Upgrading Air Intake System - Anyone tried velocity stacks?

[theastronaut]

I remember seeing this on IG and Facebook. I'm sure it took a while to fit without hitting the firewall.

The engine is moved forward 2.125" for more firewall clearance.

[F3BZ]

couple of outfits make ITB kits for the 1.6/1.8 Miata engine. their names escape my memory right now but one i contacted at the time had the TB pairs available in different lengths and intake horns at different angles. in other words probably some combination that would fit into the festiva bay without a lot of mods to the sheet metal but maybe at the expense of some performance.

[Sid_RallyX_82]

Any improvement on the intake side would be more noise, other than simply replacing the air filter with a K&N unit (PN 33-2222 for those who are curious). Which is pretty much useless without removing the designed-in airbox restriction. And you only really notice the higher decibels on the intake when you floor it.

I maintain that the K&N filter is useless anyway, even with airbox mods, because even the stock paper filter will flow more air than the tubing between the airbox and the intake manifold can flow. In other words, a waste of $50. A dyno test might show a 1-2 HP increase for the K&N, but the butt dyno can't tell.

The single biggest restrictor is the airbox, by design for less noise. Without correcting this, there is no point in doing manifold-to-head port matching, or intake headwork. The connecting tubing you can't do too much about, because of the restriction of where it connects to the throttle body. You would have to find a larger and compatible throttle body.

Is there a write-up on improving the intake? Looking for all the specific tricks

[firebush357]

Is there a write-up on improving the intake? Looking for all the specific tricks

There were some write ups way back in the day talking about bigger throttle bodies but I don't think the gains were substantial. I have read conflicting statements but your best best would be to port/polish the head and take the valve guides down and smooth out the harsh angle inside there. There were some members that made custom plenums with supposed gains but that is a lot of fab work.

[theastronaut]

Another option would be to fab a simple intake flange with stubs to run sport bike carbs. I'm looking into doing this on a b3 powered autocross build.