I found one in the carb of ''Crusty'' when found in a barn It made no difference so I chucked it!

Chris

Location Prayer mat in the shed

Call me an old sceptic, but if a bit of mesh in the inlet could make any identifiable difference, why would car makers not use it instead of spending astronomical sums on other areas affecting fuel consumption! I'd like to see an independent test...
By the way, I've got some small bottles of snake oil if anyone's interested.

Location: Up a hill outside Northampton

For what it's worth,this thread brings to mind a device of similar ilk that was around in the late'50s and '60s.
It went by the name of the Mangoletsi "GM Manifold Modifier". It introduced a machined venturi into the entrance of the inlet manifold where the carb. bolts on.
This reduced the cross sectional area of this part of the manifold and supposedly improved fuel atomisation.
It was tested by such respected bodies as the AA and, on economy runs showed something like a 5% to 6% improvement in consumption.
It was widely adopted by the GPO on Morris Minor vans and by other utilities.
From personal experience I can verify that it did, indeed, improve fuel comsumption but at the expense of attainable maximum speed and general top end performance.

"You are old when you can't remember what happened yesterday but can recall minutiae from 50 yrs ago with perfect clarity"

Aaaaah! Ian Mc.

Location: Shropshire

I've an interesting one which is a variable air inlet which was tapped into the exhaust manifold and operated by a bendix cable in the outer end which was pulled when the car got up speed(!!!). The guy who let me have it as a curiosity when I bought some A7 spares from him said it worked brilliantly. The car would surge forward and go much faster. When the speed dropped you would push the cable back in. He stopped using it as he was burning out valves on a regular basis. If I can dig it out from the back of the workshop I'll post a pic.

Location: Shropshire

Didnt some modern cars introduce air into the exhaust to "afterburn" the gases and clean them up?

Steve

Location: Shropshire

Steve.

Yes they did / possibly still do. This was not common practice for UK spec cars, but there are quite a few imports with a small air pump to achieve this. There is a Subaru one which looks ideal to use as a supercharger on a 7!

Exhaust gas recirculation is used on most modern cars to help clean up combustion for the cat to work. This is one of the reasons cars around 8 or 9 years ago sudenly wern't as powerfull or as fuel efficient as they had been! A small amount of exhaust gas is mixed with the charge, this raises the temperature of the charge and slows the burn rate. All part of a closed loop engine management system, where induction and ignition timing are constantly monitored and adjusted using knock sensors and at least one Lambda sensor in the exhaust.

I have simplified this slightly and written this from memmory, so please excuse any minor errors!

all the best

Stuart.

Location: Devon

PS

Sorry I didnt explian that very well!

The exhaust gas slows the burn, allowing higher compression ratios and leaner mixture without the engine knocking (pinking)as well as a more thourough burning of the fuel.

Location: Devon

Stuart, yes EGR valves are also a troublesome area on some cars!
Back to Austin Sevens and more on topic, I thought about fitting an air filter now I have the SU fitted and considered piping the engine valve chest breather into it (with a seperator to remove oil) to cut down on fumes.
The subject of inlet design is interesting and certainly the shape and temperature of the walls can effect the fuel delivery so maybe this device would work in a manifold that was poor to start with? Of course such mods in more modern machinery are derided as spoofs or snake oil because the modern components are optimised more and therefore there are little if any gains to be had. Our more crude cars tend to respond better to stuff like this given there inbuilt deficiencies.

Steve

Around 1960 I had a device from my father's collection of bits and bobs which had an adjustable spring loaded valve on an air passage to the side of a flange which fitted between the carb and the manifold. This could be adjusted to admit extra air when there was manifold depression. I did not use it for long because I did not find any benefit, probably as a result of keeping my foot down most of the time! I seem to remember plenty of bangs in the silencer on the overrun.

Location: Cottenham, Cambridge