Miata Mailing List: March 1996, Message #140
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   From: Jon Richings 
Subject: Jackson CAI Observations
   Date: Sun, 3 Mar 1996 16:57:08 -0500

I just got a Jackson CAI (sorry Bill, I got one locally).  And thought I'd
pass on some observations for those thinking of trying it, or has already
and wants to compare notes.  First I should say that I live in the UK so
some details may differ, though the kit is the standard Jackson issue.  I
hadn't even seen one before mine arrived (anyone else in the UK got one ?)
but I assumed that it would be a very simple installation given that it's
only a replacement airbox. Unpacking the kit, though, had me wondering -
lot's of bits and the instructions made it sound intimidating.  If I had
ever seen one installed before I wouldn't have worried, I just couldn't
visualise it.  Following the instructions to the letter it went in very
easily.  The first stage being to strip out the existing
cleaner/airbox/ducting which amounts to about 75% of the black plastic under
the hood.  Removal and replacement of the thermostat was easy but messy.
Putting in the new ducting pipework is straight-forward but the new airbox
seemed a less then perfect fit.  The airbox just sits ontop of the plastic
lugs which stick out of the top of the radiator which seems a little crude
and the rear/left bolt of the airbox lid would have rattled on the top of
the righthand thermostat bolt if I hadn't chopped 5mm off it's length.  My
kit is missing the two brackets that secure the box to the airmeter and the
box to the wheelarch, but it seems very solid all the same.  I will either
track the missing parts down or fabricate my own but it doesn't look like
either is essential right now.
The instructions were good and well illustrated but missed a few details
when describing the removal of the ducting at the intake and the old airbox
- maybe there are a couple more mounting points on RHD cars.  The airmeter
extension loom has no perfect place to run and finding a good place to put
the plug/socket assembly so that it doesn't rattle against the body takes
some imagination.  But these are quibblings - I really enjoyed the
installation and I think that is a good sign.  Anyone who is wondering if
they could do it themselves probably could.  Just take it slow and study the
drawings well.  It would also have helped if I'd had a Miata manual.  The
whole job took me about 2.5 hours and I was disapointed when it was over
because I was having such fun. Two more observations: it looks like RHD cars
have the brake servo on the other side so the the new mounting place for the
hood prop (which has to be relocated) isn't there.  I am going to put a
front strut brace on soon and Dealer Alternative have a prop relocation kit
to accompany that which will solve the problem (order's coming soon Bill).
In the meantime a strip of wood is serving just fine.  The other thing is
the noise; I wasn't expecting any change in sound but I was immediately
confused by what sounds like a rasping exhaust note.  Infact it's the top
lip of the airbox vibrating at high revs.  I am undecided whether I like it
or not but if I decide not then it would be a simple matter to put some
weight or strength into that plastic moulding and damp the vibration away.

So what about performance ?  Well it's not dramatic, but very noticeable.
Previously I felt that the engine picked up it's skirt and ran only after
4000 to 4500 rpm, now it seems to get going a little lower, maybe 3800.  And
once up there it does breath much more easily.  Acceleration is improved and
easy.  Still looking for more power right at the bottom though.  My timing
is at about 16 DBTDC.  Anymore and it is hell to start on cold, damp english
mornings.

Three questions:  

The Jackson kit just replaces the miles of Mazda ducting and tiny 'mouth'
with 6 inches of pipe and a huge mouth.  Why didn't Mazda do this ?  It
would have saved a lot of money in complicated plastic mouldings.

Anyone got comparitive info on the hp advantages of different headers and
catbacks ?  My next mod will be header (manifold here) and exhaust.  I'm
currently favoring Jackson and Borla respectively but for no more reason
then most people rate them.

What can I do with the huge hole left where the airbox used to be ?  I
thought the spare tyre might just fit bit no such luck !

Sorry this post went on a bit.

Jon.

Nimue - 91 BRG
Team...ing with rain.