I was wondering if anyone knew any small modifications you can do to your engine to increase your MPG such as adding an aftermarket air intake or exhaust system? I get excellent mileage out of my D15B7, but it would be great to save even a little more at the pump with gas getting as high as they are. Any ideas or suggestions?

 

No modification really increases you gas mileage. Adding an aftermarket intake is a debatable subject. The only thing you can really do is drive slower and keep your RPM's low. If your really serious about your gas mileage investing in a ScanGuage II would be good. It just hooks up to an OBD II port but I see you have a 95 Civic so that wouldn't work for you.

 

HAHAHAHA. No real modification really increases your gas mileage! What a joke!

Of course it does. Change the efficiency of your engine and you can see real world gains. The D15B7 is my personal favorite, little 1.5 Liter just sips gas. I once got my old 93 Civic D15B7 getting 65 MPG (63 MPG average). I once drove it 95 miles on just $2 in gas!!! Of course stating that is always SOOOO controversial. You make your engine more efficient, especially with intake and exhaust and correct tires, advanced timing, lean fuel/air mixture, double platinum tipped spark plugs, etc., and you will get much better gas mileage AND performance at the same time

 

Fuel economy and performance don't tend to go hand-in-hand on engines without DI. In the simplest terms, performance is directly related to how much air (and consequently fuel) you can cram into the combustion chambers and blow it up. The more fuel you need to reach an ignitable AFR, the worse fuel economy you're going to get. Keep in mind that efficiency and performance are completely different animals, and engines have an rpm range where they're most efficient. Sit at the right engine speed while cruising and you'll see huge improvements in fuel economy.

And with the fluctuations in gas prices, saying you drove 95 miles on $2 is (intentionally) misleading. Five years ago, I could fill my civic from dead empty to completely full, pay with a $20, and get change back. Now if I throw a $20 down I'm getting well under half a tank ('01 mustang, 14gal tank vs '94 civic, 12gal). That's not even touching on the subject of price variation depending on location.



OP, you could always lower the car assuming you're talking highway mileage. Air going under cars causes a massive amount of drag (that's why most cars made in the last decade or two have at least partial underbody panels. It's also why trucks and SUVs get such terrible fuel economy; it really has less to do with the engine size than it does with ride height.) and the lower you make a car, the less air goes under the car, causing less drag and better highway fuel economy. There's also the (very cheap) option of simply getting plastic sheeting and smoothing out the underbody of your car as much as possibly, especially around the rear bumper. Again, this would be drag reduction, not engine efficiency.

 

Not intentionally misleading. It was 2 years ago, when I had my 93 civic. :P I knew someone would get their feathers ruffled. The only cars that I've heard that beat mine in MPG are the 80 MPG Diesel Volkswagon and the Aptera Wingless Bird

 

i read about getting new spark plugs and increasing gap by 20% or so... if i buy premium spark plugs, is it really worth the investment to buy new wires.. buy then right away??

also, how would i go about increasing the gap of a spark plug?

 

Q also, how would i go about increasing the gap of a spark plug?

A. I use a flat head screw driver. easier than screwing in a light bulb.

 

Something to bear in mind in terms of mileage is driving habits, of course. Aside from the obvious strategies that we all know, an unusual one to be aware of is your usage of the brake.

Every time you use the brake, you nullify energy (momentum of the car) that you created by using gasoline. Obviously, you have to use the brake in order to get from Point A to Point B safely, but it helps to remember that whatever rolling momentum the car has was (except for downhill coasts) created by gasoline, so you might as well look to make active use of as much of it as possible. Braking more than necessary just means you're throwing away gasoline.

 

Another thing that manual trans owners can take advantage of is coasting with the car in gear, rather than in neutral.

When the car's still in gear, the ECU will cut off the fuel injectors so you won't be using any fuel. When you let it coast in neutral, the ECU just thinks the car's idling, and still feeds fuel to the engine to keep it running.

Although this has been verified by my Scanguage II in my OBD-II car, this is a feature that's been pretty common to most fuel-injected cars within the last 20 years or so.