Re: Alfetta efi conversion

[James Montebello <jamesm@domain.elided>]

If you can get them, the SPICA manifold would be the nicest way, and would
probably be much less expensive than the aftermarket throttle bodies.
Given the rate that SPICA is removed for Webers in this country, I'd
imagine there are quite a few manifolds available.  Try to get a '71 or
later manifold, and include the complete airbox assembly, if possible.
This includes an adjustable idle air bypass, with one hose from the airbox
into a central plenum, then four hoses from that plenum to each TB.
The '69 had four hoses from the airbox to the TBs, no central plenum.
Once complete, the whole thing will look just like a factory SPICA setup,
since the pump itself is mostly hidden by the airbox, so the fact that
it's not there won't be apparent.  Finding this as a set shouldn't be
hard.

Three things I can think of that will complicate an EFI conversion done
this way:

 - mounting a throttle position sensor will require some fab work.
   You can use the bellcrank that normally goes down to the SPICA
   pump and use a GM-style lever-arm TPS, though working out the
   geometry will be a bit tricky.
 - the SPICA injectors are long tubes, so the manifold mounting bosses
   have passages that are about 3x longer than required for EFI
   injectors, so some machine work will be required here.
 - the area 'past' the throttles is very small, so if you're using
   a MAP sensor as part of a speed-density system, you'll find that
   you'll get wild fluctuations in the MAP value from intake pulses.
   You can fix this by either using a very small ID tube to connect
   to one TB, or by plumbing all four into a plenum (you can use
   the idle air bypass hoses for this, though you'll then have to
   come up with a way to control idle).

As you might guess, I've been eyeing doing a SPICA->EFI conversion
for quite some time. :-)

james montebello

On Thu, 1 Aug 2002, Josh wrote:

> Hi all,
>
> I'm in the middle of planning out a conversion from webers
> to efi for one of my alfettas. I've got the ecu/sensors/fuel
> pretty much worked out, but I'm still trying to decide on
> the best (cheapest?) throttle body arrangement. So far I've
> come up with 3 alternatives:
> 1) DCOE style throttle bodies - the neatest, but most
> expensive option (about AU$800 a pair for cheapest ones)
> 2) gut an old pair of carbs, and incorporate injectors in
> the carb body or manifold, or replace the rubber mounts with
> aluminium runners and stick the injectors there
> or 3) machine a spica manifold to accept efi style injectors
>
> option 3 sounds good to me, as I could use the spica
> throttle bodies as well, but here in australia we don't have
> many spica equipped cars - so I can't even have a look at
> these bits to see if my idea might work. Has anyone done
> this before? Is there an obvious reason why this wouldn't
> work? Is there an easier way?
>
> Josh
> --
> to be removed from alfa, see /bin/digest-subs.cgi
> or email "unsubscribe alfa" to majordomo@domain.elided
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided