Does an exhaust leak affect A/F (tailpipe probe) numbers on a dyno? If so, to what extent?

I would think that the tailpipe may sense leaner if there is enough exhaust gas velocity to pull in fresh air at the leak site.

Any experience or opinions?

Thanks guys,
Herb

 

bump

 

I would say its possible, if the exhaust leak was big enough.

 

Exhaust leak will cause you O2 sensor to read incorrectly. If you have one you should fix it.

 

My buddy has an 02 Ram Air T/A with a ton of mods.... anyway he was haing a problem with the left bak running too rich and eventually caused a failure in the bottom end of the motor. The builder said something about washing out the motor because of too rich of a condition. He gets a new motor and the same results. They found a cracked weld in the cat. they fixed the exhaust and the problem went away. It was a very expensive result from a small crack in the exhaust. He has LS-1 Edit so he has a laptop in the car and can monitor the engine at all times, but he still could not straiten out the really rich reading from the left bank O2 sensor.

Hope this helps!!!

 

Thanks for the replies and the info guys.

The leak I have is after the cats - basically where the Cat-back attaches to the end of the mid pipes. The crappy custom Flowmaster setup on the truck (there when I bought it) was welded in place and welded poorly. I need to cut off the Blowmaster, dress the ends midpipe and bolt a stock cat-back on it.

I'd like to dyno it this week (no time to swap the pipes first) and don't want to waste my time and money if this leak is going to jack up the A/F readings at the tailpipes. I want the dyno run specifically for the A/F to check the safety of my mods before I run it at the track.

Herb

 

It will definately mess up the A/F reading coming out of the tail pipe. I would not go to the dyno if you are worried about the accuracy of your A/F levels with your leak.

Zach

 

How large of a leak will cause lean conditions and inaccurate readings? I think I have a slight leak between my midpipes and Magnaflow catback. I noticed some black soot near that spot. It's after the cats so will it cause a problem? I will probably address the problem anyway, but I was wondering how urgent it was since it's after the cats?

My thinking is that, since it's after the cats, it shouldn't be a problem? I mean, I know some who run cutouts....

 

If it's after the O2 sensor I wouldn't think it means anything. If it's before the O2 sensor it would.

 

seems like you would be bleeding exhaust gases..always have pressure in the pipe cat whatever...reversion could happen at the header maybe...when in boost..pressure should go up...

 

My thinking has always been similar - if it's after the cats and O2s, its only an annoyance - not a problem.

However - I know I have excess ambient air getting to the mufflers because a have tremendous 'burble' when I let off. This has worsened as the leak has worsened (to the point that it sounds like a cowboys farm truck!).

My main concern is if there is a suction effect at the leak caused by the high velocity exhaust gas under load or at WOT (similar to a venturi effect of a syphon fed paint gun). If the ambient air can enter the pipe under load, it will lean out a tailpipe reading. This artificaiaaly lean condidtion will make to nervous about racing the truck. I don't mind being JUSTIFIABLY nervous, but...

Is there a prefered method of A/F senser over the tailpipe probe? Where would I install a bung to sample in a better place? Can most dyno shops support a threaded in A/F sensor connection? Are the size and threads standard (same as O2)?

Sorry - I feel like Andy Rooney with all these questions.

Herb

 

My magnaflow housing cracked...it made poping noises on decel...I think the word you are looking for is...induction..or eductor