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When the kit was under development, we started with a Garrett GT-1544 turbo which, on paper, looked like the right one. That turbo worked OK, but just didn't meet the HP and torque goals of a 50% increase, so we started over and developed the kit with the GT-1548 turbo. Much better!
The 919T with the GT-1548 turbo makes more HP than a CBR1000RR up to 9500 RPM, where the 919T's power starts dropping off. At 9500 RPM, the turbo is still making 7 psi boost, so the airflow restriction is in the 919's intake ports, throttle bodies and cams. Head porting, bigger valves and bigger throttle bodies would certainly help airflow and power above 9500 rpm. If you wanted to spin the motor over 9500 rpm, you would also need better rods and rod bolts, and higher pressure valvesprings. But, the objective was to develop a "bolt-on" kit that didn't require a lot of engine mods.
The smaller GT-1544 turbo works OK, but the GT-1548 turbo, which has a bigger compressor wheel and housing, makes more power. Both start making boost at 4000 rpm, but the GT-1548 flows more air at 7 PSI, so you have much more power from 5000 rpm on up, with no difference in turbo lag or ride-ability. Peak horsepower is 140 HP at 9000 rpm, and peak torque is 85 lb/ft at 8000 rpm, compared to 94/58 for the stock bike. This was on a Dynojet corrected for Denver's altitude.
The 919T makes quite a bit more power and torque than the CBR1000RR in the midrange, which is just where you need it. At 7000 rpm, the 919T is making 17 HP and 14 lb/ft torque more than the CBR1000RR.
DISCLAIMER: This turbo system does not include a "Get Out Of Jail Free" Card!!
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