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MG MGA - Fuel Vapourisation (it's summer)

Ah, the old favourite.

Slow traffic, water 190 deg, rough running! Clears when I can get away.

I guess it is vapourisation around the carbs. THe fuel supply pipework isn't particularly close to anything hot so I suspect heat is affecting the carbs themselves or the manifold.

Are there any suggestions for additional insulation or air flow improvements? It's not as though the water temp has got particularly high!
Graeme Williams

Graeme

Some of the guys say the bilge fan in the carb ventilation ducting helps although it did nothing to inspire me. i have found that the Moss 7-bladed asymmetric fan shifts a mega amount of air round the engine and I have not had any vapourisation issues since fitting it.

Steve
Steve Gyles

The previous owner was telling me that he had thought about fitting an ally head, Steve. Any thoughts on that?

Moss show two 7 blade plastic fans. Both have the same wording , one is twice the price of the other (looking at MGB engine)
Graeme Williams

The Moss 7-blade plastic fan, part number 434-332, is a ticking time bomb. My experience implies it will fail around 10,000 miles, give or take some, and when it does it will likely damage the radiator. The problem is molded plastic with no reinforcing fiber, so the plastic will fatigue and crack with service time. Moss knows about this, but has not replied to the issue, and it is still available in their catalog. See the faulty part report report and photos here: http://mgaguru.com/mgtech/faulty/ft080.htm

The little bilge blower is a $20 part with 20-minute installation, and it works a treat.

The best solution is to install an original equipment type cell core radiator, and all the cooling problems go away. Modern VT radiator cores with lots of small water tubes and lots of fins restrict air flow to cause unnecessary temperature rise. This is all about the amount of air flow that is required to carry away the heat (and the cell core is much more efficient).
Barney Gaylord

Greame, I agree with Steve that fitting a better design fan seems to prevent fuel vaporisation. They do appear to move more air through the engine compartment and therefore cool the float chambers better.

You will find that fitting an additional electric fan will have the same effect too.
Roger Martin found that fitting one stopped his car from boiling over on on the many long climbs over the mountain passes on our traverse of the Pyrenees a couple of years ago.

A bilge fan fitted into the carbs cool air supply pipe does work but it is really noisy.

I have been thinking about trying a small CPU cooling fan (as fitted inside a computer casing) instead of the bilge blower.

It would be almost silent in use, far less expensive and I think it may well provide sufficient cool air to do the job.
I used to have an Airchamber storage tent for my car and it had 2 such CPU cooling fans which easily maintained the inflation of the tent.

Consider that the a float chamber cooling fan is only needed when the car is stationary when the engine is usually just ticking over.

May be worth a try?

Cheers

Colyn

Colyn Firth

It is interesting that it was happening at only 190, I have never seen it at such a low engine temp. I am though not an expert living 400 miles further north and only see it ocasionally.

Paul
Paul Dean

The bilge blower trick absolutely works ! It cured my fuel vaporisation woes completely.

For example, we went to the Harpenden Common show this year and had to queue for over 30 minutes to get access. Normally we would have conked out as the temperature was hot that day, but with the bilge blower running, she didn't miss a beat. Ticked over lovely. Several cars had to be pushed in due to overheating. I've wired it to a double switch (headlight type) on the map reading light, first pull the light, second pull the bilge. Works well and leaves the dash looking original with no need for an extra switch.

Yes, the blower is loud, but I would rather that than break down. We had got to the point of not taking the mga out on a hot day for fear of traffic queues, but now we can enjoy her without worry.

I have considered ceramic coating the exhaust manifold to try and lower the engine bay temperature to negate the need for the blige blower - that may be this winters project. Has anybody zircotec'd their exhaust manifold with good results for keep temps lower?
C Wilson

Hi

Louvres are the way to go, temperatures are high here but fortunately we don't have the traffic. Not had a problem since mod.

Barry

B Bridgens

C,
I just had my new Maniflow exhaust manifold ceramic coated, both inside and out, by Camcoat of Warrington.

