Anyone good at tuning for emissions test?

[Terminal_Crazy]

Only things I've found (I'm in England and have an annual emissions test)

Retard the timing from 34 idle to 20. Helps heat up the O2's and cats.
Increase the idle to as fast as allowable 800 upto 1100

I have a single 3" pipe & cat back to the rear muffler and 2x 3" outlets. I've found sealing one up and reducing the one with the sniffer pipe in will allow the CL to target properly.

On a normal test Lamdda shows up as lean, over 1.03 (limit), but with high HC. Sealing the tail pipes usually pulls it down.
I think the reversion sucks extra air into the pipes & the low flow rate DOES NOT work with the short test pipes they try & stick in.
This also makes the car very hot.

HTH
Mitch

[Hellbilly]

Only things I've found (I'm in England and have an annual emissions test)

Retard the timing from 34 idle to 20. Helps heat up the O2's and cats.
Increase the idle to as fast as allowable 800 upto 1100

I have a single 3" pipe & cat back to the rear muffler and 2x 3" outlets. I've found sealing one up and reducing the one with the sniffer pipe in will allow the CL to target properly.

On a normal test Lamdda shows up as lean, over 1.03 (limit), but with high HC. Sealing the tail pipes usually pulls it down.
I think the reversion sucks extra air into the pipes & the low flow rate DOES NOT work with the short test pipes they try & stick in.
This also makes the car very hot.

HTH
Mitch

I have a true dual 2.5" exhaust and they put a cone around both of them when testing. My O2 sensor it heated and before testing I'm running it up and down the highway a couple times to make sure everything is warmed up good.

Their test pipe is like a 8" vacuum hose so it's going to pick up any and everything that comes out the exhaust.

[Fast355]

This was from the last year my 83 G20 van had to pass a dyno test here in Texas.

It had a Vortec head TPI engine with a fairly mild hydraulic roller cam.

Generally speaking, retarding the timing will help reduce NOx and HC emissions. Retarding the timing lowers the peak combustion temperature and raises the exhaust gas temperature. CO emissions are from running too rich. If the test is run under much load, raise the PE activation point to a higher TPS/RPM setting. Run the tank fairly low and add a gallon of denatured alcohol will help lean it out and burn cleaner. Do not be afraid to pull 6-8* of timing out of it where the engine is loaded for emissions testing. With aftermarket aluminum heads that have a decent combustion chamber, a stock L31 Vortec timing table would certainly help reduce the NOx emissions. I ran the machine in a test mode to make sure it would pass prior to the actual inspection being performed by a co-worker at the time. At this point I had a 2.5" dual in/dual out catalytic converter on it, thorley tri-y headers and had tuned the fuel tables with a wideband. I had also played with the proportional duration values as well as the 02 sensor switch points to keep the AFR swinging very close to stoichiometric, it had a swing of about 1/2 point richer and leaner than stoich in closed loop. That alone really cleaned up the emissions readings. Garbage into the cat = garbage out the tail pipe. I had the stock L31 timing map from my 97 Van programmed into the TPI computer when this test was made. One other thing I have personally witnessed as well. Higher octane gasoline seems to burn more controllably, and the HC and NOX readings are typically a bit lower with 91 or 93 octane than they are with 87.

[Hellbilly]

FAST I think you're the one that helped me get this thing running a few months ago.

I finally got a WBO2 put in today, about to go test logging. Hopefully I did it right. Lol

So had already pulled a total of about 5 degrees before this test. Also had about half the tank with 91. The test before only had about a degree more and it had lower HC, but higher NOX.

I'll do some logging and adjusting this week and keep posting here for tips. Try to run the dank down and fill up with higher octane. Biggest PITA about all this is them wanting to know what you did to try to fix it every time you test, then trying to get you into the state sponsored repair program lol. I'm running out of parts to tell them I changed. Wish I had somewhere to go sit on a dyno with a sniffer, sounds like that would make things allot easier. The test here actually checks several speeds though, not just high and low. They have a graph on a screen that goes up and down several times and the have to match wheel speed to it.

[Hellbilly]

FAST I think you're the one that helped me get this thing running a few months ago.

I finally got a WBO2 put in today, about to go test logging. Hopefully I did it right. Lol

So had already pulled a total of about 5 degrees before this test. Also had about half the tank with 91. The test before only had about a degree more and it had lower HC, but higher NOX.

I'll do some logging and adjusting this week and keep posting here for tips. Try to run the dank down and fill up with higher octane. Biggest PITA about all this is them wanting to know what you did to try to fix it every time you test, then trying to get you into the state sponsored repair program lol. I'm running out of parts to tell them I changed. Wish I had somewhere to go sit on a dyno with a sniffer, sounds like that would make things allot easier. The test here actually checks several speeds though, not just high and low. They have a graph on a screen that goes up and down several times and the have to match wheel speed to it.

Here's a little test run with the WB. Everything looks lean. Where should I be making changes?

[dave w]

Perhaps the WBO2 tuning spreadsheet available here will help with figuring out the changes: http://www.gearhead-efi.com/Fuel-Inj...ng-Spreadsheet

[Hellbilly]

Perhaps the WBO2 tuning spreadsheet available here will help with figuring out the changes: http://www.gearhead-efi.com/Fuel-Inj...ng-Spreadsheet

Thanks Dave . I'll take a look this afternoon

[Fast355]

FAST I think you're the one that helped me get this thing running a few months ago.

I finally got a WBO2 put in today, about to go test logging. Hopefully I did it right. Lol

So had already pulled a total of about 5 degrees before this test. Also had about half the tank with 91. The test before only had about a degree more and it had lower HC, but higher NOX.

I'll do some logging and adjusting this week and keep posting here for tips. Try to run the dank down and fill up with higher octane. Biggest PITA about all this is them wanting to know what you did to try to fix it every time you test, then trying to get you into the state sponsored repair program lol. I'm running out of parts to tell them I changed. Wish I had somewhere to go sit on a dyno with a sniffer, sounds like that would make things allot easier. The test here actually checks several speeds though, not just high and low. They have a graph on a screen that goes up and down several times and the have to match wheel speed to it.

Sounds like an IM240. There are some Mustang dynos that have an IM240 mode and a 5 gas analyzer. I was able to use one at the trade school I was attending in 2004 when my 1983 G20 had a Q-Jet on it still. We used my van in my driveability class because my instructor was a former GM lead tech and knew the Q-Jets like the back of his hand. We went through the Q-Jet, then the van went on the dyno. A twist here, turn here and a few other small tweaks had that 200K mile 305 passing the smog test easily and it gained like 5 mpg. From memory I had to buy a new GM PCV valve, EGR valve and a Deceleration valve for the thing. A former shop that had worked on it had shoved a BB in the EGR vacuum line and a ball bearing in the deceleration valve. The EGR delete had the NOx as a gross fail and the deceleration valve had it extremely rich on deceleration. The decel valve opened under high rising vacuum and allowed a steady stream of air to bypass the carburetor through a 3/8" hose attached to the PCM hose and aircleaner, leaning it out.