test pipe result in a more accurate a/f reading?

[Hiitman]

im trying to get as accurate a reading as possible on dsmlink with my wideband. so i was wondering, should i ditch the cat and just throw on a test pipe. well...cant really throw it on because the previous owner welded the cat to the center section of piping. instead of the catback starting at the cat it starts back by the rear diff (thermal exhaust). anyway. rre said that they would weld a bung "further up" for a better a/r reading. problem is they welded it right infront of the rear o2...still behind the cat. so should i ditch the cat in favor of a test pipe and also should i stick the rear o2 back in?

 

[turbosax2]

Well, if you decide to go with a test pipe there is no point in having the rear o2 sensor in because all it does is make sure the cat is working properly. You can avoid the cel with dsmlink.

 

[Hiitman]

thanks for the info. ive already got it unchecked. but will the testpipe result in more accurate a/f readings?

 

[turbosax2]

I can't answer your question but have you considered relocating the bung just before the cat?

 

[Black95TSIawd]

A cat distorts the wideband reading if the sensor is placed after it. There is no other way around it. Either get rid of the cat or weld the bung in front of it.

 

[Hiitman]

thanks for the input. testpipe it is. definetly want to get that a/f reading as accurate as possible. do you recommend a different fp with my setup (or know of a vfaq that helps decide what to set) or should i just go with whats recommended for a 2g?

 

[Black95TSIawd]

just use the base 2g setting.

 

[aero_sallee]

thanks for the input. testpipe it is. definetly want to get that a/f reading as accurate as possible. do you recommend a different fp with my setup (or know of a vfaq that helps decide what to set) or should i just go with whats recommended for a 2g?

Also make SURE you don't have any exhaust leaks pre-wideband O2. They will throw off the reading if any outside air is allowed to be drawn in.

 

[spyderturbo007]

Also make SURE you don't have any exhaust leaks pre-wideband O2. They will throw off the reading if any outside air is allowed to be drawn in.

Aero is correct. I'm running 650cc injectors at a -35% correction or so, just installed Methanol Injection and my WBO2 is reading 12.5:1. Did a smoke test on the exhaust system and found out my DP is leaking. So it does make a huge difference in the AFR's.

 

[Hiitman]

smoke test?

 

[spyderturbo007]

Yep. My buddy owns a garage and has a smoke machine designed to attach to your battery and a compressor. It has a 10' switch, so you can plug the nozzle into the exhaust adapter and walk up and down under the car looking for leaks while still controling the smoke flow. Hook it up, plug the tail pipe and pump the exhaust full of smoke. It creates a couple pounds of pressure in the system so you can find the leaks easier.

Then all you have to do is look for where the smoke is escaping. Worked pretty darn good, except he didn't have a giant adapter to fit the tailpipe on my EVO 2 exhaust. I just used a piece of rubber that I cut a hole in and held it over the tailpipe.