MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Kenlowe benefits

Hi.

I just bought an heavy duty 13'' electric fan from Kenlowe. Car is a 1973 BGT. Was this a good move?

I plan to remove the metal fan blades that come with the car. I heard the new fan will cat as a blower and should only kick in while in traffic. Is this true?

Car has never overheated since replacing the radiator and overhauling the engine.
Always a little below N and rarely goes above N when stopped.



How much more power gains should I get from teh electrical fan? 5%?

Car is mildly tuned (carb needles, K&N filters, fast road cam, .040 overbored pistons, more compression, lighter flywheel)


Thanks, Valter.
Valter >99 VVC & '73 BGT<

Hi Valter

Good idea the fan, it cools well at idle when you might need it most. Bad news re bhp increase, with my old rolling road I never saw a difference with/without mechanical fan, my new rollers may show a difference but I am sceptical. Removing the mechanical fan reduces noise.

Peter
P Burgess

Can't see any point on a road car. These cars run in desert states without overheating, so if there had been a cooling problem it would be better to fix that than simply try and work round it. It's how the thermostat is set that governs when the fan cuts in. Factory thermostats on V8s and the later 4-cylinder cars were designed to cut in around mid-way between N and H, which is still well within the 'normal' range of course. People fitting after-market fans tend to be paranoid and try to keep the needle on N all the time by having the thermostat set too low, which is pointless - a running electric fan is noisier than a mechanical at idle as well as taking more power out of the engine!
PaulH Solihull

Hi Paul

I don't think the original Bs were developed to drive in today's traffic conditions. As you go down the line of car engine cooling requirements they are tighter and tighter, early Bs would fail. The rubber bumper Bs and the V8s had electric fans as standard showing progression. The electric fans are most effective at idle compared to the mechanical fan. It is idling conditions, in modern traffic when the 'modern' cooling of electric fans becomes a requirement. The other problem is getting hold of staggered tube radiators.

Peter
P Burgess

Thanks for your comments.

When I bought the car in UK the radiator was so blocked that it overheated in any circumstances. Really! I watched the water temperature gauge go as up as 80psi!! That means: in the oil pressure gauge range!!! Both needles almost touching each other :-)



However the car never stopped running. Massive! It was just one trip before I completely restored the car.

Afterwards it has been perfect. The electrical fan idea came to reduce small vibrations, noise and release a few more horses.

Thanks, Valter.
Valter >99 VVC & '73 BGT<

I've never seen my 73 roadster go more than about 1/4 the way from N to H even stuck in traffic for ages in very warm conditions in France. I've seen the V8 almost touching the red in similar conditions - and that is twin electric fans! However since sorting out the fan electrics even with the ambient approaching 40C it only got mid-way from N to H. When the coolant temperature goes up the efficiency of the cooling system goes up correspondingly and it becomes self-limiting. I maintain that if any MGB is steaming or losing coolant then there is a problem that needs sorting, especially in the UK! A pal's 78 MGB (electric fan again) used to regularly vomit on switch off, until I found the 15lb cap was lifting at about 8psi! The V8 did similar for some time, then started constantly pushing coolant out, but that was the water pump sucking in air.
PaulH Solihull

When the coolant temperature goes up the efficiency of the cooling system goes up correspondingly and it becomes self-limiting.

What do you mean by this statement Paul, can you clarify please?

Peter
P Burgess

The hotter the coolant becomes in relation to the air surrounding the radiator i.e. the atmosphere the more heat transfer out of the coolant there will be.
PaulH Solihull

Surely it gets to the point where the radiator is of insufficient size to dissipate this heat without the aid of an electric fan changing the surrounding air faster than a mechanical fan at low rpms where air flow through the rad is at a minimum? IE if the air is pretty static how can the heat be dissipated? It has to be air in motion to cool. So if the air flow is stagnant will the temp of the air not go up at the same rate as the heat in the rad and therefore not reject heat?

