DIY Active Map Clamp, How To make your own Active Map Clamp (Gen 3 3SGTE) Options

[presure2]

so while browzing around for the symtech active map clamp that both dustin and jim use, i came across this diagram on one of the srt-4 message boards,
its a DIY active map clamp.
heres a link to the original post on srt4forum.com
http://www.srtforums.com/forums/f75/how-bu...p-clamp-349656/

the part # in the diagram in the link for the diodes is for 50 of them, since you dont need 50, i modified the diagram with the pt# for 10 diodes.
heres the diagram:



here are a couple links for the parts to build one.
first the potentiometer, PT#271-342


http://www.radioshack.com/product/index.js...oductId=2062307 it costs 2.69$

the diode is 1N914 Radio Shack PT# 276-1122 whic gives you 10 diodes, and costs 1.49$

http://www.radioshack.com/product/index.js...oductId=2062576

according to the radio shack website, the store right down the street has these parts in stock, and they open @ 10am, so imma run down in a bit and grab the parts.
once i build it, ill install it and detail how to use it.


For those of you that dont understand how it works, here's a quick break down.

the map sensor on the 3rd gen 3sgte puts out a 0-5 volt signal that tells the ecu how much pressure is in the manifold.
the higher your boost level, the higher the voltage getswhen you reach max boost. when you reach right about 18psi, the ecu sees the max voltage allowed before boost cut happens, and the car bucks and tells you "STOP IT!" lol
with this device, you can "clamp" the voltage at a level just below boost cut, while allowing the sensor to work as normal below that level.
that way, you can boost above 18psi, and not hit boost cut.

:edit:
went and got the parts, assembled them, and took some pics.
ill install and test it later when Jenn gets home from work.

the pot



the diodes



here it is assembled.
power wire closest to the adjustment screw, 2 diodes wired in series, with the band at the tops (i forgot to take a pic without the heat shrink, so i just stuck a couple of the diodes in the pic for refrence) and the ground last.



once i install and test it, ill report back!

[stephen_lee]

3waystunna is correct. use zener diodes, these allow everything above a set voltage to pass through it, essentially leaving only the set voltage on the other side. EX: pin 1 of diode is at map signal, pin 2 is grounded. diode is 4.9v. map put out 4.8v, diode does nothing. map wants to put out 5.0v, diode passes just enough current to drop it back to 4.9v.

the diodes you have only allow current to pass one way. EX: pin 1 is grounded, pin 2 is at signal wire. no matter what, the system works as normal. reverse the pins, and the map signal is grounded 100% of the time.

the pot in your case complicates things, but it will work if you swap those diodes for a zener type.

btw, this is really just a passive system... "active" would use some sort of IC, transistors, and voltage regulators to accomplish the task.

EDIT:
whoa, whoa, wait. the original design is NOT A CLAP AT ALL. actually, it is basically just a FCD. lowering the voltage somewhat is ALL ranges of map operation.

add the zener diodes and it should work as you intend.

This post has been edited by stephen_lee: Oct 5, 2010 - 12:16 PM