VVT or VCT?????

[Challenging Times]

Ok, here's a question about the 5.7l... With the 6 spd manual trans, my Challenger does not have the MDS. Does this mean its the VVT and not the VCT? What are the major differences between the 2 other than a bit of chamber size?

[Tbird100636]

Ok, here's a question about the 5.7l... With the 6 spd manual trans, my Challenger does not have the MDS. Does this mean its the VVT and not the VCT? What are the major differences between the 2 other than a bit of chamber size?

Variable Cam Timing (VCT) is another name for Variable Valve Timing (VVT).

[Challenging Times]

Variable Cam Timing (VCT) is another name for Variable Valve Timing (VVT).

So, if VVT is VCT, then why the 2 different terms? Checked my window sticker... Mine is VVT... So, its also VCT? I'll have to do more research i guess.. Thaks for the response!

[Mymopar]

I think the difference is in the way it works. With the VCT it works by having a "special" cam sprocket attached to the intake cam. This sprocket is actuated by oil pressure by a solenoid that regulates the advance or retard of the cam. This sprocket also costs big $$$$ to replace.
Knowing this perhaps VCT is for dual cam cars.
VVT perhaps is for single cam cars that operate on a different principal that I am not completely familiar with so I won't go into it.

[ARoss]

VVT is Variable Valve Timing. VCT is Variable Cam Timing. The Hemi's have VCT. It's two different methods to achieve the same results. You'll mostly see VVT on overhead cam engines like on a Honda, Toyota or Nissan. Most cam-in-block engines have VCT.

[gr8crash]

I thought it had to do with the MDS function. Since MDS isn't on the manual cars it was VVT i think? Figured it was just 2 diff methods to end up with the same result of power, mpg etc

[Challenging Times]

VVT is Variable Valve Timing. VCT is Variable Cam Timing. The Hemi's have VCT. It's two different methods to achieve the same results. You'll mostly see VVT on overhead cam engines like on a Honda, Toyota or Nissan. Most cam-in-block engines have VCT.

Uh, sorry, my hemi is VVT... Right off of the window sticker...

[Steve HR Hooligan]

Mine has VCT due to the way the MDS works. The 6 speed cars do not have MDS only the autos. Here is the link to this kool site that explains in detail how the MDS works.

http://www.moparmusclemagazine.com/t.../photo_01.html

[stevesrt8]

variable cam timing IS variable valve timing.

VCT is VVT. Since the rotation of the cam relative to the crank is changed, the timing of the valve events is also.

The new Eagle is a winner!

[Mymopar]

variable cam timing IS variable valve timing.

VCT is VVT. Since the rotation of the cam relative to the crank is changed, the timing and duration of the valve events is also.

The new Eagle is a winner!

True but I think they use a different means to achieve the same end result.
The Mazda's are VCT, a special cam sprocket is used on the intake cam (dual overhead cam). The exhaust cam is unaffected by the VCT, it always rotates teh same n omatter what.
Now having only one cam for the Hemi, I don't see how it can be the same method as VCT.
I think we are interested in figuring out how the VVT works.

[Alfa Charger]

variable cam timing IS variable valve timing.

VCT is VVT. Since the rotation of the cam relative to the crank is changed, the timing and duration of the valve events is also.

The new Eagle is a winner!

I think (not 100% sure) that duration and valve events are not changed on the Hemi, only the timing.

VVT and VCT are different names for the same thing. Since VVT was invented by Fiat, Chrysler can call it VVT now!

[stevesrt8]

the duration will not change, hence my edit.

Chrysler moves the cam drive with an elegant sprocket design. Honda switches lobes completely by moving a follower over. BMW has some engines with no cam at all! They control the valve directly with a HS solenoid.

All different means to the same end.

[lieu910]

the duration will not change, hence my edit.

Chrysler moves the cam drive with an elegant sprocket design. Honda switches lobes completely by moving a follower over. BMW has some engines with no cam at all! They control the valve directly with a HS solenoid.

All different means to the same end.

I don't know that elegant is the word I would choose. This sproket design for VCT has been around for some time and has been used by Mazda, Ford, and GM.

The system has had it's share of failures and problems accross the board.

You guys will quickly learn that cam or valve spring changes will result in big VCT headaches.

I can tell you on the Ford side, the 3V Mustang uses the same VCT system and most guys changing cams and springs use a VCT limiter or a complete VCT lockout.

I use limiters in my S197 that limit travel to 20 degrees as opposed to the factory 60 degrees. This prevents a piston to valve collision.