Different function between MAP A and B

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davidj
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Different function between MAP A and B

Postby davidj » Mon Jun 12, 2006 11:46 pm

Hi All,

I’ve searched through the forums but have had no luck. Can anyone tell me why there are two MAP sensors ? From the forums, it looks like MAP B handle boost cut etc. So which determines engine load ?

I am looking at connecting and intercepter to change boost limit and possible A/F mix


Thanks

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James
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Postby James » Tue Jun 13, 2006 6:44 am

Map A sense vacuum and small boost signals and map B sense low vacuum to high boost levels, they have some overlap which the computer checks, and if it isnt right then it throws an error code.

A fuel cut defender works sweet if you put it on Map B, an air fuel hack thingie should work aswell on map B but youll only be able to change the mixtures on boost.

davidj
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Postby davidj » Tue Jun 13, 2006 2:52 pm

Thanks for the info. Had a feeling that would be the case based on the pressure/output curves in the manual. I actually thought about hacking the software on the ECu. Done this will a saab turbo I used to have. However, using one or more intercepters (Silicon Chip kits) will be much simpler for now.

Cheers

Colza
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Postby Colza » Tue Jun 13, 2006 7:36 pm

If you want to use the 'Digital Fuel Adjuster' project then i'm afraid you are out of luck. They dont work with the City ECU, it realises you are messing with it and throws error codes.

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James
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Postby James » Tue Jun 13, 2006 7:46 pm

I think you could make it work but you would need a considerable amount of electronics knowledge, I think you could probably change the input and/or output stage and make it work. It was probably a problem with a small offset somewhere or maybe the output or input impedance needed fiddling with.

davidj
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Postby davidj » Tue Jun 13, 2006 9:39 pm

Thanks for the heads up. Yes you a prob correct, it may have something to do with offset and/or input resistance. Now that I know others have had problems I will look at the front-end citcuit on the ECU before connecting anything.

Cheers

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James
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Postby James » Tue Jun 13, 2006 10:01 pm

Both map sensors go through some funny thing in a plastic block and then go through an SMD LM358 buffer and then through a 1 of 8 analog multiplexer to an 8 bit ADC and then via digital to the MCU, thats the best I can tell from tracing the paths on the ECU.

MSM5204RS is the ADC, TC4051BP is the analog MUXer, The 358 has a funny chip number on it too, starts with J.

If you are interested in doing some research on the ECU function I have a whole pile of datasheets for some of the chips and a description for every IC in the ECU.


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