RE: [alfa] Re: Downsides of bigger injectors?

["Peter Webb" <webb.p@xxxxxxxxxxx>]

> What would the downsides of switching to bigger injectors be?
> Decreased low rpm torque? Increased fuel consumption? Also, in an

AFR from Lambda would correct any mixture problems in closed loop mode.
When open loop such as WOT, the L-Jetronic goes lean.  My AFR logs show it
lean about 5K RPM @ WOT.  Low end torque is determined by air not fuel.  The
amount and velocity of the intake sets the torque range determined by runner
length, plenum volume and air velocity.  However, a lean mixture on accel
will detonate and while it might feel faster, you're very close to blowing
up the engine.

> injected engine isn't it air flow, rather than fuel supply that
> limits performance?

Not always.   AFR is calculated by the ECU in closed loop.  Open loop is
used during warm up and at WOT.  What L-Jet doesn't have is an accel
enrichment cycle.   The ECU detects snap-swing of the AFM door but that's
the closest it gets to accel detection.   It uses a switch type TPS which
makes it nearly impossible to do true accel enrichments like a digital
system does.   A potentiometer type TPS, or TPSdot determines accel
accurately and enriches accordingly.

The larger injectors will make you rich at warm up and rich at WOT, just
where you want it.  Lambda tries to get you to 14:1 AFR.  Power is made at
12:1.  EGT is lower.  Combustion is slower.   You can advance the timing a
little more with the richer mixture as it helps prevent detonation.

All good things for performance.

For your 164 (current part # 0 280 150 702 186 cm/3) try:

0 280 150 706  215 cm/3  85-86 Porsche 928
0 280 150 701  240 cm/3  3.2L BMW
0 280 150 905  245 cm/3  1.8T VW

These (as your 164 uses) are high-z o-ring type injectors design for PWM
type injection (Motronic).   The numbers I listed yesterday are for the barb
type fuel rails and are low-z for peak-and-hold type injection
(K/L/LE-Jetronic).


-Peter
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