Engineering Judgement 101: The Sanity Check

I've documented numerous failures of engineering on this site but this is a new one.  Many were issues where I substituted engineering judgement for a calculation.  In this case, I performed the calculation and had full confidence, but I didn't pass the sniff test!

I'll start with an image of shame:

The air filter on the left is what I have used since I installed the new engine.  The one on the right is what comes with an RX8 cold air intake conversion kit.  The left one passes the equation on the K&N website but fails the sniff test.  This I did not observe during the engine installation.  Another episode of skipping the details to finish the project faster.

Not sure how the K&N website works, but it should have been obvious that the left hand filter is for a moped!  I wonder if that's because BB's motor is a rotary.  The formula is displacement x max rpm divided by a constant.  BB's displacement is technically 1.3 liters, although some have argued it should be double that because a rotary gets more combustion cycles per revolution than a piston engine.  However, the proper filter is 3.5x the little guy!  Not explained by this argument.

Fortunately, my brother Brian, got me an RX8 filter for my birthday.  He hadn't realized that I had installed a custom cold air intake so he got a performance version of the OE filter.  It was 11" x 17".  So, I looked at that huge filter and thought "That's damn big compared to my miniature filter".

I  then removed the moped filter, which I found to be covered in mud and road debris.  It's amazing the engine would actually start!

At first, I thought I could add the new filter by shifting the intake tube to the right.  That was nowhere close, as the new filter is a monster!  I did some time on the garage floor (always good times!) and figured out a new location.

I bought a 90 deg fitting from Summit Racing and it successfully addressed the problem.  The filter is now a few inches farther above ground than before.  Hopefully no water will get sucked up the few times I get caught in the rain!

I've only managed some neighborhood drives so far but she feels peppier!  I'll report after the first autocross that I manage!

Keep on having #funwithcars !