Today I took my s4 rx7 for a smog test and barely passed,unfortunately I have to retest Being the shop found my evap lines going to the canister were reversed and failed me just for that. Now I have to retest but being that I am so close I'm worried I may not pass the HC part of the test. Any input of what can improve my HC results will be greatly appreciated. Here's my setup

S4 rx7
JDM s4 turbo motor
Aftermarket universal o2 sensor
Haven't touched timing but upon checking it appears to be 3 marks off for leading and 1 mark off for trailing
Port air diaphragm forced completely open ( I still get a light amount of airflow through the split air pipe)
Stock cat
Brake booster has a leak I can hear

 

Get a new cat to swap in and out.
You could try running it on alcohol but people have mixed results and normally don't do it right.

 

I don't think a cat will help my HC result, from what I understand the cat will be the result of the NOx reading which is well within the required level. Feel free to çorrect me if I'm wrong

 

You are wrong.

 

Perhaps a better explanation may help????

 

From the FAQ.


I'd take it straight back after an oil change and 10 hail mary's.

 

a new cat would help, but this is california and the only legal cat is the one you have or a new one which costs as much as your car is worth.

timing also affects emissions quite a bit, though it's not listed on many rotary emissions diagnostic threads. i'm not sure what you mean by the timing being off by a few ticks, there is only 2 ticks on the factory pulleys(1 for lead and one for trailing). if you have an aftermarket pulley set then you'd have to ask the manufacturer what each mark represents. retarding timing will usually lower HC levels, so if your timing is advanced then you should adjust it back temporarily.

to clean out a converter i usually do a water injection treatment on the engine, which helps burn off carbon deposits from oil and normal usage.

 

Thanks for the info guys, I am due for a oil change, RE I will double check the timing and report back

 

Our cars are equipped with three way catalysts. First stage, in front of the air injection tube, oxidizes NOx. The other two stages, located behind the air injection tube, oxidize carbon monoxide and unburned hydrocarbons.

 

the core on most factory cats is also plated with platinum, platinum is the best oxidizer and most efficient but also the most costly to produce.

universal cats use lesser quality precious metals as an oxidizer, hence they are less efficient. adding more cats offsets the issue in most cases but it also hurts performance, and still does not address the issue that california implemented with the OEM cat law.

 

Magnaflow has CARB approved cat.

I didn't think they cost that much.

 

Just came back from the same smog shop. I did the oil change and to my surprise no change to my 15 mph and 25 mph sniffer test, exact numbers all across. So it passed for now i'll take it but I will continue to troubleshoot and hopefully net better results in 2 years.

 

i don't know where the whole myth about oil causing high emissions came from, but unless it's sludge and loading up the engine then it shouldn't make a difference.

 

i agree now that I have seen it with my very own eyes

 

Always figured it would be better due to the fuel dilution and what not when it gets injected. Guess that one is debunked.

Thanks for the results Gregs22.

 

I just received the second link cat from Magnaflow and the inlet and outlet pipe are too small. I think the stock exhaust size is three inch but the inlet and outlet on the cat are about an inch too small. I may try and order the first link one but It looks like you won't be able to use the heat shields.

 

Those two cats are also advertised as direct fit, but I think that only means the lengths, not the inlet and outlet size. I ordered for my 90 T2

 

the stock pipe size is 50mm, which is like 2.25" OD