SD2- Emissions tuning help needed


Jul 20, 2010

Eric help!

My '87 GN passed emissions a couple years ago when I had a 6.1 chip on E85 and 80lb injectors (rest of mods in sig). Cat is on as well as the EGR (I'm assuming as I don't remember it being taken off).

I went to the SD2 and have not been able to pass.

1st time I had all of the parameters to open loop and whatever the default parameters were (98 or 99) with the following results:

(Photo 1)
HC- 1.30 Pass
CO- 20.20 Fail (need to be under 15.00)
NOX- 1.61 Pass

The following mods were made because according to the testing place if you have only a CO failure it is due to overfueling. This last time around I went to closed loop and set Param #2 (Idle), Param #3 (Cruise), Param #5-7 (Low-Mid-Mid/High) all set to a target A/F of 14.0 using a PLX WB, which I am assuming is on the gas scale as I have not changed it. The following results were obtained: (See Photo 2)

(Photo 2)
HC- 0.88 Pass
CO- 22.91 Fail (Need to be under 15.00)
NOX- 0.91 Pass

As you can see I brought the HC and NOX down quite a bit (not that it was needed) but the CO actually went up.

How can I get my CO under 15?


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I would not expect the SD2 chip setup to pass emissions, unless its absolutely perfectly tuned to hold 14.7 AFR, which is not easy. (A MAF is better at things like that.) But there is also no EGR function in the chip.

However, in order to get CO down, you typically need to go leaner, around 14.7-15.0 AFR. If that doesn't work, you might need a new cat converter.

If you still have a stock-type narrowband O2 sensor installed, you might be able to enable narrowband mode, which can hold closer to 14.7 in many cases.

Thanks for the input. The first time round I did not have the closed loop enabled so I'm assuming that on that first round it was using the narrowband...?

I'm new at the tuning thing so I did not want to go too lean. I can try again with everything as above set for an AFR of 15.0 and try it again.

If the above does not work then I guess my next option would be to order an emissions chip from you. Would this work since my IAT sensor has been moved to the doghouse?

Are there other "tweaks" in the emissions chip that would have a better chance at passing?
No it does not use the narrowband for anything unless you turn on narrowband mode. But I wouldn't go that route yet, as it gets confusing.

Params 2 and 3 are target a/f for idle and cruise. Those are the ones you would set to 14.7-15.0. Params 5 through 8 are not target a/f's, those are fuel trims (see chip instructions).

For the emissions chip, it requires a MAF and stock narrowband sensor. The IAT doesn't matter. That chip has all the stock emissions programming in it, so it has the best chance of passing.

I will make the above adjustments and try one more time.

If it does not work I will order an emissions chip. I will also be sending back my SD2 chip for the flexfuel upgrade, so maybe you can ship both to me at the same time.

Thought you might like to know that your products ROCK! (Like you didn't already know...;))


Not only did I pass but I killed it! Check out the attached results...

This go-round
HC- 0.26 Pass
CO- 5.87 Pass
NOX- 1.28 Pass

I put Param 2 & 3 at an AFR of 15 (gas scale PLX) running E85, and fixed my Param 5-7 goof (going back to the default 128), and had excellent results, way under the maximums.

I had been driving the car around with these settings to see if it would stay at the set AFR and it did for the most part. I noticed that the idle fuel was trying to pull over 10% (max) so I dropped it to 126 and that seemed to keep it below the 10% (don't know if it mattered or not for the test).

Not sure how lean this setup is and would not push the car this way, but I will be keeping these setting around for future tests.

All-in-all I am very pleased with the tuning power of this setup, WELL worth the money, and could not be happier!!!

(Your results may vary.)
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