I don't understand what self limiting is? Surely once boiling point has been reached at whatever temp dictated by the rad cap pressure the coolant will boil up and blow out of the pressure cap?

Peter
P Burgess

With a mechanical fan the air is never stagnant, even at idle, and although it is with an electric fan for some of the time as soon as the fan stat cuts in again it isn't stagnant, so stagnant air isn't really an issue.

The thermostat manages the engine temperature across a certain band. As the ambient temperature reduces from, say 65F surface cooling of the block and sump (and the heater) will dissipate more and more heat from the engine, so less goes into the coolant. The thermostat starts to close, which reduces flow through and heat dissipation from the radiator, but the coolant temperature will stay around 'normal'. Eventually the ambient can drop so low that the thermostat is fully closed and the radiator isn't dissipating anything. If the ambient drops below that the temperature gauge starts showing lower than the N. Conversely as the ambient temperature goes up the thermostat opens more and more, so the radiator dissipates more heat, but the temperature gauge still remains around the N. But once the engine is producing more heat than the radiator (and block and sump) can dissipate then the thermostat is fully open, and any further increase in heat output from the engine causes the temperature gauge to rise above N.

However as the coolant temperature goes up, the difference in temperature between it and the air passing through the radiator also goes up, and it is this that causes the radiator to dissipate more heat. A radiator that has a 20 degree difference between coolant and air is going to dissipiate a lot more heat than one that has only 10 degrees difference, and it is this that makes it self limiting. It's not like a kettle, where the objective is retain as much heat as possible inside the kettle in order to reach boiling point as soon as possible. With a kettle with zero heat loss even the heat from a match would be enough to boil a million gallons - eventually. It's more like acceleration, or ultimate top speed, where the faster you go proportionally more power is required to get you even faster, for example the Bugatti Veyron Super Sport needs an extra 200bhp to increase its top speed just 14mph, from 253mph to 267mph! Likewise you you have to put proportionally more and more heat from the engine into the coolant to keep raising its temperature.

Yes, if you put enough heat into the coolant, or reduce the dissipation of the radiator enough, you will eventually raise the coolant temperature above the boiling point of the cap. But I'll go back to what I said earlier which is that these cars run in desert states without boiling. You certainly do not need better cooling than how it came out of the factory, especially for the UK. If you find you are losing coolant, steaming or boiling, then there is a defect that should be corrected. Installing an electric fan to an MGB that didn't have one from the factory is NOT the way to proceed.

I'm reminded of that series Suggs fronted a few years ago, where three people got various ancient equipment working again. When it came to a WW2 tank that wouldn't start one of them had the brilliant idea that it needed electronic ignition! Yes, it did get the engine started, but didn't they ever wonder how they got them started in 1939?
PaulH Solihull

Hi Paul

The thread has been about pros and cons of electric fan conversion, why do you not convert your electric fans to mechanical? I assume the factory thought electric was better as it must have cost more to fit em?

With regard to 1939 technology, that is what I was trying to get at, the day to day use of cars has changed significantly, more and more time spent in jams. No matter how you say it I cannot see the mechanical fan fitted to an MGB is as efficient at cooling as an electric powered fan. We are talking about build up of heat at idle not driving conditions when air flows through the rad in a most wonderful manner.

Peter
P Burgess

I just had to replace the cast iron water pump on my '67 supercharged B. It lasted only 13,000 miles and this was with carefully monitoring the tension on the serpentine belt. New cast iron pumps are extinct. The only supplier now Is Moss, who have set up a factory in China, but these are on backorder. I actually found a spare, that was still in its vacuum sealed bag that was made by County, in my spare parts bin. When I was replacing the water pump I realized that the radiator, which I had recored 35 years ago, was on its last legs. No one even had a listing for the '62 to '67 radiators except for Moss. These, too, were sourced from China. I bit the bullet and ordered one. Three days later It appeared on my doorstep. I was ready to take it to my machinist, to have a drain bung installed, when I looked at the bottom and discovered that it already had one! The core is staggered, just like the original was and the fill pipe and hose fittings are made of heavy brass just like the original as well. It is a perfect copy of the factory radiator. My only complaint was that they seem to believe that very little paint is required. I'm truly impressed with this radiator and the cost, it was even on sale, was under $200. RAY
rjm RAY

