I sent some more questions to the mechanic and I will let you know what he says. Not sure why it takes two days..?

 

Your paper on OBD is in doubt!! All STRs have CAN (as do all S-Types from 2002.5MY / 2003MY). The PCM does both CAN and ISO 9141-2. The ISO is just for OBD. The CAN is for all the car functions (such as talking to the TCM) and can also be used for OBD (much higher speed than ISO).

(However, the variant of CAN for OBD is not strictly ISO 15031 / 15765.)

You can easily find the CAN in JTIS (e.g. the electrical guide).

My AutoEnginuity switches to the CAN if I ask it to.

 

I only researched OBD which might be why all my sources only spoke about CAN for after 06+ cause thats when the US government mandated it as required for all vehicles. Thanks for the info. I knew we had a CAN system for modules talking to each other but I didnt know about it having OBD capabilities I thought that was all done differently.

 

Hummm that makes it a bit harder. I am going to reach out to some of the tuning gurus we work with that know a lot more about interfacing systems then I ever will. I am sure it can be done it's just a matter of what it will take to do it and if it's worth it.

 

Vance, what are the advantages and dis-advantages of VVT?
Thanks.

 

In simple terms it increases the duration of the intake valve in relation to how much throttle you are giving it. So when you floor it the valves will almost act like if you had high lift cams to allow more air in giving you more power. If you are just driving around normal the valves would act normal therefore letting you get the gas mileage of non-high lift cams. Not really sure how the Jaguar heads achieve it as every car manufacturer has a different way of achieving it. Honda's VTEC has "an extra intake cam with its own rocker, which follows this cam. The profile on this cam keeps the intake valve open longer than the other cam profile. At low engine speeds, this rocker is not connected to any valves. At high engine speeds, a piston locks the extra rocker to the two rockers that control the two intake valves." This pic shows how Ferrari does theirs the cam actually goes back and forth depending on throttle position. So it actually varies the timing of the intake valve in accordance with throttle position hence the variable valve timing. The only down side is more parts and maybe gas mileage if you have a lead foot.

 

The simple explanation I was given by a tech several years ago concerning the benefits of Variable Valve Timing echoes what Vance described above. In a nutshell, VVT provides quicker and greater power when you ask for it with a quick accelerator depression, yet it also allows for greater fuel economy during normal highway driving. The best of both worlds, as they say. I believe VVT plays a significant part in some of our S-Types' abilities to achieve over 30 mpg on the highway with both the 3.0 and 4.2 engines....