Have anyone seen a change in AFR after changing to a tubular O2 housing? I just change the turbo to a Evo 9 20G and changed the O2 housing to a tubular Titek Ver 2 type unit. I have not really run the car yet only 10 miles off boost since I need to tune the ECU Boost Controller. Turbo has a higher pressure actuator.

Anyways bottom line is the AFR at idle are in the 15.2~15.5 range before they were in the 14.7~15.2 range. This is off the top of my head. I am pretty sure there is no leak since I tighten everything to spec and used new gaskets.

The location of the O2 on the SS tubular housing is different than the stock cast iron unit. On the stock unit the O2 sensor is on the outlet where the downpipe is connected. The O2 in the tubular unit is closer to the output of the turbine blades. Could that be the cause? Does this makes sense. I don’t have the car with me for the weekend (I am currently at the beach) so I cannot put some miles on it to see if it goes back to where it was. Has this happed to anyone else in the past?

 

This same issue happened to me going from a megan o2 housing to an epm dump housing. I think its due to more air flow.

-E

 

You got a leak and O2 is getting drawed in at idle over sensor

 

Did the AFR stayed higher or did they went back to where it was after a while? Is the AFR at WOT also changed? Do you know if you have a leak?

 

The AFR stayed higher. The AFR at WOT did not change. I checked for leaks for about 2 hours yesterday thinking there was one but everything is tight and sealed.

 

Just out of curiosity how did you check for leaks? We are talking exhaust leaks right? I just want to check for leaks too. The only place I believe there could be a leak is on the turbine hotside to O2 housing connection. I am using a Titek Ver 2 O2 housing and the connection flange is not flat like the previous O2 units. This is the O2 I am talking about.

http://www.lancershop.com/customer/p...productid=1561

I certainly did not hear any increase in sound caused by a gasket leak, but who knows. If the WOT AFR is fine I guess it is OK. Tightening the O2 bolts will be a nightmare with everything installed.

BTW: You did not use a stock gasket did you? You need a fully divorced gasket when using dump pipes. OEM style will not work and will cause leaks.

 

the increase in AFR's is normal.


What you are doing in theory is making an easier path of air flow when you buy that housing, so in restrospect, you allowing more air to be pushed through.

Also, you should be noticing a quicker spool on your turbo, make sure you check your AFR's under WOT because if they get higher than 12:1, might want to consider to dump more fuel, but that is highly unlikely of that happening.

If you have the gasket installed properly and the O2 sensor installed into the bung correctly, the AFR's will be normal due to the increased air flow.

 

I understand the easier path and more flow path. But isn't the ECU suppose to bring the AFR back to where it was if the car is idling on closed loop. I was expecting the ECU to dump a little more fuel if that was the case.

 

Doesn't matter how flow changes at idle, in closed loop the NB O2switches to maintain 14.3-14.9 no matter what. At idle the exhaust stream creates enough negative psi to suck O2 into exhaust stream that is read over your WBO2 sensor - lean.

In open loop WOT the expected increase in exhaust flow "which was stated in causing a leaner condition" usually will not cause it to go lean unless your maps are set wrong. The increase in flow will be seen at the MAF and injector duty adds more fuel to richen it back up.

If your seeing a lean condition at idle only, you likely have a leak somewhere upstream the WBO2 sensor. You can easily diagnose this logging at idle by placing your hand over the tailpipe to create enough pressure in exhaust where O2 quits being introduced, the AFR will show closer to stoich.

 

Good point, that makes sense. I will test at WOT and if AFR are also leaner I will try blocking the tailpipe. My WB is at the end of the downpipe so I do not think the O2 will come from the exhaust exit. Change in AFR is very mild, about .3~.4 higher. I also added anti seize to the NB during reinstallation (if that matters).

 

If I get a leaner reading on the WB that means that if there is a leak it must be between the NB O2 and the WB O2 right? If the leak is located before the NB O2 then the ECU will still compensate for it. For the WB to read leaner at idle the leak should be seen by the WB but not by the NB O2. Is that right?

 

Boost/vacuum leaks can also cause a lean and often fluctuating idle.