can someone please explain to me in idiot language why Vtec killer cams don't work. it just seems to make sense that if the engine was switched over to the aggressive cam setting all the time it would increase performance, skipping the lower cam profile.

 

Valve timing is a compromise at any given rpm.. what is ideal at one rpm is marginal at another. The beauty of VTEC is that the compromise is cut in half allowing a profile that works well in the lower range and one that works well in the upper. Using a high profile at low rpm would make for marginal driveability and performance under 5K rpm and miserable idling, mileage, and usability at very low rpm.

Your running shoes are great for the track but the wrong design for wading in the creek.

 

For example, have you ever driven an old muscle car with a "full race" cam on the street. Very lumpy idle (if it idles at all) and very frustrating to drive.
Just because they're called "killer" doesn't make them good.

 

at lower rpms you don't exactly need to advance the timing, it would give you little performance gains and other unwanted things listed above. lowering the vtec engagement 1 or 2 thousand rpms is the furthest i would personally ever go.


have a safe winter,
-sam

 

Ignition timing and valve timing are 2 seperate things.

Ignition timing needs to be advanced for proper engine operation/performance.

VTEC operation changes valve lift and timing. The VTEC camshafts have low and high RPM performance profiles. Switching profiles when the engine is at a high enough RPM to take advantage of the high RPM profile.

Unless you are spending all of your driving time above 6000 RPM eliminating the VTEC is not a good idea for decent low RPM drivability.

Go find a muscle car guy with a .600lift and 300deg duration cam and go for a ride. Aside from idling at 1500 RPM, and having no low RPM power, no vacuum for power brakes, not wanting to start, never passing an emmisions test they are a great at drag racing.

Some domestic Iron V8's can use a set of Rhoads lifters. Which bleed oil away at low RPM to reduce lift and get the low RPM power back when using a high lift/duration camshaft. Call it "cheap VTEC"

 

so even in a track dedicated car a system like this wouldn't be efficient?

 

No. Think of it this way, VTEC is the whole system, not just the upper half of it. If you throw away the bottom half you cripple it just as much as if you throw away the top half.

 

They would be good for a dedicated track car. The reasoning:
1) You're reducing rotating mass. It might be small, but it's there. Not only do you remove mass from the camshafts, but you can also remove other components on the head that are required for VTEC operation.
2) You should never be below 6K RPMs on a pure track car. Therefore, the low cams are never used. If you're never going to use something, why have it?

 

Theres really no need for the low cam on a track only car. Even from a standing start you have to drop the clutch at 6-7k to get off the line. After you start there shouldnt be any reason not to keep the car above 6k.

 

to the s2ki naysayers...vtec is designed for the best of both worlds...power on the top end and driveability/fuel consumption on the bottom end...since driveability and fuel consumption aren't too high on the track racing priority list, I'd say that getting rid of them for a little better top end is not too bad of a trade off.

Check that, it is a good trade off.[I]