Miata Mailing List: September 1993, Message #87
sponsored by



     


   From: Mike Rother 
Subject: Re:  air intake
   Date: Mon, 13 Sep 1993 09:19:33 -0400

	From: RMCELEARNEY@delphi.com
	Subject: air intake
	Date: 	Sun, 12 Sep 1993 11:18:38 -0400
	
	A while ago, Mike Rother  wrote:
	>Based on this test, here's a recipe for what may be the least
	expensive Miata performance improvement.  Advance timing to 14
	deg BTDC for a two hp gain.  Switch to a K&N air filter for
	another 2 hp.  Install an intake tube off the front of the
	airbox - collecting air from just to the left of the fan
	shroud.  

	This sounds like something worth doing.  Someone else has
	suggested that cutting a hole in the firewall and drawing air
	from the cavity just under the hood end might be a good way to
	get colder air to the combustion chamber.  My question for the
	group is this:

	Because of the angle between the hood and the windshield, would
	the air pressure in this area be slightly lower or higher at
	speed?  If higher, it would seem to be the place to put the
	intake.  Anyone Know?

This is a good time for an update on my air-intake "tests."  I did
reroute my intake to just left of the radiator shroud.  My temperature
tests showed this to be on of the coolest underhood locations - with
temperatures near ambient air temperatures.

I now have a rigid, straight, 8 inch tube of 2" diameter feeding into
the front of my airbox.  The air-intake hole at the rear of the airbox
has been capped off.  My setup is very factory looking, but it was a
somewhat tricky operation.  I have access to a full machine shop,
and wouldn't recommend this job to anyone using only hand tools.

The effect on acceleration was noticeable, particularly above 3500
rpm.  The car is mildly punchier and has a slightly more agressive
growl - which is nice in passing under bridges.  The change is mild -
like fine tuning, which is what I like to do.  The car's performance is
now more temperature dependent - getting really punchy on cool
evenings.  Haven't added a K&N air filter yet.

One refinement I had to make was an aluminum shield to keep rain water
away from the intake.  The water comes in around the headlight pod -
particularly when the headlights are open.  This is an absolutely
necessary detail in my opinion.  You may also have to be careful of
rain water if you reroute the intake to the "cavity" at the rear of the
underhood area.  I believe this is a water-drain area for the heater's
air intake.