I mostly wanted to prevent it from rusting but it looks great and it does appear to have reduced the underbonnet temperature too.

The new 1950cc engine seems to run between 175 and 185 degrees even on hot days which is a pleasant surprise and this is pretty much the same temperature range as the previous 1850cc motor.

Cheers

Colyn
Colyn Firth

Graeme

My 7-blader is the more expensive one - 12H4744 currently 54.50. The other is AHH6999Z at 29.50. I have it fitted on an 1800.

I do not know if the material is any different between the two. That said, I do recall having them alongside each other when I was in Moss earlier in the year and was more impressed with the expensive one, it seemed more substantial.

The USA Moss site seems to have just the one fan, 434-332 as noted by Barney. I cannot be certain but looking at Barney's link I think it may be the cheaper one (Europe No. AHH6999Z). Perhaps Barney could enlighten us.

I wonder if the more expensive one is a British/European moulded version? Perhaps it will not be prone to the breakages Barney has suffered? Only time will tell with me. I don't do anything like his mileage.

Steve

Steve Gyles

I'm not convinced that engine temperature has much to do with fuel vaporisation. My 2l oselli engine runs at 175 to 185 like Colyn's, but I was still get bad running in traffic.

To me, it is more about the fact that the hot air builds up and doesn't exit the engine bay when stationary and no cool air is flowing over the carbs either. A double whammy.

Even my twin radiator fans don't help and they are blowing a gale through the radiator at this point. The car doesn't overheat on the gauge, but does still suffer from fuel boiling.

The bilge blower helps both conditions, passes cool air over the carbs and helps to force hot air out through the oval vent.

Lowering the engine bay temperature by reducing the heat coming from the exhaust manifold with ceramic coating would seem sensible, but I'm not sure if it would be enough to stop the overall temperature around the carbs reaching a point where the fuel boils.

C Wilson

@Colyn

Thanks for the pointer to Camcoat, I hadn't found them.

Colin W.
C Wilson

...an additional thought. This issue has never been a significant problem for me, even before I tried out a bilge fan and 7-bladed fan. I always use super unleaded. Could this be a factor? The bilge fan now resides in the Smiths heater ducting.

Some of you may recall my experiments with the 7-blader. Stationary I had a significant blast of of air coming out the 2 vents - shown by cotton threads I attached to the vents. They were standing vertical and did not go inwards until moving quite fast. I forget the speed now, but it's somewhere in the archives. In my view this was a convincing demonstration of the volume of air the 7-blade fan blew past the carb bowls. I have also yet to see the temp gauge rise when stationary. If anything it tends to drop a tadge.

Steve
Steve Gyles

I had my intake and exhaust jet-hot coated.
Most of the heat from under the hood has been reduced greatly.

I don't get the hot engine stumble the car used to get when stuck in traffic.

S

I have never had fuel evaporation problems on my car apart from the once when an air inlet pipe fell off in front off into the radiator duct and partially masked the radiator.

I do have all the right bits on the car, original core design radiator, twin electric fans ( no engine driven fan), twin cam type inner wing louvred panels, louvred bonnet.

I did have a long discussion a couple of years ago with James at Bob West's on the subject of fuel vaporisation. They were struggling to restart an original race MGA after every pit stop at a very hot Le Man's Classic and they asked to borrow my big NTG Fan to see if it would help.

It worked fine but I suggested that as a last resort they could also perhaps try fitting a fuel return pipe from the carbs back to the fuel tank.

The idea being to have fuel flowing continuously in through the rear float chamber, then on to the front float chamber and then any unused fuel would flow back via a new pipe to into the tank.

This continuously flowing action should keep the fuel much cooler than the standard non return system as it would not stay long in the hot zone.

You may have to increase fuel pressure a little to make certain of enough supply but I personally think that the standard fuel pump would be up to the job.

Also, you could introduce a coiled section into the return pipe to help cool the fuel even more.

