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Discussion Starter · #1 ·
I'm currently installing my AEM water/meth kit with the Aquamist DDS3 failsafe. I have the DDS3v8 module. I'm going to have SSP use Tephra to switch maps with the failsafe. Does anyone know how to wire the DDS3 module to the ECU? I've read that the ECU needs 5 volts from the failsafe. I don't think the DDS3v8 outputs 5v. I've read somewhere that some units will require a resistor and/or relay, but no instructions on which components and how to wire them. Also, which pin(s) do I go to on the ECU? I think I'm supposed to use either pin 11 or pin 12 on the DDS3 unit. This is all so confusing! I would message Tephra, but I don't want to bother him with it. I hear he's pretty busy these days.

Any help would be much appreciated.
 

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i wish i had my car outside to snap pics of the wire i cut. i helped T beta test map switching. my fail safe (cooling mist) runs 5v until an error occurs then drops to 0v on error. the drop to 0 instantly trips the maps to teh "safe" mode.

one of my old posts: http://www.evoxforums.com/forums/showthread.php?t=33569&page=5

if your fail safe is opposite, then you'll need to wire in a relay to trigger the 5v->0
 

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Discussion Starter · #3 ·
i wish i had my car outside to snap pics of the wire i cut. i helped T beta test map switching. my fail safe (cooling mist) runs 5v until an error occurs then drops to 0v on error. the drop to 0 instantly trips the maps to teh "safe" mode.

one of my old posts: http://www.evoxforums.com/forums/showthread.php?t=33569&page=5

if your fail safe is opposite, then you'll need to wire in a relay to trigger the 5v->0
Thanks for the info. I think the problem with the DSS3v8 is that the signal that comes out of the "Map SW" pin is higher than 5v, and Tephra was very clear that it must be below 5v. I'm not sure if it is normally open or normally closed. It doesn't say whether it outputs a constant 5v, or 5v when the failsafe is activated. Hmmmmm.....

So when connected to the ECU, we want it to be 5v until the failsafe is active, then 0v (OPEN)? Which pins on the ECU do I use? Also, where did you find pins for the ECU?
 

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Thanks for the info. I think the problem with the DSS3v8 is that the signal that comes out of the "Map SW" pin is higher than 5v, and Tephra was very clear that it must be below 5v. I'm not sure if it is normally open or normally closed. It doesn't say whether it outputs a constant 5v, or 5v when the failsafe is activated. Hmmmmm.....

So when connected to the ECU, we want it to be 5v until the failsafe is active, then 0v (OPEN)? Which pins on the ECU do I use? Also, where did you find pins for the ECU?
i had a few drinks so my google skills blow right now; but we cut the wire coming from the fuel tank pressure sensor or something along that line and used it. i tapped into it along the wire loom along the drivers side door. the resistors are in place to drop the voltage down; it doesn't have to be 5v->0 but a relatively high voltage ->0 will work

ahah! found an old pic of the wire i cut and tapped into:
http://forums.evolutionm.net/ecuflash/497325-tephraxmod-v1-4.html#post8395440
 

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you really are drunk, aren't you :neener: Let me hold your hand.
thanks!

i really am having a hard time finding the thread where T asks something about using a "worthless" fuel sensor of some kind for map switching on the usdm's and many of us replied with "hell noes give us switching!" then i cut that wire he said; added a resistor to be cautious and tested it out by pulling the power wire off of the meth kit to force a failure to make sure i switched maps.

fun times indeed :) i even found my ecu benching kit today cleaning out the garage. glad i never needed it.
 

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Discussion Starter · #7 ·
I just found a wiring diagram that says the trigger is closed until the failsafe is activated, then it goes open (0v, correct?). It doesn't say the voltage, but I've read that it is higher than 5v. You mention that it has to be "relatively high voltage", but Tephra was VERY clear that the ECU cannot accept higher than 5v. In fact, he suggests 4.9 volts. There was even a discussion about not using certain diodes with a 5% tolerance that would allow over 5v on the high end of their tolerance. I assume a relay is only used when the failsafe is normally open?

Do we not need the wire that you cut? It wont cause a CEL or anything? I thought the trigger went to an unused pin on the ECU (pin 119, or something like that).

