[T2] A/F ratio measurement

[Sami Dakhlia]

Hi everybody,

Chris beat me to it. Today was a glorious day! Thanks to Chris, we
were able to find out that my year-long automotive hyperchondria was
misplaced. When I left his home and drove back to Topanga, I actually
had a wide grin on my face, fearlessly pushing the accelerator pedal
to the floor. The CHT gauge did not give useful readings, the sender
not being in positive contact with the head; it read about 280 F. Oil
temp readings were about 220 F. Climbed up to 240-250 F as I climbed
the Topanga's Fernwood with up to 21 degree incline in 1st gear.

Chris wondered about pre- or post-cat O2 sender placement. I don't
know enough about the chemistry of catalytic converters to respond,
but found this potentially informative link:
http://www.dtec.net.au/Lambda%20Testing%20Pre%20Vs%20Post%20Converter.htm
Their conclusions are, quote:
- When engine conditions are stable there was no noticeable
(significant) difference in readings before and after the catalyst.
- When mixtures were altered rapidly or/and conditions changed there
was a delay until the post reading stabilised.

I'm going to post this finding on the previous thread, for proper
closure. Bottom line, the '75 FI system designed for a 1.8-liter
engine can adequately cope with a 2-liter engine, i.e., not cause a
lean-running condition at WOT.

Cheers,
Sami


On Mon, Aug 8, 2016 at 9:56 PM, c.dreike <c.dreike at verizon.net> wrote:
> Howdy Volks,
>
> Spent a couple of hours today with Sami D.  looking at his engine. Sami's
> complaint is high head temps when going up a steep long hill in a low gear
> (am I correct on that?). (kinda sounds like Mike Soultanian's problem we
> heard about a couple years ago. Don't know if he ever figured it out)
>
> We set up a wide band A/F sensor on the outlet of the tailpipe with an angle
> bracket and hose clamps. We seemed to be getting reasonable readings. 11.8:1
> under heavy acceleration and around 12.5:1 under lighter loads. This evening
> I was thinking about this and realized that he has a catalytic converter on
> his exhaust system. Is there a difference if we had measured upstream of the
> Cat? Rather than downstream as we did?  Do we have an accuracy problem
> because of the cat?
> Thanks "Brain".
>
> BTW we were able to check compression on cylinders 1 and 3 at 120 and 117
> respectively. Should be OK I would think.
>
> Spark plugs were brand new with about 50 miles on them. Mostly freeway
> driving. Clean as the proverbial whistle. No carbon, the insulator white as
> can be.  Any ideas?
>
> Chris
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