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Which cams are currently top of the pack?

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Which cams are currently top of the pack?

 
Old 08-24-2018, 08:56 AM
  #11  
 
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Originally Posted by DavidNJ View Post
BC lists that cam as 232°/228° at .050" lift. but doesn't give the centerlines/separation, incorrectly stating that the cams have variable timing. They also list the same cam timing for their turbo cam.

What cam timing were they installed at? Straight-up or with a couple of degrees advance with 104°-106° separation it should have a lot of mid-range. That would be a typical short track oval cam. For a turbo, I would guess they would be installed close to 116°/114° centerlines with around 112°-115° separation +/ a couple of degrees (both with their .050" opening/closing around TDC).

How did BC configure the cam? What were they installed at?
I'm not sure, actually! I really don't know much about timing yet. I had it installed by my tuner and then immediately dynotuned, so I don't know what they set timing to. I knew they had worked with that model of cam before on a well-known time attack S2000 so I just let them do their thing. The Stage 2 cams do retain VTEC functionality.

My relative weakness in low-end and mid-range may have had as much or more to do with the simultaneous downgrade to a dented stock exhaust than the cams. My point earlier was mostly that the cams made so much top-end power that at that RPM they more than compensated for the negative change from a straight-through 70mm exhaust to a dented stock exhaust.
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Old 08-25-2018, 10:59 AM
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^ did you notch/grind down your rocker arms during the cam install?
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Old 08-26-2018, 10:13 AM
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Originally Posted by circuitclub View Post
^ did you notch/grind down your rocker arms during the cam install?
The Toda spec sheet below references modifying the rocker arms. Big cams sometimes require aftermarket arms which can have a bigger roller on the rocker, lighter weight enabling higher revs, and more than enough clearance.

Rocker arms are highly stressed and already under pressure for lighter weight to enable higher revs with more aggressive cam ramps. Haphazard grinding could yield 'interesting' results. I'm surprised that I couldn't find any YouTube video on it or any aftermarket company offering modifies arms or to modify rocker arms as a service. It seems the go to action is to get the aftermarket VTEC killer rocker arms from Ferrea or Skunk2.

Originally Posted by thomsbrain View Post
I'm not sure, actually! I really don't know much about timing yet. I had it installed by my tuner and then immediately dynotuned, so I don't know what they set timing to. I knew they had worked with that model of cam before on a well-known time attack S2000 so I just let them do their thing. The Stage 2 cams do retain VTEC functionality.

My relative weakness in low-end and mid-range may have had as much or more to do with the simultaneous downgrade to a dented stock exhaust than the cams. My point earlier was mostly that the cams made so much top-end power that at that RPM they more than compensated for the negative change from a straight-through 70mm exhaust to a dented stock exhaust.
Intake tuning, exhaust tuning, and cam timing work hand in hand. The exhaust system downstream of the header effects back pressure, possibly the effectiveness of exhaust tuning. There are papers and computer programs for all of it. It involves runner length and diameter, plenum volume, header tube diameter(s), header merges, merge collector design, and cam timing.

Changing just one could adversely affect another. The real development of these occurs when multiple cars with big budgets are involved in very competitive racing. Other than that, provided their is a big enough budget for parts and tuning time, while an individual engine can be tuned how can it be objectively evaluated? How would the tuner know that a compromise in one area (e.g. to gain more power) created a bigger problem in another (e.g. throttle sensitivity coming off the corners).

Mr. Sideways has been using an intake manifold that has allowed him to do some tuning.

This is a link to the spec sheets for the mildest Toda cams, posted in a 2006 thread: https://www.s2ki.com/forums/s2000-na...3/#post8090665. They were 255/250 at 1mm with 13mm/12mm lift. More interesting is the intake was at 100deg centerline, exhaust at 102.5deg for 101deg separation. Intake opens 27.5deg BTDC.

Big duration, big lift NA cams will bring piston to valve clearance into the picture as a big issue. This is a video on that:
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