<VV> Re: Turbocharging using EFI

[Craig Nicol]

<snip>
Can you explain or point me to a resource  for information on EFI and
turbocharging as it applies to a Corvair Turbo.  I have an opportunity to
buy a n'new in the box: Holley TBI system and wonder if it would have
application on one of my two Corvair Turbos ('63 Spyder, 66 Corsa Turbo).
Bill
<unsnip>

Hi Bill,
I think the leading guy in Corvair turbo EFI is in Denver; his name is Chuck
Riblett, Blackhawk Engineering.  He has the Turbo EFI setup (including
programming) and it's about half of what Clarks wants for their 140 setup. I
don't have his email, but you can get it from Steve Goodman,
(rearengine.steve at worldnet.att.net)

Also, here's a link to a thread on the topic. (Using "Mega squirt ecm)

http://www.vv.corvair.org/pipermail/virtualvairs/2007-October/067175.html

A couple of points to ponder:
Most of the Holley TBI units that are for sale used or uninstalled are their
first gen units.  These were basically 100% unsuccessful and AFIK, all have
been removed.  This system is characterized by an ecu with three knobs for
low/middle/high or some such.  The system was reliant on a throttle position
sensor that lacked stability and didn't have the required sensitivity. Every
change of weather or temperature required recalibration of the ecu. 

I have no information about second generation Holley "digital" TBI units
except to say that I've heard nothing bad about them.  Having said that,
it's unlikely that they are compatible with turbocharging and it's also
unlikely that there are existing fuel maps for a small displacement engine,
turbocharged or not.  99% of the application is for 350 cubic inch V8
engines.

As you evaluate EFI possibilities, note that some are not compatible with
the wide range of intake pressures present in a turbocharged engine.  The
buzz words are applied to the MAP (Manifold Air Pressure) sensor.  If it's
compatible with a 3-bar sensor - it's turbo compatible. 1-bar = the range of
atmospheric pressure from about 15psi to 0 (atmospheric pressure to a
complete vacuum) and these are the intake pressures present in a normally
aspirated (non-turbo) engine.  A 3-bar sensor can measure from about 45 psi
to 0 and thus can accommodate up to about 30# of boost. 

Please note that programming the ECM is 90% of the job.  To develop a good
program for an aftermarket unit such as "Mega-squirt" can easily take 200
hours.  I'm right in the middle of helping a guy out of his Mega-Squirt
crisis - I will note that at the front end he blew me off when I mentioned
the 200hr number.  Now he believes me. 

Are you familiar with "fuel maps" and very strong with computers and engine
theory?  If so, you would be a good candidate for an EFI project and I'd be
happy to assist you in any way I can. 

 Craig Nicol
'66 140 EFI (GM)
'65 140 EFI (Nissan/Bosch)