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The VIPER Garage  |  How To Instructions  |  How-to section  |  Deactivating the rear 02 sensor reliably and cheaply, allowing Cat removal.
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Author Topic: Deactivating the rear 02 sensor reliably and cheaply, allowing Cat removal.  (Read 1532 times)
RTTTTed
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Viper Nation - ezine
« on: February 04, 2012, 03:27:29 PM »

When I bought my 2001 GTS in Ohio it ran amazing.  Driving back from Ohio (3,000+ miles) caused the car to cruise OK, but WOT was a lot of blacks smoke and a lot of noise, ... not much "GO".  The CEL engine code was for Catalytic Convertor issues (rear 02 sensor programing).  Looking under the rear of the GTS I saw that the connectors were plugged into "Simms".  I plugged the connectors back into the stock 02 sensors which were still installed in the exhaust. 

YAH, it ran pretty good again!  I did a lot of 'tuning' on my Vec and easily could lose power, but couldn't reliably get the WOT to work consistent.  It seemed that after a thousand or so mile I'd need to reprogram the Vec or switch from 02 rear sensors to Simms or back.  All the tuners I spoke to said that didn't make any sense.  I also figured that it made no sense.

Removing the Cats from any car with rear 02 sensors will quickly or later cause a Check Engine Light/CEL and/or a rich fuel dump situation.  The rear sensors are to prevent you from removing the Cats and/or signal a rich mode if the Catalytic Convertors are in danger of melting down (destroying your mileage).

To fix that problem I bought 2 sets of "Sparkplug non foulers".  These are like a sparkplug spacer with a chamber at the electrode that has a small hole into the cylinder.  Purpose to keep oil from splashing out the spark?  To keep actual drops of fuel from shorting out the plug?  What ever the case may be, from some "Ricers" I learned that the OBDII rear oxy sensor program added to all ECUs for emmissions requirements could be rendered obsolete using a couple sets of sparkplug nonfoulers.  The OLDER sparkplugs that used the 13/16" sockets (18mm threads nowadays) were the size of the 02 sensors and screwing 2 together and drilling out the top one to 1/2" opening allows the Oxy sensor to 'read' a chamber that has a much smaller hole allowing only some exhaust gases acess to the 02 sensor which causes the 02 sensor to read that everything is good!  Viper have dual exhaust and use 2 rear sensors meaning that to do this upgrade you will need to buy 4 non-foulers.  Usually a 2 piece package (buy 2 packs). 

My GTS does often have a gasoline smell which is sometimes caused by removing the Cats.  JonB and several tuners believe that you are better off (not to mention enviromentally friendlier) if you run Hiflow Cats.  My gas mileage improved - end of my story.  No arguement from me.  I need that couple miles to the gallon and the extra horsepower lost to Cats.  My cars are not even close to stock.  750 or 1000hp exhaust flows going through that exhaust would be severely restricted by platinium/ceramic heat retention chambers.

Instructions;

Buy 4 18mm thread sized sparkplug non-foulers.

Drill 2 through the centers with a 1/2" drill.



Screw drilled non-foulers into stock non-foulers and tighten together.



Unhook electrical connectors and remove rear oxysensors from exhaust.  Located inside sills on side exhaust at in rear wheelwells on rear exhaust cars. 

Use a 'touch' of never-seize on the oxysensor threads (careful not to use too much and keep away from sensor end) before screwing sensor into the non-foulers.  Instal non-foulers into exhaust with oxysensors in the non-foulers. 

Re connect the sensor's elec. and put everything back together.  If your car had a CEL, clear that and you're good to go. 

This is the best cheap solution I found. 

SCT programmers can write a program that will eliminate the function of the rear sensors, but the heater check circuit still stays active so the sensors actually have to be screwed in anyway or you'll get a sensor CEL for teh heater not working.  Why the SCT can't removed the heater check circuit program???   Who knows?  :idk:
« Last Edit: August 30, 2016, 07:49:41 PM by RTTTTed » Logged
1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
RTTTTed
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Viper Nation - ezine
« Reply #1 on: February 04, 2012, 05:53:51 PM »

 :)  I forgot the warning.  These changes (simms, non-foulers and Cat removal) are probably illegal in most states and probably all Provinces.  Check.

There are laws allowing Cat "Test pipes" ...   Not sure if they have a time limit or not?   :lol: 

At an SRT tech session Dick Winkles said that in a good running car, the only time the Cats do much of anything is upon cold start.  Personally I find that on some cars the Cats are so restrictive that the boost pressure can actually increase 3psi just from removing the Cat/s.  Newer models are MUCH better and the Cats are much smaller containing less toxic materials inside.  Newer Cats are basically Hiflow from the factory and have "blocks" of material for the exhaust to flow through with spaces between.  The newer Vipers may come with low restriction Cats compared to the older Gens?


« Last Edit: August 30, 2016, 07:50:14 PM by RTTTTed » Logged
1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
RTTTTed
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Viper Nation - ezine
« Reply #2 on: October 25, 2017, 09:30:12 AM »

LOL, "the Viper Store" sells the spark plug non-foulers for 'only' $49 plus ($20?) shipping    :P
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1999 1200rwhp TT GTS - ART, 2001 Roe sc GTS- (4 sale), 440 Duster restomod (sold), 3x Stealth TTs, 92 Daytona IROC with T3, 580whp/1080wtq Cummins pickup.
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