Ntense90crxsi

I have a plx wideband in my car now with a external wastegate setup with a open dump, with unmetered exhaust exiting the car before the wideband sees it, is that effecting my a/f readings, the wideband is in my stock o2 location?. Please, any info would help tremendously, I am just wondering if my wideband is useless right now.

Tchleung

That's how everybody does it. The only way to get a reading with the dump tube exhaust gases as well is to ahve the wieband before the dump tube like in the manifold.

Or to route your dump tube back in the downpipe. eitehr way, the readings don't realyl change at all when open vs close.

Ntense90crxsi

anyone else have a opinion on this?

Ntense90crxsi

bump

BlueShadow

I dont think it should affect the AFR readings because the exhaust is only going out. It's different from say having a hole in your exhaust before the WB sensor. Then that exhaust leak could throw your AFR's off cause it might be sucking in outside airn through that hole.

lucidvtec

i've actually heard different...from what i've been told by a tuner is that the more boost you run the more off ur a/f ratio can be if ur runnin a open waste gate...he said it had some thing to do with flow...around 10psi it might not be a big diff...but the higher the boost level the more it gets off...i dunno if it's true ...anyone here this

Ntense90crxsi

I just read a couple of places that it is dumping fuel from the exhaust that the wideband can't meter, like a big exhaust leak really. I read also that a couple of people went from open to looped and it changed their a/f's.

scartail

I would agree with this statement. And shouldn't the exhaust mixture be relatively consistent, so as long as your not sucking in air to change the mixture (a small hole... if high pressure flow over an orifice, it can create vacuum.)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BlueShadow &raquo;</TD></TR><TR><TD CLASS="quote">I dont think it should affect the AFR readings because the exhaust is only going out. It's different from say having a hole in your exhaust before the WB sensor. Then that exhaust leak could throw your AFR's off cause it might be sucking in outside airn through that hole.</TD></TR></TABLE>

SOHCmaster

I call for a challenge and test to be performed on this issue and post results...
Personally I dont believe it hampers o2 readings since under boost load exhaust is under flow along with wastegate and feel the exhaust under WOT is still enough flow to meter the o2 with proper a/f readings.

Ntense90crxsi

well if enough people believe it does effect the a/f's then I might be up for the challenge, I just want to be confident in the a/f's I am currently tuning at with the on board wideband.

beerbongskickass

Thinking about it, I don't see how it could be that much different. Just because your letting a little exhaust gas out before the wideband, shouldn't mean the rest of the exhaust gas is going to be any different.


Modified by beerbongskickass at 1:48 PM 7/18/2005

adseguy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by beerbongskickass &raquo;</TD></TR><TR><TD CLASS="quote">Thinking about it, I don't see how it could be that much different. Just because your letting a little exhaust gas out before the wideband, shouldn't mean the rest of the exhaust gas is going to be any different.</TD></TR></TABLE>

Yep. Remember we are talking about a ratio hear. If you have 80% of your exhuast going through your wastegate and only 20% through your exhaust it shouldn't change your AFR's becuase it's still a ratio. You start to encounter problems with an Open Downpipe or a post turbo exhaust leak because then you can get what I'd like to call contamination. If you have an incorrectly placed O2 on an open Downpipe or have an exhaust leak you will ALWAYS have leaner AFR's. That's because fresh air is able to mix in with the exhaust and throw off your numbers.

If the numbers where significantly different I think high horsepower cars whould be tuning AF in a different manner then just sticking a wideband in the exhaust

End discussion