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MG MGB Technical - Kenlowe or OE electric fan

In city traffic, I notice when the fan starts up, it never really gets the temperature down. I fitted a new radiator this year and the thermostat opens up OK. Would a Kenlowe work better?
c cummins

In my 1975 roadser, i have a large fan from a Peugoet installed in front of the radiator. I fabricated the mounting bracked and a shroud from light alloy shet metall and the shroud is in contact with the radiator, only seperated with a rubber profile as used on the hood and it works great. If i compare it to the single stock fan in one of my GT's (1978) fan technology has moved foreward a lot!
You should look for the largest fan that you can install with the lagest blade area and with a shroud to avoid ventilation looses. There is only little difference putting it in front or behind the radiator if the profile of the blads drags the air into the right direction.
Before starting do a check first, is your fan running in the right direction?

Ralph
Ralph

Yes, a Kenlowe fan will work better, especially if mounted behind the radiator in what is known as the "puller" position. Pullers are more efficient than pushers, as all the air going through the fan will have passed through the radiator; not the case with a pusher. A 12" fan will fit nicely and pull significantly more air through the radiator than the standard fan.

Paul K

I fitted a Spall fan to my V8 roadster, similar price to Kenlowe on E bay, but evidently flow a lot more air, a 12" sucker fan has proved a big improvement on the old Kenlowe pusher previously installed.
M Barnfather

As I have problems with clearance between the front pully and Rad I have fitted two SPAL fans. One pulling and one pushing, both shrouded.
One is bottom right pulling and the other top left pushing. Both 10". They overlap a bit in the centre but this should not be a problem.
The puller is driven from the thermostat and the pusher is run of a manual switch. I have a LED fitted instead of the Light Dimmer knob, so if the fan is running in auto it is green, running in manual is red and both on gives yellow!!
I have not tested them yet but they look as if they will do the trick.
I believe it is best to have the fan pulling so fitted behind the rad, and that 1 big fan is better than 2 smaller ones.
The SPAL fans seem to be good quality at better prices than Kenlowe.
Dave
D M Tetlow

The OE fan *should* get the temperature down so if it isn't there is something wrong somewhere. Either the engine is generating more heat than it should, or that part of the radiator core where the single UK fan is mounted is partially blocked, or the fan blades are the wrong way round, they are rotating the wrong way, or due to bad connections the fan simply isn't spinning as fast as it should. On my V8 (twin fans, like 4-cylinder cars in the US) I found I was losing 2v at the fans in various places. The earth circuit is poorly designed as it is a long run of standard gauge cable going right back to by the fusebox, and is shared with the headlights. Paradoxically the 12v supply to both fans and headlights is a heavier gauge, although on the V8 it is off the green circuit which can be heaviliy loaded anyway. I provided an additional local ground for each fan at its mounting bracket and a direct supply from the alternator to the cooling fan relay. This made a huge difference to fan speed and effectiveness.

The 4-cylinder car uses the ignition relay rather than a colling fan relay, but you need to check the volt-drops at the relay, inline-fuse (one of the two white/brown to green), thermostatic switch, fan connector (both 12v and earth connections), and earth connections leading back to the body.
Paul Hunt 2

Hi,

As I wanted a seriously big fan on my V8 conversion. I fitted a Kenlowe 14" fan, as a pusher, in front of the radiator.

A couple of points are worth making:

Firstly, the 14" fan is not on Kenlowe's website listing but it is available. Ring them and ask. It is a good bit of kit. There is also a very heavy duty 13" fan available but it draws 25 amps - yes, that is right, 25 amps normal running, start up 35 amps plus! As my supply (one of Dan Masters' Powerblock systems) couldn't supply that much current, I stuck with the 14" fan.

Secondly, as the fan covers nearly all the front of the radiator, the valance at the bottom has to be cut away to mount the fan onto the front of the radiator. It is a shrouded fan and fits very closely.

