shatner saves said:Pushrod engines with a single camshaft also makes running multiple valves, cam phasing, or VTEC type systems really difficult.
Ray III said:And VTEC on a Ford motor... sheesh. Have a seat.
351CJ said:For the 37th time: The Ford VVT system is NOT like Vtec system. Vtec varies the lift, the Ford VVT varies the cam timing relative to the crank.
Ray III said:Now where did you get that from? Large turbodiesels that can benefit from it have four valves running off a single camshaft. Two valves wee used on the 5.0 because it maximizes cylinder swirl and inertial supercharging for torque, not to mention how much stronger the heads are without pecking all those damn holes in it, not because they just couldn't get four valves in the head.
Variable cam timing could be pulled off much more efficiently on an overhead valve motor, because there is only one camshaft to fool with.
And VTEC on a Ford motor... sheesh. Have a seat.
Ray III said:Read the guy's post. It wasn't MY idea.
shatner saves said:And I said "VTEC type systems" not "VTEC." Sorry I couldn't remember off hand what the trade name porsche, toyota , BMW or anyone else is using for their variable lift valvetrain geometry.
351CJ said:BMW does not use variable lift, they use variable timing. Once again Ford doest NOT vary lift, only timing. BMW's name is VANOS or in the case of their engines that vary both the intake and exhuast timing, independently, it is called Duo-Vanos.
"Vtec like" would correctly refer to systems with variable lift.
"Vanos like" would correctly refer to systems with variable timing.
Although BMW gets the hype, I think Porsche had variable timing before BMW did. I don't remember what their trade name is though.
Valvetronic is cool, those cars don't have a throttle! The infinitely varible valve lift/duration handles all intake metering.shatner saves said:As a matter of fact, BMW does do a variable lift on their 745 (V8) and 760 (V12) called "valvtronic". These cars also have dual vanos and variable length intake runners. BMW's system is unique because valve lift is steplessly variable. I think it works by altering the cam follower lever ratio. Crazy stuff.
Porsche's system is called "VarioCam Plus", which alters cam timing and valve lift. Like VTEC, it alternates between two different cam profiles.
GinoGT said:Putting the VVT on a Cobra R engine could have some amazing results. Remember, that's a DOHC engine. Being able to change the timing on the camshafts on a DOHC engine will allow you to control the intake and exhaust timing SEPARATELY, not just one general shift. This then leads into being able to control the valve overlap, which is like changing one aspect of the camshaft profile.
Individually cam phasing a DOHC engine can give some very impressive gains into the torque curve. I think that one make one seriously badass engine.
351CJ said:Ford does not yet have a VVT system that does this. The Lincoln LS / T-Bird system varies only the intake cam timing - the exhaust cams are fixed.
But you have pointed out one of the major advantages of DOHC heads vs SOHC heads. That is, as you have pointed out with DOHC you can vary the intake and exhuast valve timing independently.
Time for Ford to get with the program and put this type of VVT in the 32 V mod motors.
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