Emissions

Following are the emissions reports for the owner of a '96 Dakota. Sniffer tests are required in the area of Virginia where he lives. Unfortunately, there were other changes besides the MPI that took place between these tests so this isn't a true indication of the effect the MPI alone might have on emissions, but at the very least, we know that the MPI can pass emissions, and with flying colors at that! (Clicking on a picture of a report will show you a larger version.)

The "before" test, taken in 1998. Mods done to the truck at this point were:

K&N FIPK
JBA Headers and Y-pipe
3" Gibson Cat-back
Mopar Performance PCM
Taylor "Spiro-Pro" Wires

The "after" test, taken in 2000. Between the previous test and this one, the following items were added:

MPI Intake
24lb injectors
Hughes Cam, Valve Springs & Retainers
F&B Stage I TB
Roller Rockers
Double Roller Timing Set

Summary:

15mph readings 25mph readings

Limit Before After Net change Percent change Limit Before After Net change Percent change

HC (ppm) 107 33 52 +19 57.6% increase 103 63 30 -33 52.3% decrease
NO (ppm) 786 342 419 +77 22.5% increase 712 488 381 -107 21.9% decrease
CO (%) 0.59 0.12 0.20 +0.08 66.6% increase 0.57 0.28 0.03 -0.25 89.2% decrease

As you can see, although the 15mph emissions readings did go up somewhat, the 25mph emissions went down! Given that the stock 19lb injectors were swapped out for 24lb units and a more agressive cam was installed, any emissions changes can probably be attributed to them, as opposed to the MPI. But, at the very least, we now know for certain that adding the MPI does not result in an automatic sniffer fail. Far from it! :-)

FYI: The above truck was not "prepped" in any way for the test. The owner wanted to see exactly what the results would be so he just "drove it in off the street". I'd like to express my profound thanks to this individual for that and especially for sharing this info with us. Thanks, Rich! :-)

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