davepnola

Is there a way to verify the Vario cam is working ? The car seems sluggish lately . Thanks

davepnola

Anyone ?

porcho heat

Unplug it and see if it feels any different?

Sluggishness can be related to many things, but I doubt you'd feel it just if VarioCam wasn't working

Variocam kicks in anywhere between 1500-3200 or so RPM, up until around 5000, at around 4500 you start getting the benefits of the dual resonance intake which is commonly mistaken for VarioCam, IIRC

luckett

...

jtsporsche

what is variocam? ive never heard of it but the way porcho heat describes it it kinda sounds like a porsche vtec.
and what is a dual resonance intake?

jpk

Variocam and the intake/exhaust resonance is the trickery that the Porsche engineers used to pull another 28 horsepower out of thin air. Those are the main differences between the 208hp 3 liter in the 944s2 and the 236 hp in the 968.

Variocam works on the chain drive between the intake and exhaust cams in the 968 head. Essentially it has a hydraulic cylinder that shifts slack in the timing chain to advance/retard the intake cam relative to the exhaust.

The resonance intake/exhaust is a way to optimize airflowthrough the engine, resulting in slightly higher than atmosperic pressure forcing air into the engine at certain rpm ranges. On the intake and exhaust manifolds, there are resonant chambers that, at certain engine speeds, accelerate the air flow through the engine. This was really one of the first automotive applications (at least at that scale) of computational fluid dynamics (CFD) computer simmulation to tune the engine airflow. Pretty cool stuff for the late 1980's, but getting more and more commonplace now.

Techno Duck

To expand on what John is talking about, here is a cutaway shot of the 968 intake manifold..

FRporscheman

short answer: yeah, variocam is like a porsche vtec.

Van

Wasn't Variocam first? Wouldn't that make Vtech the Honda Variocam?

FRporscheman

Variocam was introduced for the 1992 model year on the 968. VTEC was introduced in 1988, and VTEC-E in 1991.

Van

Good to know.

jtsporsche

interesting, so only 968s '92 and up have this variocam?
and is the variocam/resonant intake & exhaust one package? if you have one than you have the other?

ANDRÜ

Well since 968s where made after 1992 then yes.

Matt Marks

You can unplug the the variocam solenoid power wire (the one that's in the middle of the intake manifold. Sorry no pics), and apply voltage to it. If you can hear the solenoid click, it is extending/compressing meaning that it's changing the timing. Not sure from memory if you can put 12 volts on it or if it's in the 5 volt range, but that's the easiest test.

Of course, watch the polarity and have the car off (else you wouldn't hear the solenoid).

I'm sure there is a much more involved write up on 968.net

bleucamaro

The DOHC engines have only the exhaust cam driven by the timing belt (just like an 8v), there is a chain with sprocket connecting the 2 camshafts. In the 944S / S2 the tensioner between them is essentially static, applying equal tension to both sides of the chain. On the 968 variocam the tensioner slides, changing the effective number of chain links between the intake and exhaust cam sprockets, this advances the intake cam timing. The Variocam consists of the electronic controller and the chain tensioner. The resonant intake is the cast manifold pictured above. If you have a 968 then you have both. If you built a frankenstein motor, you might only have one. They probably work best together.