This was posted in the TDI forums:
Hey fellas! So we have a 2009 Sportwagen TDI "clean diesel" with the DPF - diesel particulate filter. The car NEVER smokes, even under hard acceleration, and we love it! Over 14K miles since we bought it in September!
I know that the Benz's and new Toureg/Q7 TDI motors will be using a Urea injection system.
From wikipedia:
"The solution is injected into the exhaust system and releases ammonia. This reacts with the nitrogen oxide emissions and is converted into nitrogen and water within the catalytic converter."
So I was thinking I could try to incorporate a similar system in our new Sportwagen to make our car run even cleaner. However, rather than mess with the separate tank to hold the Urea mixture and all the fancy computer controlled metering system, I had an even better idea. From the same wiki article: "Urea is, in essence, a [human] waste product. It is found in and extracted from urine."
This was easier than I expected, and I was able to kill 2 birds with 1 stone! I rigged up a small funnel and some tubing that runs down next to the gearshift, through a small hole in the floorpan, and through a 1-way valve into the exhaust pipe. This is very important- the valve has to be upstream of the catalytic converter or it won't work.
On long road trips where a bathroom can't be found, I can either collect my urine in a jar and pour it into the funnel, or with some creative yoga inspired stretching, I can pee straight into the funnel. My wife, of course, has to use a bedpan.
Here is a shot of the underside of our car- you can see the exhaust valve that opens and closes to adjust the backpressure of the whole exhaust system. The O2 sensor is just upstream of that, and there is a catalytic converter just upstream of the sensor. (see the 2nd picture)
In the 2nd picture, the heat wrap obscures the opening for the one-way Urea valve.
I really can't tell if the exhaust is any cleaner, but I'm hoping that when we take it for the yearly emissions check that they will allow me to introduce some urea into the exhaust stream as they "sniff" the tailpipe. Once I have conclusive proof of cleaner exhaust, I may consider perfecting and marketing a kit. For example, when I pour the urea into the funnel and it hits the exhaust pipe, it makes a loud hiss and some steam comes back into the car. It's not so much the odor is a problem, but the steam fogs up our panoramic sunroof. I'm sure a small sponge wedged in the tube (or another one-way valve) will help alleviate this minor problem.
Another upgrade could be a bedpan with a drain that leads out the back and through the seat, down through the floor. Something that would make my wife more comfortable, and also enable us to remain seated and belted while doing a number 1.
Ralph
