MAP sensor

I bought a Bosch MAP sensor some years ago, a 0 281 002 119 which went to 2 bar, for NA you could use the 0 281 230 004, this was a automotive MAP sensor sold for aftermarket use. I don't know if the specific part is still available or superceded as the Bosch site make finding the info hard, maybe they removed it. It fits your requirement though of 5V supply and analogue output. You might also look at the ones used by Megasquirt, IIRC they would also do and last time I looked a year or so ago were stocked by RS.

Make that last part number 0 261 230 004 see here

Thanks for the heads up - despite using electronics suppliers I never thought to try them. Got exactly what I wanted from Farnell - at about 15 quid rather than the

75 or so for 'car' ones. Only difference is it has Molex connectors rather than an automotive one.

In message , "Dave Plowman (News)" writes

I've used one off a Rover 827 (Honda V6 engine). This is found in a big black plastic box with other sensors and solenoids in it, and is connected to the inlet manifold by a length of vacuum pipe. It's easy to remove and is physically robust. As you say, it uses a stabilised

+5V supply and has a linear transfer function up to approx 1.7 Bar.

Perhaps other EFI Rovers or Hondas from the late 80s use the same one.

Thanks Chris, but hopefully sorted when it arrives from Farnell. Just another question since you seem to be on the programmable ignition wavelength - the kit has the option of a knock sensor. Worth the bother - and any idea where it (they) fits on a Rover V-8?. And same question about which to use?

Dave, std ones as used on the later DiscoII (Thor engine) and P38 rangerover (both Gems and Thor variants) are fitted either side of the block on an extra boss that is cast in next to and slightly above the middle core plug on each side of the block. I think they work on a stabilised 5v supply..... Badger.

That was my fear that they were sort of built in. I'm thinking of fabricating brackets that attach to the exhaust manifold fixings.

Dave,

I think the main thing is you have a good solid fixing to the block without flexure as they're basically an acoustic pickup, you wouldn't want possible relative movement giving false indications (noise).

Indeed - I assume they're just some form of contact mic. I was thinking of supporting it by a bracket, but actually using epoxy to stick it to the block. But open to better suggestions. ;-)

For a solid fixing, I would suggest drilling and tapping the block. No doubt they would break into the water jacket, but a pair of brass inserts screwed in with sealant, maybe using 'Loctite Retainer' so they wouldn't easily unscrew if the sensor bolt became tight, would not cause any problems as far as water leaks were concerned, and I can't think of a better way to get a really solid fixing.

With a central blind hole tapped to suit the knock sensor, you'd have a fixing as solid as any OE fitted one. I certainly wouldn't advise you glue them. I don't think they would stay glued for long.

I could make the inserts for you if you decided on that method. All I would need to know is the water jacket thickness, (easily checked after drilling) and the sensor bolt diameter.

If you're interested, I assume you still have my email address. Mike.

*If you're doing nothing, how do you know when you've finished?*

That's good. I used to have an account with Farnell but as their printed catalogues dried up, and they pushed more to the website I stopped buying from them and switched to RS. I didn't have a RS catalogue but I found RSs website vastly superior to Farnells and it still is by the look of it. I found using Farnells website a waste of time when it might take an hour to get an order together that would take 10 minutes with the printed catalogue.

Hmm. It would certainly make for a good fixing, but I'm not sure the sensors - being a type of microphone - are a) waterproof, b) would cope with the pressure of the coolant and c) wouldn't get confused by the sound of the coolant rushing past the diaphragm. The circuit does include a high pass filter to remove unwanted noises from those to be sensed but My feeling is it wouldn't filter that out. Of course it's only guessing on my part.

My thoughts were to support if firmly with a bracket bolted to the exhaust manifold fixings as well as gluing to the block. Although some subsequent research on Google shows contact may not be necessary.

That's very kind, Mike.

I do indeed.

I'm not sure there's much between them once you suss them out. They are both slow if you have a slow connection or computer.

I tend to use Farnell/CPC cost wise. And Rapid. RS tend to be a last resort. ;-)

You missed the part about the sensor fixing being blind. Imagine a solid plug screwed into the block. Say 12mm long. The plug is then drilled 10mm deep and tapped to suit the sensor, so the sensor never contacts the water. Im thinking of the sensors that are mounted on a flat surface, and retained by a bolt that passes through them. The ones like a thick washer, for want of a better description. Mike.

I should have added that the same principle could be used for the type that screw into the block, but for that type I'd need to know the thread spec of the sensor, which could be an odd thread. Mike.

It was mainly that the printed catalogue had the data in it with the component so I could make a decision quickly, I found the Farnell site presentation poor and the data had to be downloaded if present. RS at least had quite a bit of data on the webpages detailing many of the components so was far quicker to get an order together.

Must look at CPC as I haven't in awhile. Got a nice shiny new Maplins in Bath now so for odds and ends I can pop in there and pick them up.

Bosch ones are shown here

and shouldn't have any problem with bits getting wet from the look of it if you tapped right through into the water jacket.

That's the type I'm thinking about, but ideally they should be bolted to a flat surface. Unlikely with a cast block. Another disadvantage is that replacing them for whatever reason would allow water to leak from the cooling system. The brass adaptors idea overcomes both those problems. Apart from that it's a much more elegant solution. :-) Mike. Mike.

CPC *is* Farnells...

Maplins is useful and convenient, but not as cheap, and just doesn't have the range of Rapid & CPC. Like Dave, RS is a last resort!