Hi, I was wondering if there are any issues with dyno tuning with a tailpipe mounted O2 sensor versus one in the downpipe. Does the fact that this is so far away or the fact that it is dual outlet exhaust throw off the reading? I've heard it's slower to react, but could it be more finely tuned in the DP?

I feel like my car might be running rich, but according to the tailpipe method, it's good. On the street, even with the highflow cat, it 'backfires' (pops) anytime I let off at a mid-RPM, so could that be another indication of running rich, or is that normal?

Thanks.

 

sorry no deffinate knowledge here but...

chris from ams used the tailpipe method when he tunned us in hawaii and he said it was fine basically similar readings compared to doing it though the dp. He tunes many high powered evos so i trust him

 

Do you have a cat? If not, the tail pipe sniffer should be good on a WOT pull.

If you run a cat, I think a wise tuner would remove the cat while dyno tuning.

That's my opinion, no data to back it up.

 

Cat affects AFR in non linear way so the AFR the wideband O2 sensor registers after the cat is NOT the same AFR as before the cat. If you are tuning close to the edge do not read AFR after the cat. But, if you are tuning close to the edge there should be no furry friends under your car.

 

I was wondering that. I really wish I would have thought to have the WB bung welded in when we had the DP out. Maybe I'll do that before the next tune anyway. Do you know how much the cat would throw off the AFR when taking the reading after?

Thanks.

 

Tailpipe sniffer is a poor way to measure afr. It can be diluted from the outside air.

EVERY car we tune in house is connected well upstream of the catback.

 

Most exhaust shops can weld a bung in 10 minutes at $10-$20.

Cat effectiveness is non linear and depends on a several factors.

 

From Innovate Motorsports hope this helps ...

Sensor Placement. The sensor bung (or boss) should be at least 8" away from the combustion cylinder (at or after the collector if you have one, unless you're installing a sensor for each cylinder). To avoid condensation running into the sensor, it should be installed at the side or on top, NOT on the bottom of the exhaust pipe, for example between the 10:00 and 2:00 position. If you don't have a bung, any muffler shop can weld one in for you. If you have a catalytic converter, install the sensor before it. If you have a turbo, install the sensor AFTER it.

 

If you don't already have an aftermarket downpipe, AMS makes one that already has the bung welded on for a wideband 02 sensor it also comes with a plug.

 

I have the AMS o2 downpipe that comes with the bung for the wideband. If I don't have one right now, will the shop use the bung I have or just use the sniffer?

 

honestly probably easier to use the tailpipe sniffer ... depends on the shop tho

 

If you already had a wideband gauge installed in your car they can/may use that as a reference. Plus you can see yourself if the car is rich/lean based on how you drive. Probably one of the best purchases you can make for your car's safety.