O2 bung B4 or after cat for dyno

**cpa** · February 26th, 2002, 03:00 PM

I was planning on getting a separate O2 sensor installed for dyno tuning. What impact does the cat have in terms of reading air/fuel ratios? I've only been to a dyno where they stuck a probe up throgh the tailpipe (reading after the cat), but the shop I plan to go to uses a Motec to connect into a separate sensor bung. They recommended putting the bung on the header before the cat for reading the air/fuel ratio.

One other random question - anybody have experience with Comptech's adjustable FMU?

**AMslp_late** · February 26th, 2002, 05:04 PM

For the most accurate reading you put the o2 sensor BEFORE the cat. If you put it after the cat you will get unaturally lean readings.

**cpa** · February 26th, 2002, 05:57 PM

I'm going over to AEBS off Miramar. You can call them up for their price quotes, but they're reasonable. I haven't found any other good dynos in town that actually work or know anything about imports.

**217gsr** · February 26th, 2002, 06:12 PM

I've been to AEBS before for dyno tuning. If Roger is still the person there doing the tuning, you're in good hands. How much do they charge now? I thought that they weren't doing anymore business with non-wholesale or non-businesses.

**cpa** · February 26th, 2002, 06:40 PM

Roger is still there, he worked on my car the one time I took it there, which is why I want to go back. Not to avoid your questions on pricing, what they do or don't do, etc. but I don't like quoting stuff for someone else's business. I don't have any personal relationships there, I just walked in. Next time I go in, maybe we could get together over there.