Engine analysis results. Whadya think?

[davis911s]

I had my car on the scope today. Here were the results

HC 200
CO .12
O2 5.3
CO2 10.1
AF ratio 19.6

This was at about 1000 Rpms - my tach isn't working and I forgot to look at the scope's screen.

The AF seems a bit high for what I have heard.

the guys at the shop said the HC was GREAT, they couldn't get over it. They kept saying new cars don't even get that low.

What does everyone think?

Shawn

[pjv911]

Looks a little lean. Does it idle smooth ? It should be a little on the rich side to run smooth. Its great for emissions testing though. The 02 is a little high (to much oxygen in the exhaust) This is commonly accompanied by a low grade misfire or maybe a poor exhaust gasket pulling in outside air between exhaust pulses.

BTW new cars would fail emissions if hydrocarbons(unburned fuel) were higher than 120 ppm here in New York.

Kurt Williams

[Early_S_Man]

Shawn,

Way too lean! If you had head temp gauge or exhaust gas temp readings ... they would be well into the RED ZONE!!!

While good hydrocarbon emissions are laudible ... burnt exhaust valves are a real possibility! I don't believe you should be higher than 16:1 ... for the health of your valves. I also think the tech where the scope was ... should have known this simple fact, too!

[davis911s]

Thanks guys so richen it up. What should I be looking for in the windows? Best case!

It is real hard here with NO Porsche experts anywhere.

The car is idling ok and I wouldn't be surprised with exhaust leaks. There are two broken exhaust studs, and the gaskets were not replaced the last 3 or 4 times I had the exhaust apart.

Shawn

[jyl]

Here are my car's results, from a recent Calif smog check:

At 2289 rpm:
HC 0000
CO% 0.11
CO2 14.8
O2 0.9

At idle 870 rpm:
HC 0007
CO% 0.01
CO2 14.6
O2 0.9

No AF reading unfortunately.

Any thoughts? This is a good thread, I've never known what those mysterious numbers meant before.

[davis911s]

IGNORE those readings

I went back to the shop, they actually admitted the readings are off on that scope. So we hooked up another one. We actually had two sniffer pipes in at the same time. They were both WAY different! And the GOOD scope didn't have a functioning AF mixture!

So I set it to where it sounded good and idled well, I will try to get to a different scope before I leave for the roundup or just rely on the spoark plug reading method!

Shawn

* also when it was on the scope I played around with the mixture and it made little or NO difference with the scope's screen, even with 1/4 or 1/2 turns

Shawn

[Wayne 962]

I think that 1.5% to about 2.5% is good for most CIS cars...

-Wayne