As the title states.. I figured that this would be the place to ask this. Just wondering if having the front 02 sensor unplugged on my evo IX would cause any problems besides a CEL?

 

I wouldn't do it Bad things may occur.

 

Yes you will run RICH/lean as hell..that is the sensor that takes the base readings for fuel. You need that one. Mine went bad after using leaded fuel a couple of times..car ran super rich when it failed

 

when my o2 sensor went out when my car was stock, i got 130 miles out of a tank on the highway... i knew what it was and fixed the problem immediately, u need the front o2!!! unless u have AEM EMS

 

An unheated "unplugged" 02 sensor in the exhaust stream will die quickly.

 

if you are running your car in open loop mode all the time, then I guess you dont need the front o2 sensor. If you are running closed loop in cruise mode then you realy need it.

 

Thank you!

 

^^^^This

 

Correct. If you're running forced open loop, the ECU will not pole the primary narrowband o2s, as the engine will not be in closed loop o2s feedback. Your tune must be SPOT ON though and must be perfect in all rev and load ranges to insure safety. If you unplug the o2 sensor, it will throw a DTC.

I run in forced open loop almost exclusively. The only time i allow closed loop feedback, is at very high rpms and low load cells. If you have a good tuner or can tune well, i highly suggest this, as you can lean out the idle/part throttle/cruise areas, which will give better fuel efficiency. It also helps with fueling consistency in the vacume/boost transition areas.

Contrary to popular believe, a AFR of 14.7:1 is not best efficiency. Best efficiency at low loads is 15.2-15.7:1. Also, you can get away with really lean AFRs at idle too. I tune for 16.5:1 at idle on my own car... The engine is not under any kind of load, so the risk of detonation and high EGTs is minimal. This has been verified many times, most recently was this week. I have my head off my car as i write this. My piston crowns and head are immaculate as are my cylinder walls. I have tuned many engines this way.....it's a perfectly acceptable method for idle/low load cruise. Regarding tuning under boost, this is a much different story, as i am known to be a very conservative tuner.

 

Standalone EMS yes....Stock ECU no

 

Huh? The stock ECU handles open loop just fine. It will work just as good as a standalone. Remember, the stock ECU is a standalone. lol.