If there's a vacuum leak, expect codes but even if no codes car can't run as it should. Possible damage to cats whether codes or not.

 

When the tech refitted the entire exhaust with new 2.25" pipe we were able to view inside the recently installed new cats and they were fine. The first pair of hi-flow cats got cooked when the tube running from the EGR to the passenger exhaust manifold rotted open, causing a massive exhaust leak. The exhaust is good to go save the O2 sensor extenders which are to arrive in a day or so. Still, a top-side vaccume leak may persist. Presently, she's at the indy Jag tech for inspection. New rear wheel bearings, Mina Galleries lowering/sort springs, and new CAT struts are going in too, then off to the body man for repairs and paint. Oh g-d....

 

Where do you buy the O2 extenders? Do you have a brand name? Thanks.

 

What are they claimed to do? How? Are they not just "snake oil"? Explain please...

 

burnhydrox.com $6.50 each. Need two, one for each down stream cat.

 

Thanks for the info!!!

 

No-one?

 

Are you asking what the O2 extenders do? They move the O2 sensors further away from that cats and the upstream O2 sensor so that the two sensors (i.e., the one upstream and the one downstream) don't communicate with eachother with near identical readings, which will trip the CEL. If you have high-flow cats and are not getting the CEL for O2 sensor issues, then you will have no need for them

 

I know they move them away but why is that useful? If they fail to read the O2 content properly then either you'll get codes or the wrong fuelling. How is either of those good?

I can see an argument for the downstreams being moved away a bit, on the basis that the cats don't work adequately so you try to hide that fact (*) from the sensors. But the upstreams? Surely you want them where they normally are? If not, why not?

(*) bad for the environment and you'd hope illegal

 

The ECU reads gases at the downstream O2. Yes, hi-flow cats allow hydrocarbons to slip by thus not better for the environment. Moving the O2 sensor somewhat out of the exhaust stream doesn't eliminate it from the stream.

 

No it's not the downstream it uses for fuelling. It at most gradually trims the learned values based on the downstream. It uses the upstream for fuelling, which is why I think you do NOT want an extender there.

 

Like you said, the O2 sensor after the engine but before the cats (so we do not get confused with this upstream/downstream talk) is the one the car uses for fueling. That is not the one you use an extendor on. You use it on O2 sensor one after the cats and before the muffler.

Like this....

Engine--O2 Sensor A Pre-Cat--Catalytic Converter--O2 Sensor B Post Cat--Muffler

The one that you use for fuel determination is the "O2 Sensor A Pre-Cat" and that one you do NOT use the extendor. The one you do use the extendor on is the "O2 Sensor B Post Cat"

So while the O2 Sensor A Pre-Cat is doing all the important air/fuel reading, you just leave it alone and let it do its thing. The O2 Sensor B Post Cat is pretty much just gauging how the cat convertor is working, that is the one you put an extendor on.

FWIW, I had a Subaru WRX that had no catalytic convertors on it, they were all removed (it had a total of three! For one exhaust! One on the up-pipe which made the turbo lag forever!) and I used a CLE eliminator and my car showed no issues in tuning, it appeared to be running like normal totally fooled by the CLE eliminator, so I am sure the extendor is even safer.

 

It's really hard to confuse upstream and downstream!

So what is it that the extender does (other than the blatantly obvious moving them away i.e. the extender bit)? No-one knows?

 

My guess (and keep in mind I am no mechanic, and I only learned about extendors last week lol) is that they just create enough of a gap between the pre and post cat O2 sensors so that they don't read near identically. I would imagine thats all they do. My mechanic friend who did the work on my car said when they are too close together on a OBD1 cat converter (like the 5000 series Magnaflows) they will read nearly identical readings, thus your car thinks there are no cats. You may have better luck with the 9000 series Magnaflows, which are OBD2 like our cars were made for.

 

The O2s are NOT going to read anything like alike, not least because the upstreams are wide-band and the downs are not.

I suspect my guess is right, that they're putting them where there's semi-unchanging gas because it's a siding, so the downstream O2s fail to see the exhaust gas properly and thus overlook it's not the way it should be. But it sure would be nice to have some science facts posted.

 

I had the car on the lift again today to cure leaks at flanges, so I snapped some pics for you bfsgross. These are pics of O2 extenders installed (one pic shows both cats and both extenders, the other is just of the driver side cat & extender)....






Huge thanks to Billet Design Motorsport in Pompano Beach, FL for getting me in so quick and taking care of their post-install leaks so fast while I waited 15 mins.

 

Sorry for incorrectly explaining the O2 sensors. Thanks to UnderPressure for posting the pics.

 

Great pics! Just one question, you used the Extenders on the o2's only on Downstream? or also on the Upstream o2's?

 

Chris, the extenders are to be used only on the downstream O2's.

 

I'm about to discover the joys of sensor positioning myself (fingers crossed!).

I just thought to suggest an answer to the question about why fitting the downstream O2 sensor-extender would provide a fix; this may be because of laminar-flow in the exhaust - the extender pulls the sensor-tip out or the main body of gas flow. The closer the sensor-tip is to the outside diameter of the pipe the slower the gas is moving (slightly more time for the reactions to have completed post-cat? Presumably the tip would also be slightly cooler due to the sensor conducting a slightly greater % of heat from a lower-concentration of heat due to the slower-moving gas at the periphery). I think JagV8 suggested something similar just worded a bit differently when he said the sensor would be in "semi-unchanging gas because it's a siding". What do you reckon?