ttAmerica RoadsterAWD

Guys, after much anxiety over having a back-yard Ruf conversion, I was surprised my car passed with seemingly excellent, almost unbeleivable (to me) numbers. Does this make sense to you guys in the "Know" about what our engine should be doing, or am I running too lean??

IDLE: (actual RPM was 943)
O2: 0.5
CO% must be < 1.2 tested at 0.02
HC (PPM) must be < 220 tested at 16
Dilution CO+CO2(%) must be 6.00 tested at 14.64

AT 2500 RPM's: (Actual RPM was 2613)
O2: 1.6
CO% must be <1.2 tested at 0.01
HC (PPM) must be <220 tested at 14
Dilution CO+CO2 (%) must be 6.00 tested at 12.66

A)Tech placed the sniffer only on one exhaust pipe

B) Car is "officially" C2, non turbo (didn't want to get into an OBD-2 compliance problem with my 1996 engine on a 1993 car)
C) 92deg ambient temp
D) about 2000 feet above sea level

Thanks in advance
Jaime

sfbanchs

congrats!!

ca993twin

Jaime,

Great going! Here are Rufus' numbers (different measurements in California):

RPM: 923
%CO2 8.4
%O2 9.1
HC (PPM) Max 100, Avg 17, Measured 16
CO% Max 1.00, Avg 0.00, Measured 0.07

RPM 2409
%CO2 13.9
%O2 1.6
HC (PPM) Max 130, Avg 12, Measured 8
CO% Max 1.00, Avg 0.10, Measured 0.17

David in LA

Jaime - Quick question as I've seen your posts and car on Rennlist many times but never asked...Did you do the engine swap and mods or did you buy the car that way?!? Did Andial do the work? Great looking car btw

911/Q45

Hard to tell if your AF ratio is too lean by this test. Idle and steady 2500 rpm don't use much injector capacity. Wide open throttle and high rpm would be where you need to measure AF.

ttAmerica RoadsterAWD

Whewh! Given the allowable numbers it looked like I was running too lean. Great for the environment, bad for my engine. Thanks for the info.

Steve, thank you for the comps. Looks similar to mine, so I feel better
David, the engine was already in the car, I just found Ruf parts here and there to convert it
Q45, the tech said it was specifically the BMC washable air filter that made such good numbers

Jaime

Droops83

True, plus the measurements shown in the smog test are all cleaned up by the cats, they don't say how lean or rich you are actually running. CO is only useful when measured before the cat. You would need a wideband O2 sensor to tell how rich or lean you are actually running, especially under load. The 5 gas sniffer we use for diagnosis/ smog pre-tests displays air/fuel ratio as well as all the measurements in you smog tests, and that measurement is accurate, however, even after the cat. But, pretty much any car w/ perfectly functioning O2 sensors and cats will show about 14.7 AFR at low RPM anyway, that's what they are designed to do. Again doesn't tell you much except that you're probably running OK and will pass smog!