Stock ECU closed loop defeat?

[GWILLS]

Running a 96 LS400 with a Bullet M90 on stock ECU.
I would like to know if there is a simple way to defeat the closed loop in the ECU?
At the moment it will stay in closed loop for about 5 seconds at wide open throttle, before it drops into closed loop
AFR in closed loop is around 15.5 then when it finally drops into open loop the AFR drops to about 11
could I run a relay to disable the O2 sensors after 85% throttle position would this force the ECU into open loop?
Is this going to create any other issues?
really would like to keep the stock ECU, drives great, nice trans shift points, good smooth power other than the lean initial bit.
I also have a Snow water meth that I have not fitted yet to assist with the knock retard that I am sure it has
thanks

 

[rdm20fan]

You can purchase 2 spark plug DeFoulers. You need to drill a hole in one of them so the O2 can fit through it, and then screw it into the O2 bung hole in the exhaust.

Actually you would need 4 (2 for each side)
the ECU wants to see the rear O2's react slower then the from O2's doing this makes them act slower even if the cats are not working.

After doing this, you can actually remove the cats from the car. Now this is not legal, and the fine is something like $1500.

Look it up on Youtube. it will show you step by step how to if you are confused. The defoulers will cost you less then $20 for all 4 and some time in the garage.

Now the real issue is your cats are probably bad on the car, and causing a restriction in the exhaust. just an FYI

 

[rdm20fan]

This is what the sparkplug defoulers look like. they are in the help section at your local parts store, or you can find cool looking ones on Ebay.

http://www.wrxtuners.com/forums/att...can-i-get-oxygen-sensor-dummys-img1345cq3.jpg

 

[GWILLS]

Hi, Thanks for the reply
Do you think the lean burn is due to stuffed cat's?
Would that give an engine light?
I was thinking and suggested by the dyno guy that it was a factory computer thing in an effort to squeeze a bit more economy out of them
Currently both rear o2 sensors are removed from the exhaust but still plugged in, one removed by a rock up a mates crappy dirt road, the other is now a galled mess where the thread was
have new threaded sockets to weld in when I get around to ordering new o2's
have also got a wide band o2 sensor and gauge to hook up to see what is actually happening
But at the moment it now feels rich in the lower rev ranges even bogs down a little has far less audible detonation there is still a small amount that can be heard at about 5k WOT and fuel economy has dropped a bit wont really know what the ratios are doing until I get my gauge fitted.
just confirming with the spark plug defoulers are you saying to screw two together with the o2 sensor on each side?
That's a neat trick to fool the ECU
Too many projects/toys not enough time!

 

[rdm20fan]

The spark plug defoulers get screwed together, but first you have to drill out the bottom of them. The O2 wont fit in it unless you drill the hole in the bottom larger. You screw the 2 of them together (After one is drilled out) you screw the O2 into the defoulers, and you screw the whole unit back into the exhaust.
The ECU is looking for the second O2 to react slower then the first set. Meaning the cat is doing something and it is getting a slower reaction. By moving the O2 out of the path of the exhaust it still reacts, but reacts slower.
You have it out of the exhaust all together. Its not reading anything near what the first O2 is reading.
There are some videos of this on youtube if I'm not doing a decent job of explaining it.
If you purchase them, you will see what I mean as you cant put the O2 sensor in the defouler. it will bottom out.
Or to make it easy you can just purchase the entire unit on ebay that you just unscrew the O2, and screw it in the exhaust bung, then screw back in the O2.

No, a blocked cat would cause a rich condition as it would slow air flow. Taking the cats out will cause a lean condition.
a free flowing intake, or exhaust can cause a lean condition, or lots of other issues. Blocked fuel filter.