SE 251 and SE 257 cams under boost
#1
SE 251 and SE 257 cams under boost
Greetings all. New guy here hoping the gain some insight from some fellow gear heads. Was wondering if anyone here has experience with SE 251 or SE 257 cams on a supercharged bike.
My current engine build focused more on TQ and drivability than on brute power. But now I want more. It's a TC 103 with Branch/Okeefe Performance Touring (PT) heads, TR 555 cams, Procharger - 14 psi, 9.2:1 CR; D&D Fat Cat Exhaust with BB Baffle, and a SE 50mm throttle body
The last Dyno was 160 hp 140 tq with a 10 psi pulley. I have not dynoed the 14 psi pulley yet. Letting the Thundermax ECM learn a little longer. I'm thinking about the cam change because my seat of the pants dyno was not impressed with the power increase after the pulley change. The Branch/Okeefe PT heads are are ported for low and midrange TQ but I think they MAY have a little more flow potential left in them under boost.
Any thoughts on which cam would be the better choice. The SE 251 cam has more lift and decreased valve overlap which would decrease the amount of boost lost through the exhaust during the overlap period. The SE 257 has increased lift and duration with only one degree more overlap. This would allow more compressed air in and maintain the near identical overlap pressure loss.
Would I benefit more from the decrease in overlap of the SE 251 or the increase in duration of the SE 257?
CAM LIFT DURATION OVERLAP
TR 555 .555/.555 244/246 44
SE 251 .579/.579 244/250 32
SE 257 .569/.569 252/260 45
Branch/Okeefe PT Heads
Intake valve 1.9 / Exhaust valve 1.610
It would be nice to hit 180 HP with small port/valve heads and a 50mm throttle body.
My current engine build focused more on TQ and drivability than on brute power. But now I want more. It's a TC 103 with Branch/Okeefe Performance Touring (PT) heads, TR 555 cams, Procharger - 14 psi, 9.2:1 CR; D&D Fat Cat Exhaust with BB Baffle, and a SE 50mm throttle body
The last Dyno was 160 hp 140 tq with a 10 psi pulley. I have not dynoed the 14 psi pulley yet. Letting the Thundermax ECM learn a little longer. I'm thinking about the cam change because my seat of the pants dyno was not impressed with the power increase after the pulley change. The Branch/Okeefe PT heads are are ported for low and midrange TQ but I think they MAY have a little more flow potential left in them under boost.
Any thoughts on which cam would be the better choice. The SE 251 cam has more lift and decreased valve overlap which would decrease the amount of boost lost through the exhaust during the overlap period. The SE 257 has increased lift and duration with only one degree more overlap. This would allow more compressed air in and maintain the near identical overlap pressure loss.
Would I benefit more from the decrease in overlap of the SE 251 or the increase in duration of the SE 257?
CAM LIFT DURATION OVERLAP
TR 555 .555/.555 244/246 44
SE 251 .579/.579 244/250 32
SE 257 .569/.569 252/260 45
Branch/Okeefe PT Heads
Intake valve 1.9 / Exhaust valve 1.610
It would be nice to hit 180 HP with small port/valve heads and a 50mm throttle body.
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06-30-2022 06:11 PM