Sorry, my knowledge of electronics is fairly limited.
 

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I just found a wiring diagram that says the trigger is closed until the failsafe is activated, then it goes open (0v, correct?). It doesn't say the voltage, but I've read that it is higher than 5v. You mention that it has to be "relatively high voltage", but Tephra was VERY clear that the ECU cannot accept higher than 5v. In fact, he suggests 4.9 volts. There was even a discussion about not using certain diodes with a 5% tolerance that would allow over 5v on the high end of their tolerance. I assume a relay is only used when the failsafe is normally open?

Do we not need the wire that you cut? It wont cause a CEL or anything? I thought the trigger went to an unused pin on the ECU (pin 119, or something like that).
to be honest i when i blew my block several months ago i was pissed and "disconnected" from the community. now that i am weeks away from getting it back i have been more active. so i may be slightly out of the loop. the last i heard we were using that wire to trip the ecu, i hope someone else can chime in and correct me if it has been updated.

irregardless of pins; keep it under 5v by using resistors. the specific one is dependent on the kit you are using; but ~3.3v->0 should be big enough. if you use a giant resistor that you are going from 0.05v ->0 you may run into issues with sensitivity and tolerances. T is right though; do not go OVER 5v as you run a risk of burning up your ECU.


now you have me reading hundreds of posts to see if the failsafe pin has been changed!

edit: latest info i have found (jun 8): http://forums.evolutionm.net/ecuflash/497325-tephraxmod-v1-41.html#post9376920
 

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Discussion Starter · #9 · (Edited)
irregardless of pins; keep it under 5v by using resistors. the specific one is dependent on the kit you are using; but ~3.3v->0 should be big enough. if you use a giant resistor that you are going from 0.05v ->0 you may run into issues with sensitivity and tolerances. T is right though; do not go OVER 5v as you run a risk of burning up your ECU.


now you have me reading hundreds of posts to see if the failsafe pin has been changed!

edit: latest info i have found (jun 8): http://forums.evolutionm.net/ecuflash/497325-tephraxmod-v1-41.html#post9376920
I found that post as well. The problem I'm having is that my DDS3v8 unit is quite a bit different from the wiring diagrams that Tephra posted in the "TephraMod V1" #2 post. In his wiring diagrams it shows the resistor on a wire coming from the failsafe box going to chassis ground, NOT on the white/black wire going to the ECU.

Here is the wiring diagram I'm using:

http://www.aquamist.co.uk/forum/gallery/DDS3v8/third-party/AEM.pdf

Correct me if I'm wrong, but the most sense I can make of it is this:

Clip the white/black wire. Run a wire from the MAP-SW1 pin on the DDS3 unit to the forward section of the white/black wire with a 250ohm resistor in between. I'm confused as to what to do with the rear section of the white/black wire. Leave it hanging? Ground it? I'm also not sure if I do anything with the MAP-SW2 pin on the DDS3 unit.

And if I use a 250ohm resistor, how can I be sure it will put the voltage in the correct range if I don't even know what the original voltage is coming off of the failsafe unit?

Sorry, I just didn't expect the wiring to be this confusing.

EDIT: I know the wiring diagram I'm using says "FAILSAFE METHOD: BOOST CUT", but the Tephra setup should still use pin 11 (MAP-SW1). Not sure about MAP-SW2.
 

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Discussion Starter · #11 ·
Thank you! I was really worried about the voltage coming out of that thing. So it's 12v. Still leaves me two questions:

-What do I do with the rear section of the white/black wire I cut?
-Do I need to run that black ground wire to the ECU ground like in the diagram you posted? I thought a regular chassis ground would work.
 

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Thank you! I was really worried about the voltage coming out of that thing. So it's 12v. Still leaves me two questions:

-What do I do with the rear section of the white/black wire I cut?
-Do I need to run that black ground wire to the ECU ground like in the diagram you posted? I thought a regular chassis ground would work.
wire: i taped it up and did nothing else with it.

i don't see why you would need to wire a ground to the ecu ground unless your instructions tell you to for another reason other tahn fail safe. i used that diagram as a reference to show how to get 12v flowing out of the failsafe and trip the same way i had mine set up. a 10k resistor will put you a little over 1v which i would think is high enough to give the maps the "ok"
 
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