wideband error with open wastegate?

[90T04]

I have installed a wideband o2 sensor in the downpipe right after the turbo. I have a custom turbo setup with an external wastegate opening to the atmosphere.

My question is this: How much is it going to throw off the readings when that extra exhaust is dumped? Will it still read accurately sampling a smaller volume of the same A/F ratio gas? Or does it need to sample everything that comes out of the engine to calculate the raito?

The reason I am concerned is because while non WOT driving, the a/f ratio as displayed by the Zietronics ZT-2 is perfect, right around 14.7:1. Then when in WOT, my mixture richens to 10.5:1. I am trying to lean it out to around 11.8. but it seems that no amount of leaning with the MAFT and the E-Manage is doing any changes.

I just want to be sure that when I am changing settings on the MAFT, if the A/F ratio really is leaning out, but my wideband is just getting a bad reading, that I dont blow something up.

Thanks for any advise in advance.

Ryan

 

[chevyeater]

I've got an open wastegate on mine and the wideband is very responsive to changes that I make at WOT. If 10.5 is bottomed out on your wideband, it may take pulling quite a bit of fuel to get it back "on the chart". Take it to a dyno and compare your wideband to thiers if you aren't convinced of the accuracy of yours.

 

[90T04]

I think you may be right, it may just be "off the chart." I just cant imagine it being that freakin rich. They're only 550's, and I have the MAFT setup for stock 440's just to get it to lean out a bit. And you would think there would be some black smoke out the tailpipe, but who knows. Ill have to hit up the dyno.

Thanks for the advise.