TT Oversteer

So I took my '77S 3.2 conversion to the California Smog Refereeeeee to get it smogged (it was an Idaho car previously). All the original stock 3.2 emissions equipment is in place and the car passed the visual and fuel tank pressurisation checks. But.....when it went on the rollers it failed the emissions test miserably. HC max allowable at 25 mph is 86 PPM. I tested 268. NO max 717, I tested 1435. Only 70k on the engine. Compression is 150 to 155 all around. Plugs look very nice and tan, not black. I can smell a little exhaust when idling and it doesn't seem to pull as strong as I think the 3.2 should so something is up. But where to start? The only adjustment on the Motronic system is CO and that is the only parameter that I easily passed. Any thoughts before I take it to the shop and hand over the credit card?

Amber Gramps

You gotta look up my numbers. I passed without a cat with HC @ 77 PPM when he said I would have passed at 100 PPM.


https://rennlist.com/forums/showthre...ht=passed+smog

Brett San Diego

Adjustment of the fuel mixture (setting CO) is carried out by measuring the CO level pre-catalytic converter. During a smog check, the exhaust gasses are measured post-catalytic converter by a probe stuck in the end of the tailpipe. The catalytic converter changes the composition of the exhaust gases so you can't really say anything about the tune of the engine by reading the gases post-catalytic converter as in the smog check. It sounds like you should begin with a fuel mixture check/adjustment carried out by a competent Porsche specialist with an exhaust gas analyzer.

Brett

old man neri

Just curious but was your car good and warm when you took the test?

TT Oversteer

Yes, I drove about 45 minutes to the test site at ambient temp of 87 degrees. Oil was warmed up to about 220. The car sat for about 30 min before the tech started it and stuck in the probe. Should have been warm enough to pass if it was going to. I am going to have the mixture set as per Brett's suggestion and try again. I'll also run a tank of "Guaranteed to Pass" through it as I should have previously to clean out any deposits in the combustion chambers. It's a little frustrating because I took the car to a local Porsche shop before the smog test and had the guy sniff the exhaust with a gas analyzer. He looked at the numbers and said "It's running pretty clean, you should have no problems passing smog". Funny considering how far out of parameters the actual test was.

old man neri

A cat will cool off a lot in 30 min.

TT Oversteer

Agreed. But how long do you think it would take to heat up again when the engine and oil are already heat soaked? I'd bet less than a minute. This could explain a less than optimal reading but there must be more going on for the readings to be completely outside parameters.

Amber Gramps

I don't know why he said this, but the guy I went to said early morning checks always produce lower numbers.

Droops83

I would question whether that cat and/or O2 sensor are working at all with those emissions levels. Get the CO level and the basics checked as suggested, but at the same time it is wise to see if the cat is actually doing anything. They can go bad, and no amount of heating it up or BS chemicals in the gas tank will help if that's the case.

TT Oversteer

Maybe I could talk the guy into testing my car at 1:00 in the morning. But, seriously, now I'm thinking the O2 sensor or one of the other sensors that talk to the computer might be bad causing the Motronic unit to improperly control mixture. I'll take it to a shop rather than just throw parts at it and let you all know what shakes out.

g-50cab

+1 - If it's a stock 3.2 - you should have better numbers than that.

Peter Zimmermann

Chris, all that I can say is that you are wise way beyond your years!

I'm curious, is this car being measured as a '77, or a 3.2 car of the engine year?

TT Oversteer

Per California smog rules a car modified with a newer engine is tested to the standard of the newer engine which is a 1989 carrera 3.2 in my case.

Houpty GT

http://www.rx7club.com/showthread.ph...06#post5131106
Nice little problem solver. You can imagine the problems the dirty Wankel engines have passing a test. I would also recommend moving to another state.

Brett San Diego

Or buying a 74 or earlier car. That's the current law. 74 and earlier are free and clear of smog checks. (Although according to what Oversteer says, his 89 engine would still have to be tested it appears... but, if they don't know about the engine swap....) It used to be a 30 year rolling thing on smog checks. Any car 30 years of age or older was exempt. I was looking forward to my 78 becoming exempt this year, and then they changed the law.

Brett