Fuelly Forums - Found another air filter test, some exhaust discussion, etc

https://www.autospeed.co.nz/cms/A_111486/article.html

This one sets out to prove that a drop-in high-performance filter element (K&N, etc) does not affect power in the OEM air box. Surprising results take it further, showing that an old dirty filter is no worse than a new filter, and that entirely removing the filter is barely any different from even the dirty filter.

They use a pressure gauge to measure on both sides of the filter...

Quote:

In normal cruise, the gauge shows a pressure drop through the whole intake of 5 inches of water ? very little.

At full-load, full revs, that rises to 20 inches of water, which is getting too high for max power development.

{but the filter is old and extremely dirty}

In went the new filter and onto the road went the car. And at maximum power the intake restriction remained exactly the same ? 20 inches of water.... The brand spankers new clean filter made no difference to intake flow over the old, filthy filter. Y?see, that old filthy filter still flowed very well...

But aaah, you?re saying. What about without the factory filter in the box at all? Well, we did that test as well and if we were paid for imagining things, we might have seen a fractionally lower peak pressure drop ? say, 19.5 inches of water...

To put it as simply as possible, there?s no problem with the flow of the factory filter ? even when it?s dirty.

And we?ve seen the same story on everything from an Audi S4 to a Subaru Liberty RS to a Nissan Maxima V6 Turbo to a Commodore VL Turbo to a Honda Insight to a Toyota Prius to a....

In nearly all cases, in a standard or only slightly modified car, it?s not the factory filter element which is causing the restriction. Instead, it?s likely to be the snorkel going into the airbox, or even the shape of the airbox itself.

Here's an article from the same site on flow/pressure testing for intake and exhaust:
https://www.autospeed.com/A_111109/hD...s/article.html

A good idea is presented: Rather than spend big bucks on aftermarket high-performance stuff, you might try getting OEM stuff from a more powerful vehicle, which you may get cheaply or free.

Interesting FE projects, some of which have been posted before:
https://www.autospeed.co.nz/cms/A_111509/article.html
- Air conditioner controller, not much use for us here as presented but easily modified for different inputs
- DIY oxygen (O2) sensor/Air Fuel Ratio (AFR) monitors for narrowband and wideband
- "FuelSmart" which is claimed to (approximately) show BSFC so you'll know if you're being too light on the throttle

DIY AFR meter in more detail: https://www.autospeed.co.nz/A_0217/cms/article.html
DIY Open/Closed Loop monitor: https://www.autospeed.co.nz/cms/A_171...popularArticle

Every time I look at that site, I find more and more interesting stuff.