Date:         Tue, 4 Jun 1996 14:52:59 -0400
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Ryan75@aol.com
Subject:      Re: TDI Eurovan

In a message dated 96-06-04 13:42:15 EDT, you write:

>I've often wondered about this. In the early '80s, GM started pressurizing
>their carburetors, and some ad guy with a lot of contempt for his
>customers' mechanical knowledge, called it a "throttle body injector",
>which is a name that could in truth be applied to any carburetor,
>pressurized, computer-controlled, or not.

Throttle body injection (TBI) really is fuel injection, just not as
sophisticated as we're used to.  Instead of one fuel injector for every
cylinder, there is one injector placed in a throttle body (it looks like a
carb, with throttle valve and the injector) that supplies all of the
cylinders.  It's inexpensive, easy to retrofit to existing engine designs,
has fewer moving parts than a carb, and is easier than a carb to maintain.
 Plus, it's a great marketing tool for the advertising department.  Bosch
even has a system of this design, called Mono-Jetronic.  Even VW has used
this system in Europe, on cheaper models and as a carb replacement (factory
installed, not a retrofit).

>Sounds to me like manufacturers with real fuel injection, immediately
>got on the bandwagon with names like "direct injection", which seems
>to mean "ours is REALLY fuel injection".
 
Please see my previous post in direct injection.

>Besides these, anyone know what "Tuned port injection" refers to?
>Inquiring minds want to know.   :-S

Tuned port injection (TPI) is closer to what we think of as fuel injection,
as compared to the previously mentioned throttle body injection.  In this
case, each cylinder has its own injector (oooh, aaaah, GM has finally caught
up with the '68 Squareback <g>), much like every VW with fuel injection sold
in this country.  The system is really more comparable to the Digifant
system, in that each injector is electronically controlled and uses a wide
array of sensors and  a computer to get the best efficiency and power.  Once
again, as Steve suspected, a bunch of marketing hype for something that has
been around for some time.

Ryan