Anyone see any downside to this? (apart from the extra work! )

Colyn
Colyn Firth

Interesting range of comments..... thank you everyone.

I have vents in the bonnet so in my case it doesn't resolve the problem.
Got an electric fan too...... doesn't solve the problem.

I would be interested to know how I can tell what the spec of my radiator is? Would a measurement of fin spacing or whatever enable me to tell whether it conforms to the "ideal" spec?

Can anyone give me more information on a bilge fan and how it fits. I too had wondered whether a cpu fan would do the job. Annoyingly I binned what would have been a suitable fan off a Dell a few months ago. One of life's "why am I keeping this cardboard box full of outdated bits off old computers* that I'll never use again" days!

*substitute cars/cds/car mags etc
Graeme Williams

Graeme

The core of the original rad is 2" thick. Many modern cores are thinner. That's a starter for 10.

The Attwood Bilge fan is a snug (interference) fit inside the trunking. Type Attwood into the archives search engine. There are lots about it there that should answer your questions. I think Barney also has a page or two.

Steve
Steve Gyles

Found them Steve! Bl**dy Hell, that's a long thread for the MGA forum - more typical of the Sprite and Midget section where 200 posts are not unusual.
Graeme Williams

Graeme
At the risk of stating the obvious, do you have a heat shield fitted and is it in good condition?
Graham
Graham V

I'll check that out Graham. I thought I was seek advice as a guide before I started poking about. Obviously there is a real mix of opinions I guess because there are fundamental differences between the cars in the first place.
Graeme Williams

I probably don't have a great deal new to add, but just to support other's comments.

My MGA used to overheat dreadfully; 225F plus coming up the long climb to my home in summer, and boiling over when switching off.
Unfortunately my radiator's top and bottom tanks had been butchered to fit the conventional (and nigh on useless) replacement core prior to my ownership which precluded the option of re-coring my radiator with an original MGA-style cell core (aka "V Cell") radiator core.
I fitted an aluminium radiator (custom designed for my application from PWR in Queensland) which completely solved my overheating. In fact I recently changed my 72C thermostat for an 82C thermostat.

Despite our higher ambient temperatures here in Australia, fuel vaporisation for me was an infrequent and minor issue, manifest with irregular running for perhaps 10- 20 seconds when restarting after a long hot run. But even this was completely eliminated after Jet coating (i.e. ceramic coating) my exhaust manifold. It's extraordinary, but I can (lightly) put my finger on my exhaust manifold when the car is at normal operating temperature without burning it. I wouldn't dare try that with an uncoated manifold! It has proven to be a remarkably cheap yet effective step to take.
What amazes me is that something that is so obviously effective can in any way be controversial. Just look at this current and extraordinarily long series of exchanges:
http://www.mgexp.com/phorum/read.php?1,3339600

Attached is a photo of my own coated manifold. The somewhat garish choice of finish was not mine, (the folk doing my cylinder head porting work arranged it, at my request) but thankfully it's not too obvious being mostly hidden by the heat shield, inlet manifold etc.

T Aczel

I forgot to add that I just use the original steel MGA fan, and a radiator shroud.
No additional electric fans or after-market engine driven fans have proven to be necessary.
T Aczel

Colyn says he had his ex manifold ceramic coated in and out, and that reduced his temps. Sounds like it decreased the size inside the pipes just enough to better the exhaust scavenging, resulting in lower temps.

T Aczel had overheating problems until a new Alum radiator was installed, something about a rad shroud, and ceramic Jet coating for the exhaust man. Now it runs so frigid he needs a hot thermostat to keep it from icing up, thanks to the Jet coating.
Sam Coleman

Colyn says he had his ex manifold ceramic coated in and out, and that reduced his temps. Sounds like it decreased the size inside the pipes just enough to better the exhaust scavenging, resulting in lower temps.

T Aczel had overheating problems until a new Alum radiator was installed, something about a rad shroud, and ceramic Jet coating for the exhaust man. Now it runs so frigid he needs a hot thermostat to keep it from icing up, thanks to the Jet coating.
Sam Coleman

Just checked out my rad!

