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12v or OBDII?


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...smell like cabbage
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Discussion Starter #1
I know this topic has been covered before and there are quite a few threads talking about both but I'm currently confronted with the choice of either doing the free 12v mod or spending $200 on an OBDII ecu to fix the lean out problem. Do you think it is worth spending the money for the ECU and not touching the fuel pump or is completely replacing the ECU overkill to fix the problem. I know some say the 12v mod doesn't work but others swear by it. I'm just still confused after searching and would like more input. Thanks.
 

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the 12v mod isnt going to fix the lean spot, you can try if you insist though.....obd2 is what I would do.
 

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no the 12v mod will not fix the lean spot, but going to an OBDII ecu is overkill.

What fuel computer are you running? When I just had a VPC/GCC I was able to simply tune over the lean spot by adding more fuel to that rpm band, and was able to do the same with a mapecu... I imagine the same would be true with any piggy back.
 

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Boost Creep
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Where is the notorious lean spot on OBD I cars again?
 

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?!!?HABBA BABBA??!!
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The OBD1 "lean spot" cannot be tuned out if you are making more than about 430rwhp, nor does the 12V mod help. OBD2 swap is the way to go IMO.
That is a ridiculous thing to say I assume. I would imagine any type of fuel management. SAFC, VPC/GCC, MAP, etc piggybacks would be able to just add fuel in the notorious RPM range. :run:
 

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That is a ridiculous thing to say I assume. I would imagine any type of fuel management. SAFC, VPC/GCC, MAP, etc piggybacks would be able to just add fuel in the notorious RPM range. :run:
well you assumed wrong.

This is a notorious issue for OBDI equipped Supras. Do a search and you will see....don't assume.
 

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no the 12v mod will not fix the lean spot, but going to an OBDII ecu is overkill.

What fuel computer are you running? When I just had a VPC/GCC I was able to simply tune over the lean spot by adding more fuel to that rpm band, and was able to do the same with a mapecu... I imagine the same would be true with any piggy back.
Im just running a safc2 and i have no lean spot.. any pull i do...as soon as i'm at
wot my afrs read roughly 11.5 all the way accross the board
 

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?!!?HABBA BABBA??!!
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well you assumed wrong.

This is a notorious issue for OBDI equipped Supras. Do a search and you will see....don't assume.
Please tell me how I assume wrong. WHY cant a lean spot be tuned out when a piggy back system can add fuel at given rpm intervals?? I didnt say it still wont be on the ECU. I meant that it can be TUNED.
 

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...smell like cabbage
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Discussion Starter #14
So it seems that OBDII is the way to go. Running an AFC of some type isn't really necessary though because it seems the AFRs are in the low/mid 11s just by going to OBDII with no tuning right?

I do plan on going standalone in the near future but I don't feel like having my AFRs in the 13s until then.
 

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Hardtopper
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I discovered I was affected by the infamous lean spot on the dyno. After spending several hours worth of research here, I determined going OBDII was the only way to go (besides standalone, which I quickly ruled out). And to reiterate, believe it or not - NO, a piggyback will NOT 'tune' out the lean spot.


Cliffs: This subject has been beat to death for YEARS. The solution is either OBDII or Standalone. The caveat is, if you have a big single that spools after 4.5k RPM or so, you most likely won't be affected.
 

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Glad to be back
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Cliffs: This subject has been beat to death for YEARS. The solution is either OBDII or Standalone. The caveat is, if you have a big single that spools after 4.5k RPM or so, you most likely won't be affected.
So If i'm in TTC I probably don't have much to worry about?
 

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...smell like cabbage
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Discussion Starter #17
So If i'm in TTC I probably don't have much to worry about?
Hmmm that's a good point, I didn't even think of that. I have the E-TTC done too. However now that I think about it, in TTC they hit before the second turbo would come on in sequential mode. Around 3.5k for me. I think the lean spot will still be an issue.
 

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Hmmm that's a good point, I didn't even think of that. I have the E-TTC done too. However now that I think about it, in TTC they hit before the second turbo would come on in sequential mode. Around 3.5k for me. I think the lean spot will still be an issue.

Yea I see what your saying. Oh well I guess its just a good excuse to go stand alone.
 

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The OBD1 "lean spot" cannot be tuned out if you are making more than about 430rwhp, nor does the 12V mod help. OBD2 swap is the way to go IMO.
You should be able to tune this out with some piggybacks. There are some (MAPECU2) that can modify the stock o2 sensor input to the ECU, even while it is in closed loop mode. This allows you to tell the ECU it hit it's target 13.2 (or whatever) when the actual AFR is 11. Takes time, but you can tune your closed loop for smooth transition to open loop with nice AFRs all the way.

That being said, I still went to OBDII :)
 

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I believe the lean spot is not so much the RPM range in itself, but the transition from part throttle / open-loop operation to closed-loop wide-open throttle is when the leaning gets out of hand. This can be down to TPS or both TPS and RPM or even load.

Well I assume that is the case (someone please don't shoot me down lol)

I know I know, to assume makes an ass of u and me lol :)
 
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