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Things I've done to make a car more economical in fuel

Before I tell you about the crazy things I've done to make a 40 miles per gallon car do 80 miles per gallon, I'll put this in perspective. It was in the late 1970s and it was a basic car of the time, an Austin A35 van, contemporary with the Morris Minor. This was long before speed traps nonsense, and long before car engines included fancy "engine management" black boxes or other dodgy secret proprietary stuff to stop you being able to do your own maintenance and custom adjustments. I was a student, of engineering, and later computer science. If you dare to try the sorts of things I'm telling you about, on your own risk be it!

I knew the Austin A35 van was never going to be the fastest or the sportiest or the most swish-looking of vehicles, but I knew I could make it excel in a different field, that of fuel economy. This also fitted nicely with my ideas about careful with money!

The best modification I made to the car was the unorthodox change to the choke control. On cars of that period, if it was very cold and would not start, you could pull out the choke, like a stop on a church organ, and it would put more fuel into the engine, giving it an extra chance to start, without having to resort to getting the starting handle out and manually cranking it over. (The obviation of starting handles on modern cars is, I feel, a retrograde step). Anyway, the choke would normally be used for putting more fuel into the engine. It was also well known that if you accidentally left the choke out when driving around, it would be a terrible waste of fuel. So, what I did was to turn that idea on its head by adjusting the cable on the choke so it was in effect possible to push it in further than the normal end-stop.

The newly adjusted choke cable gave me the ability to put LESS fuel in than normal. This "negative choke" effect worked very well, although it required a bit of extra skill in the driving, as the engine could not idle in that mode, and it required continuous nursing along to keep the now manually controlled air/fuel ratio about right. The result was a lean burn engine! OK, it got a bit hot, but I drove at moderate speeds, and I watched the temperature as well as the oil, so I could control it. In some ways it was as if the engine was running on fresh air, as the amount of fuel an engine really needs is a lot less than it is normally supplied with! Someone said the over-egging of fuel in normal cars is done to keep the engine cool. I consider that a waste of fuel. So, lean-burn it was! (My ability to use the unorthodox choke soon became second-nature, and the process just ran in parallel).

It's a known fact that if you drive around with tyres that are halfway to being flat, you'll waste a lot of fuel. So, I did the opposite. I pumped those tyres up to well over the correct pressure and drove around with the car virtually bouncing around on tiptoe. At one point I had dared to put the 25psi rated tyres up to 50psi. This is of course dangerous, but most of the actual danger comes from the assumption that the driver will drive at 70 or 80 mph. I drove at more like 40mph, so it was nowhere near as dangerous as might be assumed. Admittedly the downside was that the super bloated tyres tended to get worn more in the middle of the tread where it was blown up like a balloon. However, I knew that if the tyres needed replacing, it was always possible to get some from scrap cars without much cost, and this would easily be covered by the fuel saving.

You can see that some of these ideas were particular to the time and to my own circumstances. They don't hold true for everyone. So, if you like to speed, or you don't happen to have a readily available supply of old tyres, you are better advised to keep the normal tyre pressure!

However, one thing with tyres still holds true: The Tracking. A bicycle has no tracking issues because it's only got one front wheel, but a four wheeled car has two front wheels which are locked to roll along parallel lines. What if they are out of adjustment and aren't truly parallel? Then, it's like the wheels are cross-eyed, either pointing inwards or outwards. This causes unnecessary wear on the tyres and wastes fuel. Hope is at hand, however, as many garages will perform "free tracking check!". They are onto a good thing, as almost everyone's tracking is off-true, and there is a small charge for correcting it. Well worth while spending the money to save more than that in fuel.

If you are too mean or too shy to go and get your tracking checked, you can test it yourself by putting some multiple sheets of cardboard on your driveway and running over them to see how they shift. Then use a pipe-wrench to tweak the track rod ends. Well if you want to get covered in muck just to save that much then it's up to you. Even I would go and get a garage to test it, and I am the meanest stingiest person I know!

On a later vehicle I saved more money by replacing the wheels with bigger ones. By then it was a Leyland EA Post Van, and instead of the standard 14 inch wheel hubs, it had 16 inch wheels which came from a bigger vehicle. This meant the machine did ten inches more distance for every rotation of the wheels and improved the economy of the vehicle greatly. It also improved its top speed, though obviously not at the same time!

Of course what would really save money on fuel is to have a Miles Per Gallon Meter. I had considered building such a thing, but considering this was in the 1970s, when if you wanted a computer you had to solder it together yourself, write the computer programs yourself, and load them with a portable cassette recorder, it was considered tricky. The trickiest thing was the display, as the legal system had outlawed any kind of fancy digital displays on the basis that they could be used for watching television while driving. Anyone with any sense at the time knew this was yet another case of the law being an ass, and retrospectively it all seems preposterous now in-car sat-nav is commonplace, but I kid you not; having a computer display was illegal on the basis you might watch telly on it!

