Lambda and EGT position for Megasquirt

Right, I'm going to be fitting both wideband Lambda (LC-1) and an EGT probe into my standard 16v exhaust for the Megasquirt conversion. Now my question is, where should I mount them? My first thought is to mount them pretty close to the head to get fast sensor response, but then I thought that it would be better to mount them further down where the runners join up, so that the MS doesn't just see the A/F ratio and exhaust temps from only one cylinder.

Thoughts please....

The g60 and other vag 1s are fitted in the cat just after the first downpipe flange. I have mine there aswell as my wideband.

Flusted wrote:The g60 and other vag 1s are fitted in the cat just after the first downpipe flange. I have mine there aswell as my wideband.

Indeed. My old 9A valver's lambda was there too. That was were I was considering, but wasn't sure if I'd benefit from having it closer to the head.

Best place for EGT is where all the manifold runners converge, just before the turbo.....but it's worth noting that if your EGT probe breaks off, kiss goodbye to your turbine wheel!

With this in mind, I mounted my EGT in the same place Audi mount it on the 1.8T 225 engine....in the downpipe just after the turbo.

The common or garden Bosch LSU wideband probe loses accuracy past 850 deg C, so you don't want to mount it too close to the turbo. I'd say about 18" away from the turbo is optimal, cause you don't want it too far away so that it's too cold for accurate idle and part throttle measurements.

Check this guage out, awesome - [You must be registered and logged in to see this link.]

Would you apply the same logic about where the runner converge on for a N/A setup, as I want to fit the MS to the 16v in standard trim first? Obviously you don't want the Lambda too far away as it needs to be warm before it will function properly. I'm not sure if the Lambda sensor that came with my LC-1 is heated or not...

Yes mate, on NA, I would stick the probe in the manifold just before the downpipe. You can have the O2 near the manifold too for better response at slow engine speeds (much cooler exhaust gas). I doubt a 16V NA will get as hot as 850 deg C!

I say it loses accuracy at > 850, but that's not to say it just melts and won't work at all. Many high performance engines go open loop at wide open throttle anyway and the lambda is ignored.

Yeah the LC-1 is a heated wideband setup..... one of the quicker ones to warm up actually.

thought the rule was 10" from the exhaust port or turbo side,also dont mount the sensor pointing up as water will collect in the sensor and kill it over time.

So, mounting the Lambda and EGT on just one of the runners would be fine? I've also seen them mounted at an angle as well, so not perpendicular to the wall of the manifold, is that done for a reason or purely for ease of fitment in the applications I've seen?

I've seen o2 probes right next to the turbo in the MK5 GTI and as far as 2 feet away in a stock VR6, so there are no "rules" as such, but rather application specifics and best practices etc.

MK5s are pure emission whores, but it's not "ideal" to have a probe that close to the turbo....and I bet people who mod MK5s with bigger turbos have to lose the cat and move the probe further down the down pipe

Yeah, agreed on the lambda boss, avoid mounting it where exhaust born moisture could collect and damage the probe.

You can also use a 45 degree lambda boss providing your probe has enough "reach" into the exhaust stream.