RX7 Mapping session

The day had finally come! So here is a very brief recap of what's been done to get the car ready for mapping:

Oil change, including new filter

New spark plugs checked and installed. 

Power FC Physically installed in the car and recalibrated to factory base map. (See previous posts) 

HKS Intake kit fitted

Now that the above work is complete, plus a good visual inspection of car carried out it was time to map it up for UK fuel. Jaan uses 100 RON Super unleaded but the best we can get in Northern Ireland is 97 RON. Therefore it is very important to map the car for our fuel. 

As with all rotary engines, they don't like high boost pressures above factory levels as this can quickly destroy the Apex seals in the engine, resulting in a rebuild. For people choosing to modify an RX7, they generally improve fuel supply with larger pumps and injectors, plus larger intakes, turbos and intercoolers to achieve more fuel and air flow through the engine. Even with a larger turbocharger, the aim is to maintain a low pressure, but increase the VOLUME of air passing through the engine due to the larger turbo. 

My tuning aim was to achieve a safe condition using the factory set with the sequential twin turbos running stock boost pressure and to calibrate the fuel and timing so that there was minimal "knock" and safe air /fuel ratios when using UK fuel. I am happy to maintain factory power so using the factory fuel and cooling system. The only aim is to calibrate the air/fuel ratio and ensure that I can rev the engine right through to redline on boost, safely and experience the engine for myself. 

I started by installing my Zeitronix Air fuel gauge but hanging it off the Hand commander on the dash. Then I connected the DATALOGGIT kit to the ecu and connected this to my laptop. I could then install the Oxygen meter in the exhaust and connect it to the DATALOGGIT. This allowed me to view the Air fuel ration on the dash mounted gauge and at the same time digitally log the readings to my laptop when doing a power run. 

Removing the kit from the Sti

Once I started the engine and let it idle, I took a couple of test logs to ensure that the readings were correct and all the equipment could "communicate" with each other. 

I can't stress how important it is to WARM UP and COOL DOWN a rotary engine. DO NO rev it after initial start up. Be patient and let it come up to operating temperature before driving. 

Once ready, I went for a half hour drive to warm up the gearbox, diff and driveline before starting the power runs. 

Basically I hot record on the laptop then drove the engine in 3rd or 4th gear to redline when safe to do so. I then replayed the log and made changes to the main fuel map based upon the air fuel reading at each RPM point. Once the changes were uploaded into the ECU, I did it all again. 

The boost generally maintained 10PSI with a spike to 11 around 3500rpm once the primary turbo go going. It held a sold boost pressure the whole way up the revs once the second turbo spooled and the pressure dropped back to an average of 10.7psi. This was all controlled by the ECU and you have the ability to control the duty cycle and increase/decrease as required. However, I was seeing very low KNOCK readings, meaning that the engine was running well at that boost level on the fuel it had. I then did 3 more power runs with the engine screaming to nearly 8200rpm. After a few more weeks, I was happy and decided to keep map 4 as the final map. 

I can always go back and make more changes, and there are so many factors that you can change such as the timing of the leading and training spark plugs, the fuel (that I have modified) and the boost pressure. The Apexi even lets you change the turbo setup and so many other factors. However, as the car was now calibrated with  the new HKS Filters, all the readings were good as the engine now sits. Unless I make any new changes to the engine, then I won't need to make any more mapping changes. 

Ill get some videos of the car driving over the summer, but lets say for now, it feels perky and sounds incredible! Plus, it really turns heads either sitting still or on boost!!!