The core is less than 2" - looks closer to 1 3/4, poss less.
There are 12 fins per inch.

This was a USA import and the rad is marked Curt's Rad Services.

Is all that good or bad?
Graeme Williams

Sounds like a recore...The originals did better as Barney states.

I saw a lot of MGBs get recored radiators over her in the states that lost there efficiency.

There was a time here in the states that radiator shops were condemning everything that came into their shops just to make the sale.

Unfortunately the new radiator cores just didn't have the cooling capacity the old originals had.

I noticed that back in the mid 1990s
S

The ceramic coating does seem to help Sam but I must admit that i don't really understand how a 40 micron thick ceramic later inside and out can help prevent the heat from radiating through into the engine compartment.
Maybe it just helps direct more exhaust heat out through the pipe.

I had mine coated mainly to keep the manifold in its new condition as long as possible.
Colyn
Colyn Firth

Graeme
Whether your radiator is efficient or not, I wouldnt think it is the reason for vapourisation. Not at 190 degrees
Graham
Graham V

Graham
But if the general engine temperature is fairly warm ie 190-ish, add into that the heat from the manifold and my thoughts are that that would probably take it over.

I am convinced it is the problem. Happens in heavy traffic after about 5 or 10 minutes if I am in a stop/start situation. I have experienced this three or four times this summer on very hot days (yes, those three or four days!). Once I get moving it clears itself after a few minutes.

I have ordered an Attwood as it seems an easy solution for 25! Hope this will take the stress out of traffic congestion.
Graeme Williams

Graeme
Can I ask what is an Attwood?

Paul
Paul Dean

Paul:
THe Attwood is what's called a bilge fan! Yes, my reaction too. It's a bit like the sort of thing you use to extract steam from a shower enclosure but it wedges in the air vent tube next to the rad on the carb side of the engine.
Opinions are a bit mixed but it has Barney's blessing and various other people's (not sure where Steve sits on this one) as it blows a gale across the line of carbs and so cools them sufficiently to prevent fuel vapourisation. You just turn it on when you suspect you may encounter a problem.
There are about 25 to buy and apparently (I hope) the 3" will neatly wedge in the existing tube. Quick wire up and hey presto!
Various archive threads (including a very long one) here and info on Barney's site too. Also Google "attwood bilge fan"

Opinions are mixed, but then the whole overheating issue since to draw different responses and solutions for different cars. I have a vented bonnet which some people swear by, but I still get problems.
Graeme Williams

Graeme
Whilst some people run at less than 190 dF, I honestly don't think 190dF is anything but absolutely normal.
On normal operating temperature, Barney says "If you want hard numbers, then use a 180d thermostat and expect 190d on a moderately warm day"
Let's hope the bilge pump sorts it for you. I run mine to the redundant fog light switch.
Graham
Graham V

Graeme

The Attwood bilge blower is a very powerful and nicely made motor. Some people swear by it for cooling their carbs in traffic. I put one in based on the recommendations, but as I never had issues with vapourisation I rarely used it, other than testing to see if it still worked. I did go as far as putting a temperature probe between the carbs and to be quite honest I don't recall seeing a lot of difference. I must check the archives on this point to see if I mentioned the figures. If so, it might be worth my while doing a similar experiment with the 7-blade fan.

The bilge fan is now in the Smiths heater ducting where it does a good job significantly increasing the airflow through the heater.

In my opinion the 7-blade fan does a far more superior job blowing air round the area. Ok, some may argue it's heated air rather than the cool air through the duct pipe, but, because of its power, the shear volume of air flow makes the radiator cooler and keeps the ambient engine compartment temperature below the critical vapourisation level. It's also less noisy than the bilge fan.

