ok im hoping to have the car running real soon now. anyway, my wideband o2 sensor is in the downpipe. i have it set up now running open dump from the wastegate. will my o2 sensor work right or do i need to fab up a pipe to put the wastegate dump back before the o2 sensor? i think i need to plumb it back in. thanks

 

I'm not an expert but I think your wideband may be off if you do not have it dumping before it.

 

yeah youre losing all that exhaust out of your dump so itll be off. it sucks, but mine is exactly the same. u could switch your pre cat 02 sensor to where your wideband is, and weld another bung in after the dump is returned to the rest of the exhaust... i think i said that right?

 

I don't see how your A/F ratio would change with an open DP. Your sensor will still be reading the same exhaust gas, I don't see how your a/f mixture will be effected by the amount of exhaust gas in your pipe.

So does that mean more exhaust gas = richer? or less exhaust gas = leaner? Or the other way around? I still don't understand why your a/f ratio would change depending on how much gas travels through the pipes.
Here is a link on how Wideband Sensor work: http://www.innovatemotorsports.com/resources/news3.php

 

tanc i was actually thinking that too. the innovate is calibrated to fresh air before being placed in the exhaust. you would get about half exhaust passing through lets say. i was thinking maybe that would give me the correct reading.

 

i figured you would need all the exhaust coming out of the motor to get an accurate a/f reading

 

The afr isn't going to change because of less air passing through by anything that's significant. The only problem would be if you afr isn't consistent (doesn't spike and dip alot--think heartbeats). You might get spikes on the afr monitor once an awhile when the wastegate starts, but the readings should be good besides that.

 

awesome to hear. thanks

 

So how does an open wastegate cause your afr to spike?


Your afr will read accurately with an open dump.
Your afr will not spike because of your wastegate opening.


Thats it.

 

To be honest I don't know why. I still have a wideband (innovative motorsports) and had a turbo for awhile and when my wastegate would start I'd get a momentary spike (sometimes off the chart lamda readings) and then it was fine. The wastegate wasn't an open dump--didn't have the turbo in long enough to try. The spikes are still there when I change gears or let go of the gas completely while engaged but those are normal. I'm not sure if the airflow is momentarily disrupted or if my 02 sensor is just overly sensitive to quick pressure variences but it happened fairly consistently. Never really thought about it before until now but my sensor is pretty close to my cat--don't think that would affect anything but it could be a reason I suppose.