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Understanding Turbo Boost

Created on 2011-03-09 by IPD Staff

What is boost anyway?

If you have a boost gauge on your turbocharged car you’ve probably watched that little needle swing all over the place and wondered what it is telling you. If you have a turbocharger car without a boost gauge you’re missing out on all the entertainment.

Boost is the term that people use to describe the air pressure in the inlet manifold. This pressure is essentially the force feeding of air into the engine. An internal combustion engine is an air pump with a little fuel thrown in. In order to burn fuel and make power, air has to be present. The ratio of air to fuel has to be within a specific range. What this means is that you cant just put in more and more fuel in order to increase power, you have to put air along with it. With a non-turbocharged (or supercharged) engine, the amount of air the engine can ingest is the amount that atmospheric pressure can push into it. That explains why engines of this sort make less power at higher altitude. The atmospheric pressure is less and therefore the airflow into the engine is less. With a turbocharger installed, the heat of the outgoing exhaust is harnessed to run an air compressor. The air compressor can increase the amount of air the engine ingests by compressing it first. More air, more fuel equals more power. The amount of this pressure is a function of your right foot. The more you lean on the gas the more the turbo comes into play.

Does all this extra power consume more fuel? You bet it does. So here's the punch line. A boost gauge is a great monitor of how much power the engine is making and also what kind of fuel economy you can expect. You can use it like an economy gauge. Less boost is better fuel economy, more is just the opposite.

So lets summarize: less is more, more is less. Probably only makes sense to an economist.

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