Steve
Steve Gyles

Just checked the archives. I stand corrected on the temp changes with the blower. It does lower the temps significantly, but as I said above I never had vapouristion probs anyway so these were tests purely out of interest to me. There was something like a 14F difference at the front bowl when moving with the blower on and 30F difference when stationary. With my car I found that I had to put a deflector on the blower to direct the cold air at the carb bowls. At 40mph the front bowl measured 112F with the blower off and 98F with the blower on. At idle the bowl measured 132F blower off and 102F blower on.

Now to do the same test later on today with the 7-blader.

Steve
Steve Gyles

Ah, I now understand. I was aware of the bilge pump solution but not the Attwood name.

Considering it is regarded that the vents in A shroud do not help cooling and may even suck air in rather than remove it at speed I do wonder how much bonnet vents help? Look nice and racy.

As a minimal sufferer (few jams and Scottish temperatures, although some big fast climbs) I think I am just going to pull the bonnet catch if I think I am in danger of getting the problem and see if this eliminates it. Has anyone tried this unsophisticated solution?

I do suspect Steve's use of Premium petrol may be part of a solution as I really do believe part of the problem is modern petrol. I really don't remember it around 1970 when I was doing high mileage.

Paul

Paul Dean

Graeme
why dont yu wire up the bilge blower so that it comes on with your electric fan?
I woud guess that the fuel problem only happens at the temperature range that your electric an thermostat cut in.

Colyn
Colyn Firth

Just to correct any misunderstanding, it is a bilge fan/blower, not a bilge pump. A bilge pump is used to pump out water that migrates into the bottom of the hull (bilge). A bilge fan is used to ventilate the same area of noxious and flammable fumes prior to firing up the engine. Some nasty fires and explosions occur on boats when the fan is not run first.

Steve
Steve Gyles

I did a run. OAT air temp was prob much the same as 4 years ago (26C). The only changes in the car since then are the 7-Blade fan and an 82 stat instead of 74.

I attached the temp probe to the front of the front carb as before. At 40 mph I got 102 F which is 10F cooler than the metal fan and about the same as running with the bilge fan on. Stationary, after a few mins heat soak, I got 132F which was the same as the metal fan. These temps should be factored with the hotter stat, in that the 7-Blade fan was blowing warmer air - perhaps up to 14F warmer. but guessing more likely about 10F warmer.

So I could perhaps argue that the correct comparative figures could be mid 90s at 40mph and 122F stationary. This would compare very favourably with and better the bilge fan switched on when moving, but about 20F ish warmer than the bilge fan when stationary.

However, the real bonus of the bige fan in this thread scenario is that it can be run before engine start-up to reduce the heat soak. The 7-blader only comes into its own when up and running

Steve

Steve Gyles

Steve: thanks for the information. I went for the bilge fan as a straightforward and inexpensive solution. The 7 blader would be next, and if push comes to shove, the radiator. Overheating of the main cooling system hasn't been an issue yet (touch wood) but vapouirsation def has, and is close to causing a "can't move" scenario if it worsened.

Colyn: connecting with the electric fan is a good idea. I have a manual switch for that as well as the tstat so best of both worlds.

Paul: to add to your idea of pulling the bonnet catch, the advantage of louvres is that you could put the bonnet up on its stay and drive by looking through the louvre slots!
Graeme Williams

Graeme
As a short term fix, I have read pulling the choke can sometimes temporalily clear vapourisation.

Paul,
Last year I was stuck in a long traffic jam heading into Henley on a hot day. As the guage continued to increase, I pulled the bonnet catch in desperation, but it made no noticeable difference.

Graham
Graham V

I just stumbled on a website with an interesting idea of fitting parallel heatshields
http://www.vord.net/cars/helga/mga-fuel-vaporisation.html
Graham V

It sounds like a great idea and of course there is a far easier variant if like me you have a spare heat shield, and only a margina issue.. Next time I have carbs of I will try fitting one standard heat shield each side of the insulating spacers, nothing to loose much to gain and no cost in my case.

