Hi everyone,
I'm working on a Series 1 RX-8 and I would like to better understand how to properly tune the Renesis for E100 using VersaTuner.
The fuel situation here in Brazil is quite different from what most US/European tuning discussions are based on. In practice, the fuels available to me are:
E32 gasoline – 91 octane
E25 premium gasoline – 98 octane
E100 – hydrated ethanol
So we don't really have the same easy access to E0/E10 premium gasoline that most base maps are designed around.
My initial plan was to run the car on the E25 98-octane gasoline, but since E100 is widely available here, relatively inexpensive and has very good knock resistance, I am considering eventually making the RX-8 properly calibrated for E100.
The car is naturally aspirated and I am not looking for an aggressive power tune. Reliability, consistent fueling and safe operation at high RPM are more important to me.
I would particularly like to understand how VersaTuner users approach the additional fuel requirement on a Series 1 RX-8.
From what I can see, the RX-8 calibration does not appear to have the same straightforward global ethanol/fuel scalar that some other Mazda platforms have, so I would like some advice before making large changes to the VE/fueling tables.
My main questions are:
What is the preferred method for scaling fuel for E100 on the S1 RX-8 in VersaTuner?
Do you primarily modify the VE table, AFR tables, injector characterization, or a combination of them?
Has anyone here actually run a Renesis on E100 with the stock ECU and VersaTuner?
How much injector duty-cycle headroom is available with the stock 6-port injectors?
Since E100 requires substantially more fuel volume than gasoline, I'm particularly concerned about injector duty cycle near 8,500–9,000 rpm.
Are larger injectors required for a stock/near-stock naturally aspirated Renesis on E100, or can the stock injectors supply enough fuel?
How are you handling cold-start enrichment?
This is probably one of my biggest concerns because hydrated ethanol can be significantly more difficult to start when cold.
Are there specific cranking, post-start and warm-up enrichment tables available in VersaTuner for the S1 that should be adjusted for ethanol?
For lambda targets, would you recommend tuning directly in lambda rather than trying to convert gasoline AFR numbers?
Does anyone have logs from an E85/E100 RX-8 showing MAF, load, injector duty cycle, commanded lambda and actual lambda at high RPM?
How much additional ignition timing, if any, has proven useful on an NA Renesis with high-ethanol fuel?
I'm not interested in adding timing simply because ethanol has higher knock resistance if the Renesis does not actually benefit from it.
My intention would be to start conservatively: establish a good gasoline baseline, log the car extensively, then transition to ethanol while monitoring fuel trims, commanded/actual lambda, injector pulse width/duty cycle, knock retard, EGT-related behavior where possible, coolant/IAT and fuel pressure.
The car will also have some reliability-related changes, but the engine itself will remain naturally aspirated.
I'd especially appreciate input from anyone who has calibrated an RX-8 for E85, E90 or E100, since most of the information I can find regarding ethanol and VersaTuner appears to concern the DISI/MZR platforms rather than the Renesis.
Thanks!