Quote:
Originally Posted by NASSTY
As I broadly understand it, NOx is mainly affected by timing.
CO and CO2 is more a fueling issue.
Mando, is your set up running closed loop? If not, unabling closed loop should fix alot of your tuning issues as the ECU will trim up your A/F ratios to 14.7:1 which is what your cats need to work properly. I assume you're using aftermarket EFI.
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Further info: I spent some time at uni tuning a race engine for the FSAE competion the unis do, NOx is timing based but also fuel mixture based as fuel mixture controls combustion temp, which is the driver for CO or NOx as the outcome from the combustion process. Looking at the numbers you can see that NOx is low, but CO is high, so it's off tune. Once it is tuned back to stoic conditions (14.7 is stoicometric fuel combustion ratio) then NOx will come down and CO (and CO2) will come up. What the Cat does is help eliminate the NOx (which is why the manufactures put in better cats to reduce CO2, lean it out = better fuel economy and less CO2, but more NOx which is taken care of by the Cat convertor). So your tuner in this case would put less fuel in, to lower the CO/CO2, but increase the NOx which in any case the cat should be taking care of anyways.
THC is the total hydrocarbons, which is either too much fuel, or
oil bypassing rings/etc in an older engine. But cause theres too much CO/CO2 its more likely a fuel rich tune (12:1), which is good for power, but bad for the test which is likely to prefer a 15-16:1 (lean tune).
Hope this helps.
Nathan