nikh667

iTrader: (1)

As title really guys, getting ideas together as to equipment i'll be looking at collecting to at least start learning process with data logging some pulls. Looking at wideband sensor options that fit into tailpipe with Innovate clamp - just wondered as to opinions relating to accuracy of AFR readings with catalysts still in place.

I've read elsewhere as a rule-of-thumb that approx a 0.5 leaner AFR reading may be obtained. This sound about right, tuners? Anything else to be aware of time-delay wise due to being in tailpipe.?

Thanks for advice.!

adz556

iTrader: (5)

I don't know about with catalytic converters in place but when my mates car was mapped, the AFR displayed was around 12 at tick over but when he started to drive it was near enough spot on 14.7.

I've fitted (not back on the road yet) a wideband sensor in the top of my downpipe so you get the best reading possible.....Have you considered doing that? Mine is the innovate wideband sensor and gauge set up.

Hope that helps!

nikh667

iTrader: (1)

Looking at the tailpipe solution as may have opportunity to log more than one car, therefore looking at the portable idea. Is having a wideband in the tailpipe how mappers/dynos function.? Just wanting to check potential accuracy before I decide.

piehole1983

iTrader: (7)

I don't really have any input with regard to tail pipe accuracy but when I installed my Zeitronix ZT-2 wideband controller it stated in the instructions to install the sensor at least 16" away from the turbo because it's too hot to go any closer. It's a Bosch sensor too. It doesn't say anything about a maximum distance. When you think about it, the exhaust gases cant really change when they are moving through the system unless there's a cat or silencer before the sensor perhaps. Also, all the tuners seem to take a reading right at the end of the tail pipe so they must be confident that its accurate at that point.

piehole1983

iTrader: (7)

Oh, just a side note. The cable to connect to the sensor is 10' long!

nikh667

iTrader: (1)

That's ideal. Like I say have read a thread over on NASIOC stating that as a rule of thumb a wideband in the tailpipe of a catted scoob will give a reading 0.5 leaner AFR (so 11.5 at tailpipe would equate to 11 at engine).

ALi-B

iTrader: (1)

Thats pretty much right...typically "post cat" sensor activity generally follows that of the pre-cat sensor, but at a lower voltage and a slight delay with little activity at constant throttle.

Two issues you are likely to come against; exhaust leaks...even pinholes will affect tailpipie readings, also the tailpipe can suck back a bit of air between firing pulses, so the sensor has to be in as far as possible.. And catalyst efficiency, mainly with sports cats or cheap cats with a smaller area of monolith (or a failed/contaminated cat, or not up to temperature), whereby it is unable to burn all the hydrocarbons, leaving an excess of oxygen - which you'll detect at the tailpipe. Therefore it should be used as a general aid combined with other measurements (knock activity, MAF intake value, OBD data etc)rather than a sole means to tune/monitor an engine.

The Rig

iTrader: (13)

I located my wideband at 3 points to determine where was best on my 95 wrx, in the headers was a tad rich, in the tailpipe was a tad slow at responding and where it is now in the downpipe seems best