Variable Valve Timing - to keep or not???

[scottyd2506]

I've searched this topic on the forums, internet and read in magazines, but still can't make up my mind. Everytime I think I have my mind made up about whether or not I should keep the VVT on my L92, I find something else that changes it. I was going to go VVT, then I found out that it would be quite a bit cheaper to get rid of the VVT, or so I thought. I went on to the Pace Performance site and found the performance package from Mast Motorsports has gone down in price to 2300 for computer, cam, springs, harness and a few other parts including dbw pedal. Frank had a good point with the fact that any local performance shop should be able to tune non-vvt, and harder to find someone to tune vvt. Then I read the latest Hot Rod article and it seems the VVT is pretty easy to tune with the Mast software ($399).

So I need your guys' input as to whether you think it's worth it to keep the VVT or just drop it and go to a regular LS3 cam setup. I don't completely understand the VVT set up, but keep reading it has so much potential. One thing I'm wondering is whether where I live would impact my decision. Where I am, it is mostly mountain therefore lots of hills. I used to have a Dodge Ram with the MDS but never noticed a difference since I'm in the mountains. Would this be the same with VVT? I know a lot of guys are dropping the VVT, but why if it's supposed to have so much more potential.

Here's what I've come up with so far:

Pros:
- better performance at higher rpms
- 5 - 10 % better fuel mileage
- potential is more than non VVT motor

Cons:
- Not very well known set up. Mast Motorsports is the only place that sells a plug n play set up, although it is supposed to be very easy to install and tune
- May be harder to find someone to tune it. Any performance shop should be able to tune a non VVT computer.
- Cost is a bit more. A LS3 cam set up would be around 1k for the computer and about 1k for the cam, springs, water pump, etc. The Mast set up is about 2300 for computer, cam, springs, harness and a few other parts. Another 300 to get some spacers to run a LS3 serpentine set up.

If anyone has any suggestions/advice, etc. on this topic, please feel free to jump in. Any advice is greatly appreciated. I'm sure I'm not the only that is trying to make this decision and hopefully this thread will help others as well. Thanks in advance.

The VVT thing is just advancing the cam or retarding it slightly...

Advancing the cam gives more cylinder pressure, and more low end.. Retarding the cam kills off some cylinder pressure, but has more top end power..

The intake closes after bottom dead center ABDC is what calculates dynamic compression or cylinder pressure..

Retarding the cam will push a little more air back through the intake just slight on the power up stroke.. This will also not only kill off some dynamic compression, but increase gas mileage..

That's why the Toyota Tundra's 5.7 Iforce engine can get 381 Crank HP and still get 22 mpg. With 4 valve racing heads, this isn't a ton of power, but the concept would be great to use on a superior engine like the LSX Gen3-4 GM engines... imagine

if your building a high performance engine.. don't care about torque... then you do not need VVT.. my Ls1 powered Camaro has 411 RWHP and gets around 30 mpg hyway driving easy..
big cams kill off cyl pressure... 3600 stall converter... no need for ultra low end for heavy weights truck or towing.
I'm sure that with VVT I'd have a little more top end power, and more low end too.. maybe 10-15 low end rwtq and 10-15 top end rwhp

in a 4500-5500 lb truck, the VVT would be better...if you want performance, and still have good low end, plus MPG..

in the long run, who knows how long the VVT will hold up...
if something breaks at 80k or 150k, you have bent valves or broken pistons...maybe trashed heads..



I got to say I have mixed feelings.. 10-15 years from now when we know they last or start to break, then we'll know.