tb30570

I'm looking for a set of downstream o2 sensor simulators for the OBX long tubes I'm installing.

has anybody tried any of these brands?

http://www.afterthoughtsauto.com/o2sim.html

http://www.ecrater.com/p/7719787/uni...nsor-simulator

My understanding is that the engine controller is monitoring the delta between upstream and downstream. If the simulator is stand alone (no input from upstream), how does it accurately simulate the delta?

Am I better off adding down stream bungs and using spark plug defoulers?

lucky131969

The 02 sensor operates within a range, if it goes out of range, the PCM assume there is a problem with CAT efficiency. So the simulator just outputs a "perfect" range.

What is a spark plug "defouler"?

tb30570

a spark plug defouler is a spacer for spark plugs to keep them from fouling on old engines. if you drill out the end of the defouler, it can be used as a spacer for o2 sensors. the farther the sensor is from the exhaust flow, the less exhaust gas it reads. Autozone sells them. I tried using a defouler on a different car, but there wasn't enough room to sweeze it in.

http://www.energeticforum.com/renewa...n-foulers.html

tb30570

bump

dougbfresh

The delta is for determining catalyst efficiency. You can tune the rear O2's out with a tuner.

tb30570

I had the downstream tuned out on my other car, I had to get a tune anyway with 14.5psi of boost. A tune costs about $400 where I live.

I can get these simulators for about $50 each. I'm just wondering how well these simulators really work. I've seen a lot more expensive simulators, so I'm wondering why such a difference in cost. Has anybody tried these $50 simulators?

tb30570

looks like I'm not the 1st to ask the question.

http://forums.corvetteforum.com/c5-g...simulator.html
http://forums.corvetteforum.com/c5-t...simulator.html
http://forums.corvetteforum.com/c5-z...ead-horse.html
http://forums.corvetteforum.com/c5-t...imulators.html
http://forums.corvetteforum.com/c5-t...d-no-cats.html
http://forums.corvetteforum.com/c5-t...simulator.html

I found another brand for a total of three:
http://fasttoys.net/shop/product_inf...roducts_id=375
http://www.afterthoughtsauto.com/o2sim.html
http://www.ecrater.com/p/7719787/uni...nsor-simulator

The best info I found was from 2006. Not sure how true any of this is anymore.

Y2Kvert4me
10-16-2006

Tuning the rear sensor codes out is probably the most elegant and surefire solution.

The 02 sims work fine, but I've not found them to survive very long. I'm on my 3rd set. I don't know if it's the heat that kills them or what, but where they connect to the harness puts them in very close proximity to the header tubes.
If you get them, try getting some sort of heat shield or insulating material to wrap them in...may help them last longer, I dunno, the heat cuplrit is just my theory.

Something else to wonder about...I don't know how many companies actually manufacture the sims, but one of the larger manufacturers decided recently to quit making the sims.
Of course, lots of distributors/tuners currently sell them, but I suspect that manufacturer supplied a lot, if not all of the sims to the market, and if that is the case, these may become a very scarce item, very soon.

rickkym
10-17-2006

The sims are simply an oscillator that supply a 'close-enough' sine-wave signal to the cars ECU. If you tune the O2's out you sometimes still need to put a resistor in the heater circuit (2.2K and 10 watts I think?) or you'll get the CEL light. I'm not clear on which specific years need the resistor or if tuning the O2's out was just not done correctly.

As for them going bad, I would suspect heat to be the culprit as well. On my 96 Supra-TT I've got the simulator spliced into the ECU and have never had a problem. I built another simulator just like the Supra's and have it on my '97 because my driver's rear sensor has been complaining. So far I only have ~400 miles on the simulator but it's working fine. I just stuffed the 555 timer and resistors/capacitors in a film can and have that tie-wrapped to the bell housing.

The rear circuit (AFAIK) is the same for all ODB2 cars. The schematic is availble on the net and takes about ten dollars worth of Radio Shack parts. Could be if you got mil-spec components they'd last forever. I did see one simulator potted into what looked like a regular water-tight connector that looked really slick. Mine looks totally ghetto.

lucky131969

This is kinda funny. You are responding your own questions, and posting links to threads for yourself.

helga203

:wi lly:

tb30570

The OBX long tubes already have the downstream bungs welded in. I'll have to look pretty hard at defoulers if they fit.

dougbfresh

???????

lucky131969

I'm still confused at what you are trying to achieve. If I understand you correctly, you are proposing to try a spark plug defouler with the rear O2's........to what end? Even if they are not in the exhaust stream, they will still throw a code, due to not responding correctly. You have three choices:

1) Have a tuner turn off the codes
2) Run the simulators
3) Live with the codes

tb30570

I've never gotten the defoulers to fit on my cars before, but there are a lot of others who have. According to them, the defoulers work with no trouble codes. This is 2nd hand information to me, so I can't confirm if they are correct or not. It's pretty cheap to try though, and it won't hurt anything if I can get them to fit.

Here are some links to other forums with this topic:
http://www.ls1tech.com/forums/genera...-defouler.html
http://www.energeticforum.com/renewa...n-foulers.html
http://dodgeforum.com/forum/2nd-gen-...o2-sensor.html
http://www.google.com/url?sa=t&sourc...97L6tTWx2_X9OA
http://6crew.com/forum/showthread.php?t=8511
http://www.google.com/url?sa=t&sourc...xNeMn6-sFcCcJQ
http://www.google.com/url?sa=t&sourc...O6sJNm173rH8ZQ
http://forums.evolutionm.net/evo-how...ouler-how.html
http://www.civicforums.com/forums/22...on-w-pics.html
http://www.honda-tech.com/showthread.php?t=1841240

dougbfresh

Just plug the holes and tune the sensors out.

tb30570

I'm planning on installing an A&A s/c next winter. I don't want to pay for a tune twice, it's not cheap.

tune cost $400.
simulators cost $50/each ($100 total).
defoulers cost $10.

lucky131969

A dyno tune cost $400....not turning off the rear O2 codes. If you have a relationship with the shop you plan to use, they might do it for next to nothing.

tb30570

that might be. I'll have to look into it.

tb30570

I bought the spark plug defoulers for about $10. I figured for that cost, I might as well try it and see if it works. There was plenty of room for the extra length when installed to the rear OBX long tube bungs.

The parts store didn't have any deep M18-1.5 defoulers, so I bought two sets of shallow. I screwed two defoulers together to acheive the proper length. Due to the diameter of the o2 sensor probe, I needed to weld the two defoulers together because there wouldn't be much left of the threads after drilling it out.



The o2 sensor didn't fit into the defoulers at this point because of the diameter of the probe.



Using a 5/8" drill bit, I drill out the outer chamber of the outer defouler. The minor diameter of the M18-1.5 threads isn't much larger than 5/8", so it had to be centered well.



Once the defoulers were drilled out, the o2 sensor fit.





I finished installing the long tube headers yesterday and drove around a little. The last time I took out a cat, it took a week before a trouble code popped up. I'll post again after a few weeks with the results.

lionelhutz

Hmm, headers with cats? You should get a tune anyways and they rear O2's should work fine since the cats are still there.

Peter

tb30570

the headers don't have cats