Caffeinated21

I was reading on how stuff works that about a variable valve timing system ferrari uses (http://auto.howstuffworks.com/camshaft6.htm) Basically, the cams are cut so that a actuator can push them and change the cam profile gradually. Which got me thinking...OHV engines have a great advantage in being compact and lightweight, however, as of now, they have no variable valve timing. Couldn't this Ferrari system be applied to an OHV engine? The only problem I forsee is that one cam is already actuating four valves, there might no physically be enough room for variable profiles...which presented another idea...why couldnt you have a two camshafted OHV engine? This would prob. allow three valves per cylinder instead of two, plus that ferrari valve timing, while still maintaining a weight and size advantage over OHC layouts.

Incubus

If you're putting an extra camshaft, why not just put them over each head? I know compact, but there are also advantages to the OHC engine.

Caffeinated21

Yeah, i suppose you're right about the two camshaft idea, but that was sorta tacked on at the end anyway

Slamnasty

GM actually already considered variable timing on the LS2, which is of course OHV. I have not heard that they ended up putting it on the LS2, so my assumption would be that they dropped the idea for production. Couldn't guess as to why.

I imagine variable timing on one camshaft would be a lot easier and less expensive to do than on 2 or 4 cams, although even doing it on OHV engines might have it's own challenges, since the cam in OHV engines is just above the crankshaft in the block (correct me if I'm wrong). This in turn would likely make the engine longer in some way and present packaging issues, whereas OHC engines can move that stuff above the engine to the heads.

dragonacc

GM was going to use cam phasing on the LS2 but decided against it because they could meet their goals without using it. Basically it's just a computer adjustable cam gear that moves the cam timing forward or backward. It's not as good as true VVL because you can't control the intake and exhaust valves separately. GM was also looking at using a 3 valve OHV setup on the LS7 but decided against that also. It used one cam and intake rocker arm was designed to actuate two valves instead of one. It was a cool idea but apparently didn't meet durability standards.

Caffeinated21

I suppose the reason, in my mind, GM would wanna add variable Valve timing even if they didn't "need" it to meet there power goals would be refinement. Perhaps its not as important a selling point here in America, but I have a feeling it is a bigger deal among european consumers. If the magazines are to be beleived, and GM shortened the dimensions of the new vette with europe in mind, then obviously this market is important to them. So while the vette's monster V-8s generate some amazing numbers, the lumpy idle, etc might scare away some rich europeans who are used to the smooth sound of a porsche flat6.

tafka TMB

The Cadillac Sv-16 show car had a V16 (2 v8's) with on-demand displacement (and maybe VVT).

"The project started more or less with the idea of a V-16 engine, to push the limits of street-legal power (and some would say decency) and to celebrate Cadillac's heritage. The Fleetwood coach cars of the 1930s featured 16-cylinder engines, the first of which powered a 1930 Series 452 and the last of which rolled off the line in the 1940 model year.

Though the engine's fundamental design is simple, with two valves per cylinder, it includes some modern materials and technology, such as lightweight titanium-alloy valve springs and variable valve timing. Dual-overhead-cam engines have more valve-timing flexibility, but the XV-16's single camshaft features electrohydraulically actuated dual-equal cam phasing, which offers some of the efficiency benefits and performs exhaust gas recirculation (EGR), a pollution control, in lieu of an external system.

Because of the XV-16's prodigious torque

QUIKAG

It is my understanding that GM has variable valve timing on the new 3.9L 240hp pushrod V6 that is going into the Pontiac G6 GTP. The GTP model also offers a six-speed manual.

That should provide some nice competition for the new Eclipse, Accord Coupe, etc.

rockville

Check these out:
http://www.acarplace.com/brands/gm/xv8-engine.html
http://www.carcraft.com/techarticles...GM/index3.html

I think it would be cool to see this motor in production.

Caffeinated21

Funny how whenever you have a random idea that seems logical (even those two cams in the block, my god, somebody has already done it...