MAP Operation

Funky Diver · Post by **Funky Diver** » Sat Jan 22, 2011 8:09 am

POK, so my MJ is running with MAP, not TPS.

I'm going to be running bike carbs, and as such each cyclinder will have it's own header and carb. Now the easy bit is getting the manifold tapped and air lines in for MAP, that bit I "get".

As I'm also doing other things with my car, how does the MAP sensor on the board work? I'm guessing it's a guage sensor rather than differential?

Basically... the four lines are coming off the manifold, to a coupling to join them together, then into my reservoir (and old Vacuum tank off an Audi R6) to even out the pulsating, then to MJLJ.

What I would like to do, is insert differential sensors into each of the four manifold vac lines, to measure their relation to each other under driving conditions (as well as data log it) so that I can get historic data as to the performance of each carb / cylinder combination to more effectively tune the carbs to the cylinders themselves. I appreciate it isn't exact science, but it'll also (very quickly) highlight any running issues too.

Is doing this going to cause issues with the MAP sensor working effectively?

NITROPIXIE · Post by **NITROPIXIE** » Sat Jan 22, 2011 6:01 pm

You may be able to use the four MAP sensors and then use an averaging circuit to combine all four MAP sensors to produce a single MAP input and at the same time produce a bar graph for each of the runners for a visual output.

Would use a bit of circuity and some processing to achieve this though.

Funky Diver · Post by **Funky Diver** » Sat Jan 22, 2011 7:37 pm

That's precisely what I aim to do, although the electronics aint that difficult. Standard MAP sensors output 0-5v, so it's quite straight forward converting that into a readin which is then represented visually.

I just need to decide whether to run the sensor in Parallel to the one mounted on MJ, or in series, however, my uncertainty is surrounding whether it will then have a knock on effect on the MJ's readings.

The simplest way to do it would be to run a vac pipe off each runner on the manifold, then Tee off just before the plenum to four MAP sensors. Possibly overkill, but hey, that's all good for what I want to achieve. I just don't want it looking all a bit spaghetti and bolognaise under the bonnet (hood).

NITROPIXIE · Post by **NITROPIXIE** » Sat Jan 22, 2011 8:25 pm

Ahh, slightly different to what i suggested.

I thought about using the electronic signal produced by each of the four MAP sensors to produce a single signal to the megjolt, instead of using a four way joiner and a smoothing reservoir. So each runner would be mechanically separated but electronically joined together.

Then use each MAP sensor to produce a bar graph which would hold out as max for that runner per ignition event as you would only see a difference in MAP every time that the cylinders valve is open.

Funky Diver · Post by **Funky Diver** » Sat Jan 22, 2011 8:37 pm

Exactly..so the real challenge is in maintaining continuity so that the MAP on MJLJ can do it's thing, but yet I can still monitor the data coming out of each runner. It would also be feasible (in some way) to check the fuel pressure going into each carb in the same way, but that's a story for another time, lol.