How does an air intake improve performance if the engine inlet size is not changed?

Dominic-Toretto

Dominic-Toretto

Dominic-Toretto

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Title really,

Say you have a car that is mildly tuned. If you are changing only the filter to one with a bigger internal diameter and keep the stock intake tubing and engine inlet, how does this increase performance?

Does shoving more air in to the intake increase velocity of the air as it goes down to the inlet, can more air even fit in to the stock piping / inlet?

I understand the idea of intakes that relocate to pull in colder air, as colder air is denser and heavier, allowing more oxygen to enter through the inlet in the same volume of air and increases velocity. But as a above, on a non relocated intake, how does increasing the size really help? If at all
 
Many say it doesn't :D

For any worthwhile gains you'll probably need to fit a better exhaust (full exhaust, not just a catback) and get it tuned as well though.
 
Arguably it doesn't.

I remember seeing some testing of Golf GTI intakes on a flow bench and even upsizing all the intake pipework doesn't make massive flow gains - the sort of stuff you'll only notice when you're pushing the tuning to the limit.

In a lot of cases, intakes are more about the noise than the performance.
 
I imagine a larger surface area of filtration will allow better airflow, also the length and diameter of the pipework can be modified to create a venturi effect which aids airflow.

Gains are usually minimal but the induction roar tends to please people.
 
If it flows better then it has to be more porous. A bigger surface area will only stop it getting clogged as quickly.

But if you want the best sound, get one of the stainless steel mesh filters :D
 
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Making the air easier to draw in will make it flow faster. Same way as lifting up the back of a laptop from the table will make it run cooler normally as it's easier for the fans to draw in air.
 
David Freiburger and the Steves (Brulé and Dulcich) did sort-of test this on Engine Masters. A lot of the air filters they tested were a heavy restriction on the engine that they were dyno'ing. And even without touching the intake, carb or heads they were able to gain power just by using a filter and/or housing that directed air down the carb venturis (like with velocity stacks - an unfiltered velocity stack made five more peak hp than having nothing at all on top of the carb).

Engine Masters episode 27 if you have Motor Trend On Demand (think they're still doing 14 day free trials as well).
 
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