I thought I would check the boiling point of petrol but what I found was it varies quite dramatically but a couple of points come out. Firstly higher octane higher boiling point, and secondly adding ethanol lowers it. No real surprises. Hence it is not surprising the problem is a lot worse now than it used to be.

I think Colyn made the point about how does such a thin ceramic coat make such a difference. To me this suggests quite a bit of the heat may be by radiation in which case colour of coating should make a significant difference but I don't suppose anyone has tried a black one versus a white one, a rather expense test. I would go black.

Paul
Paul Dean

Paul

That probably accounts for why I do not appear to have vapourisation problems. I said above that I always use super unleaded 98 octane and my understanding is that it contains a lot less (if any?) ethanol than standard unleaded.

I guess you get what you pay for. Go for the cheaper stuff and you suffer vapourisation, higher potential for pinking, hotter running engine and less performance; then pay loads of money for fixes.

Alternatively, pay about 5p a litre more for super unleaded and enjoy the performance, no pinking, no vapourisation, cooler running engine and no sticking plaster fixes (oil coolers, electric fans, bilge fans, etc) - they become just optional to suit your whims.

I went the super unleaded route for the performance and no pinking - it is a sports car.

Steve
Steve Gyles

Sorry, Steve, doesn't tally! I always use the nearest I can get to 5*, normally Shell "top of the range" as Dellboy would say.

If you fit two heat shields, I wonder whether there would be an advantage in sandwiching a suitable insulation material between them?
Graeme Williams

Graeme

I would definitely say no to extra insulation. Air is a great insulator, and it will be circulating as well.

Paul
Paul Dean

Graeme

One thing to cross off the list then. How is your timing? Was it timed with the 5*? The odd degree could make all the difference to the engine heat.

Steve
Steve Gyles

Steve
I agree about using the higher octane fuel. And running on is another thing that has improved significantly. That was always an embarrasing moment!
And on the sort of mileage I do, the difference in cost is minimal
Graham
Graham V

Oh and meant to add, I also fancy the idea of that double heat shield too. Cant see a downside so that must make it a no brainer?
Graham
Graham V

Just had a look at that double heat shield link. Another example of sticking plaster in my view. His carb temps after the mod are much the same as my tests from 4 years ago in 26c OAT (10c degrees warmer than his test) with a totally conventional and original cooling system. I would put money on him having the wrong radiator core.

Steve
Steve Gyles

Steve

Not much but This year I have had one traffic jam incident and a couple after short stops, e.g. loo stops, and I believe that I have the same core as you so there is more to it than that. After all something has changed and at least part of it is fuel, yes I am sure premium fuel is better.

What really surprises me is people getting a problem at such a low temp as 190. In my traffic jam issue engine temp was rising well above this, not boiling though.

Does anyone know exactly where the vapour forms?

Paul
Paul Dean

No one seem to have noticed my earlier fuel return pipe suggestion, or maybe it is just too "Off the wall" for most to be taken seriously.

I am certain that it would eliminate fuel evaporisation as the fuel would not be standing around the float chambers for long enough to absorb enough heat.

It would be continuously be circulating from the tank, then through "both" float chamber banjos and then back to the tank. So it would use the fuel tank as a 10 gallon cooling system.

You would have to fit a banjo with a double outlet to the front carb and a new length of fuel pipe to return to the tank.
I would fit a return connection into the fuel filler hose so to avoid having to drill another hole into a perfectly good tank.

I would also fit a convenient fuel tap into the return pipe so that you could experiment with how much fuel returns to the tank to control the amount of fuel you wish to recirculate.

The tap could even be opened to allow extra fuel cooling just on hot days when the car is idling in traffic or when you have to stop the engine to fill up at a fuel station.

Colyn



Colyn Firth

I had this drawn up some years ago, but never put it on my website. Use two rear (dual branch) banjos on the carbs. Use a second primary fuel hose to replace the original hose between carbs. Install a 2-psi pressure relief valve on the outlet of the front banjo, and route the return hose back to the fuel tank. That will provide 2-psi fuel pressure at the carburetors, and also recirculate all the excess fuel the pump can deliver (at 2-psi). The fuel pump needs to produce 3 to 4 psi (at least at low flow), and the more flow the better. Suggest also installing the Airtex fuel pump to increase fuel flow.

