What is "cam-in-cam" technology?

[DSG2003SVT]

I've been lurking on here for a while, but this will be my first thread and second post. I didn't see an introduction section, so I figured that I would introduce myself with my first thread. My name is Nathan, I've gone through several fun cars (most recently a 2003 Cobra), and a Viper is next on my list. I considered a 2nd gen GTS, but as I grow more fond of the new body style, I'm leaning more toward a 2006 coupe. Whichever Viper I end up getting I'm sure I'll enjoy it very much. The VCA ia a great source of info from what I've seen so far, and I'm looking forward to spending more time here.

Now, on to my question. I've worn out the search button on this, and I just can't seem to find anything. What is the "cam-in-cam" technology that is mentioned on the SRT site in the Viper engine section? Is it just another version of VVT? If so, is there anything that differentiates it from any other VVT, or is it better/different for some reason?

 

[GTS Dean]

I have no clear idea how that works. My wild guess is some sort of hydraulically acutated coaxial arrangement that controls intake and exhaust lobe separation/valve overlap. Alternatively, a hydraulic acutator that advances or retards cam timing relative to the crankshaft. Advanced cams help torque, ******** cams help horsepower.

 

[grcforce327]

http://www.mechadyne-int.com/vva-products/concentric-camshafts

http://www.sae.org/automag/technewsletter/070402Powertrain/04.htm

 

[DSG2003SVT]

grcforce327, that was a very interesting read. Props to DC for doing something like that with the Viper, that's pretty...cool...for lack of a better word. Thank you for those links, that's been eating away at me ever since I saw it. The first production pushrod car with VVT, the Viper makes history again.

 

[GR8_ASP]

I know Tim Lancefield very well. Worked with Mechadyne back in 1995-2000 on various VVT systems. The concentric cam is basically that. One set of lobes driven by the outer shaft and the others by an inside concentric shaft via a pin that inserts through and operates in a small window. Works reasonably well with large base circle, large journal camshafts. A bit complex when both intake and exhaust are phased as a phaser is located at both ends.

 

[Warfang]

"Although the Viper SRT V10 VVT valvetrain now is the technology leader for cam-in-block engines, it's known that GM has a small-block V8 in development with variable intake- and exhaust-valve timing in a three-valve configuration. We may not see a four-valve pushrod gasoline engine, despite use of that valvetrain in diesel V8s. However, cam-in-block pushrod gasoline engines have a high-tech, high-performance future, and both Chrysler Group and GM keep engineering teams on the job of developing it."

Sounds like GM has something similar coming for the vette.

 

[GTS Dean]

Except for how the lobes are attached to the two shafts, I had a pretty good idea of how the things work, eh?

 

[DSG2003SVT]

Except for how the lobes are attached to the two shafts, I had a pretty good idea of how the things work, eh?

Yeah, I was going to say that you were almost on the spot with your guess. You guys really know your stuff here.

About the GM version of a VVT V8, I wonder if this is going to be for the new vette Z07/Blue Devil/SS/whatthehellever, or if it will be for all of the new vettes. I'm also curious that if the new Z07 indeed goes to 650+, will DC bump the Viper up even more? Possibly introduce the 675hp Mopar Performance Viper as the new ACR or some other special edition. Hopefully, congress won't stick their noses into this, and we can continue to watch the HP wars escalate.

 

[NOTVETTE]

Good write up on Viper "cam-in-cam" technology on page 31 of latest Viper Quarterly (Summer '07).

Also a real good article in Road and Track magazine (August '07) on page 107 addressing a host of different "variable-valve" technologies and which manufacturers are using what.

 

[Viper Specialty]

if I recall, the outside of the camshaft is attached to a drum-like device in the front containing a helical gear which is attached to the inner camshaft. There is then an engaugement disc which contacts the outer drums "tracks" and the teeth of the helical gear. When you move disc back and forth, you bias the inner cam Vs the outer cam. My guess is that they are using a PWM controller to read the cams position, and bias oil pressure from one side of the disc to the other rapidly, to change its position back and forth, almost like a hydraulic "stepper motor"

 

[black mamba1]

Yeah, I was going to say that you were almost on the spot with your guess. You guys really know your stuff here.

About the GM version of a VVT V8, I wonder if this is going to be for the new vette Z07/Blue Devil/SS/whatthehellever, or if it will be for all of the new vettes. I'm also curious that if the new Z07 indeed goes to 650+, will DC bump the Viper up even more? Possibly introduce the 675hp Mopar Performance Viper as the new ACR or some other special edition. Hopefully, congress won't stick their noses into this, and we can continue to watch the HP wars escalate.

DC is aware of everything GM is planning for the Vette and the SRT guys have told us not to worry...no matter what GM does, SRT says they will be ready to respond and top them. Now, since our Vipers are heavier than the Vette and tend to be geared lower, any Viper expecting to beat a 675 hp Vette will need close to 750 hp MINIMUM, and as much as I hate to say it, the Viper might even need traction control to have any chance of hooking up on street tires.

 

[grcforce327]

DC is aware of everything GM is planning for the Vette and the SRT guys have told us not to worry...no matter what GM does, SRT says they will be ready to respond and top them. Now, since our Vipers are heavier than the Vette and tend to be geared lower, any Viper expecting to beat a 675 hp Vette will need close to 750 hp MINIMUM, and as much as I hate to say it, the Viper might even need traction control to have any chance of hooking up on street tires.

A viper is geared "HIGHER",not lower! Numerically higher # = geared lower!!!