I am an automotive technician specializing in European performance cars including but not limited to Porsche, Mercedes, BMW, Jaguar, Volvo, etc../Forged Steel Valves

In Houston, Texas the emissions testing for cars now includes a "dyno test" under load while measuring exhaust emissions.

The "dyno" runs at low speed during the test and tends to load the engine as if the vehicle was climbing a steep hill in high gear.

Some of the performance cars I am working on (Porsche, Turbo Volvo, Jaguar) have a hard time passing the NOX emission standard.

If I add a small amount of alcohol while the engine is running under load can it reduce the combustion temperature and reduce the NOX output?

As I have also been toying with a water injection system to increase mileage, wouldn't this water injection system also reduce the NOX?

Any comments on my questions, or any other thoughts or experience with this problem are welcome.

I'm guessing that if the alcohol has a lower adiabatic flame temp, then yes it could lower the overall combustion temperature which in turn can lower your NOx. Should be some literature on this in any book on combustion. If you can, run the engine at a certain RPM (preferably high)on usual fuel whilst recording the temp until a stabilized or steady state temp is reached. Then do the same experiment but this time once you ahve reached the steady state temp, add small amounts of alcohol to see if there is any change in temp. If the temperature drops by say 100 degrees then you'll probably have a reduction in NOx.

If the cars are fitted with three way catalysts then it's either: not enough catalyst to reduce all the NOx to N2 and O2 or (more likely) the closed loop biasing being too lean. Three way cats have a very low tolerance to running lean (less than 1% lean will drop converter efficiecy to ~20%) but a fairly broad tolerance to running rich (2-3% before significant CO or HC breakthrough). Hence manufacturers 'bias' the fuelling slightly rich to ensure that on aged catalysts there is little or no breaskthrough of NOx. One way to check this is to measure the rear O2 sensor voltage using the appropriate scan tool. If it's reading ~0.2V at steady state speed and load then the mixture entering the catalyst is too lean (it should read ~0.6V). If this is the problem it's difficult to 'fix' as this is something that is calibrated during the development phase of the vehicle so you need specific tools. The two main options (if available) are to retard the spark or introduce EGR both of which will reduce engine out NOx emissions significantly.

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