Can I pass emissions with a 300 hp M20 turbo setup?

[jc1000]

Hey guys, I live in Salt Lake county in Utah and just learned that even with classic plates I will need to pass emissions. Some people register their cars in different counties to get around this but I don't want to do that. Some local E30 guys said I should still be able to pass "as long as I get a decent cat and a proper tune." Does that sound right? They also confirmed that pre-96 cars "only need to pass a sniffer." I am willing to invest in a good high flow cat if that is what it takes to pass emissions. Just want to hear some more opinions.

My planned setup: 2.7i (stock ETA bottom end + 885 "i" head) with a turbo, though I am also considering swapping in i pistons and shaving the block to boost compression.

[Panici]

Are you running a standalone ECU?

With a good Cat and full fuel table control, you should be able to make it pass a sniffer test.

I've never tried to tune for optimal emissions, but I imagine it's balancing your NOx / CO / HC / (whatever else they measure) emissions based on how lean or rich you run it.

Aside: Make sure you're not burning any oil or you'll poison your new cat.

[jc1000]

Panici thanks. Yes, I'm planning on running a MegaSquirt PnP.

[e30davie]

What is the actual test? idling when warmed up? or cold?

MS PNP has the ability to use closed loop wideband to target AFRs. I do it on mine, I currently target the AFR target table below ~70% TPS. I have mine setup to about 15% authority to change but I have my VE table dialed in to about +/-5% or so.

The question is though, what is the best AFR to pass your required test? and I dunno what it is for the m20, I just use 14.7:1 on cruise and idle on mine. Just about need a sniffer to tune it so you know its good to go before you turn up for the paid test.