More Rover V-8 questions.

That sounds like a plan given that it's got to be downstream of the throttle body :)

Even if your plenum doesn't have a convenient spout to stick it on it should be easy enough to weld on an aluminium boss. A mate of mine can do that for you if you like.

And will a later plenum fit the earlier engine without other

Might be best asking in the Pistonheads forum

There are quite a few in there with V8 TVRs and the like and also a couple running Megasquirts.

Well the existing electro/mechanical extra air valve is mounted remotely and plumbed into the plenum via steel pipes and hoses. Reason being it is mounted on the heated inlet manifold to obtain engine temperature. It would tidy things a lot to get rid of this.

I've not actually seen one of these in the flesh - but it looks like they need a sort of bowl shaped seat to seal on. But where the air intake is to them is still a mystery. ;-)

Ah - thanks. Yet another forum to read. ;-)

The heated one will work fine. You need it in the exhaust gas stream, in an ideal world sampling as many cylinders as possible.

Weld a boss to the exhaust with MIG, I've done it on an Audi, 'tis easy. Pinto spark plug thread size IIRC which for me looking in the junk box was a tractor wheel nut which I machined down to a nice boss in the lathe.

Julian.

As I said that might be difficult - and would be downstream of many joints, and I'm told you mustn't have even the slightest leak before it.

The manifold is cast iron and the rest SS. I could place it in one downpipe after those two branches from one side join - but that would make access difficult. I have a local place that does TIG for SS.

Well you'll have to make good joints :-)

But I've fitted mine in the downpipe post turbo, so there's a few joints - never had the slightest bother. Look at modern cars, they all seem to have two sensors, pre and post catalyst, there's a few joints there already....

Or MIG, I've done SS with SS wire with my Clarke jobby, it's a P of P with the correct gas and plenty of practice on something of similar thickness first.

I say you've really got to go downstream, maybe use two, one for each bank and a switch? It's little use sampling the output from one cylinder if that's suffering from an air leak around the inlet manifold gasket - common(ish) on a V8?

Julian.

So what's the problem with replacing this with the stepper motor driven IACV and using the existing hoses?

Welding a cast iron manifold is a very bad idea. It usually cracks eventually when the component gets very hot in use. Some people do specialise in it but it's still a PITA. You have to get the item as hot as possible before welding, often to red heat, which takes a lot of gas and then cool it slowly afterwards. Mild steel or SS is a PoP with TIG. My mate can weld glass to paper with his TIG. He even once built up the crowns of a set of racing Jag straight 6 pistons to raise the compression ratio because they couldn't find high comp pistons in the time available and astonishingly enough it ran and didn't chuck all its bits out through the side of the block.

I've helped him out a lot in the last couple of years and he never charges me for welding anything up so ask if you want something doing.

I'm not really familiar with what's available. Do they come as a complete unit with pipe in, pipe out? The one I've seen a picture of appears to be just a valve which fits into a housing - and I assumed that housing is part of a main casting. Hence the query about using a later plenum.

Ok - so that's out. It was at the back of my mind that it was difficult - there used to be dry stitching methods used for cracked blocks etc.

I've actually got a local SS exhaust place that make them on the premises. Lovely pipe benders, etc. And TIG welding. Reasonable prices too. So I think I'm settled on fitting two narrow band sensors - one on each downpipe just after they combine. So that's only the manifold to downpipe joints to worry about rather than an extra two if I fitted only one where it all combines. Now all I've got to work out is the best way to combine the electrical outputs from them - a simple mixing circuit or a switching one.

I think you're trying to overly, and pointlessly, gild the lily by running two sensors. You do get mixture distribution problems between individual cylinders on V engines but if you're sampling all four on one bank I doubt that would be a markedly different average to that on the other side unless there were actual engine problems that needed fixing anyway. I assume this is just normal closed loop operation with a narrowband sensor? If so remember the voltage output is not linear wrt mixture. It just goes from very low (0.2v or so) when leaner than stoich and then jumps immediately to very high (0.8v or so) just above stoich. Whether it's 0.2v or 0.3v below stoich or 0.7v or 0.8v above it makes no odds and averaging both banks isn't really going to change this.

If you're trying to do something more complex with wideband sensors like run a specific WOT ratio then you could be forgiven for thinking there would be a marginal benefit from averaging the banks but in fact if you set the mixture for best power on a dyno on the one sensor it will take everything on the other bank into account anyway. Two sensors can't improve any mixture distribution problems unless you have also separate control of both banks in the ecu. The only other way to improve mixture distribution is change the manifold.

The reason some production V engines with single output ecu control have two sensors is not to improve the average mixture control but to signal a fault on either bank which, in the USA at least, means it's then illegal to keep running the vehicle. I'm assuming this is not your ratio decidendi.

Some have a boss or ''platform'' already incorporated for mounting the sensor, all you have to do is drill and tap. Haven't a clue what yours are like.

Julian.

Ah - right again. So if only four out of eight is good enough would the same apply to only two? That would mean I could site the sensor closer to the engine - which seems to be a good thing. Unless I'm wrong about that too. ;-)

I dunno how good the early EFI RV8 is in this respect - everything manifold wise looks symmetrical apart from the air intake which is on one side only.

Indeed not - plenty of warnings that the MS isn't suitable for the latest emission regs.

Thanks again for the info.

Ah - I haven't looked. The EFI system was first used for emission control on US spec cars - but I dunno if they had lambda sensors or where they were fitted. I suppose they must have had since a cat would have been fitted. Or even if they used the same manifolds. The UK EFI engine has different ones to the carb. cars. And there are different types used for other installations.

Same as a few makes by the sounds of things. Many old Audi's from the late

80's-90's with Bosch K-jet found there way to the States. These vehicles had a Lambda controlled fuel system and a cat - it was a form of primitive electronic control of fuel pressures on what was essentially a hydromechanical system. Many of the cast iron manifolds on the European spec cars had the boss for the sensor - but it hadn't been drilled.

Feeling lucky?

Julian.

Bulls eye. There is indeed an undrilled boss on the nearside manifold - exactly where it's most convenient for fitting and wiring. None on the offside one. Can't imagine why I'd not noticed it before - although I've never needed to remove that manifold. The other one I did many years ago - to replace a stud Kwikfit broke.

You wouldn't have spotted it because you wouldn't have been looking for it. (if you follow) Sounds like the WTG. M18*1mm pitch IIRC, but check because I'm not 100% certain

Julian.

I've found a new Bosch 'universal' sensor on Ebay that seems to be a reasonable price - and the part number agrees with one said to be suitable in the MS manual. So have ordered it up. It doesn't give the thread details on Ebay, though. I've got a pretty fair selections of taps here so hope I've got the correct one. Otherwise more expense. ;-)

No, no. Not 'more expense' (bad thing)

It's 'more tools' (good thing)

I've believed that all my life. Unfortunately something's gotta give. I created a new cupboard under the stairs to move out lesser used tools from the workshop. About 2 cubic metres in size. Which hasn't made a scrap of difference - despite being now full. ;-)