CP

Hi,

I spoke with Neil at Orton at length about their Rotrex charger kit for the Cayman line (both the Cayman S and the base model). They run 0.6 BAR boost (max) and adds about 85 HP. The torque curve is also much more useable than stock. Sounds very interesting.

http://www.caymanclub.net/showthread.php?t=6729

I have one burning question. The Cayman runs pretty high compression: 11 to 1 range. They do not lower the compression ratio. Is it engine harikiri to run a charger at 0.6 BAR without reducing compression? Neil does not think so.

Thanks for the education.

CP

Macster

My info is that with a high compression engine, running about 5 to 6 lbs of boost is about as much boost as the engine will take "safely"... This is the range of boost bandied about anyhow.

0.6 BAR is about 8.7lbs boost (if my math is correct) so that's on the high side...

If the boost figure is accurate, the setup relies upon the engine controller's ability to deal with incipient detonation very quickly to keep the engine safe.

This means retarding the ignition advance. Trouble is this results in higher combustion temperatures so even though the engine's saved from detonation, it must deal with an increased heat load, on top of the heat load from the supercharger's heating of the incoming air. You don't say if there is an intercooler which would lower this some.

Now it could be the kit comes with a chip update/reprogram, that might add some richening to keep the detonation down at part throttle.

(Full throttle the engine controller can throw emissions concerns out the window and go to a rich mapping that allows the engine to deliver maximum power.)

Sincerely,

Macster.

CP

The Orton kit comes with a water-cooled inter-cooler to manage the intake air temp. Neil felt that the inter-cooler is sufficient to keep the engine temp. under control. The ECU is re-mapped to address any possible detonation issues.

The kit does not come with additional oil cooling. If I consider this kit, I will seriously consider added oil coolers and high speed fans to lower engine temp. where possible.

It probably should also have better down-stream breathing (better plenum, headers, and free-flow CATs) to optimize performance. I guess we can find other tuner products for these items separately.

CP

JEC_31

If you're thinking about supercharging, I highly recommend Corky Bell's book Supercharged!. No stone is left unturned, no topic undissected.


Macster is completely correct in that engine management is the key to engine survival, and that intercooling is also highly important to avoiding done-blowed-'er-up syndrome.

Intercooling and well-tuned control is what makes boosting high-compression cars possible. It's actually a great combination, because you get the excellent efficiency and responsiveness off-boost and then the amount of power made is greatly multiplied when boost is on.

My 0.02:
One relative unknown is the head's combustion chamber's detonation resistance by design, by not having hot spots or shrouded valves and by having excellent quench characteristics. Does anybody know if the heads are unique to the Caymans, or are they shared with the Boxster or early 996?