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Old 02-18-2012, 12:16 AM
1fastredsc 1fastredsc is offline
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Join Date: Apr 2010
Location: Carlsbad, NM
Posts: 19
Originally Posted by whunter View Post
Emission gas readings are irrelevant, the only EPA spec for 1985 and earlier is opacity.

Your vehicles failed opacity??
No state can legally fail these engines for any other reason.

Three points whunter:
1) The opacity emissions test will not be a problem for CO or NOx emissions as both gases are relatively transparent. Opacity is mainly a good way to measure the health of a diesel engine in order to get a rough idea of it's health (too much soot or HC are signs of a unhealthy engine, or running way too rich when loaded).
2) The government sets up emission standards for both the engine itself at the design level and out the tailpipe for after purchase validation of a properly operating vehicle.
3) I've ran experiments on diesel generators during my college days. I saw first hand what different loads, EGRs, and biodiesel will do to a diesel engines emissions and efficiency. Just like anything else, it's all a balancing act. Some things, like EGRs, that are meant to reduce emission also reduce the thermodynamic efficiency of the engine which results in less power and worse fuel economy. This is the reason that some diesels can see an increase in fuel economy and power after advancing the injection timing a little past OEM specs (of course not too much).

I'm not suggesting that anyone shouldn't remove their EGRs, quite the contrary, I'm a big fan of it on old diesels especially when you live out in the middle of nowhere like i do and have no mandated emission testing. I like the improved throttle response and fuel economy. I'm just realistic with the consequences as well. By the way, testing has shown that modern vehicles run so damn clean that in some cases the exhaust coming out of those vehicles is cleaner than the air that went in. For that reason, I removed my EGR and balance the air quality by driving in front of a new car when possible .
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