injectors and 02 sensors

[Bruce Plecan]

----- Original Message -----
From: Andris <askulte at emerald.tufts.edu>
To: Do It Yourself EFI list <diy_efi at efi332.eng.ohio-state.edu>
Sent: Tuesday, December 07, 1999 8:31 AM
Subject: injectors and 02 sensors


| 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.

I've held them on for 45 mins with no detectable damage..

| 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...

The above is obsolete from all I've seen, in the last year.
The trick is the min off time that allows the injector to actually relax,
and be predictable in it's openings.

| > 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?

Just answered in another post.

| 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.

No, no, no, the cats run at an average of slightly richer then Stoi, and
never run steady state 14.7:1, unless by accident.

| > 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!

Gar is still a work in progess on it, and several others from time to time
are still working with various ideas, about them.
Grumpy
|
| Andris/SPD
| Z28tt-89 IROC T56 DFI Twin Turbo
|