happysem

iTrader: (5)

Ok, so if you read my thread in the Texas section, you should be caught up to speed.
https://ls1tech.com/forums/texas-mem...ng-my-car.html

But this is a more technical question;
Why do you think my car failed emissions?

Car is a 1995 Z28, 64xxx miles, all stock when I bought it except for the K&N CAI.
Seafoamed fully when I bought it ~6 months ago.
Now its got PaceSetter Long Tubes (non-race, still has AIR/EGR) 2.5" Catted (Walker brand cats IIRC) X pipe, into Dynomax Bullet Mufflers, untuned.

Was it the cats I bought?
The bullet mufflers?

This is a 100% DD car that will hardly see the track, so I need it to pass emissions/inspection easily, I live in a pretty strict area, been warned several times for the mufflers being dumped...and I don't want to deal with this anymore.

But I've got some time to get it to pass, so I feel like I've got 2 options;

Drop the current true duals exhaust and go with a quiet Y-pipe/catback set up with cutouts for when I wanna be loud.

OR

Keep the current exhaust and just get better cats/mufflers.
If I do this, what is a better choice?
I think I'll want full size mufflers, not bullets if I do this, or maybe just one muffler in stock location with dual in/out.

Anyway, what do you guys think?

97Z28SS

iTrader: (5)

If it were me I'd finish the exhaust you have by running over the axle and out the back and place the mufflers all the way at the rear of the car like most new performance cars do.
However that being said what did the car fail emissions for that info would help greatly?
Has you car been tuned at all?

djjab57

iTrader: (17)

need to know what part of the test u failed

happysem

iTrader: (5)

During the sniffer part, my Nox levels were too high.

djjab57

iTrader: (17)

You can buy some of the stuff to put in your tank called pass or something like that, Also make sure your car is running at tempature when the test is done. It helps when the car is hot

flame

iTrader: (13)

I went through this years ago. Pacesetter LT's with catted y and stock cam failed on NOx. The location of the EGR tube on the Pacesetters doesn't provide enough back pressure for the EGR valve to open. The EGR on these motors is a back pressure sensing valve. Put all the vacuum to it you want and without back pressure on the valve it will not open. I ended up manually lifting the valve during the test to get a pass...........its all about who you know.............

See the link for testing and operation http://shbox.com/1/4th_gen_EGR.html

happysem

iTrader: (5)

Thanks for that link, I wonder if my EGR is messed up, my car did just overheat, which it never does, but it was fine after I let it cool down.

It also says thats where spark knock may come from, maybe thats why he thought my plugs were bad?

Smoke Em

where are the cats located?

Spartan7

iTrader: (7)

What were ALL the readings? We need HC, CO, and NOx. High NOx is generally caused by high combustion chamber temperatures, which the EGR system helps negate.

I had LTs and a cam on my Camaro, and it passed NOx easily. And this is in CA. But without the other smog readings we can't accurately help you.

Puck

iTrader: (17)

You need a tune bro!

happysem

iTrader: (5)

Sheet;



Cats are located almost right after the collectors, and yeah...I would love a tune but thats out of the budget at the moment.

I'm still wondering if the EGR is bad/failing, but I'm really not sure how to tell, that link helps but I'm still kinda meh on how to figure it out.

Thanks guys!

Spartan7

iTrader: (7)

CO and HC look good, so I'd lean towards the EGR system. A lean condition or knocking can also cause high NOx.

How is the engine running? What fuel are you using? Check around for any vacuum leaks. I would also take it to a different place, if he's whining about plug wires then he's looking too hard. His plug wires might very well have been the issue.

happysem

iTrader: (5)

The engine feels real solid, I've noticed no loss of power or strange sounds, there is an exhaust leak somewhere around where the header seals up on the block but thats it.

Always running 93 octane.

AChotrod

iTrader: (17)

That could be your problem. O2s arent reading correctly with that header leak

Smoke Em

^^ check that first, i think your close enough so something stupid is throwing it off.
was the car hot ?

happysem

iTrader: (5)

Alright, I'll investigate the leak further.

Yeah, the car was definitely warmed up by the time it was on the dyno.

160 t-stat so it heats up a lot idling.

djjab57

iTrader: (17)

Stock T stat is 180, so a 160 will just cause the water to start flowing sooner which makes it run cooler but as long as its normal operating temp it should be good and not cause the knox high

tom falco

High NOX to much cylinder temps. EGR NOT WORHING OR LOW FLOW is the number 1 cause of high NOX. Engine running lean engine running hot to much initial timing fans come on to late ETC. You have to get that motor to run cooler. Install a 180 stat and run the fan. NOX is easy to fix Just think TO HOT.

SS RRR

iTrader: (2)

If I'm not mistaken the EGR operation is controlled via solenoid and vacuum.

flame

iTrader: (13)

Go read the link on testing. Put all the vacuum in the world to it and it will not open without backpressure.