Screamer Vs Plumbed Back - External Waste Gate (Tuning/afr)

[Kane_R32]

Has anyone thought about the tuning issues with running screamer vs plumbed back waste gate pipe?

Obviously exhaust gas is being vented to atmosphere with a screamer, exhaust gas contains unburnt fuel, so would that mean that the O2 sensor is getting an incorrect reading in terms or rich or leanness of the tune because it is only seeing say 80% of the true exhaust gas?

This could also play a part in plumbed back systems which enter back into the exhaust after the position of the O2 sensor, which also isnt seeing the correct AFR readings. Obviously most tuners place a wide-band up the rear of the exhaust to tune, but if we are running factory ECU (with Nistune) which uses the factory O2 sensor could this create lean/rich conditions?

So my thought was, to have the waste gate pipe plumbed back into the front pipe, and have the O2 sensor moved from the factory position (5-6 inches from the Turbo) to somewhere just before the cat.

[t_revz]

02 feedback is only used on cruise when gate is shut.

Under load 02 is ignored

[rondofj]

My thoughts: it doesnt matter whether 20% or 50% of the air is unseen by the O2 sensor, the RATIO of the air to fuel (afr) remaibs the same of the escaped exhaust gas after it leaves the manifold, so regardless of the QUANTITY of gas goin thru the sensor its still measuring the correct afr.. Please correct me if weong?

[Kane_R32]

02 feedback is only used on cruise when gate is shut.

Under load 02 is ignored

So its using AFM voltages yeah? Would explain alot then lol

My thoughts: it doesnt matter whether 20% or 50% of the air is unseen by the O2 sensor, the RATIO of the air to fuel (afr) remaibs the same of the escaped exhaust gas after it leaves the manifold, so regardless of the QUANTITY of gas goin thru the sensor its still measuring the correct afr.. Please correct me if weong?

This makes sense, but what if the waste gate wasn't mounted centrally (in my case) on the manifold and the cylinders closest ran leaner/richer then the rest. But I think above is on the mark.

[HYPED6]

My thoughts: it doesnt matter whether 20% or 50% of the air is unseen by the O2 sensor, the RATIO of the air to fuel (afr) remaibs the same of the escaped exhaust gas after it leaves the manifold, so regardless of the QUANTITY of gas goin thru the sensor its still measuring the correct afr.. Please correct me if weong?

You sir are correct. You get a gold star

[GTSBoy]

O2 sensor measures gas (O2) concentrations. Not mass flow rates.

[DVS JEZ]

Kane u seem to be getting confused.

The wastegate doesnt bypass unburnt fuel etc it just bypasses amount of exhaust gas.

Ron is 110% correct saying it doesnt matter how much exhaust gas is bypassed it still has the same exhaust gas crom te screamer as the tailpipe

[Kane_R32]

Is it safe to say the ECU (Nistune) doesn't use the O2 sensor during WOT?

[R31Nismoid]

Yes that is what you were told in the very first post.

The O2 is only referenced on CRUISE.