Project 718 Cayman T: Part 12 – E-Motion Suspension Components and Track Update

These are the calculated mass airflow values from the Accessport; I don’t quite understand how the Porsche ECU calculates this value as it seem to be about 1/3 low compared to where I expect them to be. Anyway… The logs were all taken at slightly different conditions, but the trends track with the boost levels. The Protune is a chunk higher mass airflow more than the Base tune which correlates with the boost pressure difference. The RENNEN hampered by 91 oct is in between the two. Then the higher flow wheels of the RENNEN take off and keep on flowing. The RENNEN passes the Protune at about 6500 rpms and maxes at ~170 g/s. The Protune maxes at ~153 g/s and the Base flows only 120 g/s. So the RENNEN on 91 octane was flowing about 11% and 42% more respectively. I threw in the COBB off-the-shelf 91 octane tune for reference and you can see it has a lot of unevenness with it.

The ECU has some engine model which calculates an actual torque value that the engine is producing. The lines are more squiggly when the ECU applies some timing correction which reduces torque. The stock turbo on both the Base and Protune only hold the torque flat until about 6000 rpms after which the torque drops towards redline. The RENNEN turbo however, the torque stays basically flat all the way to 7500 rpm; a flat torque curve to redline was a goal of mine for this build. Notice this torque line is also quite smooth and this was due to zero timing correction on this pull. So, it feels like a high flowing NA engine where the torque stays flat and the horsepower keeps on climbing all the way to redline. For me personally, this type of torque curve is easiest for me to modulate at the limit in the twisties. Maybe it’s just from many years of driving and riding the S2000 and CBR 600RR.

Thoughts of water injection have been dancing in my mind to better take advantage of the RENNEN turbocharger. I could keep on using the race gas concentrate, but the coating of orange manganese all over everything the exhaust flow touches makes me think it’s not great for the long term durability of the O2 sensors and catalytic converter. Anyway, the RENNEN on 91 octane is holding about 330 lb-ft of torque at redline. With 93 octane, I’d guesstimate it would hold about 360 lb-ft of torque at redline, which would be a big chunk more power. The Protune is at about 310 lb-ft and the Base at 255 lb-ft on 93 octane with the differences being about 7% and 30% respectively to the RENNEN on 91 octane.

I used my homebrew dyno calculator as Virtual Dyno was giving me some funky results. I also threw in my S2000 for fun. Base tune, 93 oct = blue line, Protune, 93 oct = green line, RENNEN, 91 oct = purple, S2000, 91 oct = aqua. Like the boost, MAF, and torque values from the COBB Accessport, the RENNEN on 91 octane doesn’t overtake the stock turbo on 93 octane until the top end. Why do the torque curve shapes of my calculated torque at the wheel differ from the ECU engine model calculated torque? For everything that spins on a car, the friction goes up exponentially. So while the calculated engine torque is staying relatively constant with engine speed, the spinning friction of everything (bearings, axles, etc) is increasing exponentially with increasing speed. That’s all just a half-baked, semi-educated guess.

The stock turbo makes peak power at about 6500 rpm and drops from there. With the RENNEN (purple), the power curve just keeps on increasing. At redline of 7500 rpm, the RENNEN on 91 octane is making roughly 20% more power than the stock turbo Protune on 93 octane and 30% more than Base, 310hp vs 255hp vs 230hp at the wheel based on my rough calcs. And this is through the stock cat and exhaust aside from my custom X-pipe tip. I bet 93 octane would allow the RENNEN to make around another 25whp over 91 octane and shift the whole curve up to where the stock turbo Protune on 93 sits. Did I mention water injection has been bouncing around my head? Also, my old S2000 setup made some good power, but it did have the advantage of about another 160cc of displacement. It made about 370hp on Church’s dyno which I always took to read crank power. My calcs ballpark the S2000 at 325 hp at the wheel. 370 hp * 85% is 320 hp, so my calcs are in the ballpark.