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Discussion Starter #1
As I understand it, when you are cruising your car, or at idle, the standard ECU goes into 'closed loop mode' and adjusts the air-fuel for economy.

At WOT the ECU goes into 'open loop mode' and adjusts the mixture for maximum performance, using built-in fuel maps.

Then why does the A'pexi S-AFC have a high/low throttle position option ? It would only be necessary at WOT to have the S-AFC adjust the air/fuel signal.

Or am I missing something :stupid:
 

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I believe the ecu goes into open loop mode at 30% throttle. I noticed on my air fuel gauge that the readings would bounce back and forth between lean and stoich at anything under 30% throttle. As soon as I hit 30%, the gauge would read rich all the time, indicating that the ecu was going into open loop mode.

The S-AFC takes the inputted low and high settings and extrapolates the data based on throttle position.
 

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overdeveloped beater
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The SAFC can be tuned t provide separate tables based on throttle position. You don't need to correct much on the lo-throttle side unless you like absurdly shitty milage and black sooty deposits on your tailpipe! You want to adjust the threshold between the lo and hi so that as you increase the throttle, you'll pass into your hi-thr tables when you need it most.

Careful tuning and testing will net great results....and show mistakes....
 

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Discussion Starter #4
I'm interested in the A'pexi or the HKS (=more expensive), but I'm still wondering if it would give noticable gain in performance.
I'm in favor of more low-down torque, I mostly do city travel.

Currently I have a MRT exhaust system, which gave +8bhp on the dyno and soon to be fitted an ITG panel airfilter. (btw my car is a MY01 Impreza 2.0GX)

I have asked around for chiptuning and have received two offers of about 700 euros. Both of which use a piggyback computers to alter fuel and ignition. (don't know which make of piggyback)

Will I feel a difference, with just using an S-AFC (or Super AFR) or do I have to look at a piggyback solution with ignition timing ?
 

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I'd recommend looking into the GReddy E-Manage. You get air flow meter (MAF or MAP) based adjustment (the "additional injection map") and throttle based adjustment ("Airflow adjustment map") plus you get timing control (based on afm input), can run additional and/or larger injectors. The E-Manage is a pretty sweet piggyback.
 

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Discussion Starter #6
Will do....but I hope there is a Greddy dealer in Belgium.
Or could it be tuned by any respectable shop with a dyno ?
Thanx
 
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