If you’ve been following this Blog recently you know I’ve been interested in testing several bolt on performance upgrades for my DB9. One of those upgrades was a Secondary Cat Delete Kit (SCDK). You can learn about how I installed it by checking out my other article here. I wanted to learn if my car would still pass a stringent California Emissions SMOG test with an SCDK fitted. Read on to find out if it did.
The idea behind a SCDK is to remove the redundant downstream catalytic converter that the car was originally fitted with. A DB9 has 6 catalytic converters when it leaves the factory. Four Primaries (two per bank, each serving three cylinders). Downstream of the Primaries for each bank is a Secondary catalytic converter.
The purpose of these Secondary cats is a bit of a mystery. There are no oxygen sensors surrounding it, so its not being monitored by the powertrain control module (PCM). It may be there as a polisher for the exhaust stream. Or, it may have been fitted by Aston to make the car a Global car able to be sold in other markets that required it. All this is a guess of course.
Why remove the Secondary Cat?
Breathing is everything in an engine. Sucking air in, and expelling exhaust out. It is suggested that removing the secondary catalytic converter will improve three things:
- Increase engine efficiency and power by removing back pressure the secondary cat creates in the exhaust stream.
- A slightly more aggressive ‘snarl’ in the exhaust note since the secondary cat acts as a form of muffler.
- Reduce the vehicles weight by about 10 pounds, further improving handling, mileage and performance.
Is it Bad for the Environment? Let’s find out.
I live in California, USA – land of the most stringent auto air quality emissions standards in the world. I wanted to know if the DB9 would still pass a California SMOG test with the SCDK fitted.
To make the test even harder I opted to take it to a Star Certified SMOG test station that looks even that much closer.
Like all Californian’s I’ve had my DB9 SMOG checked every two years since I’ve owned it, and its passed every time. I keep it in good running order, so I am not surprised.
With my SCDK installed I took my car to a local Star Certified SMOG Test Station. I didn’t attempt to skew the test at all, I just showed up and turned my car over like anyone normally would. Sitting in the waiting area and looking through the glass I could see them open the hood, inspect the system, read the labels, stick probes into the tailpipe and even use a mirror to inspect under the car. Their computer tester did its testing.
They also stopped to pose and take selfies with the car.
Five minutes later I was told it passed with flying colors and they handed me my certificate! Check it out.
So for $69 USD I have the answer on whether it will pass or not. Now you know too.
Is it legal?
I suspect the answer is technically a ‘No’ in the United States. Generally anything that modifies the emission control systems on a stock vehicle would not be looked upon kindly. This is a blanket position. If you fitted something that even improved the emission standards it would be considered illegal since it was a modification. I am just doing all these mods as a test, and will of course return my car’s emission system to stock after the test is complete.
Am I worried about any environmental impact? Of course. I don’t want to ‘Roll Coal’ and kill all natures critters. But I’m not convinced there is any significant additional harm in this change either. It passed the stringent SMOG test before. It passed the test after. I will sleep fine knowing that the sky will still be blue tomorrow and my car won’t be its downfall. I’m sure you’ll have your own opinion on the matter, and feel free to leave it down in the comment section below.
With the emission test passed, lets get on with something fun! Next up with be an article comparing the sound of the exhaust note before and after the SCDK is added. After that will be a trip back to the Dynamometer to see if its really adds the promised power gains.
Here is a short clip of me being really happy it passed!