Would Changing the Exhaust on a 2.3 Ford Ranger Help Performance & Gas Mileage?

The Ford 2.3-liter four cylinder is one of those unsung heroes of American performance. With performance potential belied by its diminutive proportions, this motor might rightly be considered the genesis of the modern high-performance four cylinder as we know it today. From dirt tracks to drag strips, from road courses to car shows, the 2.3-liter's performance potential is limited primarily by its builder's pocket book and vision.

Four-Stroke Engine Basics

The Pinto 2.3-liter -- as it's known amongst Ford enthusiasts -- is a four-stroke, overhead-cam engine. The first stroke is the intake stroke, where a piston dropping in the cylinder creates a vacuum to suck air and fuel in through the intake valve. The intake valve closes and the piston goes up to compress the mixture. The spark plug (or plugs, for a Ranger) ignite the mixture for the power stroke and expanding gases shove the piston downward. The exhaust valve opens and the piston goes back up to shove those used gases out of the cylinder.

Exhaust Flow

Engine displacement is a fluid thing, dictated by far more than mere static factors like bore and stroke. For most engines, around 20 to 40 percent of the room in the cylinder is taken up by used exhaust gases instead of fresh air and fuel. That means an instant 20 to 40 percent drop in effective displacement, and an even more drastic drop in power. Exhaust gases don't just take up space in the cylinder; they're also very hot, and every moment that they spend in the cylinder head instead of the exhaust imparts that much more heat to the cooling system and the combustion event.

Performance

Regardless of the engine, a better-flowing exhaust will always make horsepower over a poorer-flowing exhaust. That's not even a question. The question is how much power the exhaust will make, how much of it you're replacing and where you expect that power to occur in the rpm band. The ideal would be to just remove the entire exhaust system and replace it with a single tubular race header; a 1.00-inch inside-diameter tube measuring about 36 inches in length will put you in the right range for a street engine that won't see more than 5,000 rpm or so. For a 7,000 rpm screamer, you'll want pipes measuring about 1.4 inches in internal diameter and about 26 inches in length. Past the header, anything you do will decrease power, including bolting a catalytic converter to the header or installing an exhaust pipe and muffler.

Fuel Economy

The same principles that apply to horsepower apply to fuel economy, at least insofar as efficiency and cylinder filling are concerned. Hot exhaust increases in-cylinder temperatures; not necessarily a bad thing within certain limits, but the temperatures encountered here will do nothing to enhance efficiency. A larger-diameter exhaust pipe, high-flow muffler and high-flow catalytic converter -- where legal -- will always free up a bit of fuel economy, but be careful where header selection is concerned. The short, fat header pipes that enhance your high-rpm horsepower will kill torque at low rpm, and that's what you need for fuel economy. For torque at 2,500 to 3,500 rpm, you'd want to use equal-length header tubes measuring a tiny 0.75 to 0.80 inches inside and a massive 65 to 75 inches in length. That's the ideal, anyway; 75-inch-long pipes aren't exactly practical in the real world. The point is to go for very long, thin header tubes for max fuel economy, and short, fat tubes for maximum horsepower.

References

• "The Ultimate American V-8 Engine Data Book"; Peter Sessler; 2010
• Turbo: Real-World High-Performance Turbocharger Systems"; John Pfansteihl; 1998
• The Ranger Station: Ford Ranger 4-Cylinder Lima Engines
• Wheelspin.net: "The Four Cylinders of Fury" 2.3 Liter Resource Page
• Wallace Racing: Header Primary Calculator