TBI and DYI_EFI list

[John Hess]

Sorry for my last post,  I read "TPI" rather than "TBI".


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From:  John Hess
Sent:  Monday, March 31, 1997 9:36 AM
To:  'diy_efi at coulomb.eng.ohio-state.edu'; 'Corey L. Cole'
Subject:  RE: TBI and DYI_EFI list



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From:  Corey L. Cole[SMTP:corey.l.cole at boeing.com]
Sent:  Thursday, March 27, 1997 10:50 AM
To:  diy_efi at coulomb.eng.ohio-state.edu
Subject:  Re: TBI and DYI_EFI list

Tom Cloud wrote:
>
> >I'd agree that the OEM systems are the way to go with stock engines 
which
> >have a later model counterpart with EFI of some sort i.e. early and 
late
> >small block chevy or ford.  It's fairly sophisticated and reliable 
stuff.
> >
> >My problem is I want to TBI something that never had injection and 
was
>
>         [ snip ]
>
> >If any of you have some insight on how exactly to get some of this 
OEM stuff
> >to adapt inexpensively, please share it.  It would seem that the 
EFI wouldn't
> >know if it were installed on a ford, chevy, or packard, but what 
how do I
> >pick out what I need?  What should I look for in my local junkyard? 
 Then
> >finally, after I get all the components, how do I tune it for my 
application?
>
> aaarrrrrgh .... this is the point I keep coming back to.  You're
> either stuck with retrofitting an existing oem app with the stock
> unit designed for it, or building your own.  Someone please tell
> me it's not so.
>
> MAF systems seem to overcome those problems, but I share your
> feeling for the simplicity of the carb look-alike TBI unit.
> For one thing, it might help pass some nosey inspector's visual,
> since the rest can still look stock.
>
> Has anyone done any fiddling with TBI / MAF combinations?  It'd
> be interesting if the MAF could be put in the air cleaner intake
> to look almost stock.
>
> Tom Cloud <cloud at peaches.ph.utexas.edu>

Why would you use MAF with TBI?  It's my understanding that TBI is 
usually
hooked up to MAP, which is the functional equivalent of "vacuum 
control" that
carbs use.

Actually, the '85 through '89 systems were MAF.  '90 to '93 (not sure 
of the date) were MAP, and then many applications changed back to MAF. 
 Reason.  The MAF maintains proper tune over a wider range (of engine 
modifications, temperature variations, altitude variations, etc).

However, I'm not so sure about using MAF with the stock aircleaner 
from a
practicality standpoint.  It would have to be placed upstream of the 
filter,
which would make for a short MAF life.  Then there's the issue of the 
size
of those things (Although I seem to remember seeing a while back in 
some mag
that researchers had come up with tiny, single chip airflow meters 
that were
the size of postage stamps.  They were saying that you could put one 
of these
in each runner, and have a very accurate EFI system.)  Sorry, got off 
on a
tangent.

Anyways, that's my put on why you shouldn't do it (although you could 
if you
wanted to...)


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Corey L. Cole                     | Cole's Law:  Thinly sliced 
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