So i've finally figured out how to reliably get the RX-8 to transition from closed loop to open loop, so i decided to finally make a Versatuner video that reviews all of the key tuning parameters that i feel are critical for rx8 performance and reliability. hopefully this helps people already using Versatuner and also encourages those who have NOT used ECU tuning software to give it a try by de-mystifying the concept.

UPDATE: In the video i promised to share the tuning files, so they are linked below. They are view only; you can probably download and edit on your end from a local copy.

By downloading and accessing the files linked below, I agree to only use the Versatuner tune file for personal educational purposes and will not install the tune file directly onto any vehicle. I understand that the MAS scaling and air fuel settings on this map may not be appropriate nor safe for my car. I understand that installing this tune on any vehicle other than the car on which it was developed may result in undesirable operation or potential damage to the vehicle. I understand there are no warranties or guarantees expressed or implied with this tune file and agree to download at my own risk.

DEMO TUNE FILE - FOR EDUCATIONAL PURPOSES ONLY:
DEMO Tune File

Fueling Tool:
Fueling Tool

 

I'll pull in some discussion from the video itself:

• Why did you choose those AFRs?
  • The short answer is it's my best educated guess on an AFR profile that balances engine output and fuel consumption with heat and engine life. My research suggests that the "ideal" AFR window under which naturally aspirated gasoline engines make close to peak power ranges from about 13.3-12.8:1 AFR with typical pump gas. The leaner ratio is great for low- and mid-range to achieve higher combustion temperatures and efficiencies. As rpms and load and thus thermal and mechanical stresses climb, i decided to err on the side of safety for the exhaust system and the engine seals and springs by running richer and keeping exhaust gas temperatures (EGTs) in check. Once i got REALLY high in the rpms, people said that 12.5:1 works just fine for power, so i decided to really err on the side of richer since the engine is pretty much at it's limits. Plus i don't spend much time at those extreme rpms, mostly just transients when i need a few more mph without shifting. So in short, i designed an AFR profile that ranges from the leaner side of "ideal" for power in the low and mid range, and the richer side of "ideal" at high rpm.

 

With the mention that those are open loop enrichments. Meaning in plain language that you'd wish to get those but no guarantees you'll be even close. Today you're getting 12.5, tomorrow 12.9, the day after that 11.4, when your fuel pump grows old you might even see 14.3. Like using a blind tape measure that has no measures on it but you kind of remember where the markings were.

 

Yes, you're clarifying that the ECU is just delivering fuel based on a table with no feedback, correct? It's true, that's why it's probably a good idea to data log frequently and use a lambda sensor if you're doing serious racing.