I would endorse Paul Hunt's comments about the need to use the power effectively. Dan Master's system uses a dedicated relay and a dedicated earth. I would use a feed directly from the battery, through a 30A fuse to an ordinary relay, then onto the fan and finally to a GOOD, CLEAN EARTH all using 25A cable and good connectors. The control side of the circuitry can use much lighter cables.

I have had a thermostatic switch fail 'closed' and managed to drain the battery. Perhaps it is worth using an ignition-controlled supply for the relay control circuit.

This system has worked well this year - but that's not much of a test!
P L Hills

I disagree with some of the advice in the posts above. A fan is always best positioned in the part of the system with the greatest mass flow. This is always before the radiator and not behind where the air is hotter and less dense. (see SAE J2082)

Putting the fan behind the radiator probably comes from either convention (when replacing a mechanical engine driven fan) or due to the ease of installation.

Some fan manufacturers like the fan mounted behind the radiator as it adds a little extra environmental protection, but if the fan is a fit-for-purpose fan you should always consider mounting the fan in front of the radiator if access allows.

Adding a cowl greatly increases the fan overall efficiency. Some after-market fans are manufactured with a cowl to increase the efficiency; these would be a good choice.

Adding a proportional speed controller (temp vs. speed) will vastly reduce the energy consumption and prevent engine temperature fluctuations when stop-start driving in traffic etc. this type of installation reduces the stress on head gaskets, hoses and core plugs and avoids fuel vaporisation and high under-bonnet temperatures.
MG Mike

Hi Mike

I spent some time deciding which fan to use, and contacted a few suppliers.
What they all agreed on though was that it was best to fit the fan behind the radiator.
I believe that the loss due to driving hotter (thinner) air was more than compensated for by the more efficient process of pulling air through the radiator. Also having the fan in the front causes air to be diverted as it is an obstruction when the fan is not running. They all also agreed that the cowling was very important and a good seal to the radiator was important too.

I opted for two fans instead of one mainly due to the fact I did not want to cut the lower panel infront of the radiator, and that the current drawn would be less as I would supply each fan with its own cable. I fitted one in front and one behind in opposite corners of the radaitor.

My car is a V8 but it is not heavily tuned and I have had the headders ceramic coated inside and out so the temperatures under the bonnet are not as high as they could be. The original twin fans worked OK but I decided that the new designed fans will be more efficient and quieter. I opted for curved blades which are slightly less efficient but quieter.

After all this though all new cars I have seen on the market today have the fans infront, so I could be talking a load of @%&$. :)

Dave
D M Tetlow

"always before the radiator and not behind where the air is hotter and less dense"

That may well be true, but puller fans (i.e. behind the rad) are inherently more efficient than pushers, which fling a significant amount of air off the ends of the blades and not through the radiator, even when shrouded. A shrouded puller is best.
Paul Hunt 2

Hi Paul,

From what source are you basing that “puller fans (i.e. behind the rad) are inherently more efficient than pushers” this is simply not true, please read SAE J2082. it is one thing to give your opinion but stating that a “shrouded puller is best” on the basis on hearsay or perceived logic is poor advice to anyone who does not know.

Regards,

Mike.
MG Mike

I think the main point is getting lost here, the standard electric fan works fine if everything is in good working order, a Kenlow isn't needed.
Ron
R. Algie

Mike

It would seem to me that putting a fan in the pusher position has two problems.

First, if it is not shrouded you will get the tip losses that Paul refers to.

Second, if you do shroud the fan you are effectively reducing the air intake area and thus reduced airflow at speed. You are also forcing air through only part of the radiator when compared to a shrouded puller fan with a resultant loss of cooling capacity/efficiency.

Just my observations.

HTH

Larry
58A
69C in restoration
72BGT daily driver
Larry Hallanger

I think the debate re: the science of pushers versus pullers is missing a vital point: It's how the fan was Designed!

