well i just got back from a dyno because they were having a dyno day where you can get 3 baseline pulls for 40$. i'm running a dc header to a stock exhaust right now on my ls/vtec and i was just wondering how accurate the wideband is when connected at the end of the exhaust?

before i went to the dyno, my friend did street tuning for me where he put the wideband in the header, and the a/f ratio was a consistent 12.5-13:1 ratio. now i went to the dyno today and it was at 15:1 and it had a "dry" smell to it where it seemed there was enough feul (so said the guy)

now i wouldn't think there would be any changes to the a/f ratio because i just street tuned it last week. my assumption is that the reading of the wideband is incorrect because it was connected to a skinny tailpipe on a stock 92-95 civic exhaust system.

is my theory correct or am i just running too lean? i plan on getting my friends wideband to see what my a/f ratio is pretty soon

 

A "sniffer" o2 can read lean compared to a o2 run in a bung further up the exhaust. The sniffers also have filters that need to be cleaned to read properly so you never know.

 

in the pdf manual that came with my innovate LM1, it says that a wide band in the tail pipe will be far from accurate if you are using a catayltic converter...

 

thanks for the response guys, at least i got the dyno for free since i was having that problem. i'll let you know if i was leaning out of not when i put the wideband in.

and also he said that there was a dry smell which means that it was leaning out when he was doing a 3rd gear pull on the dyno. isn't there alot of variables for it to have a "dry" smell? i never really even heard of leaning out causing a dry smell

 

They are not that accurate at all. Most dyno's in my area do not use a wideband connected to the tailpipe. They tend to read alot leaners also.

 

Andrew, when we tuned my cousins turbo gsr at DSR, we did 1 dyno pull with opendownpipe and 1 pull with closed stock exhaust and the run with the closed exhaust ran richer than the open exhaust..