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Old 08-08-2012, 08:01 PM   #1
TurboQueef
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Default AEM Water/Meth Failsafe (how to trigger limp mode)

Good day,

I am currently using water/meth for safety only but am considering using it more aggressively. I have been researching the AEM failsafe kit.. looks pretty impressive.

I would like to know if anyone out there is using this kit to trigger "limp mode" in the stock ECU.

My specific questions (2005 STi) are:

* How do you trigger "limp mode" with the AEM kit?

* When you trigger "limp mode" can you confirm what happens in the ECU.. My guess is:

When limp mode is triggered...

The fail safe fuel maps are activated.

The boost target KCA additive low map would be activated.

The timing advance multiplier would go to zero.

Thanks for the feedback

Jeff
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Old 08-09-2012, 01:31 PM   #2
OC_Nooby
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id like to know as well!
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Old 08-09-2012, 04:25 PM   #3
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Me too!!
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Old 08-09-2012, 07:13 PM   #4
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from my research i gather most using the AEM failsafe will use the output to trigger the ECBS to run w/g pressue ie 15psi...

FWIW...that's what i plan on doing...
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Old 08-09-2012, 08:35 PM   #5
TurboQueef
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My understanding is there is a way to trigger limp mode using a wire behind the kick panel. The AEM website states: "Late-model Subaru WRX STi owners can connect the low side driver to the "limp" wire behind the kick panel..."

I am looking for information about this topic.

My specific questions:

* Where is the "limp" wire located?

* What tuning tables in the ECU are enabled during "limp" mode?

Thanks,

Jeff

Last edited by TurboQueef; 08-09-2012 at 09:07 PM. Reason: clairify request
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Old 08-10-2012, 10:57 AM   #6
TurboQueef
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I am getting good feedback on a post I made in the RomRaider forum.

I am in the process of confirming the feedback directly with AEM Tech Support.. I will provide updates to this post when I confirm everything.

Here are key points (unconfirmed at this point)

* Pin #15 on connector B137 of the 2005 STi ECU is the safe mode trigger point. We need to ground this pin to force limp mode.

* When pin #15 is grounded, it forces dynamic advance to zero and switches to failsafe fuel maps.

Here is a link to the RomRaider post: http://www.romraider.com/forum/viewt...hp?f=15&t=8679
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Old 08-10-2012, 11:49 AM   #7
BlazeRex
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Good info! I've always wondered about this
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Old 08-10-2012, 04:40 PM   #8
TurboQueef
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Quote:
Originally Posted by TurboQueef View Post
I am getting good feedback on a post I made in the RomRaider forum.

I am in the process of confirming the feedback directly with AEM Tech Support.. I will provide updates to this post when I confirm everything.

Here are key points (unconfirmed at this point)

* Pin #15 on connector B137 of the 2005 STi ECU is the safe mode trigger point. We need to ground this pin to force limp mode.

* When pin #15 is grounded, it forces dynamic advance to zero and switches to failsafe fuel maps.

Here is a link to the RomRaider post: http://www.romraider.com/forum/viewt...hp?f=15&t=8679
I just confirmed using my continuity tester that pin #15 on connector B137 goes to the female side of the little green connector that is used to flash ROM to the ECU. The female side of the green connector goes to pin #15 and the male side goes to ground.

I still need to confirm that grounding pin #15 zeros out the IAM and triggers failsafe fuel maps...
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Old 08-13-2012, 07:00 PM   #9
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Does the WRX have the same failsafe?2003 WRX
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Old 08-13-2012, 08:19 PM   #10
TurboQueef
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Quote:
Originally Posted by OC_Nooby View Post
Does the WRX have the same failsafe?2003 WRX
The thread I found (Aquamist forum) did not have details regarding WRX... My guess is the ECU has the similar capability but not sure how to trigger it.

Here is the link to the forum.. you may be able to search and find answer...

http://www.aquamist.co.uk/vbulletin/index.php

Jeff
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Old 08-22-2012, 01:28 AM   #11
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Interesting. What would be the advantage of this method over just cutting the boost via the EBCS?

I also read somewhere that you could tap into the stock temp sensor circuit and force the ECU to go to a different timing table that's reserved for high coolant temperature conditions. It could be a good way to run another tune that's safe for when your meth runs out but you would still have decent performance, say for a track day or something.
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Old 08-22-2012, 10:33 PM   #12
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2010, the LS1 guys do it with nitrous as a cheap wet kit alternative. I know that carberry has a mapswitch function for the 16bit ECUs. Might be something to look into.
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Old 08-25-2012, 03:12 AM   #13
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Quote:
Originally Posted by shaman View Post
2010, the LS1 guys do it with nitrous as a cheap wet kit alternative. I know that carberry has a mapswitch function for the 16bit ECUs. Might be something to look into.
Huh? What is a wet kit alternative? And there's no carberry or mapswitch for 32 bit ECUs that i know of.
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Old 08-25-2012, 03:32 AM   #14
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Fool sensors to run different timing and fueling.

http://ls1tech.com/forums/nitrous-ox...tor-trick.html

It's an IAT vs. the CTS, but the idea is the same.

Sorry, I hadn't looked for a 32bit answer to the Carberry as newer Subies are a little out of my price range.
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Old 09-25-2012, 01:05 AM   #15
2010 WRX Limited
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Delayed response: That's a good idea. It's a bit annoying to go straight to wastegate spring PSI as soon as the meth runs low... but really it doesn't happen enough for me to care to do this mod. But it's pretty cool anyway.
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Old 10-07-2012, 01:26 PM   #16
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Quote:
Originally Posted by 2010 WRX Limited View Post
Interesting. What would be the advantage of this method over just cutting the boost via the EBCS?

I also read somewhere that you could tap into the stock temp sensor circuit and force the ECU to go to a different timing table that's reserved for high coolant temperature conditions. It could be a good way to run another tune that's safe for when your meth runs out but you would still have decent performance, say for a track day or something.
The advantage of this is it would not only cut boost, but use your failsafe fueling tables.
Meaning if your running 12.5 :1 GAS and meth brings your final mixture to 11.5 :1 and ran out of meth at 25psi, you'd be done. 25psi on 91 octane at almost 13:1 AFR... goodbye engine.

BUT, if your fueling is switched to your failsafe table (usually quite rich, 10.5 :1 area) you'll probably have a knock episode and drive away from the disaster.
If I start running meth, I'll probably run it to ground out my EBCS as well to be on the safe side. I dont remember what settings the ECU runs in failsafe for boost.

Other advantage is that it wouldn't run advanced timing, just your base timing table. so it's already technically pulled SOME timing...

The sensor input you'd have to fool is Intake Air Temperature, theres a table you can modify to specifically adjust this in the ECU. You could use a small relay with a resistor i believe...
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Old 10-08-2012, 02:10 AM   #17
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And according to the MAP on my 2002 WRX im looking over now, along with running a richer fuel mixture, the ECU itself would cut boost.

TurboQueef thinks that this failsafe function it zeroes IAM to go into the safe fueling table... if this is how it does so, "Boost control Disable" under the "Boost control limits" section in romraider says its disables when IAM gets down to 6 or less. (16 bit)

So this means no boost beyond spring pressure, no advanced timing, and a richer fuel table will all be enabled by grounding this test mode lead at the ECU.

Has anyone tried this setup with meth? I'll be testing the theory at least when I get another taxtrix cable!
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