Quite possibly it IS less efficient to work as a "puller", but if the fan manufacturers insist that this is how their fan is designed (to last longer, perform better, or what have you...) then this is how they need to be installed.

Just as your car would rather push itself in 1st gear, You would rather push your car in 4th gear! Thus I assume that science would rather PUSH the air but the FAN would rather pull it! :-)

That being said, I've always tried to mount fans as pullers. They don't block the airflow to the front and the manufacturers recommend this way. (The "older" fans use to work only 80% of optimum in the reversed direction until the industry standard was to make the blades reversible for either usage.)


Now, MY question is this: of all the purported "CFM" numbers out there of numerous fans, which fan is REALLY the most powerful? My 74 B likes to get hot when pushed (4000 RPM+) now that I have an electric fan. Never had this problem with the fan blade on the water pump ("N", always), but now has it with a 9" Perma-Cool. (Which, to be fair, I think is the "standard" fan rather than the High Performance.) I need to do better at simulating the CFM of the bolt-on fan (which was linear to the engine speed. Alas, an electric fan is limited by it's revs.)
Obviously, I'm trying to save the horsepower. I can run 3500 rpms and not get hot. More, and it creeps up.... (And I mean 6000 rpm equals 225F!) This is NOT a timing, tuning, etc. issue-- I'm talking about a problem that occurred directly resulting from the fan blade being removed and the electric fan being installed! (And this change ONLY.)

Thoughts on which manufacturer makes the best cooling electric fan? I've heard Zirgo, but have zero experience with them.

Remember a '74 radiator is limited to a 10" fan at best (9" fits better) with only a 2.5" depth (as a puller.) I don't want to cut anything, fabricate a larger radiator, etc. I just want the best electric fan for simulating the water pump fan. The radiator cools fine as long as the airflow is up. it is NOT a good "disapatory" radiator. (The '77-on in the States was larger to make up for the fact that it would not have constant airflow through it. But it also had two 8" fans to blow on it!)
Granted, I'm asking the radiator to now do something it wasn't intended to do. I'd like to try the best electric fan possible before giving in (and putting the blade back on.)

Thanks for your responses in advance,

M
Max Fulton

Hi Max! Good to see you on the BBS!
rick ingram

An optimum designed fan installation requires the manufacturers ‘fan curve’ (sigma dP vs. CFM) to be matched to the resistance of the system. Even if you can get the ‘Fan Curve’ data for the fan you would not know the resistance of the system air flow, so we tend to guess, or choose biased on what is available, often a good match as the dP is very low for this type of fan.
The volumetric flow will not change due to the position of the fan on either side of the radiator, but the mass flow *will* and it is mass flow that determines the cooling efficiency of the fan.
Heat lost can be found by the formula; q=mCpdT
Where m is the mass of the substance, Cp is its heat capacity and dT (delta T) is the change in temperature.

The important factor for fan location in the above is the dT, if the fan is before the radiator the mass flow will be greater and you will have a greater dT (for instance if the air in to the radiator is 15degC the air out may be 25degC, this is a significant increase in dT) and *will* effect overall performance.

I believe that some fan manufacturers advise placing the fan the exit side of the radiator;
1) for ease of installation.
2) to offer some protection from the environment. (but not heat, so why do it?)
3) ease of fan replacement or maintenance. (in some cases)

On the flip side, less current will be drawn by a fan on the exit side of the radiator, perhaps this is where the ‘belief’ that it is more efficient comes from? But the fan will be in a hotter environment (not good for fan bearing life, this is what ultimately kills the fan)

However, there is no good thermodynamic reason to place a fan on the exit of a heat exchanger.
MG Mike

