968Forums.com - variocam switch points

Do any of the chips for the 968 alter the variocam timing changes? I would love for mine to kick in a little lower in the rpm range...

I found this thread on the old forum titled "Truly Free Horsepower " that got me thinking

Quote:"The same thing was true in my previous car. When i bought it i was sure the engine was basically sound but underperforming. The moron mechanic who had overhauled it for the PO not only left WAAAY too much slack in throttle cable but also had the cam timed off one tooth. The funny thing is that since one tooth advanced killed so much power i decided to try one tooth retarded in addition to the stock position, and it turned out to be terrific. Much better low end than stock and no noticable top end loss, maybe because i also had a chip and an exhaust.

The remarkable power boost from the cam "mis-timing" was one of the things that attracted me to the 968. So much power for so simple a thing gave me a lot of respect for Porsche's simple variocam approach to variable valve timing.

http://65.61.16.109/forum/topic.asp?whichp...=&TOPIC_ID=5868

anyways im just wonderin

None of the chips mess with the variocam. A quick review of how it works

The timing belt drives the exhaust cam, and that in turn drives the intake cam. In between the two is the variocam mechanism that varies the lobe center angle between the two cams by 15 degrees. Lobe center angle is also the term for overlap.

At 1500 RPM and below, there is less overlap to help burn the mixture more completely. This is an emission setting because I don't think anyone drives around at 1500 rpm.

At 1500 to 5500, there is more overlap to help cylinder filling. They call this the torque setting.

At 5500 an above, the overlap is reduced for, as porsche puts it, "optimum efficiency power". Optimum efficiency power? I guess that means fuel economy.

Anyone who has built a performance motor knows that picking the right cam is crucial. Usually the more overlap, the more high RPM power you get, at the sacrifice of low rpm torque. I wonder why at 5500, just when the fun begins, they reduce overlap? Soley for fuel economy?

Maybe there is something to be had here, if you don't run afowl of the DME fuel and spark maps......

wow i been reading old threads like crazy but that was the most concise explanation i have got, thank you Greimann!

would it damage the car to try and run with variocam locked on or off that would make it easy to find out how the car works at each setting individually, i could rig up something to activate the variocam manually or even monitor the incoming signal and only switch at the low rpm points, i have been looking at apexi v-afc controllers for ideas, they can only be set to engage at one setting and disengage at another, i don't think there can be multiple engagement or disengagement points, also it can only be set to engage at 3000 rpm and above, which sucks and makes it not usefull for this engine, but it give me ideas <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />

you guys have been at this more than me, i'm just throwin ideas out there

No one that I have heard of has really tweaked the variocam. It seems to be a bit of black magic that is built into the computer. It is a simple on or off setting. There is no inbetween. I Have also read somewhere that the shift points are varied slightly based on engine or oil temperature. I have often though about installing a telltale light somewhere to see just what is going on. There should be no issue with running it unpluged, or with a manual switch.

I question, though, whether toying with it could yield positive results. Consider that the intake manifold is a highly tuned resonant chamber, and the two systems my have operational synergy designed into them.

Here is the cam timing specs:

[attachment=296]

Monitoring the engagement via a light sounds like a good start to get an idea of whats going on, when i run new cables for my stereo i will run an extra one close to the variocam sensor....

I'll try meter the cable too see how much voltage is applied over the weekend...