METRO MILEAGE TIPS (as promised)

[Fatslicks]

So I just filled up my Metro for the first time since getting it last Friday (which is great for the amount of driving that I do). I got 39 mpg out of my first tank, without so much as popping the hood.

What I'm wondering is--what have you all found to be the single biggest mileage increaser? Is it a mechanical mod or a change in driving style? I want to definitely work on some mechanical changes/upgrades, so I'm curious as to what your experience tells you are the biggest hitters?

[dwendt1978]

Adjust the nut......behind the wheel. Is the biggest increase in fuel economy.
Slow acceleration, 45-50mph on back roads and 55 on the highway. No idle time. Proper tire inflation.

These things have made my XFI net 54.55 mpg, 55.82, and 62.5 on my last 3 tanks. And it has 165000 miles on it.

[doug7x]

Disconnect the cold air intake...let it breathe the nice, hot air from under the hood, & advance your timing to 8-10 deg. BTDC...Listen for pinging when hot...you may want to back the timing back a degree or 2 if it's pinging too much.

[Fatslicks]

Originally Posted by doug7x

Disconnect the cold air intake...let it breathe the nice, hot air from under the hood, & advance your timing to 8-10 deg. BTDC...Listen for pinging when hot...you may want to back the timing back a degree or 2 if it's pinging too much.

Why does the cold air drop the fuel efficiency? I used to have a '70 Nova with a pretty snorty 283 in it (kind of the opposite of a Metro), and one of the big performance mods (fuel economy and horsepower) was a cold air intake. My understanding was that the cold air was denser than the ambient hot air in the engine compartment and allowed for a more efficient burn.

Is this a misconception? I definitely noticed a big increase in power and efficiency when I set it up in my Nova. Can anybody explain why ?

[doug7x]

Yep..cold air IS great for HP, but nowadays, with the ECM controlling our mixture, it sees the colder (more dense, more O2) air coming in, & then it enrichens the mixture to keep the ideal gas/air ratio (if I remember it right, 14.7 lbs. of air to 1 lb. gas). The warmer the air is, the less gas it will take to keep your ECM happy. This is also ONE of the reasons we get so much better mileage in the summer than in the winter.

[Fatslicks]

That seems to make sense--a carburetor squirts in the same amount of gas whether it's hot or cold, so if the air is colder and denser it will make better use of the atomized fuel that's alread there.

I tried being a little more conservative with my driving/shifting on this last tank of gas and went from 39mpg up to 42.5mpg. Not too shabby. I'm planning on driving a few more tanks before I start doing any mechanical mods (just to get a good average baseline). I really appreciate this forum. Virtually all of the questions/answers that I've read here seem to be genuinely helpful and with some experience and knowledge behind them...not something you see on lots of other forums.

[doug7x]

UPDATE ...since I replaced the timing belt & re-set my ignition timing to 9 deg. BTDC (was at 11),...last 3 tanks were 58.4, 58.4, 59.1. WITH THE A/C running about 1/2 the time. (it's been hot in the Chicago area) I DO BELIEVE that 9 deg. BTDC is the optinum setting. (& it doesn't ping anymore) What do you folks think?

[Woodie83]

The optimal setting is as far advanced as possible without pinging. Every car, engine, tank of gas, driver, weather conditions, geographical condition is different.