radiator or fan.
Jack Orkin

Colin,

I have a '67 1275, and run an 11" Spal low profile puller (no. 30100411 @ 970 cfm), which slips neatly between my Speedwell aluminum radiator and the rack. I think (though am not positive) that my radiator is thicker than the stock unit (which I've sold, or I'd measure for you). The Spal cools the core down quickly when it comes on and has worked flawlessly for years.

Tom, owner of Speedwell and longtime spridget racer, prefers pullers to pushers, which he feels block natural airflow through the core. His partner and track mechanic might beg to differ, but he's gotta pay the rent.
JM Young

Rob,

Isn't what you are saying about wrecking the alternator only true if it is disconnected after it has already started charging? I have always thought that if the alternator is turned off before the ignition is turned on, that no damage would occur. That is, no current will be produced if the initial current is not offered to the alternator. However, I haven't actually tried it.

Charley
C R Huff

Charley, only going by experience, although it may have already been on it's way out. When I went to Le Mans this year my Alt kept going onto full charge intermittantly. I got fed up with this so stopped, disconnected it (after switching off the ignition), and continued the 200 or so miles on battery. Next day I re-connected it and it was dead.

I'm sure I have read somewhere that because it uses magnets as soon as it rotates it generates volts and without a load voltage spikes zap the regulator.

Rob
Rob aka MG Moneypit

Modern fans blowing forward is a new one on me. Surely the fan needs cool air from outside to cool the radiator. Hot air from the engine bay would take longer to cool the rad. After all, it's the coolant that needs to be reduced in temp. eg. cool coolant= cooler engine bay.
Unless the fan was wired the wrong way round ;)
I honestly have never experienced a forward blowing fan, but I have been retired for three years :)

Bernie.
bernie higginson

I wasn't aware that there were magnets in a Lucas alternator.
Dave O'Neill 2

A dynamo has a stator coil and a rotor coil. Current applied to the stator generates an electric field, the rotating coil intercepts the magnetic lines of force which generates electricity which is fed outside using a commutator. The commutator makes the current output (almost) DC. The regulator controls power fed to the field coil providing more current (and hence stronger magnetic field) when lots of current is needed by the Battery and Car.

An Alternator can have two configurations. One uses permanent magnets in place of a field coil plus a rotating coil to generate electricity. The other uses fixed field coils and a rotator made from a multi-pole magnet. Whichever configuration is used the output is AC (usually 3 phase) which must be rectified to turn it into DC. A stack of diodes does this. The power is regulated by monitoring the battery voltage. Low battery voltage lets lots of current through, higher voltage lets less current through. The regulator is a solid state circuit having an input, an output and a sense connection.

So in essence, a Dynamo has coils, an Alternator has magnets and coils. So an Alternator with disconnected output still generates electricity, whereas a Dynamo doesn't (although there is a small residual magnetic field in the metal around the field coils which will allow a dynamo to generate a small amount of electricity).

Rob





Rob aka MG Moneypit

Maybe Rob. If you are right, the alt on my BGT must be toast now, but I think it already was. One day the charge light did not go off when I turned the key off, so I unplugged the alt and just ran on the battery. I ran it like that for 6 months or so.

I guess if you wanted to get fancy, you could graft an AC clutch to the alt and stop it from turning that way.

Charley
C R Huff

This is the fan set up on my 1500..


Nick Nakorn

An alternator can have permanent magnets -- it's called a magneto.

The alternators used on Spridgets DON'T have permanent magnets. They have electromagnets.

And if you're alternator has a functioning surge diode, then running without a battery won't kill it. But the key there is "functioning". If the surge diode is kaput, it can't ptotect the alternator. So unless you really have to, don't run the alternator with the battery connected.
Lawrence Slater

Yes, I see now. A case of engage brain before operating fingers? I expect modern designs for Alternators have all sorts of protection circuits to make them more reliable especially considering the power they need to provide in a modern car.

Rob
Rob aka MG Moneypit

Colin, I'm quite near you (Gnosall) and I also compete in Hill climbs including Loton Park.
I campaign a Tiger S6 with a pretty standard Pinto engine and this was suffering overheating in the same conditions
(start line-ups and end of run. In the latter its not so critical because there is usually time to switch off and cool down. As well as fitting a more forward positioned alloy rad. I also fitted a rear-of-rad electric fan, directly wired and thermo switched. On all but the warmest days, this has virtually cured the problem. (Naturally, ignition and mixture settings can also have a dramatic effect on temps.) The fan I fitted is 12 or 13 in. dia. and cost around £25. It's worked very reliably for 2 seasons so far so perhaps best not to worry if it doesn't have a Kenlowe or Revotec label?
I'm looking to change to a Spridget too reasonably soon if I can find a 1098 or 1275 at a reasonable price.

P de-Ville

good morning
while we are on the subject of electric fans....
!500 midget, would anyone recommend the fan marketed by accuspark. I use their electronics and all is fine
but is their fan any good. There is also one by Davies Craig....extra thin. Any feedback would be welcome
rgds tony
a boyle

Tony,

As I said above, the Spall 11" low profile has worked best for me. I've also got the 10" Hayden that Moss sells sitting in a box in the garage, and which I'll let you have for the shipping charge to the UK plus a cheeseburger ($5.00 around here). I ran it for a few months but it's virtually new. Cooled fine in New Mexico 90-100 degree weather, but I wanted a fan that covered essentially all of the core, which the Spall does. If you're interested, send me an email and it's yours.

Joel
JM Young

This thread was discussed between 02/09/2014 and 14/09/2014

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