How to make a car more fuel efficient?


It ain't broke, don't fix it!
Registered Senior Member
First of all, it's important to note that the way a driver drives has great influence on the fuel economy of the car. That, and making sure the tire pressure, engine/transmission fluids, and air filters are all maintained and clean.

That said, I'm wondering what ideas people have for making a car a good deal more fuel efficient. I'm thinking along the lines of more crazy mechanical trickery then simply maintaining the car correctly and driving nice and granny-like.

And so, sci-forum gear-heads, I ask thee to go nuts here. What could one mechanically do to a car to make it more fuel efficient without severely sacrificing it's utility (cutting hunks of the ceiling out or something). A few ideas I had...

#1: Put a performance-grade oversized air filter. Sounded like a good idea, and would improve power output, however from what I can tell from online reports, fuel economy is not improved very much, maybe a percent or two. This might because while a bigger filter would allow more air into the engine, it doesn't remove the fact that it doesn't take too much of the engine's power to begin with to suck air through the filter in the first place.

#2: Undersize the wheels and lower the suspension. Lower to the ground, a car should have a little less wind resistance, while smaller wheels at higher pressure put less rubber on the road, reducing rolling friction.

#3: A big freaking tappered cone at the end of a car with a non-aerodynamic tail-end. Not exactly what you'd think of as a sexy car... but hey, what can you do...

#4: Bolt an electric motor somewhere in the drive-train, make a coarse hybrid system of some kind.

I dunno, go crazy, think of somethin!
Disagree with some of the stuff you said, but not smart enough to counter argue it.

I was told that one thing you can do, particularly with large engines is to get an aftermarket chip. You can get a huge increase in millage and power with some.
Make it as light as possible. Don't cut the frame or outer panels, just remove or unbolt everything that is not needed. Tear out sound deadening material. Remove the passenger seats. Fashion fairings to cover the rear wheel openings. Attach a flat sheet of plastic underneath the car. Create an airdam in the front, very low to the ground. Cover most of your radiator, you don't need it all. Inflate your tires to the maximum listed on the tire. Disconnect air conditioner. Remove outer mirrors and replace with ones behind the window. Use a lighter weight oil.
Interestingly, I've heard of an idea some automakers are looking to do to the ICE that's relevant to this. Keep a separate tank specially for ethanol. The idea is that, like a hybrid, you only use this more readily igniting fuel when more power is needed.

There are only a few principles you need to follow to make a car super efficient, most of which were already covered.

--decrease air and tire resistance as much as possible
--make the car as light as possible

Once the car is going, resistance is the only reason the car needs any power to keep it going. So in theory you only really need substantial power when you're accelerating, not when you're cruising. That's how hybrids work, and that's how this ethanol hybrid engine works.

So I'd say after you make the car as light and the least resisting as possible, give it a midget engine for cruising, and something separate to give it a boost when it needs gusto, like nitrous or a turbo. That's probably a terrible idea.
how about switching your car to run with bio-diesel?

many online methods and conversion equipment.
haha, thanks cosmic... :p

Just so we know, I'm not actually looking to do any of this, I just thought it'd make a neat thread is all.

I do have a question, scifes, are you talking about getting a gasoline engine to run on bio-diesel? I didn't think that was possible, I thought only true diesels could do that? I'd imagine if I had a diesel, that'd be pretty cool, but being in America, where hardly any diesel's exist outside of large pickup trucks, I dunno... wonder if one could make bio-gasoline...

the ethanol-hybrid idea is kinda cool, only issue I could see (minor issue) is that unlike the home-brewing of bio-diesel, home-brewing your own ethanol is pretty illegal here :-(. I would love to have a car I could fill up with moonshine though :)
next step in hypermiling

we have the opportunity with all the high tech equipment available to ramp up gas mileage. They're have/or are working on smart GPS systems which will tell you when you're near points of interest. HOW about dropping in the information for traffic lights in your GPS. So, as an example, your 75 metres ( rough 200 feet ) from a traffic light (maybe you can't even see it because its just over the hill ) and you're smart GPS 'sees' that you need to slow down
or end up stopping for the light ( that's wasted energy from braking/more wasted energy ( idling )/ and of course wear on your brakes and tires. Maybe we put a small led strip on your dash and hook the 'Smart' GPS to it. So it tells you about the light back of the gas...coast up over the hill...slowing..slowing...and now just as you get over the hill, the light goes green........nice fuel savings ( brakes/tires too ). Of course the game gets really interesting when we move up to hybrids. They have regenerative braking. So going with the example I just gave, suppose you hadn't lost enough speed when you hit the top of the hill to slow down enough to miss the end of the red light. Well cut in the regenerative braking. Not as good as not using energy...but you do get some energy back.
How to make a car more fuel efficient?

