Has anyone passed with just a cat-back? and has downpipe and pre-silencer.

 

Which RX7?

 

so,is the presilencer the CAT?
You won't pass without a cat and an airpump.

 

87 t2
s4

 

The down pipe replaces the pre-cat
and the pre-silencer replaces the main cat.
however, there are still those cat-backs.
so im wondering if the cat-backs are good enough just on their own.

 

Not unless you've got cats welded in the cat-back.

 

Cat backs won't affect the emission test.
Cat-backs will pass. Downpipes technically fail the visual, but you can pass the sniffer. You won't pass without a main cat and air pump.

 

There are 3 portions of a CA smog check that you must pass:

Functional
Meaning all emissions control components must be working as intended. Generally speaking during a smog check, this includes: Checking the check engine light for proper operation, checking the gas cap, checking the EVAP system, checking the EGR system if the test is a TSI.

Visual
Meaning every single emissions control components must be intact and hooked up correctly. Everything from vacuum hoses to EGR Valves. This also includes making sure there are no after market performance parts on your car, and if there are, that they have the appropriate C.A.R.B number with them. With that said, there are no C.A.R.B legal downpipes.

Emissions
Last but not least, you must pass an emissions testing of your tailpipe as laid out here: http://smogcheck.ca.gov/pubwebquery/.../ShowMake.aspx


SO, to answer your question: If the car is running well enough, and I mean REALLY WELL, yes you can pass the sniffer with just a cat. How do I know? I've seen it before in my 6 years as a smog technician. However, I'd say there is a 90% that you will not pass the sniffer unless you have a good cat AND an airpump. So even if you find a tech that will let you slide on having a downpipe and stuff (which is possible, some techs don't know what they are looking at), I still highly doubt you will pass the sniffer unless you have a functioning air pump.

 

Is it possible to do these tests on an S4 or other pre-obdI cars?

 

Absolutely

Gas cap test involves sticking the gas cap on the tester, pumping it up and making sure it can hold it's intended pressure.

EGR test involves somehow actuating the EGR Valve at idle to make sure it introduces exhaust gases into the intake.

EVAP (if equiped, most cars are) system test involves closing off the vent tube from the EVAP canister and pumping the gas tank with inert gas (nitrogen) and making sure it doesn't bleed off within a set amount of time.

The only one that is sometimes not done on older pre-obd1 cars is the check engine light test. This is because most manufacturers didn't incorporate a check engine light until the mid-late 80s. This test is done by turning the ignition to Key On Engine Off and making sure the check engine light bulb illuminates. Then, after starting the vehicle, making sure the check engine light goes off after a couple seconds.

 

I'm sure they always do the full testing at the "15 min smog check" places. It'd take them 15 min to find the EGR!

 

So I guess I just have to swap the stock parts back in for smog tests and put the mod parts back afterwards. sigh*

 

So true

 

copy/past fail

 

Take it to a no pass no pay place. They never visually checked my car.

 

ive got an NA s4 with a stock exhaust but hallow precats and passed if that helps in any way