can you upload some pics of your heat shields?

[xpress]

hi there, could you put up some pics of your heat shields and give some info on what you have done and where and if it improves things? i have to do something about the hot weather and the ticking pump syndrome! thanks

[bmcecosse]

None - and no problems......

[xpress]

Yes, but you live in siberia/Scotland lol ;)

[minor65]

Agree with BMC, None and no problems

[chrisryder]

[frame][/frame]

in this pic you can see my chequer-plate heat shield between the carb and the manifold. it serves best purpose as keeping petrol off the exhaust when the hose leaked!

you can also just about make out the tin foil wrapped around my fuel line to pump.

i'd imagine my chequer plate heat shield does a good job as you can see the proximity of my exhaust to the float chamber, which isn't normally a problem for standard minors.

i doubt this post really helps at all, a good excuse to show off my engine-bay though

[MarkyB]

Some Minors suffer from this, and some just don't.

Mine seems to be OK though I started to panic a bit when creeping very slowly to wheels day on a hot day for at least an hour, it was doing the petrol pump fandango, but the engine never missed a beat.

My friends traveller would have been in trouble after about 20 minutes, if not sooner.

There were cars of all ages and types being pushed of the road with their bonnets up, so it isn't a problem confined to Minors by any means.

I'll try and take a picture of my beer can heat-shield, made with only a Swiss army penknife and available materials this Friday

[bmcecosse]

" beer can heat-shield " -

[MarkyB]

You're just jealous .

[Declan_Burns]

Here's a photo of my heat shield-no problems[frame][/frame]
Regards
Declan

[MarkyB]

Hers is the infamous beer can shield;[frame][/frame]
The exhaust wrap around the float bowl and the exhaust is a later addition as the can wasn't a total cure.


I was under the back of the car today and noticed that the petrol pipe and the exhaust pipe are in quite close proximity where the exhaust goes over the back axle, roughly 2 inches.
Looking at my car which is OK in traffic, even in hot weather, and the gap is at least 6 inches.
Now I'm wondering if half the problem is occurring even before the petrol get to the engine bay.

[bmcecosse]

YES! That is where the problem arises - on the suction side of the fuel pump. No point/need to shield the petrol after the pump......

[MarkyB]

That is as may be, but that far from the engine bay?

It's quite a variable depending as it does on the shape of the exhaust and how it's been fitted, especially if it's a two piece system.

There isn't much scope to twist the exhaust pipe any further away as it's pretty close to the floor.
I'll have to see if there is any exhaust wrap left over.

Worth a look anyway, summer is coming!

[xpress]

Thanks all. Especially for the pics. Why is it only trouble for the suction side? Surely fuel can vapourise in the bowl wouldn't it be just as volatile there as anywhere else. I will wrap some foil around the pipe and tape it and experiment until it cures it. I presume that if it is doing the vapours that it is wasting fuel and costing extra? Maybe this would help people with fuel economy? One of those infra red Thermometers would help and knowing the temp that fuel starts to vaporise.

[chrisryder]

boiling point is dependant on pressure.

for example, the boiling point of pure water is only 100C at sea level. at the top of a mountain you can boil water at 85/90C due to the lower atmospheric pressure.

in the same way, the suction side of the fuel pump puts the fuel under negative pressure, which lowers its boiling point. once the fuel is in the float chamber it's not pressurized so boils at a higher temp.

vapourisation shouldn't affect economy as unless the vapours escape, they should condense somewhere in the system.

[chickenjohn]

Chrisryder is right- a bit of science (actually physics) for you!

The carb side of the fuel pump is pressurised from the fuel pump and the tank side is under partial vacuum when the pump is sucking petrol. Therefore it is the metal pipe going to the fuel pump that needs the shielding from heat as that is where the fuel will form bubbles and make the pump work really hard.

BTW, on the top camps at Everest- water boils less than 80C!

[chrisryder]

there was an interesting thing on 'bang goes the theory' a while ago, where they had a glass beaker with warm (70C or so) water. they pushed a bung in the top with a pipe coming out of it, and sucked the pressure out of the beaker to make a partial vacuum. and the water starts to boil. i was fascinated!

[MarkyB]

How about some measurements then?
I'm liking this as a theory, on the car with this problem it was 2 inches, 5 cm between the two pipes.

On my car which is fine, about double, 4 inches, 10 cm.

Another bit of physics that may also come in useful is that heat rises, and the petrol pipe in the suffering car ran along the top of the dome for the differential.

[bmcecosse]

Simple Physics Chris - reduce the pressure and water boils at less than 100C,(hard to make decent tea on a high mountain) increase the pressure (as in a Steam Loco Boiler! ) and the water boils at very much higher temperature - giving 'steam' above the surface and 'high pressure hot water' below the surface. As the steam is used up, the pressure drops and the water boils again at a lower temperature to release more steam - so it's a massive reserve store of ready-to-use steam. Of course the temperature also drops and- the Fireman then shovels in more coal - heating the water again and so it boils even harder, raising the pressure again.......and so the cycle repeats.......

[DaisyMayFozz]

heres mine:[frame][/frame]- that was made out of a beer can too, the black is gaffa tape[frame][/frame][frame][/frame]

i have to say that it looks a mess, and i have yet to try to see if it works (only did it today). might put some near where the fuel goes near the exhaust aswell.

[MarkyB]

I don't like to be critical but the shield on the float bowl will only have the effect of making the bowl thicker which wont help keeping the heat off it.

The only points of contact between mine and the bowl was through the screws.

Anyway here is my latest attempt at a complete cure on this car;[frame][/frame]

I would have put some foil on it too but none was available, I figure the rubber pipe will insulate the petrol pipe form both radiant and convected heat from the exhaust, time will tell.