Carbs and Injection

[Keith Walker <100662.3423@domain.elided>]

>> (This, of
course, would be consistent with EVERY OTHER
IMPLEMENTATION OF FUEL INJECTION SINCE THE INVENTION
OF THE INTERNAL COMBUSTION ENGINE, that injection
produces more power than carburetion, but of course
Alfas are Different.)<<

Unless you fit a very good fuel injection system then injection
will normally loose you power.

Most fuel injection systems used on cars are single point, and
about as performance minded as a single SU carb. With a fairly
modern engine (such as the 2L 16V 150hp Vauxhall / Opel
engine popular for putting into old Lotuss) then the first way to
get more power is to dump the injection and fit Webers. Only
if you have the money to go for a fully mapped injection systems
using throttle bodies will you get anything as good or better
than the carbs.

Alfa still used carbs on production cars up to at least 1992
(with the 1.3 33), and with the rest of the 33 range they
lost power when carbs were fitted (1.7 went from 118hp
to 110, 1.5 from 105 hp to 100hp). With the 16V it is
possible to gain power by dumping the injection and
going to carbs, but some of that is due to the small
size of the throttle bodies used on that engine.

Injections advantage is mainly getting power while
the emisions are acceptable. With Weber type carbs
if you open the throttle fully at low revs then the gas
speed through the carb is too low for them to work
properly (and accelerator pumps are a bodge to get
round this). This is fine for someone who understands
this and drives round it. CV carbs avoid this problem,
but are restrictive. Injection avoids this problem as
it doesnt care about gas speed to draw fuel out of
a float bowl.

All the best

Keith

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