Filtering of MAP sensor input.

the_bluester
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Joined: Wed Oct 24, 2007 3:19 pm

Filtering of MAP sensor input.

Postby the_bluester » Sun Jan 08, 2017 8:12 pm

I have been struggling with an E36 BMW M42 four cylinder engine with an individual throttle manifold for some time with my old E11V2. I had hell getting it to trigger stably and fire coils properly.

Having sorted that today (After six months of fighting it) and gotten it idling nicely, the MAP input has quite a bit of scatter at lower revs. Would adding some volume in a vacuum plenum taken from all four inlet runners be worthwhile to smooth the input? It will be applying the same fluctuations to the fuel pressure regulator as well though I would assume it would not be responsive enough to cause much of an issue with the fuel pressure.

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Peterson
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Re: Filtering of MAP sensor input.

Postby Peterson » Mon Jan 09, 2017 4:41 am

You can insert a restrictor in the vacuum line but it will make your map response slower.Can you go Alpha-N?

the_bluester
Posts: 165
Joined: Wed Oct 24, 2007 3:19 pm

Re: Filtering of MAP sensor input.

Postby the_bluester » Mon Jan 09, 2017 8:59 am

I can do but would like to stick with the MAP if possible, it obviously reduces any ongoing issues with having to keep the throttle sensor zeroed for the same throttle plate position. It may end up easier to go Alpha-N in the end as quick roughing of a tune yesterday already showed that quite small throttle openings bring it to near atmospheric pressure, at the very least it is going to need a full throttle map to cover the lack of part throttle vacuum. Time ill tell. I have had every issue under the sun getting this bugger to start and run per some other posts on the forums so just getting a stable idle with a closed throttle map feels like an achievement! My own car (Where the E11 was previously fitted) had zero trigger issues, zero ignition issues and was idling and free revving nicely after about one day of fiddling as soon as the ECU install was completed. Hopefully it will be the same story when the Elite goes on.

On a previous car I had these same throttle bodies and a good vacuum signal without any issues, and that was a smaller engine with a much more aggressive camshaft. I hope the bugger does not have a crook valve or something like that.

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Peterson
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Re: Filtering of MAP sensor input.

Postby Peterson » Tue Jan 10, 2017 2:18 am

the_bluester wrote:On a previous car I had these same throttle bodies and a good vacuum signal without any issues, and that was a smaller engine with a much more aggressive camshaft. I hope the bugger does not have a crook valve or something like that.

Having said that in order to save time before you dig deeper tuning it check for mechanical issues.Check everything and if found (hopefully) ok then proceed with the tune.

the_bluester
Posts: 165
Joined: Wed Oct 24, 2007 3:19 pm

Re: Filtering of MAP sensor input.

Postby the_bluester » Tue Jan 10, 2017 5:56 am

Yeah, I have been digging and cant find anything, no unexpected noises, no sign of air leaks, no odd pops through the inlet to indicate a crook valve or anything. I think it might just be characteristic of the engine.

There is a full on ITB kit people can buy for these things but they retain the stock ECU which uses an old flap type airflow meter so they would be no help in telling me if this sort of vacuum signal is typical. I flipped over to TPS load last night to at least get it driveable enough to move it off my ramps as I want to build an exhaust on another car soon and I am sick of lying on the floor!

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HaltechMatthew
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Re: Filtering of MAP sensor input.

Postby HaltechMatthew » Tue Jan 10, 2017 3:30 pm

With ITBs you need to get a signal from all cylinders and have a combined tank. Typically about the size of a finger is sufficient. Without doing this the signal is too pulsed to be of any use.

Filtering of the MAP signal is adjustable in the E11 too.

the_bluester
Posts: 165
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Re: Filtering of MAP sensor input.

Postby the_bluester » Tue Jan 10, 2017 8:54 pm

Yeah, it certainly pulses pretty sharply as it is, it is connected to all four cylinders but without much volume i suspect it is pulsing harder from 2-3 which the MAP take off point is in between.

I have roughed out a TPS based map to get it moveable so I can use my ramps again, as it is if I disconnect the line to the MAP sensor and put it against my finger I can feel the pressure pulses. I will rough build a rail to combine it and see if it makes the signal useful or not. It has not got a lot of vacuum so it might have a fair sized hole in the tuning between vacuum going to zero and a sensible throttle opening for a WOT map to take effect.


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