So last month I failed emissions due to a burnt up exhaust valve(probably a big factor in the drivability issues I've been having, and hadn't had time to look at till now, do not know how long it's been like that, car has always had a miss, and still has a slight miss, though not as bad as it was). Anyhow, I did a valve job, (just need to get past smog at this point so it was nothing fancy). I have my ignition timing currently set at 15 degrees BTDC spout out, and am seeing lambda 1.0 at steady cruise at 55-65 mph. At a stop sign or light, I see about lambda .75. Is this gonna have a shot at passing smog like this, or do I need to reduce fuel pressure to lean her out some, just long enough to pass smog, and then I'll put it back until I get her tuned(not a project for this month...) I do not smell unburnt fuel when sitting at a light like I had before I did the valve job, but my afrs aren't that much leaner at idle than they were before. I need to get her smogged by the end of this month, so I do have a small amount of time to fiddle fart around with her, but would like to do it soonerer rather than laterer...
Johnny
86 XR
At .75 lambda you do not have a prayer of passing smog. Should be .95-1 at the condition they sniff it.
86 Mazda RX7, 2.3 swap, t5, MS3 sequential, BW EFR 6758
"If you can't dazzle them with knowledge, baffle them with bull sh*t"
I thought that would be too rich at idle, looks like I have more work to do...
Johnny
86 XR
Also reduce your base timing. Having the timing advanced will not be emissions friendly. You might set it at factory recommended or slightly less.
Sometimes I drive fast....
You pretty much need to be in closed loop to pass a sniff test. You can monitor the factory O2 sensor by tapping into the signal wire (I don't remember which EEC-IV terminal, but you'll find out quickly with a search if you don't know already). You probably know this, but just in case..., in closed loop the O2 voltage should be jumping between 0 and 1 volt pretty regularly. The frequency increases with increasing rpm & load.
Geoff - 85 XR DD back in service - with a vengeance!
"Beyond the Palace, Hemi powered drones scream down the boulevard" - Bruce Springsteen
Are all of the smog controls hooked up?
Rob Hilton So Ca
Save time E-Mail Me at: rrhilton@fasterfours.com
All smog controls are hooked up. I have the LM1 as the only O2 sensor with the NB simulate to the EEC.
Geoff, I can only assume that I am able to achieve closed loop, as before I did the valve job, I had no codes whatsoever. And yet I still had a heinous miss. Still have a slight miss.
I took her out for a couple of WOT pulls on the road today, and watched the WB as she hit 12 psi(no IC yet). WB read .75 lambda at 12 psi and 4500 rpm at 70+ mph and increasing velocity. I am contemplating dialing back the ignition timing, and then the fuel pressure until she hits about .9 - 1.0 lambda on the wb. I'd probably put it all back in until I can make time to properly tune it out right. I still have to hook up the dat logger, and really want an a pillar mounted AFR gauge, but that has to wait.
Johnny
86 XR
What the lambda reading is under boost has no effect on the emissions testing. You're only concerned with the readings under the conditions they test (idle or low speed/load). Tune the fuel pressure to get lambda to .95-1.0 under those conditions and don't run it under boost until after the testing is over and you can be sure it's still safe under boost.
Ill just dial down the boost for the test too then. That way they can't wreck it...
Johnny
86 XR
