How Much More Power Will A 3-Inch Exhaust Give Compared To 2.5-Inch?
We all know a wider, less restrictive exhaust should give more power, but how much difference does the jump from 2.5 to three inches give? The Engine Masters guys from Motor Trend performed some tests to find out
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They also mentioned how much richer it was running with a 2.5 than open. I wonder how much of that power might have been regained had they tuned the carb too.
According to women that half inch matters quite alot…
Ech! This truely works with carburator engines but on a modern engine with LH-Jettronic or newer technology it wont make a difference, since the exhaust back pressure is saved in to the E-EPROM and if you fit something like straight pipes or a low cell cathalysator or like in this vid a different muffler, my friend! I have to tell you that you will barely make any more HP, in most cases you loose Power, except you are a Programmer that actually knows how to change the data on the control unit, then the engine might benifits from it and you will notice an actual power gain.
Kids, this doesn’t mean a three inch pipe will make your 1.6ltr hatchback go faster.
2.5℅ more power at the crank, that is negligible for street use. Then, if you consider that this is a HUGE engine, the effect to “normal” cars should go towards 0. So, it is a lot of noise for very little power 😑
It’s so funny seeing rednecks trying to do science and how they easily disproved (in their mind) back pressure.
Their blinding me with science
TL;DW?
3 inch made more power, about an extra 10HP over the 2.5
But what’s the equation to calculate the ideal exhaust cross-sectional area for a given engine?
I can say from experience a 3 inch exhaust on a turbo Silvia makes a huge difference. A good quality full turbo back exhaust on an S15 can give impressive gains.
A naturally aspirated 2 litre engine might not see gains from a 3” exhaust, but a turbocharged one sure as hell will.
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