PDA

View Full Version : adding a GM map sensor



benevolent
09-17-2004, 11:46 AM
i'm wanting to add a GM MAP sensor to my s14. it requires a 5vdc source.tapping the TPS(or any other sensor) seems like a bad idea.has anyone added a 5vdc source? i've found some dc/dc converters that would do the job,but they are all surface mount.like for a PC. there has to be a better option.

Goolie
09-17-2004, 03:30 PM
You could try a zener diode to supply the 5 volts....

A brief explanation (http://www.thedodgegarage.com/turbo_map.html)

you'll have to do your homework to see if they provide a stable 5 volt source...

it looks like you could possibly get a 5.1 volt, 1 (or 1.5) watt zener diode list here (http://zeus.cedcc.psu.edu/semi/zindex.html)

Enthalpy
09-17-2004, 03:39 PM
just pull 5V off the TPS. it is also 5V power.

rednerd
09-17-2004, 04:22 PM
You could try a zener diode to supply the 5 volts....

A brief explanation (http://www.thedodgegarage.com/turbo_map.html)

you'll have to do your homework to see if they provide a stable 5 volt source...

it looks like you could possibly get a 5.1 volt, 1 (or 1.5) watt zener diode list here (http://zeus.cedcc.psu.edu/semi/zindex.html)


He wants to know where to pull a 5V source from, right?

That page looks like it is using a zener to clamp the voltage. If you don't want to use the TPS source, I'd try using something like an LM7805.

Goolie
09-17-2004, 04:30 PM
My understanding of the zener diode is that you put 12 (or whatever) volts in, it outputs 5 (or whatever) volts out, and grounds the rest... making it a quasi power supply

of course, the LM7805 IS a power supply, and just as easy to implement... I change my vote to that http://forums.freshalloy.com/images/graemlins/wink.gif

mamaboy
09-17-2004, 04:42 PM
Yes, a zener diode is a one way check valve usually used in the alternator to control voltage output. it outputs only the specified amount of voltage even if 12V is sent through it. it constantly turns on and off to regulate this process

Goolie
09-17-2004, 04:55 PM
so if it turns on and off to achieve the desired voltage, it wouldn't be the cleanest source for a signal, causing all sorts of noise etc.... good to know

Hugh
09-17-2004, 04:55 PM
Just listen to Enthalpy.

There's already 5v coming out to several sensors in the car. Use whats already given to you.

mamaboy
09-17-2004, 06:19 PM
Yeah, I think the TPS operates off of 5V ground/power/ecu. The zener diode is part of the voltage regulator turns on and off hundreds of time per sec. it's so that the car has a consistent amount of voltage. if the rotor and stator isn't controlled the amount of voltage would surpass the cars limits......just though I'd wrap it up.

benevolent
09-18-2004, 12:09 AM
Just listen to Enthalpy.

There's already 5v coming out to several sensors in the car. Use whats already given to you.


yeah, i know the TPS is 5vdc,as well as a couple others.the problem there is that it's 5V right from the ECU.if i exceed the circuit capacity there,i'm lookin for another S15 PowerFC.the first one was a pain in the ass to get.has anyone actually tapped the TPS for power to another sensor?

nissandet240
09-18-2004, 04:33 AM
Can any one draw a schematic. on how to connected this for a SR. Im looking foward to this, that way I can get rid off the recirculator valve, and good bey to back firing.
cool ill have my rattleing pshh. again.

benevolent
09-18-2004, 09:21 AM
it would take some serious engineering to replace the MAFS with a MAP sensor.thast why the off the shelf products that accomplish it are fairly expensive. i just want to add one so i can log boost.

Hugh
09-18-2004, 10:42 AM
Well... I'm certain that all the 5v sensors in the car are pumping off the same 5v regulator in the ECU. If I absolutely have to, I can trace the 5v back into the ECU for you to prove it.

I'm sure the current draw of a map sensor is hard to register on an ammeter. What I mean is, the sensor uses so little power its almost negligable.

Do you have an electronic boost gauge in the car? The electronic boost gauges have their own 5v signal and map sensor. I've used this for datalogging in other people's cars before. Same goes for electronic fuel pressure, oil pressure, etc... they will have 5v.

How about your boost controller? Do you have an electronic boost controller?

benevolent
09-18-2004, 11:00 AM
no...not at the moment. i'm considering the boostkit for the powerFC,but it's kinda low on the priority list as the MBC i have is doing a fair job of things.as is my autometer "my first boostguage"tm.i'll probably go ahead and hijack my source from the TPS,as it's close to where i'm mounting the MAP.i didn't really consider that there's a relatively high current 5v regulator in the ECU.as opposed to smaller individually sized units for each sensor. didn't give it much thought i guess.anyway thanks for the insight.it'll help me out substantially.

Hugh
09-18-2004, 11:30 AM
I'm pretty sure the boost sensor for the Power FC will come off the same 5v regulator. Try tapping the 5v line at the boost sensor connection and see if its live with the boost control function turned off. (it very well should be)

You could run it straight off that connector as its intended.

benevolent
09-18-2004, 01:04 PM
i'de love to do that,problem is i don't have a boost pressure sensor.i've looked all throught the FSM literally hundreds of times throughout the course of my swap,and i have yet to see any reference to one.if i found one in the FSM i would source a stock one and drop it in like intended.i just don't think there is one on the S15.

Hugh
09-18-2004, 05:42 PM
I thought you said you had a Power FC?? THere's a connector on the side for a boost sensor.

benevolent
09-18-2004, 11:25 PM
ahh crap,i didn't even think of that.damnit.ok now i feel stupid.i thought that was for something else.

mamaboy
09-18-2004, 11:30 PM
wait, i believe maps are digital sensors. working off of pressure in the manifold...incorporating the piezo crystal...or whatever its called....i don't think they work of 0-5V analog. Rather just 0-5V binary/digital signals on/off.....somebody correct me if i'm wrong

Hugh
09-19-2004, 12:01 AM
You're wrong.

ICESoft
09-19-2004, 03:31 AM
Depends on the MAP sensor, some manufacturers use a pressure to frequency sensor (Toyota, Mitsubishi?), while others like Nissan and GM use a pressure to voltage sensor. But since this is a GM MAP sensor discussion, you're wrong like Hugh said.

I'd have a problem using the ECU's +5v supply for stuff like this, just one more wire that's not in the harness to short to ground somewhere and wipe out the ECU, or worse, short to +12v and wipe out ECU + MAFS + etc....

Also on the basis of getting 5v for the thing, easiest way without stealing it from the ECU is to use a LM7805 regulator from radio shack, a Zener is harder to set up because you need to know the current draw of the device connected to calculate the value of the series resistor. The way it works with a Zener is you have a series resistor in your 12v line that has enough voltage drop across it that the Zener can shunt any extra "slack" voltage to ground without going outside its rated power range.

<font class="small[/img]Code:</font><hr /><pre>
R
+12v in ---------/\/\/--+------ +5v out
|
\-+-\
/ \
/___\
|
Ground ------------------+-------- Ground
</pre><hr />

See this page for calculations Zener Calcs (http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/zenereg.html)

Hugh
09-19-2004, 08:28 AM
I guess I'm just a little braver than most. Besides, the connector on the Power FC was designed to run a MAP sensor. How can you go wrong?