JakeFusion

iTrader: (7)

N4cer's graph, in theory, works. But, in the real world, you don't see that due to the intake manifold design and the nature of the LS-series engines.

To articulate on what N4cer is saying:

The 114 LSA will peak later due a later IVC (intake valve closing), but it will lose power throughout the range due to the fact that it does not build as much dynamic compression nor does it have as much overlap. Because the IVO (intake valve opening) is also lower, it will begin to make power sooner.

A 112 will peak ealier because of the earlier IVC, but with more intensity due to the overlap and dynamic compression (if given the same static compression as the cam on 114). Overlap is power (until a point).

However, a change of 2 degrees on lobe separation really isn't that noticeable in terms of power or drivability.

The key to making power is to find the IVC you want for a given manifold (40-42 degrees seems to offer really good low end power on an LS-based car, 44-46 seems to offer an overall balance, and a 48-degree IVC seems to carry the power to 7k in a 346). Then to force as much overlap as you can handle in terms of drivability (and what your intake and exhaust setups will support). This is usually around 0-6 degrees overlap for good drivability, 8-13 for pretty good manners, and 16+ for more strip oriented cars.

I guess this really doesn't answer the 112 to 114 debate, but an example would be a 48 degree IVC for lots of topend power. A 240/244 112+4 provides this. It also provides 18 degrees of overlap and with high static compression (11.8:1 or so) pretty good DCR if using XE-R lobes. The 240 also has an IVO of 12 degrees.

Now, another cam can provide a better curve if the valve events are optimized. You can hit the 48 degrees of IVC by going with a 232/236 112+0. It's IVO is 4 degrees. It has 10 degrees of overlap. It will drive nicer than the 240/244, and it will peak around the same place, but it will come on sooner due to the earlier intake opening. It will also need 11.8:1 CR for the same DCR as the bigger cam. It won't make the same amount of power, though. But it would be a better "balance" for high end power without killing off too much lowend or street civility.

Ryne @ CMS

iTrader: (10)

how does your tuner scan the computer and see the overlap of the cam?? i tune cars for a living and using my datalogger it wont do that. unless he is guessing by looking at the idle KPA