my friend just spent some money on a new DP cause the tuner said that when you dont dump back into the exhaus, that the wideband is not reading all the exhaust so the reading is inacurate. is this true???

Landon

 

The oxygen sensor only samples a small portion of the exhaust gas regardless of the plumbing.

If it had to sample all of the exhaust, it would be a possible restriction...kind of like a MAF with a flap door.

 

yea thats what i thought, plus the fact that the dump tube really doesnt let a whole lot of gas out compared to the exhaust.

Landon

 

Yup. O2 only measures a concentration. Doesn't have to be exposed to all the exhaust gas.

 

Your tuner sounds correct. In Vtec is correct in stating that the O2 only samples a small portion of exhaust output, but also consider that the exhaust has rolled over it self so many times that the leftover fuel has evenly distrobuted with the contaminated air, so the reading is more uniform. Depending on how close the dump tube is to the runners, you may only be sampling a charge thats closest to the richest or leanest cyl and the overall mixture hasn't blended and has become uniform as yet.