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Old 04-05-2009, 02:30 PM   #1
hakeem
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Default ECU reset gives my STi about 75 more hp for 15 mins...why?

06 STi with ~45k miles on it, always well maintained and serviced. Bone stock all the way down to the air filter. Recently I started to get the feeling that my car was not at full power, or boost was reduced, or something was going on.

The other day I had not driven the car in a few weeks and the battery had died (my fault, unrelated). After charging it, the car felt like it had at least 50-75 more hp for about 15 minutes. After that, it returned to its old ways of having mediocre power. Now everytime I reset the ECU I am given this power burst for a short period of time.

There is no CEL and everything else appears to be normal. I've searched around for this, it sounds like limp mode, but that usually appears to be accompanied by a CEL as do most of the other problems I've found.

Any ideas? What is wrong with my subie!
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Old 04-05-2009, 02:33 PM   #2
MasterKwan
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Sounds more like you're using crappy gas and it takes the ECU a while after reset to adjust to the bad gas. If it was me, I'd log it and see what the ECU is thinking.
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Old 04-05-2009, 03:05 PM   #3
Uncle Scotty
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Originally Posted by MasterKwan View Post
Sounds more like you're using crappy gas and it takes the ECU a while after reset to adjust to the bad gas. If it was me, I'd log it and see what the ECU is thinking.
yep.......if the OP added some 100 octane fuel he may see why it is imperative to use the highest octane fuel possible to get the best power and why the stock ecu map sucks
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Old 04-05-2009, 03:14 PM   #4
hakeem
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yep.......if the OP added some 100 octane fuel he may see why it is imperative to use the highest octane fuel possible to get the best power and why the stock ecu map sucks
I am using pump 91...it's not feasible for me to use 100 all the time unfortunately. Can the stock map be modified to still provide decent power using 91 safely?
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Old 04-05-2009, 03:21 PM   #5
BlackFighter
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Ya lower boost or not redlining it.**** man i love my sti and use 93 everyday in it. Will NEVER put anything lower, b/c i know that even 93 will be lower octane with all of the mixing.
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Old 04-05-2009, 04:21 PM   #6
Uncle Scotty
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Originally Posted by hakeem View Post
I am using pump 91...it's not feasible for me to use 100 all the time unfortunately. Can the stock map be modified to still provide decent power using 91 safely?
d00000000000000d


the FIRST thing you dhould do with any of these cars is get a tune from a competent tuner even if your car is stock
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Old 04-05-2009, 04:29 PM   #7
testify
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Those are some impressive power losses/gains you seeing on the butt dyno.
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Old 04-05-2009, 04:52 PM   #8
STIBungy
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Usually when you reset the ecu, it runs like ass for a bit until the IAM goes up to 1.
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Old 04-06-2009, 09:43 AM   #9
06mattsti
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Originally Posted by STIBungy View Post
Usually when you reset the ecu, it runs like ass for a bit until the IAM goes up to 1.
+1. i have to get my dynamics multiplyer to 1 from .5 on the apv2 everytime i reset the ecu, or my car stalls when i slow down everytime.
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Old 04-06-2009, 09:46 AM   #10
Uncle Scotty
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+1. i have to get my dynamics multiplyer to 1 from .5 on the apv2 everytime i reset the ecu, or my car stalls when i slow down everytime.
that is a tuning issue that you need to address
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Old 04-06-2009, 12:32 PM   #11
flycaster
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For some [good] reason the car is quickly learning to pull timing and richen up, probably both. Frankly, you ought to be glad it's doing that - it is trying to keep your motor alive. As Scotty suggested, get it tuned pronto.
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Old 04-06-2009, 01:07 PM   #12
the suicidal eggroll
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Quote:
Originally Posted by 06mattsti View Post
+1. i have to get my dynamics multiplyer to 1 from .5 on the apv2 everytime i reset the ecu, or my car stalls when i slow down everytime.
That's a fueling issue, not an IAM issue, I have the same problem. It takes my car about a day to figure out how to idle after an ECU reset, I haven't tracked down the problem yet.

OP - sounds like your car is pulling timing to prevent detonation, probably because of the 91 octane fuel. Switch to a higher octane or get a tune.
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Old 04-06-2009, 01:20 PM   #13
hakeem
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Thanks guys. I actually mixed in 6 gals of 100 octane on Sunday and it's still doing the same thing (although it takes longer to happen). Unfortunately here in cali 91 octane is the best we can get at the pump.

Guess I'll take it in for some tuning and see what happens.
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