Why would I *want* to convert my electric fans to mechanical? I've not been saying one is better than the other, simply that *both* as installed by the factory, when everything else is working correctly, are perfectly adequate in all but the most extreme circumstances, especially in the UK. If you have a cooling problem then almost certainly there is a fault that should be found and fixed, fitting an electric fan instead is not the way to go. This thread started from a UK person asking if it was a good move to replace his mechanical fans with electric, and I said it wasn't.
PaulH Solihull

Hi Paul

Why do you think the factory upped the spec to electric fan this must be more costly but the factory must have thought it a worthwhile expense, manufacturers are loathe to lower their profits ?

Peter
P Burgess

For what it is worth, I don't believe the factory "upped" the spec to electric fans - they moved the rad forward to make room for the V8 engines and deleted the mechanical fan on that engine as there simply wasn't room for one - it made sense then to standardise on electric fans for all RB cars since they shared the same bodyshell - one fan for the 4 pots and 2 fans for the V8.

To retain a mechanical fan on the 4 pots would have necessitated a very long water pump to put the fan anywhere near the radiator,

The factory fitted electric fans are small, unshrouded, often fitted back to front, suffer from poor electrical connections and I doubt they shift anywhere near the volume of air that the plastic 7 blade mechanical fan does - even at idle.

The main issue with electric fans when the car becomes stationary or slow moving after a run is that they don't cut in till the temperature rises above normal and thus are always playing catch up - you also get heat soak which can make the engine run rough until the fan(s) cut in and then rougher still as the carbs are hit by an initial rush of very hot air.

Personally I prefer retaining the mechanical fan which gives a constant airflow especially over the exhaust manifold.

Chris at Octarine Services

Good point about the distance from rad to fan Chris, why did they move the rad? The electric fan will cut in at the temp set so is adjustable on an aftermarket fan. I still don't see the mechanical fan is better at idle than an electric fan. Certainly at higher revs the mechanical fan is superfluous. I would have thought you and Paul would have remarked on the efficiency of the large viscous coupling fans where they are pretty good at idle as they are the size of a small windturbine :)and not engaged when the temp is low enough?

Peter
P Burgess

What I don't understand is why they standardised the shell from the V8 to the 4-cylinder cars just as they were finishing the V8, and the forward-mounted radiator ironically greatly reduced the space available to fit the electric fan(s). They should have used shrouded pullers, like the RV8, which are without doubt more effective than any of the MGB systems.

Other than that Peter you seem to be missing the point, which is that MGBs with mechanical fans don't overheat - if it wasn't broke why did they fix it? If anything the later cars run hotter, they certainly give more concern to many owners with the temp gauge constantly rising to mid-way between N and H, something I have never seen on my 73. More people talk about fitting uprated after-market electric fans to the later cars, than to the earlier ones I would say.
PaulH Solihull

I suppose we will never know why the powers that B decided to make em all that way.

Modern fuels burn a little hotter than good old four star, that is a good reason to improve cooling along with the likelyhood, if a car is used daily and in jams , not just pleasure, or if driven hard will IMO benefit from an aftermarket leccy fan over a mechanical one. Have you noticed how often a fan cuts in after the engine is switched off? Must help with hot restarts?

Peter
P Burgess

Hi Paul

I reckon we ought to agree to differ, I will recommend the leccy conversion and you can recommend the original fan. People can make , as is their right, their own mind up :) reminds me of Tomater and toe-mah-toe :)

Peter
P Burgess

The mechanical fan generally results in a longer warm up time. Reduced warm up time seems to have been important to car manufacturers in the search for reduced emissions.

