Re: O2 sensor

["Jonas Karlsson" <jonas85k@hotmail.com>]

>From: "Andy Teague" <bionicpunk@hotmail.com>

>Ok, now, please forgive me for beating a dead topic, but i need to get some 
>solid closure here.

Yeah, it's pretty dead, but here's one more bullet in the head.

>I have learned this:
>1-- the O2 sensor increases gas mileage
>2-- it also lengthens the life of your cat

Simplified and misleading.
1. Running your car at a 14.7:1 air-fuel ratio will give you near optimal at 
both power and fuel economy. A smidge rich is max power, a smidge lean is 
best gas mileage. The O2 sensor is an integral component of a SYSTEM that 
functions quite well (when working) to maintain a 14.7:1 A/F ratio.
2. It won't lengthen the life of it, but having excess unburnt fuel (like 
when you run fairly rich due to not having a functional SYSTEM to maintain 
14.7:1 A/F ratio) will overheat the catalytic converter which will 
drastically shorten it's life.

>My sensor is not hooked up, and I'm pleased with the gas mileage, and I'm 
>planning to install a tri-y header and remove the cat.
>SSSOOOO...  Will drilling and welding the o2 sensor to the header (which is 
>what some reliable sources have told me to do)  Actually increase 
>performance as well?  I don't need better gas mileage, and there won't be a 
>cat, so should I go to all the trouble of modifying the header to accept 
>the sensor??  I would figure if it was so necessary, the header 
>manufacturers would put a place to mount it on all headers, not just 
>some...

Yes, modify the header to accept the O2 sensor. (technically you won't be 
welding the sensor on there, you'll weld on a threaded port for the O2 
sensor to screw into). The reason yours didn't have the port is because that 
header is designed to be used on early cars that were not equipped with cats 
or O2 sensors. Using it on later cars is technically an "off-road" only 
application, as removing smog equipment is a crime (heh, like that matters). 
You need the O2 sensor connected to have a fully functional SYSTEM to give 
you optimal A/F ratio (not to mention less stinky exhaust now that the cat 
is gone) :-)

BTW, having no cat will dramatically increase your fuel mileage (due to less 
work wasted to push out the exhaust gases). You should be happy about that.

Did it stop twitching yet...

Jonas
85 Scirocco 2.0
78 Scirocco 1.8
87 Scirocco 16V
For direct reply: jonas@metabolex.com
http://www.geocities.com/scirocco2l8v

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