The lift of the OEM VTEC lobes is really mild. Mac Attack measured the OEM camshafts in his 130,000 mile engine here. Based on his measurements, his OEM camshafts have a maximum lift at the cam (not at the valve) of .25” (6.35mm) on the intake side and .2255” (5.73mm) on the exhaust side.
So those Revolution camshafts do offer usefully more lift. It’s nice that Revolution lists the lift at points other than at the maximum so that we can get an idea of how long the cams are close to maximum lift. Unfortunately, I’ve never seen those specs for any other NSX camshafts so it’s hard to know how they compare in that respect.
Since we have dedicated low speed cams in our engines to give us a stable idle and good fuel efficiency, the high speed cams could be designed to be really, really wild, it seems to me. In their 1994 catalog, Comptech stated, “Camshafts: Only the V-Tech [sic] lobes are redesigned. They are first welded with a hard face overlay and reground increasing valve lift and duration while retaining the stock base circle. This keeps the valve geometry stock for best valve life and a smooth transition from the low lift valve [sic] to the V-Tech valve [sic].”
If Comptech went to the trouble of welding a hard face overlay onto the VTEC cams, I wonder why they decided to go with the lift, duration, steepness of the valve flanks, time close to maximum lift, etc. that they did. I’d hope they 1) designed the VTEC lobes for maximum performance given the limitations posed by the cylinder head geometry and valve to piston clearance, and 2) knew what they were doing. They had just won the IMSA GTP manufacturer’s and driver’s titles with a heavily modified naturally-aspirated 3.0 liter NSX engine in 1991, 1992, and 1993, after all.
Several years later, Toda-powered NSXs won JGTC titles. I’d hope Toda knew what they were doing, too.
If VTEC cams can be made that produce more horsepower than what Comptech and Toda designed, that would be fantastic. If that’s possible given the geometry of an NSX engine, I wonder why Comptech and Toda left horsepower on the table, though.
So those Revolution camshafts do offer usefully more lift. It’s nice that Revolution lists the lift at points other than at the maximum so that we can get an idea of how long the cams are close to maximum lift. Unfortunately, I’ve never seen those specs for any other NSX camshafts so it’s hard to know how they compare in that respect.
Since we have dedicated low speed cams in our engines to give us a stable idle and good fuel efficiency, the high speed cams could be designed to be really, really wild, it seems to me. In their 1994 catalog, Comptech stated, “Camshafts: Only the V-Tech [sic] lobes are redesigned. They are first welded with a hard face overlay and reground increasing valve lift and duration while retaining the stock base circle. This keeps the valve geometry stock for best valve life and a smooth transition from the low lift valve [sic] to the V-Tech valve [sic].”
If Comptech went to the trouble of welding a hard face overlay onto the VTEC cams, I wonder why they decided to go with the lift, duration, steepness of the valve flanks, time close to maximum lift, etc. that they did. I’d hope they 1) designed the VTEC lobes for maximum performance given the limitations posed by the cylinder head geometry and valve to piston clearance, and 2) knew what they were doing. They had just won the IMSA GTP manufacturer’s and driver’s titles with a heavily modified naturally-aspirated 3.0 liter NSX engine in 1991, 1992, and 1993, after all.
Several years later, Toda-powered NSXs won JGTC titles. I’d hope Toda knew what they were doing, too.
If VTEC cams can be made that produce more horsepower than what Comptech and Toda designed, that would be fantastic. If that’s possible given the geometry of an NSX engine, I wonder why Comptech and Toda left horsepower on the table, though.
Might was well buy the Todas at that price point.