Also standardising around the forward radiator may have been influenced by planning for the never to be produced O series B. I don't think any O series powered cars had mechanical fans.

I agree that the factory electric fans on a B are not a very good example of an electric fan instulation. Back in 1980 I fitted an electric fan from a Renault 16 in the 1966 B I had at the time. At least it was ducted.
David Witham

*Does* anyone make an aftermarket viscous fan for the MGB? I've seen one on an BMW, but that is mechanical and running all the time, and it has a two-stage electric fan as well. But that is irrelevant to the MGB. Many years ago I bought an Aerofan (anyone remember those?) to replace the standard mechanical fan, the USP of those is that as its rotational speed increases the angle of the blades flattens to reduce drag and noise. Sounded a good idea at the time of revolting Arabs and petrol rationing, but like the Sparkrite electronic ignition it languishes to this day in a garage drawer.

Wouldn't putting *more* heat into the engine bay from an electric fan running with the engine switched off, from where it can't escape when standing still unless in a good draught, make *hot* starts even worse?

An MGB electric fan should *never* cut in after the engine is switched off, they are ignition powered. How people wire aftermarket fans is up to them, Renault at one time had them permanently powered, and they have been know to fail and set light to the car and anything round it. At one time they also had the wipers permanently powered, even the intermittents, so you put the car in the garage after driving through light rain and next morning your battery is flat. Early ZS180s may well have had a permanently powered fan, but from 2003 it also was controlled from the ignition relay, and that raises another thought. Some years ago I saw an RV8 idling and the fan was cutting in and out far more frequently than my V8 does, and the temp gauge was rock steady, unlike the V8 which goes up and down a lot. I mentioned this and was told that the temp gauge was managed by the ECU and only temperature rises (or falls) outside the normal range once the engine had got up to temperature were transmitted to the gauge to prevent owners getting paranoid. I accepted that at the time, but my Celica and ZS exhibit the same behaviour, and according to the schematics on neither of those does is the temp gauge connected to the ECU, so I thought it can't be that, it must be just very tight control by the fan sensor and a far more efficient fan than on either of the electric MGBs. But I have also never seen the effects of heat soak on either the Celica or ZS, so how come? Is it the *gauge* that is designed to ignore these normal fluctuations?
PaulH Solihull

I have driven my '69BGT in air temps greater than 110 every summer here in Phoenix. I installed an electric fan 6 years ago or so and it makes a difference only when I have a lot of stop and go errands where heat soak takes over in the parking lot. With my insulated bonnet the engine bay gets very hot after a few stop and go's and the fan blows out all that hot air before hitting the road again. At speed, my car stays on normal even cruising at 115 degrees. Then again, the cooling system is clean as a whistle and the engine is tuned for the hot weather (I richen up for the winter).
Michael King

The thing that would take the fan out of the equation would be the use of an electrically powered water pump. This would provide adequate coolant flowing through the block and radiator at all times. RAY
rjm RAY

Explain? You still have to get rid of the heat from the radiator, maybe OK while underway in free air but not at a standstill. I've heard of pre-oilers, but not pre-coolers.
PaulH Solihull

Peter,

Believe me, I have looked at fitting the SDI viscous fan to the V8 - it does suffer from overheating when flat out up the sides of mountains!

With a special rad moved even further forward it might just be possible to get one in there but I might need a modified MGC bonnet too!

As for fan efficiency - I looked at some generic fan performances and that suggests that:-

The 10inch electric fan runs around 3500 rpm and will shift around 1200 cubic feet a minute (cfm) - this is being generous as I doubt the electric motor produces the 1/6hp required to deliver this.

The 13 inch mechanical fan runs at 1250 rpm (for a 1000 rpm idle) and will shift 1500 cfm - this takes 1/3hp, easily provided.

