🚀 go-pugleaf

> *** REPLACE THIS LINE WITH YOUR MESSAGE ***
> 
> Many new cars are advertising different types of fuel injection; multi-port,
> throttle-body, etc.  Would anyone care to give a short tutorial on fuel
> injection in general, and how if any these 'variants' differ from REAL
> fuel injection?  Or are they just names dreamed up by a marketing dept.
> 
> 					Thanks In Advance,
> 
> 						Mike Vehonsky

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I recently took a look at new cars and found displayed prominantly on the
back of some of the small Chevrolets "Electronically Fuel Injection."  
When the time came to look under the hood, I tried to find the pipes that
inject the fuel into the combustion chamber.  No luck.  I asked the salesman
about it.  He couldn't explain the discrepiency, a common failing among 
salesmen.  Finally at the third sales lot I visited, the salesman took the
carberator air cleaner off and showed me a small mechanism at the top of the
carberator with two wires running to it for electronic control.  According
to the salesman, this allowed a computer to pulse the gas at the ideal rate
for each operating condition.

The experience turned me off.  First I felt the manufacturer was misusing the
term Fuel Injection.  He is using a 'buzz word' that will make some people
think they are getting something they are not.  And second, I view it as 
being just another gadget to give problems.  We are really getting too many
things on car motors lately that lower the reliability and 'shade-tree'
maintainability.  One item of contention is the motor computer.  As much
as I use and respect computers, I don't care about having one under the 
hood of my car.  I don't feel the advantages will outway the aggravation.
-- 




				     Albert H. Spinks

> Many new cars are advertising different types of fuel injection; multi-port,
> throttle-body, etc.  Would anyone care to give a short tutorial on fuel
> injection in general, and how if any these 'variants' differ from REAL
> fuel injection?  Or are they just names dreamed up by a marketing dept.
> 					Thanks In Advance,
> 						Mike Vehonsky

While I'm certainly not an expert in the field, I think I can shed a little
light on this.

Tuned-Port-Injection: This is used on the Chevy Corvettes and IROC Z/28's
and specially equipped Z/28's.  It involves 8 individual injectors which
inject fuel into the intake manifold runner just before the intake port
of the head.  The 'tuned port' comes from the curved tuned-length intake
tubes which supposedly help increase bottom and mid-range torque.

Throttle-Body Injection.  This uses carburetor-like throttle bodies
which have injectors in them.  They sit on top of an intake manifold
much like a carburetor, but have computer-controlled injector(s) in
them which spray the fuel and mix it with the air.  Used on
early 80's  Corvettes & Z/28 Camaros (with two throttle bodies), and many
newer 4-cylinder applications.

Multi-Point FI:  Much like the Tuned-Port system mentioned above, minus
the 'tuned-port' intake.  Individual injectors feed the intake ports
of the heads.  On some systems, there are more than one cylinder
served by each injector.

All of the above systems are controlled by engine control computer, which
monitors engine RPM, load, throttle position, air/fuel mixture, engine
temperature, mass airflow, and other parameters to determine optimal
fuel mixture.  Most injectors are controlled by a pulse-width modulation
system.  The longer the pulse width applied to the injector, the more
fuel is delivered.  The computer determines the proper pulse widths, and
sends pulses to the injectors to control the mixture.  Some of the
more sophisticated systems control the pulse width to each individual
injector, based on the demands of each cylinder, while others compute
one pulse width, and run the engine through one cycle before updating it,
running all of the injectors with the same pulsewidth.

Hope this is of some help.


Rick Bensene
{ihnp4, decvax, allegra, cbosg, ucbvax}!tektronix!tekig4!rickb
Phone: Weekdays (503) 627-3559
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US Mail: Tektronix, Inc. - P.O. Box 500, Mail Stop 39-170 - Beaverton,
 Oregon  97077

> maintainability.  One item of contention is the motor computer.  As much
> as I use and respect computers, I don't care about having one under the 
> hood of my car.  I don't feel the advantages will outway the aggravation.

That may be, however these controls are required for the manufacturers to meet the
corporate fuel economy guidelines imposed by uncle sam. If you take the time to really
understand how they work and how to debug them, they're really quite simple.

In article <459@tekig4.UUCP> rickb@tekig4.UUCP (Rick Bensene) writes:
>> Many new cars are advertising different types of fuel injection; multi-port,
>> throttle-body, etc.  Would anyone care to give a short tutorial on fuel
>> injection in general, and how if any these 'variants' differ from REAL
>> fuel injection?  Or are they just names dreamed up by a marketing dept.
>> 					Thanks In Advance,
>> 						Mike Vehonsky
>
>Multi-Point FI:  Much like the Tuned-Port system mentioned above, minus
>the 'tuned-port' intake.  Individual injectors feed the intake ports
>of the heads.  On some systems, there are more than one cylinder
>served by each injector.
>
My Fiero V6 has multi-port fuel injection and tuned induction.  The injectors
are wired in two circuits with three injectors each.  This means that the
injectors fire three times for each engine cycle.  I don't know why this is
done except to minimize the complexity of the computer control, I guess.

I would suppose that sequential-port injection would actually have seperate
circuits for each injector and they would be fired only once per cycle.

At any rate, I believe that multi-port injection means that the injectors are
fired in groups, and sequential-port means that they are fired one at a time.

I await any corrections..

marcus hall
..!ihnp4!tellab1!tellab2!thoth

p.s.  Does anyone know the REAL reason why multi-port injection is used?
 It seems that injecting gas at any time other than the intake stroke implies
 that the mixture cannot be controlled as well.  How possible is it to convert
 a multi-port system into a sequential-port system? (probably not very :-()