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Discussion Starter #1
Here's a writeup about how to make a 2.5 BAR map sensor for your boost project using a stock map sensor casing. The sensor is good for about 22psi. You might be saying "BUT that's not 2.5 bar!" well it has to read vacuum too so from vacuum all the way up equals 2.5 bar.

Here's the small case Motorola MAP sensor: MPXA4250AC6U


This is me just gutting a case that I had spare, it's a cracked case. I just wante to see if it was feasable to even do this project.

Ever wonder what's inside? I used a 7/32" drill bit to drill on the bottom of each rivet and pry open the bottom cover:


Whole lot of sealed up going on there ^ Kind of a black rubber layer so I started digging:


And dug for like 30 minutes with hand tools until I got everything removed: (those metal tabs toward the plug go straight to the pins on the plug)



Here's the motorola small case 2.5 bar map for size reference:


This is very much going to work:



This was just a preliminary feasibility study for me. I wanted to see if it even could be done. Now that I know that it can easily be done I'll hollow out another MAP with a non cracked case and continue the guide.


The plan will be to find a drill bit of the right size and ream out the lower casing hole so the motorola will slide inside. Glue it to the bottom plate, run wires to the pads and seal it all up with RTV and some superglue.
 

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Very cool! I'll be patiently waiting for an update to this.
How soft is the sealant used to seal and insulate it all? It look about as soft as clay. Are there any foreseen complexities yet?
 

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Discussion Starter #3
materiamage on Mar/27/10 said:
Very cool! I'll be patiently waiting for an update to this.
How soft is the sealant used to seal and insulate it all? It look about as soft as clay. Are there any foreseen complexities yet?
It's like prying off RTV rubber sealant. Nothing complicated about hollowing out a map case. There are lots of nooks and crannies though. It's time consuming but pretty straightforward.
 

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Bookmarked! I would like to see how this is done step by step so I could make one. Where did you pick up the motorolla map sensor from?
 

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Discussion Starter #5
Got the map sensor from Newark.com. I bought 2, one is going to be done for a friend (luck4rmkc)

Map sensor wire colors:
GSR:
1(MAP) - yellow/red - power(5V)
2(MAP) - red/green - signal
3(MAP) - green/white - ground

I gutted my non cracked case and dug all the way down removing the stock sensor unit completely for a bit more room:


And soldered the wires that will go to the actual sensor onto the exposed pin pads:


Now it's as simple as mounting the Motorola sensor to the base, soldering the 3 wires to the appropriate connections on the sensor and sealing it up.

Easy.
 

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do you think that the height/placement inside the case will affect anything. I would guess not, since it just needs to read the force pressing on the diaphragm, and send signal accordingly.

Also wondering if you have seen
THIS. Im betting that you have, but if may help with the pinout if you dont already have it all tracked and traced.
 

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Discussion Starter #7
materiamage on Mar/27/10 said:
do you think that the height/placement inside the case will affect anything. I would guess not, since it just needs to read the force pressing on the diaphragm, and send signal accordingly.

Also wondering if you have seen
THIS. Im betting that you have, but if may help with the pinout if you dont already have it all tracked and traced.


Placement in the case doesn't matter any as long as the nipple on the new sensor is sealed inside the nipple on the case. You could remote mount this sensor just like the bigger version. They are functionally the same just different IC package.

Yep, I've seen the datasheet. The large version is the one most people run because it's easier I guess. I wanted mine to be plug and play like the expensive sensors.

Got it all tracked and traced in my head. I'll show you guys once I do it.
 

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Discussion Starter #8
Okay, I drilled the base of my cracked housing, Tried a 7/64 but that was too tight so I moved to 1/8 which was a bit too loose. I'm thinking of snagging some metric drill bits to find one where the nipple of the map sits snug in the hole.

Anyway on to the pics...

Drilled 1/8" hole in the base of my test cracked sensor:


Sensor sits right in:





It's really a matter of using some RTV to glue the sensor into the hole (Being careful not to get rtv in the hole of the sensor!) and soldering the 3 wires and sealing up the case.
 

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going to rivit the case closed? or just a lil glue.
 

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Discussion Starter #14
DARKNGL on Mar/27/10 said:
Nice.

Newark Part# for quick sale: 75C3863 or 75C3861

only newark part 75C3861, the other part doesnt have a nipple port on it. That would make it a lot tougher to do.

MPXA4250AC6U = has port - Want this one
MPXA4250A6U = has NO port - DO NOT WANT


You must use an ABSOLUTE pressure sensor type, not a relative type. Absolute pressure sensors have an internal vacuum that they reference so when they are sitting in atmosphere they are registering 14.7 (they can read vacuum). Relative sensors reference the atmospheric pressure and give you a reading above atmospheric (they can NOT read vacuum).
 

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Heh. I didn't know you were buying the small case Motorola 2.5 bar MAP sensors when you asked if I wanted one.

I wish I would have known that.

Oh well.

Looks good man. This is a classic homebrew modification.
 
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