Now that the setup has grown up a bit, if you want to build a Miles Per Gallon Meter, the technique is to gave a fuel flow meter on the fuel line (you need two if it's a diesel as you need to subtract the return flow rate), and a rotation rate sensor on the prop shaft. The computer these days would be an embedded Linux system so that's easy. The computation requires the continuous recalculation of distance covered during a small interval divided by fuel used during that same interval. Then the result is displayed as the actual running Miles Per Gallon. Once constructed, the instrument needs to be calibrated using a burette and your local Standard Mile which the council uses to test taxis.

If you like metric, a constant can be included and recalibrated for kilometres per litre, metres per gramme, or whatever you like.

Miles Per Gallon meters save money because when you are driving you soon learn what kinds of driving behaviours optimise your fuel usage.

I'm considering a similar thing for household electricity usage, which would also save a lot of money, (and the environment). Update: econometers are now (2012) becoming commonplace and are being given away by electricity companies such as E.ON and Southern Electric

Anyway, back to the old Austin A35 with it's nine hundred and something CCs of engine capacity. I got a torque wrench and tightened the bolts on the cylinder head to just a bit more than the normal amount, very carefully and evenly. This, and having no air filter, also helped in the improvement of fuel economy.

Fuel economy in a car is not just about the mechanical engineering, but the way you drive. I could see a lot of fools on the road swerving and overtaking and then having to put their brakes on to slow down for corners and roundabouts. But I realised this was unnecessarily wasteful, and I drove at an almost constant pace, anticipating the road conditions way ahead, so if I knew there was a reason to slow down ahead, I was already slowing down long before it. I didn't slow down for roundabouts much at all, and could pre-empt the slots up front so as to be able to cross over without my path crossing anyone else's. I was my own air traffic control.

When I say about "slowing down", I'm not talking about putting the brakes on, or the conventional stuff where the engine is used as a slowing down device with the gears. I would just put it into neutral and coast along. Where there were long downhill slopes I could coast along for miles. In such situations the engine could be turned off.

(Besides the fact that you need to be a better driver to get away with this anyway, the technique must be avoided on some later cars because if you turn the ignition key fully off the steering will lock* and you can end up in a ditch! In contrast, the earlier cars just had a switch which you could turn off).

Incidentally, if you feel like criticising me for driving in neutral and using no fuel at all for miles and miles, and being able to drive confidently and safely in that way, please don't. Glider pilots do it all the time.

For extra style, starter motor electricity was saved by perfect timing at the end of a slope, the ignition being turned back on and then the momentum of the vehicle being used to bump-start the engine back into life.

Most of the time, these tricks were performed almost completely invisibly without other drivers on the road having any idea any of this was going on. I'd see someone overtake me just before a hill, which I knew from memory was there, by which time I was already in neutral and with the engine turned off, and then I would be able to coast down the hill keeping a safe distance from the other driver, watching them put the brake lights on again and again and know their engine was still burning up fuel.

Talking about fuel, I also did some experiments into burning stuff other than 4-star petrol. Paraffin and alcohol come to mind, and as it's a known fact that an engine can cope with ingesting small amounts of water, I even tried collecting up all the slops after a party and putting that in the fuel tank. Surprisingly this worked, although a later attempt to run the car on stale beer failed as there was not enough alcohol in it to catch fire. This was slightly embarrassing as I had to clean the beer out of the float chamber while stranded at a road junction. This did not take long, as I'd experimented on that engine so much I knew how to perform such operations quite quickly.

In terms of a non-experimental workable solution for burning sub-standard fuels, it helps if you can pre-heat them and/or only switch them in after the engine has already been fired-up and warmed-up on conventional fuel. Much more about this is going to be added under the subject of Alternative Fuels

Gas, not gasoline, but propane gas, was another interesting automotive experiment I tried. I had acquired a gas carburettor off a fork lift truck, but this proved to be a bit limiting in terms of air flow capacity, so I did some further tests and found I could power the car on propane gas without a carburettor at all! The gas cylinder was placed on the passenger seat, and the pipe from the regulator went straight into the input nozzle of the empty air filter case. By continuous careful adjustment of the gas valve I managed to drive around without using any petrol at all. This level of manual control of a system is pretty good especially when you consider I was also manually adjusting the air/fuel ratio by the specially modified choke as well!

The problems with burning gas were twofold. For one thing, the cylinder of gas would form ice crystals and this tended to slow everything down, but worse, the cost of the gas was worked out to be more than the petrol would have cost. Maybe if a more efficient carburetor system had been used it might have been better! Nevertheless, the fact it was proved possible to drive sixty miles using a gas cylinder off a cooker, in a car which expected liquid fuel, made it a partial success.