The cheapest way is:

make sure your ignition system is at tip-top shape. Sometimes the cap on the coil corrodes and hence the spark is not as strong and energy delivered is low.

If you use radios with strong power amplifiers or internal fan for heating and colling - that is have a lot of electrical load, consider a large DC capacitor across the battery. That will improve gas mileage immediately everything being same. You may see 10 to 15% improvement. I did.
Magnet on the fuel line!!! Magnet on the fuel line!!!

(it is also good for backpain)
I never got the whole thing about spark plug efficiency or what-not. From what I was told, as lond as the spark plug makes spark, it makes a spark, setting off fuel, so who cares how much power is in the spark unless you've got a cylinder that's obviously not firing? I had the understanding that the true high-end spark-plug wizardry was more to dampen the radio interference from the ignition system, is this wrong?

Also, why would a spark system with less resistance make for a more efficent engine? Wouldn't this imply more current draw for the same voltage, and hence more power consumption without any real gain?

I really don't know, anyone want to fill me in, that'd be great. :D
Spark plugs need to provide several functions to the cylinders:

Higher energy to burn fuel efficiently
Distribution of sparks to cover the area
Consistent energy for each ignition
Temperature of the ignition
Single jolts like a clean pulse per stroke

That is why you have to make sure all thse activities happen. I have used platinum spark plugs for the last 20 years and they work great. There is no difference between a Platinum and an ordinary spark plug for the first 3000 miles. But after that Platinum spark plugs provide consistent spark energy level for a long time.

Ignition weakness or functions depend on

Quality spark plug with right gap size.
High Voltage wiring system - they degrade and leak over time.
Connection between HV wire and power transfer
Quality and condition of the Rotor and Cap
Coil voltage and consistency of that voltage per stroke
Energy transfer efficiency and power (VI) of the coil

and so on
I really don't know, anyone want to fill me in, that'd be great. :D

Try to start an engine with a very dirty spark plug. It keeps firing without actually burning the gas. Not very efficient, is it?

So whenever gas leaves the engine without burning because of insufficient ignation or bad timing, you are wasting gas and it comes out of your muffler in liquid form...
ahhh, I assumed that if there was any spark at all in the fuel-air mixture in the cylinder, it would ignite. Kinda counter-intuitive to think that even a tiny spark couldn't set it off, but hey, it must happen!
Also, the size and speed of the spark also count. The newly designed plugs make better sparks thus they burn the gasoline more efficiently and faster.

Another simple trick to make the car more efficient is to keep the windows closed, and not running AC.... ( I know)
Make it ligher. A bicycle and rider get the equivalent of 650 mpg. Although the fuel cycle is much more efficient than an internal combustion engine, the coefficient of friction isn't all that great. But when you put a decent faring around bike and rider, particularly if it's a recumbant, the mpg is approximately tripled.

So consider that an upper limit, and also consider why: A modern, high-tech bicycle weighs 10 to 12 pounds with tire pressures arond 120 psi. Thus, there's absolutely minimal rolling friction.
So apparently a typical sedan must overcome some 100 lbs. of rolling friction, read the number at work, not sure from where. As it is rolling friction, this 100 lbs. remains that force at any speed, so that the sum of the force on a car is this friction plus air resistance, which can build up to about as high at highway speeds.

Sounds like cutting back the rolling friction of today's typical car would do wonders for fuel efficiency, but I gotta wonder what the tradeoffs are. Quicker wearing out of bearings? A weaker suspension system? Harder tires with poor handling and comfort?
You could use advanced bearing systems to reduce the rolling resistance. They have been using the same grease and metal bearing for the last 50 years.