Also, another great resource after you get the .txt log file from FC Tweak is importing it into the paid version of ChatGPT. I’m using the Pro version (it’s $20 a month), and I’m not sure if the free version gives you the same features but feast your eyes on this plot it generated within seconds. This log made it super obvious that I might have a boost leak. I was only hitting around 8 psi when I should’ve been closer to 10. After reviewing the data, I did a smoke test and what do you know, a damn coupler was leaking. Hopefully that’s the fix. What’s even cooler is how clearly you can see the transition between the primary and secondary turbos, there's this little dip and then a clean ramp up, and the way it tracks that visually in the plot is honestly awesome. This is some cutting edge ****, and it only took seconds to generate from a raw Power FC log. The formula it used was simple: take the PIM V value (manifold pressure voltage) and run it through (PIM V - 2.66) ÷ 0.13, which gives you boost in gauge PSI (pressure above atmospheric). It also did way more then just those calculations but that's the gist of it, here's what else it did when I asked:

• I used TPS voltage to filter for actual throttle input — that way, I focused on moments when you were actually accelerating, not just coasting or idling.
  
• I checked WG% (wastegate duty) to understand when the ECU was trying to build boost versus just cruising — it helps confirm if the ECU wants more boost but it’s not getting it (classic sign of a leak).
  
• I also looked at knock, coolant temp, and air temp to rule out heat soak or weird timing pulls that could flatten the boost curve.
  
• And I skipped over idle and part-throttle noise by only using data when you're clearly in it — like full throttle or close to it.
  

 

Update, it was a boost leak. I'll try and smooth out the transition between the 2 turbos the best I can with FC Tweak, although it is fun feeling 2 turbos in the band

 

Nice setup in the glove box. Are you just using some foam inserted then cut out for the gage and EXT box? I want to clean mine up and have been considering 3D scanning the inside of the glove box then 3D printing an insert, but if that's foam it looks great and much easier. Unfortunately, I have the datalogit and all the mess with that so I'm hoping to update to the new box to make life easier.

 

i wish we had cool stuff like this for the S4, my microtech is definitely showing its age, hell it was showing its age 20 years ago when i bought it brand new. my hand controller feels like one of those old 80s calculators and it's still one of the best reliable options for the FC(the tune on my car is literally 14 years old and the car starts and does what its supposed to every time).

 

You can use fc tweak on an FC.

 

yeah i suppose they finally came out with an S4 adapter a while back though they weren't available a number of years ago, only the S5 had an adapter available.

not sure i want to start over with a new PFC($1300 or less if one can be found used, the EPA killed big site sales so no more ebay and more social media outlets), $400 for adapter kit and $1300 for the FC tweak kit. $3k is a lot to switch to a still rather old ECU, there's other auto tune options for the FC now, though it is nice for folks who already had a PFC.

i guess what i mean is it took too long for it to become a relevant option.

 

i don't disagree with the sentiment, however when we say auto-tune we are also under explaining what that actually is.
the auto-tune does look at your data log and the target AFR map, and suggest changes.
also it looks at the log, and checks the quality. it looks for proper grounding of the wideband, voltage dropouts, etc. since we are tuning based on AFR's, the AFR signal is really important.
i'm not aware of any other ECU that validates the data log.

the PFC Master then adds to this can can tune in real time, with fuel trims and stuff.

and, and there is a nicely written instruction manual to go along with software that is really well designed and easy to use.

 

just for fun here's a chart of mine (from 2008) trying higher boost on twins... 15-10-16.5psi

 

FC tweak is the best thing since sliced bread. I am shocked at the drivability improvement. I literally cant wait to drive the car again this weekend.

I am curious how many autotunes each of you have done thus far and where approximately you are in the tuning score? this is more just for fun

Ive done 4 logs and i am at 81%. I am gonna start full WOT pulls now. I guess i was probably slow to do this since i am so risk adverse.

One thing worth mentioning is that Xavier said is that its a good idea to do a final tweak once we consider the auto tuning to be done.