Any new tips on passing smog test?

[GOLDCYLON]

Originally Posted by Z51JEFF

Last time I got a smog check it was pretty close to the max Nox level even though the cars only got 25,000 miles. Other than a K&N air filter and open housing it’s bone stock. I’ve got a little help from our friend Mr. H,any other tips I should look into,stock air box or open housing,low power mode at the valet switch? I’m thinking about running e85 just to be on the safe side. Thanks for any help here.

MOVE off the Left Coast

[Vette73]

Get a late 60's early 70's muscle car with a stroked motor, lumpy cam and flowmasters ......Drive it and annoy the crap out of everybody.....Anybody complains just say " hey its legal"....

[Hib Halverson]

Originally Posted by Z51JEFF

Last time I got a smog check it was pretty close to the max Nox level even though the cars only got 25,000 miles. Other than a K&N air filter and open housing it’s bone stock. I’ve got a little help from our friend Mr. H,any other tips I should look into,stock air box or open housing,low power mode at the valet switch? I’m thinking about running e85 just to be on the safe side. Thanks for any help here.

Getting the 1G LT5 though the "enhanced" Smog Check can be tough.

Questions:
What model year?

One reason why the California Smog Check has become an big problem for 2G ZR1 owners is that the State, though the its Bureau of Automotive Repair (BAR), has been tightening up the standards for older vehicles. With respect to the standards that apply to '90-'95 model year vehicles, the oxides of nitrogen limits have been lowered at least twice that I know of.

The reason for this is to force old cars off the road. The Demokratik Peoples's Republik of California has been running the Smog Check since the early 1980s. With the tens of millions of cars on the road in since then, the State has a s&&t-load of data on real-world exhaust emissions.

It knows it can force a certain amount of old cars off the road if it simply lowers the cut lines on the various pollutants it tests for, one being NOx. Further the State has data showing what cars typically test near those limits even if they are "legal". The cars it most wants off the road are the ones which pollute the most but are still legal. The LT5 engine's weakness is NOx production and that's why, with California gradually lowering the cut lines, C4 ZR1s flunk when they used to pass. Eventually, when you can't pass you either have to sell the vehicle, scrap the vehicle or sell it out of state. There are some exceptions but many old cars which are in the Smog Check get black-balled because of that.

When I owned Barney, my dearly-departed Purple '95, back in the early '00s I ran up against that problem. After flunking a pre-test three times because of NOx, I decided to find out why a good running LT5 with stock cams and new cats kept flunking the low-speed part of California "enhanced" Smog Check which is used in areas of the State which have the most air quality problems.
Well, after doing some road testing, I found that the EGR valve, used on '93-'95s was calibrated to enable at 17-mph. The low-speed part of the Smog Check is done at 15-mph. Once I knew that, the solution was simple. I had Ron Zimmer, who used to do my cal work back then, burn me a cal with EGR turning on at 14-MPH.

I never had trouble with the Smog Check, again.

That said, people with '90-'92 cars still have a tough time. There are some strategies to help get engines in good condition through the test, but E85 is not one of them.

In any event, The OP's problem was eventually solved with a pass of the test and that's a good thing.