I believe I will have the same problems as Max and I have no faith in the older fans and want a better modern alternative.
I am going from a V8 radiator with twin original non shrouded fans to two 10" shrouded fans. Again like Max I did not want to cut anything.
The old fans hung in front of the radiator so did block the air flow quite a bit so the 10" shrouded pusher I have top left (just fits between the lower panel and top of the radiator) should only impede flow to part of the radiator and by no more than the original fans. Behind the radiator I cannot fit a large fan due to the central pulley so a 10” shrouded puller fan is fitted bottom right. I am told the small overlap in the centre is not a problem!!
I appreciate these two fans could be a greater restriction than the originals so the engine could run at a higher tepmerature than it previously did.
My solution would be to have the puller running from the thermostat and the pusher from the redundant Overdrive stalk switch. (LT77 box).
If the car gets too hot under normal conditions due to the impeded flow I intend to put a constant lower voltage supply to the manual fan so it runs continuously keeping the engine at an acceptable temperature, switching it to full speed if necessary. I hope to set the lower speed with a high watt in line resistor!! or use a dividing circuit.
I am using the curved quieter blades rather than the more efficient straight ones.
I was given a lot of advice from a chap who races V8’s and he has used similar fan configurations as per above when necessary.
As you may guess I have all the bits but have not finished the build yet.
Dave
D M Tetlow

"I've always tried to mount fans as pullers. They don't block the airflow to the front"

This sounds like a re-run of the arguments in the early days of powered flight as to whether a propellor was more effective at the back of the plane than in front!

When considering additional fans for my factory V8 (beefing up the supply and ground rendered this unecessary!) I remember reading comments from one supplier that they had tested curved blades and rejected them as they were so inefficient.

If you have an effective thermostatic switch and cooling fans that is all you should need - the fans will switch on and off as needed. A constantly running fan is inefficent, and is what electric cooling fans were intended to prevent.
Paul Hunt 2

Max, My son has used Spal high performance fans in a Jensen Interceptor and for an oil cooler in a Legends race car. The high performance Spal fans seem to be good but I cannot say they are the best fans. Here is a link that has specifications of many electric cooling fans. I believe the performance data is based on information furnished by the manufacturers. Maybe you have already read the article.
http://www.jcna.com/library/tech/tech0008.html
Michael Frank doesn't say which fan is best but his web site has links for more information on the fans he compares.

I have owned lots of later cars with electric fans. Most electric cooling fans will never need to come on when running down the road at 60-80 mph. They do come on in heavy stop and go traffic. Even the Jensen fans didn't run on the highway but would run very frequently in traffic. I may be missing something but I don't understand why a better fan will help at expressway speeds. Recently there was a Mazda Protege owner in a Mazda forum with an overheating engine when in traffic, temps were normal at expressway speeds. The owner found that his cooling fan had burned out and wasn't working. I have always thought that overheating at high speed was some other cooling issue, not a fan problem. Even race cars turning lots of rpms do not use a fan until they have to slow for cautions. My 2 cents.

Clifton
Clifton Gordon

I agree Paul

I hope all will be fine with out tinkering and the running temp will be the same as original. The new fans have a low resistance to through flow.

The difference in flow figures with straight and curved blades is not pronounced. The straight are better though.
Kenlowe fans have curved blades and many new cars the same. ( My BMW for one)

Over all it is all academic as you are quite right the only need to change is for cosmetic or reliability reasons as the std setup does work.
D M Tetlow

Hey Clifton! (Go NCMGCC!)

Yes, I saw that article and it didn't give me what I wanted as it didn't include Zirgo's for comparison. (They 'boast' the most CFM.)

One would think a car at freeway speed wouldn't need the electric fan running, but when do we ever know this? The only MGB that had this configuration was '77 to '80, and that was a bigger radiator! (Though the smaller R/B opening.)

Show me someone with the early radiator WITHOUT the water pump fan. (And C/B cars have a bigger grille from which to draw air through. The R/B 74 1/2 to 76 is the worst of the worst). Because that's the car I want to be, and it's currently not working. At "highway" speeds she's fine (O/D in.)-- but if I don't put in the OD and push the revs up to 4000 or more, she creeps up in temperature.

