For those that know but are not sure about the problem.
Stumble Fix under acceleration for GR/GV STI
Disclaimer: This is more than clicking your seatbelt or resetting your ECU, it may permanently damage your engine or fueling system if done incorrectly.
Problem:
This is the most prevalent issue with GR/GV STI's, our fueling system creates a water hammer pulsing effect which makes the car run lean and stumble from 2.4k-3.1k RPM (vehicle specific) during a light/WOT acceleration. For those that use OST, you may also notice your check engine light comes on if you cruise between 2.8k-3k RPM in 6th gear more than a few minutes with the code being P0171 of "Lean on Bank 1/2" or P0296 "Post catalyst fuel trim system too lean" . This will also fix that issue.
Solution:
By lengthening our fuel line, it disrupts the pulse in the loop, creating a much smoother fuel delivery to the engine.
This guy will do a much better job at explaining than I ever will, pictures included.
Tested Compatibility
- MY09 STI
- MY10 STI
- MY12 STI w/ SPT Package
Worked for 3 cars, all with the same effect of fixing the stumble.