: Does it really Matter.. Sniffer Pipe or Weld in Bung



austin
12-08-06, 10:54 AM
My first set of dyno runs were all taken with a sniffer pipe placed into the tailpipe... Now, i found a local dyno shop very close to me that does not like the sniffer method. He is insisting that i have a bung welded in before i dyno my "V" at his shop. He says he can do it for $40.00, and that it will be more accurate than the sniffer pipe. Does it really matter?

RAD69
12-08-06, 11:10 AM
My first set of dyno runs were all taken with a sniffer pipe placed into the tailpipe... Now, i found a local dyno shop very close to me that does not like the sniffer method. He is insisting that i have a bung welded in before i dyno my "V" at his shop. He says he can do it for $40.00, and that it will be more accurate than the sniffer pipe. Does it really matter?


Do you have CATs? If so, the sniffer at the end of the tailpipe would then be post CAT. The CATs alter the readings a little. Also the sniffer is just the same sensor but it is in open space, so it is not isolated inside the pipe - tho at WOT I cannot imagine that matters...

I had my car on the dyno and they put the wideband in a bung after the CAT instead of before. After I noticed it I had them move the wideband and the readings were slightly different...

BTW - $40 is a good price. The bungs them selves are worth $15...

austin
12-08-06, 11:16 AM
Yes, i have the RT high flow cats.

RAD69
12-08-06, 11:25 AM
Yes, i have the RT high flow cats.

I say go for it. They actually tweaked my fueling after they moved the sensor. I say it matters and $40 is cheap...

austin
12-08-06, 11:38 AM
So, how much did it matter being installed after the cat vs before the cat? What was the differance in your reading.

RAD69
12-08-06, 11:56 AM
So, how much did it matter being installed after the cat vs before the cat? What was the differance in your reading.

iirc .1-.2 AFR

austin
12-08-06, 12:14 PM
Ok.. Thanks... I just found this.

heavymetals
12-08-06, 03:25 PM
From my understanding, the reason you have a bung plug option is that when you use a dyno to tune the car you don't want to have the sensor as one of the "loose ends" (variables).

If your making a dyno run, then usually the sniffer goes up the tailpipe, you sign the release (maybe not in that order) and away you go.

svassh
12-08-06, 03:52 PM
It matters because you are trying to measure actual AFR. If you do it before the CAT thats what you will get. The CATS job is to burn excess fuel that ignition does not burn. Hence after the CAT some excess fuel will have been burned and your AFR readings will be off. Bear in mind the fuel is in fume form at this point not liquid.

trukk
12-10-06, 11:15 AM
My tuner insisted in installing Bungs pre-cat on both sides. He said their will be variations in AFR between the banks. Sure enough there was. Pay the 80 bucks, and get them installed.When you factor in the gains you can get from a good tune, it's worth a few buck to put the tuner in the best position to really dial it in.

-Chris

V-Max
12-10-06, 12:26 PM
Ok.. Thanks... I just found this.

austin, good example of what 14 feet of exhaust does to response low in RPMs. Everything evens out when the air starts to flow. Most of your detonation happens at high load, low rpms and near peak torque. Best to go as close to the exhaust valves as possible.