Both propane and butane worked well enough to run, and the hope was that it might be possible to run the car off methane. "Running a car off methane" is a polite way of saying "running a car off shit", as it is a known piece of technology by which, just by having two giant pressure cookers on your garden, full of shit, and a big dustbin with a desiccator element in, you can have a free supply of fuel! Pure natural gas. Local chicken farmers were quite interested in the idea, as at the time they were having to pay good money to have the shit taken away!

Another good idea for using fuel which other people were throwing away was the notion that instead of refuelling at filling stations and paying for petrol, it would be possible to refuel at fish and chip shops and power the car by burning the waste fish and chip oil. Fish and chip shops need to have a complete oil change every six weeks, so I heard, and I had high hopes of coming to a deal with enough fish and chip shop proprietors along my usual routes of travel, so that I could conveniently refuel at mutually convenient times. The downside was not merely that there were no Green Shield Stamps on old fish and chip oil, but that I was unsure of the method by which to convert the engine to run on this unusual but renewable fuel. (It has later been found that if it's a diesel engine, it will run on various types of vegetable oil without much modification. This leaves the only snag being, as usual, the UK government. See this explained further under the bio-diesel section of Alternative Fuels).

I'll include an extra few theoreticals, as these may be worthy of additional research:

Liquid nitrogen. Powering an engine off liquid nitrogen is an interesting novelty as the engine runs cold. So, instead of steam coming off the radiator the machine runs at minus 196 degrees Celsius. For practical purposes the problem is that the entropy issue involving making the liquid nitrogen costs more than the fuel would have done. If you'd like to try this, a liquid nitrogen powered engine is in effect a steam engine, so the camshaft needs the same type of modifications.

Steam. The nice thing about steam power is that you can run the vehicle off anything combustible you happen to find. This is a great advantage in terms of running costs, but this has to be tempered with the fact you need a willing passenger to keep stoking up the boiler with whatever junk you've got piled up in the back of the car. Although steam engines are not as efficient as internal combustion engines, this fact becomes irrelevant if you can get renewable combustible fuel at no cost. It has been calculated that if you have an acre of renewable forest, the harvestable wood is enough to keep a car running, and the fuel will never run out. In comparison to petrol, ie OIL, nomatter how efficient the engines are, it's going to run out.

To convert a car engine (four stroke) into a steam engine, you need to change the valve timings completely, which involves custom building a new camshaft. So, instead of the conventional "suck, squeeze, bang, blow" four stroke cycle, it has a more organic steam type "breathe in, breathe out" mode of operation. Oh, and you also need to have a much stronger air inlet manifold (as it's now working at high steam pressure), and a boiler, and a fire under the boiler which needs to be stoked up. I'd advise against burning coal, as it's not renewable, and instead it's better to burn various waste. This is not as silly as it sounds, and I have been burning gambling machines to save money for quite a while!

You have been reading this interesting review at Zyra's website (zyra.org.uk), a resource worth bookmarking as it contains loads of fun like this, as well as some helpful shopping and advice sections.

For further reading, see the Alternative Fuels page, and How to Save Money. If you'd like to see more about cars, we have cars. Some of the items available are more socially acceptable to the sane mind than some of the things on this page. If you think this is all too crazy and you'd like to see a more sensible page about saving money on motoring, even without having to make strange augmentations to your engine, see Saving Money on Car Running Costs at Stamp Demon

If you try some of the crazy fuel saving ideas mentioned at Zyra's site, good luck! Also see Inventor Resources

Almost forgot: If you modify your car, the time to tell the news to your insurance company is now, not when you need to make a claim! Some car insurance companies are much more fussy and finicky than others about such minor details as the fact that you're now driving around powered by methane gas, steam, or whatever. Some insurance companies are more open minded than others, so shop around!

* Turning off the ignition key on early cars just turned off the ignition, allowing the vehicle to coast along in neutral. Some later cars had multi-position key locks. You had to be very careful to avoid moving the key all the way into "park" mode as the steering could lock, which would obviously be dangerous! There was sometimes an inbetween position which was safe, but it's up to you to check these things on your own car. I've also heard that on cars with power-assisted steering, if you turn off the key, the power is lost from the power-assisted steering, leaving it very stiff to turn the wheel. Such stiffness is NOT present in cars without power-assisted steering. The steering wheel is reasonably easy to turn, as the steering is built to be manageable. A similar problem exists in modern cars with "power assisted brakes" which go all soft when the engine is not running. In the old cars, however, there was no such problem! Also, the old cars had a starting handle! Various of the fancy features in cars can be circumvented and replaced with more techie-friendly variations, for example getting rid of the keyswitch on diesel engines and having a manual preheater circuit, having no steering lock, and having any powered steering pump powered up via an independent switch. If vehicles were initially made with more considerate design, it would be possible to do more modifications yourself. Engine management systems are a particular problem and need to be hackable. It's important to encourage hacker culture, for various good reasons.