Around town she's fine-- the electric fan kicks in, and the revs are low.

I'm dealing with a specific instance where I'm unable to get enough airflow from 4000rpm+ into the early radiator. (Which before was spoiled by having a 12", 7 blade, huge curved fan turning the SAME number of revolutions as the motor!)

Now, I'm limited by the revs of the electric fan and the available space in which to bolt a large "replacement" for that big plastic fan!

I've found Spals to be nice units: quiet. But, I also think they are underpowered for what I'm looking for, though.

I don't care if the electric fan has to run at highway speeds. (The more I think about it, the more it seems it would have to to draw in enough cooling air at the higher rpms.) Will make up for all those times at the lower revs that it doesn't have to. :-) But, I'm trying to find an electric fan capable of the job. :-/

Any other thoughts from anyone?
Max Fulton

Simple empirical observation says that the electric Pusher setup on my 68 GT has been AT THE LEAST, as effective as the stock engine driven fan it replaced with one exception. That is that it has been MORE effective than the OE fan when in stop and go traffic. When I installed mine, that was actually all I was looking for.

A 68 doesn't allow enough room behind the rad for a puller, so I "settled" for the pusher setup. Now I am not so convinced that the difference may be as significant as was once thought.
Bob Muenchausen

Assuming that MG Mike knows what he's talking about, then I agree with him!

Sometimes engineering knowledge IS a good substitute for experience. We all try to help, but I worry sometimes that we are all free with our advice without necessarily establishing our credibility or qualifications.

Just a thought, if there is no shrouding, then a fan cannot be defined as a 'pusher' or a 'puller' - it's just a fan. It's obviously directional inasmuch as it moves air from one side to another, but it only becomes a pusher or puller as a result of its mounting arrangements?

Also, the fan doesn't need to bring the temperature down, it needs to stabilise the temperature - ie stop it going up any further. If the fan is bringing the temperature down (only for it to go back up again when the fan cuts out) then that's wasteful. I know that's what happens in 'real life' due to the realities of circumstances, but steady state would be fine.

Back to the point! Bristol traffic is probably the worst you'll find outside of London. I've got a tuned GT (big valves, HS6s, 285 cam, etc). I use an electric fan that I bought from Merlin at Castle Combe (which incidentally has instructions for how to change the blades around if you want to convert from a standard pusher to a puller) controlled by a thermostatic switch that comes as part of an aluminium tube jointed into the top hose. It works fine. I had lots of overheating problems even with this set-up until a friend 'noticed' that the £1 piece of foam that fills the gap between the radiator and shroud was missing...

N
Neil22

" if there is no shrouding, then a fan cannot be defined as a 'pusher' or a 'puller' - it's just a fan"

I don't agree with that. Regardless of whether it has shrouding or not a pusher moves air first through itself and then through the radiator, and a puller first pulls air through the radiator and then through itself. I'm sure that there is scientific techno-babble somewhere that can 'prove' that isn't the case (like bumble bees can't fly and bats only glide) but that isn't going to help anyone here.
Paul Hunt 2

It's not techno-babble, its MECHANICAL engineering. A fan moves air from one side to the other. How you fit it to the radiator defines whether it is a pusher or a puller.

The main problem with the Kenlowe 'pushers' that I have seen is that they are mounted a little bit in front of the radiator with no shrouding. Just like the OE fans. Puller fans, due to space constraints, tend to be fitted directly to the radiator. Perhaps that's why they are perceived to be better?

C Cummins - get hold of a Demon Tweeks catalogue and you'll find fans in different shapes, sizes and capacities. You ought to be able to find one that suits!

N


Neil22

Guys,

New model Kenlowe fans are shrouded and work well. From their website and discussion with the factory, their heavy duty 13" is a monster!

FWIW
P L Hills

This thread was discussed between 28/08/2007 and 12/09/2007

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