Date: Wed, 11 Dec 1996 07:56:38 -0600 From: Will Wood Subject: Re: Exh Emis Gas Analysis ? Emissions specs vary given climate and engine temp. A hotter engine will actually produce less emissions that one that's cold. I'll qualify that so I don't get jumped on the list. Most of the smog controls that are on an engine surround cold starting emissions (whether they be "physical" or "logical" as in later vehicles is immaterial). When an engine is cold, it requires more fuel to keep running (remember chokes?). Anyway the EPA and the Auto makers figured this out. It could be that the shop in question tested the engine cold, which will normally indicate higher HC readings or the latter of your statement applies. The equipment is bad or the techs aren't up to snuff. Also remember this. I live in a state that has annual smog (as well as safety inspections) and I've had variances from shop to shop. I've now found a highly reliable, reputable shop to get my work done (that which I can't do myself). I worked on my neighbors 84 Bronco (Big one) and dialed in the engine after a tune up. My CO meter read 1.5% at the pipe (spec was 2.0). They took it into the shop and it wouldn't pass. I checked it again, again 1.5%, they took it back. Again it wouldn't pass. Finally I sent them to my shop where I get my tests done. The tech immediately spotted the problem. The Techs at the first shop were using the wrong engine and tailpipe configuration for the test equipment. Instead of a 302 they were testing for a 351 with dual pipes. Moral Techs are people too. After dialing in for a 302, single exhaust guess what, 1.2% CO (I guess my meter needs calibration). Ask around for people with VWs and ask where they get work done. In this day and age there are just too many damn fly by night operations to contend with. Boy the stories I could tell ya... Regards ---------- > From: Christopher M. Smith > To: Multiple recipients of list > Subject: Exh Emis Gas Analysis ? > Date: Tuesday, December 10, 1996 7:45 PM > > > I just had my 82' vanagon in the shop to get my air flow sensor adjusted > (requiring CO measurement). The fuel/air ratio was running rich, which I > attributed in part to a new, unadjusted sensor. They also > did a total gas analysis as a pre-smog check. Priot to the air sensor > adjustment, the HC were about 1000 pre-cat converter and 200 post-cc. > After adjustment, the post-cc increased to 250, while the pre-cc HC's > remained about the same. Since 250 is borderline smog passable, I thought > I'd take it in just to see if I could pass Cal smog (assumming some > shop-to-shop variance in gas analysis). Well, the certified smog shop > indicated my post-cc HC was 30. All other gas measurements (CO, CO2) were > about the same. > > I am at a loss for such a big discrepancy in the HC level. I expected some > deviation between the two shops, but not 8+-fold. Does this indicate that > the shop has a problem with their equipment, is incompetent ? They did > find some other "potential" problems with the engine (a few I was aware > of) that they wanted to do diagnostics on (for big bucks too!, I > declined!). > > Your impressions would be appreciated. > > Chris