Sube Buggy Posted March 21, 2016 Share Posted March 21, 2016 Hi guys I have a question maybe someone can give me some info. I have a rail buggy with all Volkswagen parts so its labeled as a "historical" car on the title and plates so in my area we don't have to get emissions check for the car. to make a long story short i don't have cats or need them so can i get away without the second oxygen sensor and keep the upstream for the fuel. The second sensor generally the downstream sensor is for monitoring the catalytic converter? Quote Link to comment Share on other sites More sharing options...
Bushwick Posted March 21, 2016 Share Posted March 21, 2016 What engine? What year is the OBDII? Up O2 is important for proper engine running. Down O2 mainly monitors the cat's efficiency, and if cat is missing, will throw a code. If you want to run cat-less is most cars and don't have the ability to turn the down O2 OFF via software, you can buy 2 spark plug anti-foulers. They can be found in the same thread size as O2 sensors, and you can buy them in the "Help!" area at Autozone. You need to drill out the center hole on ONE of the anti-foulers, then thread both together and thread into down O2 bung (I strongly recommend applying a small dab of anti-seize in both including the bung and down O2 threads or they may not come back apart w/o a torch being used) and thread down O2 into that (google will show plenty of DIY help). Anyhow, the anti-foulers pull the down O2 out of the direct exhaust flow, but still allow it to sample, and it'll fool the ECM into thinking a cat is in place. To be honest, you can add an aftermarket "race" cat which is short and roughly 1/3 the size of a glass pack and not have any issues, and most likely have the same power. If cat is already gone and running straight pipe, the anti-fouler trick will stop the CEL on most engines, but it may run REALLY rich. Should definitely monitor this. A race cat will at least cause it to run normal, but make SURE the style of cat is correct for the engine. If it's a non Subaru or something you can actually tune on a software level, you could correct too rich, 2nd O2 off, etc. Other option would be carbing the engine as you'd be able to fine-tune the way it ran. Quote Link to comment Share on other sites More sharing options...
Sube Buggy Posted March 21, 2016 Author Share Posted March 21, 2016 Thanks for the reply bushwick that's probably what I'll end up doing I don't need a cat nor do I want to buy a new one so I won't be running one its on an old Vw bug chassis from the 70's so it will just have the upstream but the code won't bother me my other question is will that make the car run like crap even if I have the upstream sensor because the light doesn't bother me as long as it doesn't effect the engine to much Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted March 21, 2016 Share Posted March 21, 2016 I think a potentiometer or a small resistor network can be used to kill the code too. Just something adjusted to send - what? ~0.7V back on the sensor wire? Quote Link to comment Share on other sites More sharing options...
Bushwick Posted March 21, 2016 Share Posted March 21, 2016 If the CEL is lit, it might go into a closed loop. What engine/year are you running? If you do the anti-fouler trick, CEL should remain off, but it might run rich. I did this briefly on my Saab and it ran extremely rich, and entire pipe was sooty. Once new cat was put in and anti-foulers removed, it went back to normal running. You can buy something like this: http://www.summitracing.com/parts/mpe-53956/overview/ for $70 + tax. That's only 8" long by 4" wide. That's 2.5" pipe. Should be able to find 2" to 2.25" as well. I'm assuming you are running a Subaru engine with Subaru ECM, which for whatever reason hasn't been reverse engineered yet, so you can't simply shut the 2nd O2 off or compensate if it starts running rich or even too lean. You can run it rich, but you'll risk cylinder wash. Too bad you aren't running a Saab with the T5 engine management system, as I have the hardware adapter for those and could flash your ecm and shut the 2nd O2 off (I live in Stow). Quote Link to comment Share on other sites More sharing options...
matt167 Posted March 21, 2016 Share Posted March 21, 2016 Subaru prior to 2005, the rear O2 does nothing to the fuel trim or open/ closed loop. All it does is light the CEL and throw P0440 if somethings amiss with the cat.. Subaru after 2005 will alter the fuel and ignition map to attempt to correct the catalyst efficency if it's off.. Using an anti fouler on 2005+ electronics would be a bad idea.. My 2001 Forester has had an anti fouler in the Cat since about a week after I got it ( burned out cheap aftermarket cat ). No ill effects and CEL hasn't come on 1 Quote Link to comment Share on other sites More sharing options...
