Recirculated external WG and affects on WB AFR readings

[ulitka]

External WG leak boost through a valve guide and fresh air ends up being dumped into dump tube. If I was to recirculate an external WG, would it affect WB AFR readings assuming a WB sensor is installed close to CAT and WG dump tube is welded somewhere close to O2 housing?

 

[Killa_dsm]

External WG leak boost through a valve guide and fresh air ends up being dumped into dump tube.

Fresh air is not introduced when running a external wastegate. So no, it should not effect your wideband reading. Maybe I'm reading it wrong, but your question doesn't make much sense.

But if you do somehow get air into your dump tube that is recirculated, it will act as a exhaust leak making your wideband read leaner.

 

[ulitka]

All external WG leak air through a valve guide and fresh air will end up getting into a dump tube. Connect compress air to a bottom port of an external WG and listen/feel air flow leaking from a valve guide. So, it sounds like fresh air mixed with exhaust gas will be read by WB as leaner AFR. At this point I will have to dump to atmosphere. Or run a long dump tube to bypass a WB sensor if I need to recirculate.

 

[kawgomoo]

wow... im not sure english is your primary language so ill leave it at that.

internal or external waste gate, recirculated or not has zero affect on your air fuel ratio or its monitoring.

Wastegates are not open off boost. and there is always more pressure behind the wastegate than in front of it. That is exactly how and why it works. the pressure seeks to equalize itself moving from the area of high pressure {behind the wastegate} to an area of low pressure {your exhaust or the atmosphere}.

it doesnt matter where this gas goes. the 02 sensor basically reads the balance between oxygen and hydrocarbons. it doesnt matter what the sample size is across the 02, as the mixture will still be the same.

Think of an open wastegate dump as a straw, even though you are reducing the volume of a glass of lemonade by sucking through the straw. you still get lemonade, and the contents of the glass remain unchanged.

There is no reverse dilution because the valve [wastegate] closes before the pressure behind it is ever close to atmospheric.
h
Also, the wastegate ports are divorced entirely from the valve portion of the gate via the diaphragm. Vacuum/Boost signal never makes it anywhere near the exhaust.

all stock turbos mix the wastegate flow back into the exhaust within the o2 housing.

so the short answer is No. Recirculating the wastegate will not affect the o2 readings. However you should make the dump tube farther away from the turbo...not closer to it.