1x4x9

So I just had my '91 Miata (OBD I) running a Megasquirt PNP, smog checked here in CA to see if I might just pass without doing anything special. I know little about tuning and have simply been using a AFR map that Joe Perez gave me for a naturally aspirated car. It runs well and has plenty of pep for a NA car but clearly isn't running clean enough to pass CA smog. That, and the check engine light doesn't come one, which tipped the guy that something was fishy. He said that if I can pass the sniff test and the check engine light comes on with the ignition and then goes off, that I'll pass.

My questions are these:

1. Can anyone tell me what my AFR map should look like for a NA Miata running MSPNP in order to pass CA smog?

2. I'm wondering if there's a way to rig a timer switch that will illuminate the check engine light momentarily when crank the ignition.

I'm grateful for anyone's input.

Thanks,

Ben

jasonrobo02

iTrader: (13)

You'll probably want to post the smog test results. Failing HC vs. NOx can be caused by different issues. And if you failed significantly, it may indicate that you killed the cat with too much fuel (running too rich).

buffon01

iTrader: (9)

I ran 14.7 across the board when i was N/A and 15-16 at cruise.

1x4x9

Thanks everyone. I've attached my AFR table and the smog report. I'd appreciate any input you can give me. If I've killed the CAT, throwing in a new one isn't a big deal. At $100, I'd actually rather do that than remove the MS and reinstall the stock ECU, that is if I can figure out a way to deal with the check engine light, which seems like someone with a little electronics knowledge should be able to help me with.

1x4x9

So like I said, my tuning knowledge is pretty limited. Where on my AFR table would I go to 15 or 16 in order to replicate your tune?

Thanks,

Ben

jasonrobo02

iTrader: (13)

You can see that you failed visual for timing not being set within factory limits. Borrow a timing light and verify that MS is controlling timing properly. If so, you'll have to adjust your timing map closer to stock values.

The failure on NOx emissions is probably caused by your timing values also. My bet is that fixing timing will make you pass (and figuring out the CEL).

1x4x9

Interesting. Do for OBD I, do they just throw a timing light on it to see where you're at? I I recall correctly, when setting up the MS, you basically manually set the timing to stock (10.whatever degrees) and then let MS control it electronically. For this reason, I'm curious why it wouldn't pass visual. I guess a related question there (here's where my ignorance shines) when MS is controlling timing and say it's advancing it, can one tell that's happening upon visual? No matter, I'll check it out to see if it either slipped or if my recollection of where you manually set it for MS is incorrect.

By the looks of my AFR table, do you think the CAT should be ok?

Thanks,

Ben

jasonrobo02

iTrader: (13)

I'm not even looking at your map. Based on your HC levels on your smog sheet, I'd say the cat is fine.

The smog tech will hook up a timing light and verify base timing. I think you get something like +/-2* from spec which is 8-12* for a Miata. If you hook a light to your car without messing with MS, you should get in that range. If you don't you'll have to adjust your timing map until you do. If you read around 10* at idle, you will pass the timing visual check. But you may still have to mess with the timing map around the cells that are used during the dyno test to combat the high NOx.

MartinezA92

iTrader: (4)

-14.7 for cat efficiency.
-make timing map closer to stock numbers
-don't set your cruise cells to 15-16 AFR when you smog, because you'll probably fail NOx
-there is definitely a way to make your MIL turn on and turn off. I'd google it or something.

Uhh, your AFR table isn't going to accurately tell us if your cat is fine. I say you try to get close, and if you're still failing by a small amount, throw a cat at it.

Once timing is checked initially, the smog tech won't be looking at your timing during the 50/15 or 25/25.

Since you're failing NOx so badly, just dick with timing (read: retard, a lot) until you get it down.

By the way, a car without a cat is capable of passing HC and CO, so it is still completely possible to fail NOx because of a bad cat.

JasonC SBB

Over and over again, I've said you need the 5 gas numbers to troubleshoot smog.
That means include O2 and CO2 numbers.

1x4x9

I must say, this style of communication baffles me and the forum is filled with it. Are you talking to me? Are you saying I've missed something, haven't included some info I should have, failed to do something I should have? Complete sentences with context please. If it's not completely obvious, I'm a total novice and need complete explanations if I'm to understand everyone's input.

Thanks,

Ben

buffon01

iTrader: (9)

Maybe you need to research a bit more and at least attempt to find a solution as opposed of having other members do all the work for you. Kinda like, help us help you. Im not familiar with smog, because I dont have to undergo it, but sounds like you lack the basics and that can make it very difficult for other to help you solve your issue.

1x4x9

No doubt you're correct... and I'm doing my best, reading everything I can get my hands on. It just seems that people need to understand that there's hard earned understanding and then there's aptitude and they're not the same thing. Cryptic communication only serves to make the conversation unnecessarily difficult. As usual, I'm gratful to everyone who's contributed, including Jason. AND I'm still a novice who may have bitten off more than he can chew, trying to get his daily driver properly certified, and looking for all the help (and tolerance) he can get. I think I have enough to go on though. Thanks all.

Will manually check timing. Then be sure MS timing map is within manufacurer's specs. Then I'll redo my AFR table to pretty much be 14.7 across the board and run VE Analyze. And finally, I'll see if I can't rig a timer switch to throw my check engine light on and off at ignition.

Thanks,

Ben

Techsalvager

if you know anyone with personally with an exhaust gas anayler thats where you need to go to help tune for passing emissions.

Without you can only tune based off the info you got from the emissions testing and hope to goodness you pass next time you go back.

Did the tester at emissions give you a paper saying what is required and what the engine put out?

buffon01

iTrader: (9)

Okay, with that said I have two questions for you:

1. Who and/or how was the timing set once you switched to MS?

2. What exactly have you read about MS?

Let me suggest you read the MS manual. I cannot recall the exact link, but Im sure a Google search will yield quick results.

jasonrobo02

iTrader: (13)

Read the thread. I asked for this from the OP at the beginning and he immediately provided it.

Techsalvager

yeah my bad.