Checking Afrs Using Wideband In Tailpipe

[Swiper the Fox]

If you took measurements from a car from the tailpipe, then from the bung before the catalyst, do you actually notice any difference in AFR? I didn't think any o2 sensor is that sensitive that it could measure the difference?

The catalyst removes oxygen from the oxides of nitrogen and then combines the oxygen with the carbon monoxide to create carbon dioxide. So it really only takes the oxygen from one place and puts it in another and both before and after the cat, the wideband doesn't recognise the gases before they are split with their other particle.

Or are you referring to it effecting the result in that it is slower, not so much changing the reading?

I think your last question is what Trent is refering to.

[discopotato03]

Does anyone have links to suppliers of multi probe EGT systems ? I'm curious as to how its packaged and how it gets the message across - without necessarily data logging .

I want to set up for Datalogit and Tech Edge and probably an RB25's cast exhaust manifold .

I'm not sure if its practical to drill and tap a std manifold so are there other ways to get a usable heat reading like for example thermocouples under the mounting nuts .

The only EGT system I ever saw in the flesh was a VDO gauge and single probe , I guess you'd go cross eyed looking at 6 of those !

It's not hard to see a single O2 probe getting an average and missing an individual cylinders death throws .

If anyones interested in commenting is it the front cylinders that have issues masked by "safe AFR's" in single turbo RB's ?

Cheers , A .

[Don Dada]

Did a dyno run once with a stock 26 with the innovative LM1 sensor stuck in the tail pipe... 3" exhaust no cat.

We actually had to stop the run because ratios were like 13-14 on full load.

Then got a bung welded in about 3ft from the turbos and guess what..... ratios were in the vicinity of 11-10.5 on full load.

So i guess it does make a difference.

[zebra]

Did a dyno run once with a stock 26 with the innovative LM1 sensor stuck in the tail pipe... 3" exhaust no cat.

We actually had to stop the run because ratios were like 13-14 on full load.

Then got a bung welded in about 3ft from the turbos and guess what..... ratios were in the vicinity of 11-10.5 on full load.

So i guess it does make a difference.

Leaks in the exhaust will affect things like that

[TiTAN]

could also have been a calibration issue.

[Don Dada]

could also have been a calibration issue.

Probably .

Did the whole calibration set up thing both times though.

But i still would'nt take the chance, especially if tuning.....

[Fastrotor]

Something no one has mentioned is that pressure in the exhaust can affect the reading too. Reading the techedge site, from what i can gather it seems it will actually read richer with pressure, can anyone else read and confirm. They don't actually say it from memory, but give a formula to work it out.

Definately putting it in the O2 bung to do light load tuning and idle etc is much more responsive at low rpm's

Also something to watch for, when using tailpipe method. If your pipe going into the exhaust can only go in on an angle, it can create a Bernouli ? effect, and suck air back up the pipe at low revs/load . And on some cars the exhaust pulsing can cause fresh air sucked in and dilute readingsat idle and very low rpm.

Gary

[The Dan]

And to add to all that, if you are using the LM1 unit and the wideband sensor they supply with it, you cannot run it in the dump pipe as the gas flow is too fast for one particular sensor.

If you get the other sensor, then you can do it in the dump but the one they send you sucks wang for dump pipe measurements and it stalls on rich. EG. as soon as boost comes on it just stays at 11.7 but put it in the tailpipe and it reads 12.2 and fluctuates as it goes richer or leaner.

The holes in the end point outwards and are small so they don't gather the gases like the other sensor does. I think the Techedge one is better for that reason.

[Walk510]

Does anyone have links to suppliers of multi probe EGT systems ? I'm curious as to how its packaged and how it gets the message across - without necessarily data logging .

I want to set up for Datalogit and Tech Edge and probably an RB25's cast exhaust manifold .

I'm not sure if its practical to drill and tap a std manifold so are there other ways to get a usable heat reading like for example thermocouples under the mounting nuts .

The only EGT system I ever saw in the flesh was a VDO gauge and single probe , I guess you'd go cross eyed looking at 6 of those !

It's not hard to see a single O2 probe getting an average and missing an individual cylinders death throws .

If anyones interested in commenting is it the front cylinders that have issues masked by "safe AFR's" in single turbo RB's ?

Cheers , A .

yes i have for my car an add on to the motec m800 an E888 that allows me to run 8 egt's and log either on my dash or ecu !

also motec have what the call LTC 's (lambda to CAN) and you can run up to 32 lambda's on a CAN bus

[DCIEVE]

Does anyone have links to suppliers of multi probe EGT systems ? I'm curious as to how its packaged and how it gets the message across - without necessarily data logging .

I want to set up for Datalogit and Tech Edge and probably an RB25's cast exhaust manifold .

I'm not sure if its practical to drill and tap a std manifold so are there other ways to get a usable heat reading like for example thermocouples under the mounting nuts .

The only EGT system I ever saw in the flesh was a VDO gauge and single probe , I guess you'd go cross eyed looking at 6 of those !

It's not hard to see a single O2 probe getting an average and missing an individual cylinders death throws .

If anyones interested in commenting is it the front cylinders that have issues masked by "safe AFR's" in single turbo RB's ?

Cheers , A .

Google innovate. Theres a few display options for the laptop, half dozen gauges, coloured bars etc but the graph is most useful. The issues aren't in the end cylinders.

This is a completed tune.

It's no where neat as a system like walk510 is talking about, each box only reads 4 thermocouples so you need two of em daisy chained together -gets a bit messy when its connected to the wideband as well. You get what you pay for with motec.

[scott1600]

The Racepak IQ3 dash range is really good and reasonably priced. Around 1200 for a display and 2400 for a 512meg logger dash.

4 x egt kit costs around 1100.

Haltech sells EGT kits that output a 0-5v signal that can be used with any ecu for $300