Since our car is direct injection, it runs a super lean AFR of over 13.2:1 even at the high load parts of the map. This is with the cars 13:1 compression. The lean AFR and the high compression is probably why the car is so sensitive to air temp. The ECU immediately reacts to prevent the engine from going into detonation if intake or coolant temperatures climb.
To be super conservative considering our lame 91 octane fuel. Mitch added timing to some of our cars multiple spark maps (Mitch says late model cars like this can have up to 100 different maps and you need to know what each one does). Mitch wanted to duplicate the GT3 ignition map as a starting point but we wanted to be more conservative as the RS engine is super expensive! So Mitch at our request split the difference between the GT3 and RS timing curves.
Mitch also richened up the AFR to around 12.5:1 to be a little more conservative and to possibly make more power with our shitty 91 octane pee water.
Mitch also did a bunch of part-throttle and transient passes to help tune throttle response and help with low-speed drivability. This is stuff a lot of tuners skip because it’s tedious.
Our gains with Mitch’s tuning were amazing! Our car woke up with a maximum gain of 25 whp with a peak gain of 23 whp. Torque saw a maximum gain of 14 lb/ft and a peak gain of 7 lb/ft. Our car made 499.8 whp or 500 whp for all practical purposes. This was on a day with temperatures far from optimal for the car. The gains we experienced are the highest we have ever experienced on an NA late model car with a tune.
Surprisingly the power increases were present across the board from right off idle on up which means a lot of power was gotten under the curve. The slight amount of power loss we experienced at low RPM with the headers was now back with more! With the tune, the increase in power is readily apparent with the free-revving engine even more willing to rev.
We also noticed that the engine ran a lot more smoothly after the tune and the engine now has a smoother, less harsh exhaust note, probably due to the richer AFR with the combustion possibly no longer being finely held to the edge of detonation by the electronics. We have also noticed that the car doesn’t seem to lose so much power on a hot day. If we had run more timing like Mitch wanted to, we would have had even larger gains and if we lived in a different state and could run his normal 93 octane ignition map, the results would probably be even better!
We are super pleased with how our car is performing and to our knowledge, this is one of the most powerful GT3’s that we have seen a dyno chart for. We asked Mitch if he could figure out flex fuel which would really help us get more out of engine safely. He just sort of winked so well, maybe!