Bushwick Posted March 21, 2016 Share Posted March 21, 2016 ^ Well there you go. Sounds like you'll luck out. Don't forget the anti-seize and make sure you have enough room as the anti-foulers stacked + O2 add nearly 5" of length which can hit things. Quote Link to comment Share on other sites More sharing options...
Sube Buggy Posted March 22, 2016 Author Share Posted March 22, 2016 thanks for the good replies i really like this forum quite a bit but thats cool you live up in stow i'm about 35 ~ 40 minutes south at the most. Its a pretty good setup it is the stock ecm i got a donor car from Cleveland for 900 and drove it home with no problems. tore it apart and threw it in the buggy still working on the radiator set up i hear the procedure is rather easy, and is there any specific hose i need to get to block off the automatic trans cooler lines in the radiator or looping the heater hoses? for example you would want a high pressure line for fuel is there special lines for the radiator? Quote Link to comment Share on other sites More sharing options...
Sube Buggy Posted March 22, 2016 Author Share Posted March 22, 2016 oh i forgot to ask too, how far from the engine should i make the o2 sensor. each port on each side for the exhaust meets into 1 flange i'm assuming to put it after the flange so the ecm can gauge both sides of the exhaust Quote Link to comment Share on other sites More sharing options...
Bushwick Posted March 23, 2016 Share Posted March 23, 2016 I don't think trans cooler hoses are high pressure. I'd at minimum run an external cooler possibly with small 8" - 10" fan (like a small Summit trans cooler) if it's not getting fresh airflow through the fins or is running too hot, and just use it's hoses and clamps. If trans is older and high mileage, you definitely want it as cool as possible to prolong life, especially if it sees any off roading. The radiator side for a trans cooler should be a direct in and right back out. As long as trans fluid is out of it and you aren't planning to reuse, leaving it unplugged shouldn't matter. Otherwise either find a proper end nut or leave a small hose section and jam a bolt in it to keep corrosion/dirt out or just loop it back to itself. Try and put up O2 as close to the factory distance from head as possible, and try and avoid installing on a pipe bend as it might mess with the readings. Consider looking at VW kits for inspiration on where they are welding the O2 bung at. If you have to lengthen the wiring at all, try and use the exact same wiring (if it's 18 gauge silver wire, use 18 gauge silver throughout) and use heatshrink to protect it and consider installing a molex-style extension adapter vs. cutting your O2 up. Moisture on the wiring can actually cause codes to appear and screw with O2 readings. Quote Link to comment Share on other sites More sharing options...
Sube Buggy Posted March 23, 2016 Author Share Posted March 23, 2016 Thanks bush I'll end up doing that the transmission is a 4 speed manual so I don't need to worry about a cooler or anything but I took it on its first test drive yesterday down the road and damn is it a lot quicker off he line then the old 1600cc Vw engine. But it bogged out like it was cutting out the gas at mid high Rpms it acts like it just does cuts back in and cuts out again. The clutch isn't slipping and it idles amazing perfectly at 800 rpm revs perfect no cut outs in guessing this is because it doesn't have the speed sensor or oxygen sensor so this makes me think it went into limp mode not sure of speed or rpm on the dot but the rpm was mid high range but off the line it threw you back a little bit any ideas? Quote Link to comment Share on other sites More sharing options...
Bushwick Posted March 23, 2016 Share Posted March 23, 2016 I thought you were running an auto. Just plug the auto trans cooler lines on the radiator. You have no O2 sensor whatsoever? Or are you referring to the downstream O2? The speed sensor isn't connected? What trans are you using? Quote Link to comment Share on other sites More sharing options...
Sube Buggy Posted March 23, 2016 Author Share Posted March 23, 2016 No I haven't made the exhaust yet I am tomorrow so when I go I'm getting a bung welded in for the o2 sensor neither up or down are in its only the first piece of the exhaust manifold to a flange so that's why I was asking about the downstream catalytic converter questions but it's a 4 speed 70's type 1 super beetle transmission and I'm working on getting a speed sensor I know the wire of the ecu for the signal it should vary between 0 and 5 volts or something like that but it's also obd2 so that's why I think it's bogging but like I said right off the start its prestine Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.