That Lambda sensor on an SD1...

Finally got round to removing the exhaust manifold on my SD1 for the purpose of fitting a Lambda sensor for the Megasquirt conversion. Only to find it's not quite as simple as I thought.

There are two visible bosses - undrilled - for sensors as fitted on (I guess) federal spec cars with cats. One presumably for the oxygen sensor and one for an air pump? But that's a guess as I can't find any details - my workshop manual doesn't cover US spec.

There is one boss close to No1 cylinder and one at No7. But neither is designed if drilled to poke into the actual downpipe inside the manifold. Instead they'd go through the casting to the back of the manifold where there appears to be what could be a plenum chamber - a sort of wall with bosses for fixing screws for a cover. That's where a sensor would end up if drilled square from the bosses. And I suppose holes drilled into that plenum from each downpipe? I did wonder about fitting it after the manifold - but the individual pipes from that (one per two cylinders) are rather small and was worried the sensor would restrict them. And where they come together beside the gearbox there simply isn't room. It could easily go in the Y piece that joins the downpipes from either side together - but that's at the back of the gearbox so a long way away?

I have a later manifold from a 3.9 Range Rover (totally different and couldn't be used) where the sensor boss shows it would just go straight into one of the pipes within the manifold. And assumed mine was similar - since this is the first time it's been removed.

If anyone's interested and confused by my description (very likely) I could post a link to some pics.

Reply to
Dave Plowman (News)
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"Dave Plowman (News)" gurgled happily, sounding much like they were saying:

Sounds too far, yep - you want it so that it'll heat up fairly quickly and also react to changes in fuelling fairly quickly.

On the Saab, it sits in the elbow out from the turbo, so the 2-into-1 pipe out from the manifold sounds like the best bet to me. It shouldn't cause THAT much obstruction to gasflow. And if it does, wouldn't better manifolds be a good plan...?

Reply to
Adrian

That's what I thought - I dunno if the heater being on all the time would be a good idea.

The original manifolds are said to be a decent design - the only real reason to replace being weight saving. Each of the four downpipes is only

38mm inside diameter and the sensor would reduce that area considerably. Of course it may not much matter. The system is SS and I have to get the downpipe welded anyway - the gearbox heat shield has come adrift - so I could get a boss welded in at the same time. I have a SS one bought off Ebay.
Reply to
Dave Plowman (News)

Just as a follow up, came across a PDF on fitting one on the Tech Edge site. Not the easiest to find things on. And they recommend a wideband one is fitted about a metre away from the nearest exhaust valve - seems they are less robust than narrow band types. So at least I have a definitive answer. Now to see just where I can squeeze it in.

Reply to
Dave Plowman (News)

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