But that alone will not do much to cool the carbs during the worst heat standing still and idling conditions. With minimal (idle speed) fuel flow, the carburetors will still get hot, preheat fuel in the float chambers, and boil fuel in the throttle body as it enters the main jets (same as before). All the new system would do would be to cool the fuel a little in the pipe from heater shelf to the float covers. To make this work you have to cool the fuel in the float chambers, so the small flow from the bowls to the jets will cool the throttle body. But you can't bleed fuel from the float chamber for return to the tank, because the float chambers are at atmospheric pressure, and gravity feed would not return enough fuel to the tank, and if it did then the float valves may not pass enough fuel to keep the float bowls full.

A viable solution would be to wrap the fuel return pipe several turns around the float bowl (with intimate thermal contact) to pull heat from the bowl to the return pipe. I imagine flattening the pipe for the coil to have better thermal contact between pipe and bowl (maybe even solder the pipe to the bowl wall). Then you have five local pipes (in addition to the two coil pipes), and ten pipe and hose connectors. Start with the original hose from heater shelf to rear banjo, substitute hose from rear banjo to front banjo, pipe or hose front banjo to front coil tube, pipe or hose front coil tube to rear coil tube, and hose from rear coil tube to heater shelf to flex connect to the return pipe.

This is simple in theory, but a bit complex in practice. I decided to try the bilge blower first and it works, so I never got around to trying fuel recirculation.
Barney Gaylord

Thanks for that Barney,

my thoughts were that if the engine was running, the float chambers would be getting a little of the cooler fuel through the float valves as it replaced the fuel that was being used by the engine.

I suppose the only way to really know if this works would be to try it.

It would be relatively simple to rig up a temporary return pipe from the front carb, back to the tank filler pipe.
Then run the engine on tickover with the car stationary to see if it helps reduce the fuel vaporisation.



Cheers

Colyn

Colyn Firth

Fitted the Attwood bilge blower today. I connected it to the Fog lamp switch having thought about Colyn's suggestion of running it on the back of the engine fan thermostat. I thought that without an additional relay it might overload that circuit. I think it might be more flexible to have the two fans independent.

Very disappointed in the output!

But tomorrow I will remove it......
and put it in the right way round.

(Yes I know there's an arrow but I covered it up with the rubber insulation and so used logic.....)
Graeme Williams

Graeme
Are you sure you have to remove it - Is the polarity reversible so that you can just change the wiring over?

Graham
Graham V

Graham

Propellor aerofoil sections are only efficient in one direction of rotation. While you are probably correct about the wiring the resultant airflow will be greatly reduced.

Steve
Steve Gyles

Steve
Yes, thanks for putting me straight. Should have remembered that for example, the radiator fan always needs concave side at the rear, or have i got that wrong too!?
Graham
Graham V

Swapping the physical direction only took about 15 mins including breaking and resoldering the connections.

Been on test today.

I rolled some 2mm rubber strip around the ribs to build up the diameter of the fan body. One layer made it a nice gentle push fit into the vent tube. With the fan running no vibration was noticeable although it is noisier that the kenlowe.

I hit some traffic today and temperature rose to 192 and I would have expected the start of problems but switching the fan on I didn't encounter any vapourisation. A good start, but not a thorough test.

Just doing a quick temp check when I got home, I let the car idle and the temperature was just over 190. With the bonnet shut, dangling a thermocouple between the carbs I was recording about 68 deg C but when I switched on the fan it dropped to 57. Just short of the rear firewall, the fan had increased the temperature by about 10 deg! THat presumably is where the hot air is being displaced to.

Not exhaustive testing, but looking promising!
Graeme Williams

This thread was discussed between 27/08/2016 and 03/09/2016

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