injectors and 02 sensors

[Andris]

On Tue, 7 Dec 1999, DIY_EFI Digest wrote:
> I haven't seen any specification information that states what the maximum ON
> time is for an injector before damage occurs and this is the data that actually
> determines the extreme end of the duty cycle in the terms of maxium on time.

80% Duty cycle has been the rule of thumb for a while. You could (most
likely, not scientific, just an educated assumption, please do not
flame) run at 100% if you have fuel flowing, since the heat generated
would be quickly conducted to the fuel. The problem tends to be
repeatability above 80% but below 100% where the injector starts to close,
and then re-opens when it hasn't fully closed yet. This is similar to the
repeatability down low, around 1.7ms when you try to have short
pulsewidths on big injectors for a not-insanely-rich idle. You tell the
injector to open, and then tell it to close before it has fully opened...
> 
> So do the EGO sensors work at stoich because they were designed to work at
> this ratio, or is there something intrinsic about their operation and the
> conditions at stoich that causes this?

Catalytic converters were designed to run at stoich, so engines needed
stoich back in the day of low-turbulence high volume heads to run cleanly
for the cat. Sensors were generated to make this as easy/cheap to achieve
as possible.
 > 
> I guess the OEM's wouldn't be using them if they didn't work at stoich, so it
> doesn't really matter if it is easy to make them this way or not. A better
> question would be are they cheaper than the wide band sensors because they are
> easy to make, or because they are used on so many cars?

Volume is a huge reason. The standard 02's are produced by the tens of
millions, in is a commodity. The wide-band isn't as widely used, and if
just one or two companies make it, well, there isn't price
competition. Wide band needs a "black box" to go with it as well (which I
don't know enough about). Speaking of which - did the wide-band 02 project
ever get completed? It started when I was on the list the first time 2
years ago, and there hasn't been much in the DIY_EFI archives since
then. Any info out there? Thanks!

Andris/SPD
Z28tt-89 IROC T56 DFI Twin Turbo