Everyone's talking about saving energy and maximizing automobile fuel mileage. Something totally non-electronic that I've been using for years, that works to conserve gasoline, is a vacuum gauge. A car engine acts like a big vacuum pump, so if you can monitor an engine's vacuum with your eye, you can moderate a heavy foot.
The gauge I use on my car is a 1950s-style Sears & Roebuck instrument, but vacuum gauges are widely available today, and you can pick up a modern one at almost any auto parts store. I like my antiquated but adequate Sears gauge because it's made of metal and has a colorful 5-inch dial that indicates engine vacuum over a 270° arc. I can glance at it and get instant feedback.
If you want a modern one, there's a nice looking unit, for not too much money, on
Amazon.
It was a rather easy matter to connect the gauge to my car's intake manifold, ahead of the throttle plate. On a lot of engines there's a tiny plug that can be removed, drilled, and reinstalled. That's what I found on my car. Once the fitting is installed, a length of small-diameter rubber tubing routed through the firewall connects the manifold to the gauge mounted on the dashboard.
If there is no existing tapped hole, it's possible to find a vacuum line and tap into that with a tee fitting. Worse case, you can make a drilling on the intake manifold. I've done that on one car, using a 1/8-inch bit, drilling slowly, taking care not to drop any burrs or filings into the manifold.
When cruising, I keep the big Sears analog gauge in the corner of my eye, and try to keep it up around 20 inches of vacuum. The gauge has a green sector for high readings. By feathering the throttle you can really keep the pointer up there in the green for a surprising amount of time, without losing performance.
Bigfoot’s LamentIt's startling to see how a heavy foot causes the gauge to drop. Of course, if I accelerate hard, or climb a hill, the gauge drops to 5 or 10 inches of mercury, and if I'm more or less coasting downhill with the throttle plate closed, the gauge advances to 25 inches. But, under normal highway cruising conditions, if I endeavor to keep the gauge as high as possible for as long as possible, I see improved gas mileage.
The vacuum gauge also gives me a reassuring indication of overall engine and automatic transmission performance. If the gauge's reading was low and steady, I'd know there was something wrong that was likely affecting all of my engine's cylinders equally. That could be due to bad ignition or valve timing. If the pointer pulses, it could indicate a problem with one cylinder, such as a fouled or defective spark plug, or a burned exhaust valve, or maybe a bad head gasket.
Low vacuum-gauge indications when a car is idling can point to leakage, usually through an intake manifold gasket, or a vacuum brake booster. Typically, a gauge's needle will drop sharply every time a leak occurs. If the leak is between two cylinders, the drop is greater. In older cars, low idling readings can be caused by worn piston rings. In modern cars, misbehaving vacuum readings may indicate trouble with emissions controls.
Whiz-Bang ElectronicsIf you insist on electronically monitoring your car's performance, and yours as well, you can install something like the $180
ScanGauge Trip Computer from Linear-Logic.The ScanGauge gives you near realtime feedback. In addition to fuel monitoring, it can be used to read vehicular trouble-codes, a useful feature if that annoying Check Engine light starts winking at you.
A more sophisticated instrument is the $535
CAMP2 engine multi-meter from HKS.
The CAMP2 can be configured to indicate many engine parameters derived from a car's standard
OBD-II (On-Board Diagnostic) system. The CAMP2 can even emulate analog-style gauges. If you're more adventurous, it will display oscilloscope-like traces of engine parameters. Just what you need while paying attention to traffic, eh? Oh, excuse me; I didn’t realize you were not watching the gauge while you were talking on your cellphone.
