Dynatech Longtubes and Cats - Emissions Testing

**OA-5599** · 08-01-2009, 11:11 AM

I thought I would pass on my experience with emissions testing on my modified 5.7L.

Colorado and Denver in particular has some pretty stringent emissions laws. There is a five year grace period from testing for new vehicles, however. I purchased my Magnum in July, 2004, and within a year I had installed Dynatech longtube headers, free flowing cats, and an aggressive exhaust. I have been plagued by P0420 codes since, and have done all of the tricks to clear it (replace the o2 sensors, single then double spark plug extenders, multiple grounding, etc) but found it only goes away when I drive several hundred miles at 3,000 altitude or lower. The catalytic converters on the dynatech setup are tiny, maybe one third the size of stock, and you can look right through them.

Last month I added a Vortech Supercharger running 5.5 psi boost. Then the card came in stating I needed to have an emissions test to renew the tags.

People have had some problems with the dynatech cats being blown out or melted down; running a FA system with he increased airflow was a worry.

Anyway, I pulled into the test area and use the Diablo to clear the codes and quiet the check engine light. I still thought there was no way this car is going to pass, what with the SC and non-stock cats. They had to make two runs on the emissions "dyno" as the operator had a hard time keeping the reves within the course (there are a series of "hills" followed by a long, low rev flat, then an acceleration up to what sounded like 3,500 rpm) since when the supercharger kicks in (around 2500) the revs really jump.

Anyway, when all was said and done, the friggin thing passed! Not only that, but the tech complemented me on how low the emissions were! No $hit, all of the readings were 1/3 the max allowed or less!

So what this means is that even though I have heavily modded the system to put out a hundred or more horsepower over stock, even though I am running aftermarket aggressive exhaust, even though my mileage around town has dropped down to 12 mpg, this huge, 4,200 pound car is more "green" from an emissions standpoint than probably 3/4ths of the other cars on the road!

Hats off to Dynatech for a great exhaust system, and to Rocky Mountain Competitive Research who installed the supercharger and performed a custom tune.

I guess the moral of the story is that if you use quality parts and have them installed by reputable shops, you can create a screamin' street machine with the manners of a daily driver and meet or exceed today's tough clean air standards!

**sergeo'shemi** · 08-01-2009, 11:53 AM

nice, i am glad it worked out for you

**Sprayed Charger** · 08-01-2009, 05:58 PM

They don't use dyno's around here in chicago anymore for emissions it's just plug and play. I thought if you cleared the codes the monitors still need to be set and the car driven for a certain amount of miles before the monitors will be "ready". Congrats on passing emissions!