My last emissions test on my '88 NA was yesterday and I thought I'd share the results. Since it'll be 25 years old (from the model year) in 2013, I won't need another test. It passed again this time, though with less margin than last time. This is a treadmill/dyno test done at the same station both times.
Of course, there are many variables that could cause the numbers to change, but I did make one big change to the car between these tests. Two years ago I had a fairly new Bosel cat back exhaust on the car, which is fairly restrictive (but quiet). Now, I have one of Raptor Racing's 2.5" cat back systems, except I put in a Hushpower II resonator. The straight-through resonator Raptor sold me was way too loud. The muffler is a Magnaflow. The catalytic converter is original, but the O2 sensor is only about 30k miles old (engine rebuild).
Since the CO% dropped and NO went up, my first thought was it's running leaner. But the HC also went up. It's not using any more oil than it used to. The 25mph test is first, then the 15mph. Maybe the catalyst was a little colder this time, but warmed up for the 15mph test.
The engine is much happier running at 1800rpm with the 2.5" exhaust than with the Bosel, though I almost never drive at that rpm.
Any other ideas/comments? It's running great. I do need to check the air filter since I don't recall when I changed it last.
Of course, there are many variables that could cause the numbers to change, but I did make one big change to the car between these tests. Two years ago I had a fairly new Bosel cat back exhaust on the car, which is fairly restrictive (but quiet). Now, I have one of Raptor Racing's 2.5" cat back systems, except I put in a Hushpower II resonator. The straight-through resonator Raptor sold me was way too loud. The muffler is a Magnaflow. The catalytic converter is original, but the O2 sensor is only about 30k miles old (engine rebuild).
Code:
miles 229510 239808 limit
15mph (2nd gear)
HC ppm 55 52 92
CO% 0.10 0.04 0.37
NO ppm 128 367 1200
rpm 1782 1829
25mph (3rd gear)
HC ppm 143 162 167
CO% 0.25 0.22 0.53
NO ppm 290 578 1167
rpm 1890 1962Since the CO% dropped and NO went up, my first thought was it's running leaner. But the HC also went up. It's not using any more oil than it used to. The 25mph test is first, then the 15mph. Maybe the catalyst was a little colder this time, but warmed up for the 15mph test.
The engine is much happier running at 1800rpm with the 2.5" exhaust than with the Bosel, though I almost never drive at that rpm.
Any other ideas/comments? It's running great. I do need to check the air filter since I don't recall when I changed it last.