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Here’s Why Dyno-Testing Intake Runners Makes a Big Difference

Listen to a Toyota 4A-GE go through some old-school engine tuning.
Garage 4AGE Youtube

Engine science isn’t quite a lost art, but it’s something that is much more understood than it used to be. Now, engines are incredibly talented at everything thanks to innovations in combustion technology, variable valve timing, and engine management. But there once was a time where old school tuning went a long way, and this video of Youtuber Garage 4AGE testing several intake runners proves how big a difference small parts can make.

Using a built 16-valve 4A-GE in an ‘80s Toyota Starlet as a testing bed, Garage 4AGE went through the tedious but strangely engaging process of testing various lengths and diameters of intake runner to determine whether or not a variable-length intake is worthwhile. Of course, the 4A-GE is known to us stateside as the 1.6-liter high-revving inline-four that came in the AE86 Toyota Corolla and, once upon a time, was an excellent performance engine. The arena has moved far since then, but the simplicity of the 4A-GE makes it a great engine to experiment with.

Using tubes that fit the maximum diameter of the individual throttle bodies, Garage 4AGE tests every intake length between eight inches and simply having open throttle bodies. Conventional engine wisdom says a long runner will provide more low-end torque and less top-end power, while shorter runners do the opposite. His dyno testing shows that this is largely true, but either extreme is detrimental to performance, and a relatively long runner is actually the most effective. Still, the power difference isn’t dramatic and is only a few horsepower at most.

The most dramatic difference was in the diameter of the intake runners. Almost 30 horsepower is gained by going from a 35mm runner to a 46mm runner. It’s genuinely shocking how much power is gained by such a simple change, something that doesn’t really happen with modern engines. But when you’re talking about 170 horsepower, every last one counts. Sit back and enjoy some high-strung four-cylinder sounds. 

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