I put the Twin back onto the rollers this morning.
Here are the results on 8, 10 and 12 psi runs with straight 93 octane pump fuel, no water spray, no methanol, no nitrous, just air and 93 octane BP pump fuel. Same dyno as I used before with the same factors applied:
8 psig: 495 RWHP, 471 ft-lbs
10 psig: 523 RWHP, 559 ft-lbs
12 psig: 572 RWHP, 579 ft-lbs
The 10 lb run had the boost control set to "sharp", thus the reason you see it overshot a tad (see the drop-back). We softened up the control before the 12 psig run. While dialing in the boost control unit, the car shot to 16 psig mid range and we pulled throttle...at that pressure the midrange torque was 640 ft-lbs on the wheel. The potential here is enormous. I had the shop plot the boost curves for the skeptics out there.
I'm using
all of the maps for fuel and ignition and given the compression ration of the stock engine I feel safe here at 12 psig. Think of it like a 12 psig teddy bear.
As always...this is on a FULLY stock (never rebuilt) 1988 928 S4 engine with 178,000 miles on the clock.
I have a video of the 570 RWHP pull that I should be able to load this week.
I'm very pleased with these results, specifically considering the car will get to just about 500 HP on the wheels at below 9 or so psig.
