cv67

good advice
Ask seller to do a pretest while youre there to see if it passes and by how much. Even if you compensate him for it still worth it if you get the car you want

Sphinx

For those of you who've failed smog, I assume that you had your cats hot prior to the test? I was speaking to a friend who works for a major car company and he relayed how a friend of his with a early 2000's truck failed smog but had not gotten the cats to operating temp. At operating temp it was no problem to pass.

mike100

The interesting thing about the LT5 is that you don't want to run too hot from a long or extended idle time because the early cars don't have EGR to lower the NOx. Nox is elevated by several things--one of them being higher coolant temps. The HC and CO is a piece of cake to pass. It's the NOx (and the visual of course) that is a bit touchy.

The easiest thing to do is test with a stock chip except reprogram the radiator fans to run at lower temps. this helps a lot. If one wanted to flat out ace the test- them you could take a little ignition timing out too and cheat like VW.

odxr

I used to have a smog license In california but I got out of the business of being a dealer tech so after not using it for 5 or 6 years I let it go.Simple solution to the OP'S problem.In Cali the seller is responsable for the car to pass smog.If the seller is motivated the car will allready be smogged before its even listed for sale.Make the seller smog it.As far as a semi-legal work around-register you car in a non-enhanced area.Like at a friends cabin in the mountains.Just dont do stupid stuff like burnouts in front of a LEO or drive the car while its not running correctly.

Hib Halverson

There are some pretty significant gray areas in the above discussion.

First, while it is true that elevated ECT could contribute to elevated combustion temperature, you have to wonder what contributes more to NOx emissions, high ECT or high combustion temperature?

Hotter the cats are the better they catalyze the exhaust and reduce NOx. Problem is when you operate the car in a manner that increases cat temps, ECT goes up, too. Also, aftermarket cats usually suck at cutting NOx so put stock cats on.

The idea of lowering fan-ons will help as well as reducing the amount of antifreeze and going to a bigger radiator.

As for retarding spark, I wouldn't because retarded spark increases both ECT and combustion temperature.

Without a lot of really expensive testing knowing what temperature is most important but my wild-*** guess is this priority.

1 low combustion temperature
2 hot cats
3 lower ECT

mike100

I used to play around with BAR90 4-gas smog machines that read out the reading realtime. lowering the timing would clean up the HC/CO on many vehicles- especially the older ones where it was easy to adjust via distributor. I wish I had a 5-gas machine. There is a published fuel mixture graph that shows the window for ideal gas on the NOx is the narrowest of all the test gasses. This is why the o2 sensors should be as good as possible. I halved my NOx by just putting fresh sensors in. The old ones were still 'good enough' for the HC/CO to hit good numbers, but the NOx was barely getting there.

Anyhow, late ign timing will heat up the exhaust manifolds (later combustion) which will keep the cats lit. The coolant temp is really related to combustion temps directly as it helps pull heat out of the heads.- but mainly it's combustion temperature that makes NOx and of course fuel mixture contributes. Nox is the toughest goal to meet for sure.

I still am thinking about seeing a referee next test as there is a different standard for the ZR-1 submodel, but as it currently stands, the tech has no way to bring this up on the state's database when they enter the car's info. This would seem to be an underground regulation that the BAR isn't authorized to make by excluding the different standard. I have older tests that show a different model, test weight on the rollers, and the higher limits for the 11:1 LT5. I'm pretty sure I will still pass, but even if I can't get the answer on this matter, I'm at least hoping to get a free test at the referee this year.

cv67

Absolutely!! Let them know you want a legit smog check
Some will smog it prior to selling as they cant get it to pass, fake it then put it up for sale.

Happened to an aquaintance, not a Z but an 80 eras truck all stock everything way it was supposed to be. Seller got a fake one, sold it with no consequence. 2 yrs later the buyer found there was no possible way it could have, got records from the sellers shop and it was closed down long story short.

Buying isnt simple as it used to be pre internet.
Everyone used the Recylcer, everyone knew who had what, were honest etc made it real easy. God I sound old.

Never walked uphill in the snow 7 mi ea way so far though!
Wheelchairs dont do snow

Awemazing

I recently bought my '91 Z from Nevada, and had to register it in Los Angeles, and had to smog it. It's as bone stock as it gets. Called around and found a guy that (for some reason) would do the test, and if it passed, I payed, and if it didn't, I didn't have to pay a cent, and it wouldn't go down on the record and add one to my gross polluter status (something about the car being a "special, older car"). It passed with flying colors. I don't know if he did anything special to make it pass so he wouldn't be doing a free test, but it worked out. I was incredibly surprised that it passed on the first try.

I definitely agree that you should find someone to do a pre-test, even if it costs you 30 bucks, you know where you stand, so you can go at the real test with your best foot forward.

cv67

pretest x2 will show areas that could or maynot need improving.

Why couldnt someone take a cat say off a HD truck and weld it on to the stock manifold they are 3 stage right? Id think that would be better than the old stocker?!

odxr

Make sure you tell the smog machine operator to do the pretest offline.When I had my smog license many years ago I did a series of pretests on a questionably legal car.Went on vacation 3 weeks later and found out when I got back that a BAR inspector was looking for me while I was gone.The smog machine logged all of the pretest to BAR and from the paperwork/data trail things looked fishy.Any car thats in an as-new condition should pass.The likelyhood of a smog inspector finding a doctored ecm( think VW) are very small.The red flag that sets an inspector off is seeing ANY aftermarket parts.Currently in Komifornia you need California special replacment cat convertors and thet have # stamped into them.Example-1 of my customers (2007 chevy 1500 pu 4,3 v6)had some universal cats spliced into his exhaust system,Truck made good numbers but was failed on the visual inspection.Last november I happened across a roadside smog inspection ran by BAR.I stoped by and talked to them-they were out of Riverside county.They were working in Stanislaus county.So with all of the daily per diem allowed for employees away from home-can you say this is a smart way of spending tax dollars?My hot rods are registered in El Dorado county.They are not used as daily drivers.

cv67

ANy updates?

still think the idea of using GM 3stg (3 way?) cats may get him by. Look on craigslist for someone parting out a HD truck lots out there
Being as there are no replacements bet it would pass the visual even with a referee. The aftermarket cats dont work anywhere near as well (ask me how I know)

Too bad some testing couldnt be done measuring EGTs and compensate. Has to be a way around this to keep these on the road.