As the engine speeds up, so does the mechanical fan - at low speed but high revs (climbing hills) the mechanical fan has a clear advantage - at 3000 engine rpm, the fan will be delivering over 4000 cfm ( and absorbing about 1 hp) - way more than even twin electric fans.

Chris at Octarine Services

How have you worked out the cfm? How many vanes on the mechanical and was the electric fan the same as a Kenlowe as the fan shape has been improving to improve efficiency? Over the years of dynoing I reckon the blast across the engine is greater with a Kenlowe type fan than the mechanical fan. I have to fast idle the engine to get the same effect with the mechanical one

A cowl from the rad to fan whether mechanical or electric is the most efficient. The position of the edge of cowl to the position on the perphery of the blade is crucial too. Some of the early 80s Fords were brill at cooling with their deep cowls.

We havent dealt with possible overcooling with a mechanical fan at higher rpms.

The problem is the mechanical non-viscous fan works too hard most of the time under normal driving, this is fuel and bhp even though they are marginal quantities.

Peter
P Burgess

To add something else into the mix guys, what's your thoughts on the Aerofan? These were a variable pitch metal fan that were a so-called performance accessory in the 70's. I've got one that I've cleaned and repainted, but have yet to get around to fitting to my '73 B. One odd thing I notice about it the fan blades are for some reason set at different angles around the rotational axis. i.e. like a slightly-squashed 'X'

Worth fitting over the three-blade metal fan currently fitted, or should I just keep it as a garage curiosity?

FWIW, it was originally painted in metalic blue, but I repainted it "safety yellow" with the intention of fitting it.

Mike


Mike

I've run the flex fans and they do work very well, but they are quite noisy and difficult to live with. They also tend to be as thick as a razor blade, so you have to be careful when working around them. RAY
rjm RAY

You can't over-cool if a thermostat is fitted, except that in very cold weather the mechanical fan will be cooling the *block* more than an electric would. For the same reason a radiator blind doesn't affect the radiator directly (unless it is deployed when it shouldn't be) but reduces the surface cooling of the block from unheated air passing through the radiator core.

Never saw any useful difference with my Aerofan, which is why as I say it is still in a garage drawer. These aren't flex fans where the blades themselves distort due to air pressure, but are stiff blades on a spiral shaft with a spring. As the rotational speed increases they tend to move outwards against spring pressure, twisting on the spiral shaft to vary the pitch. As such the blades are as thick if not thicker than fixed metal blades. Mine too, is a squashed 'X'.
PaulH Solihull

Kenlowe publish their fans performance - http://www.kenlowe.co.uk/fans/consumers/fans-cpc.html

I took the figures I quoted from published data on exhaust fan performance - generally four bladed fans.
I was comparing the factory fitted fan, not the Kenlowe type, although looking at the Kenlowe stats doesn't suggest they shift that much more until you get up to the 16" size! They do have a relatively big motor body.

There is no doubt that cowling ensures that more of the air shifted actually goes through the rad core and doesn't escape round the edges of the fan. This is where the modern Kenlowes score - they are fitted to the rad core and are cowled - but don't involve the whole rad, unlike the Ford cowls which were just brilliant!





Chris at Octarine Services

Valter.
I had a kenlowe fan fitted when I bought the car, I was pleased with it in as much as I did not have any issues with over heating etc. My previous B would over heat in heavy traffic in the summer (Newbury pre bypass) as it had a smaller than standard radiator and a kenlowe solved that issue very well.

When I sent my current car in for a service with an MGB Specialist in the North of England they removed the kenlowe and replaced it with a standard fan after deciding it was over-cooling the oil cooler (located in front of the radiator). Something I didn't agree with.
I decided to reserve judgment until I had road tested the car and to be honest I cannot tell the difference between the two. So the kenlowe is still in a box.

The car has still never overheated and the standard fan is about as simple as it gets, which in my experience means reliable!


Regards.

Al
A McBride

This thread was discussed between 26/07/2010 and 07/08/2010

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.