I put my switch back in.

When I first got my Cayman I notice an odd phenomenon where if you're stopped and idling and then lightly press and hold the accelerator so that the engine speeds up to about 1000 RPM, it will reach that RPM, then dive down to normal idle, and then back up to 1K and repeat that. Its like the ECU is overshooting some correction, and oscillates back and forth.

I'd not though about this until I disabled the clutch switch this week and was feathering the clutch in a parking garage, trying to be as smooth as I could, when I realized that this unexpected RPM oscillation was occurring despite constant pressure on the accelerator and a partially engaged clutch. I think this is the reason that I've not been able to smoothly pull away at slow speeds with the switch disabled -- the engine would slow down (then speed back up) despite constant accelerator pressure. Once I realized this, I stopped, put the switch back in, and was relived at how smooth things were again.

For reference, mine is a 2007 S, 6 speed, running on California 91 octane gas.

Well I too played around with this mod today. I join the ranks of those who fail to see much benefit/value from the change. Depending upon one's driving technique the effect of this may be more or less apparent.

* If you hold the clutch pedal down while at a stop (rather than shifting to neutral and releasing the clutch to save wear on the throw-out bearing), then this mod will have no effect. Holding the clutch in for > 4 seconds exceeds the "timeout" of the timing change.

* If you accelerate rapidly from a stop, RPMs exceed the 1500 level almost immediately, nullifying any effect.

* Unless you tend to lug the engine a lot, no shifts other than a standing start in 1st will ever put your revs below about 2000 RPM - again no effect.

I went ahead and left the mod installed for now, but I may pull it out after a while.

__________________
L8apx

I did the mod on Friday, and drove the car a few hundred miles afterwards.

I really appreciate the sleuthing work by the OP. I knew the car was doing something power/timing wise at light throttle when releasing the clutch, and now I know how. It would hit me hardest when leaving my house in the morning, releasing the clutch to accel up a slight grade. If I did this at relatively light throttle, the car wouldn't respond to additional throttle -- it felt very lethargic until I had fully released the clutch. Drove me nuts. The sound was annoying as well, but not as big of a deal.

I too believe this is primarily about saving wear & tear on the car by aggressive drivers. That said, none of us are Porsche engineers.

I followed the path of pulling-apart the switch and fabricating a small jumper out of some housing wire. Worked like a charm.

The car now follows my throttle input, for better or worse. I'm re-learning the car a bit. While it's slightly trickier to drive, it does feel more natural.

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'08 Boxster S. PASM, cayman 18s, sport seats, RS60-tip, etc
'05 S4 avant
'07 gx470

Having followed this thread from the beginning I still have two questions:

1. Because the patent description talks about variable valve timing, does this clutch switch not affect ignition timing as has been assumed and does disconnecting it do something bad the the valve train?

2. Since there seems to be a almost a binary set of outcomes (some say it makes a great deal of difference, others say no difference at all) is there some basic difference in the cars? Perhaps, for example, it makes a big difference in a Cayman but not in a Cayman S. Or some other independant variable?

Good call..I don't know what I was thinking at the time. I think what I meant was, if the mod leads to the premature wear or damage of another item in the vehicle, would we be denied warranty repair? Is there any way for the dealership to tell if you've done this mod? It looks to be easily reversible so I don't think it's a huge issue but I'm just curious.

After reading the patent stuff, I am inclined to put mine back to stock and not mess with it. I'll see if I just can't live with it.

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2007 Speed Yellow Cayman GT 2.7 (retired)
2008 Guards Red Cayman GT 3.4
"Carpe Cayman"

I think you guys might be overreacting to the patent.

IIRC automakers have been retarding timing during automatic-transmission shifts for several years now. Helps smooth out the shifts, and also reduces stress on the drivetrain.

This patent, and this switch, appear to try to do much the same thing with a manual transmission. My personal opinion is that it's insurance against ham-legged drivers dumping the clutch & slamming between gears.

I'm going to leave mine "in" for a while and see if I can determine any adverse effects. The only thing I've noticed is that if I "lug" the car starting out in first I can induce detonation/ping. My guess is the switch safeguards against this as well.

Note, I can hear my car detonate a bit going up one of our local hills right at initial throttle tip-in when fully "in gear". the noise is faint, but noticeable. My ex '03 996 did the same thing.

Cheers.

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'08 Boxster S. PASM, cayman 18s, sport seats, RS60-tip, etc
'05 S4 avant
'07 gx470

NoSlack,

I would bet that you are right on target with your higher octane theory.

I know my Cayman S responds just as Nexus-6 decribes and he is in Texas and uses 93 octane and I am in California and mix 100 & 91 octane to get 93 octane.

Thanks for your post as it very well might be the explaination for the difference in results being reported.

I'm up in Seattle, WA using Premium (91, I think).

Given the bit 'o detonatoin I heard when rolling into the gas+clutch, I reinstalled the switch. I may pull it again out in a day or so. I have a hard time leaving things alone

I prefer the way the car feels with the switch removed, but it's plenty fun in stock form too...

I'd be really curious to know if this switch is market-specific. it'd make me feel more comfortable if we found out this was something to keep americans from whining about clutch wear, for instance.

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'08 Boxster S. PASM, cayman 18s, sport seats, RS60-tip, etc
'05 S4 avant
'07 gx470

I will try the mod tomorrow. What I have noticed is that this car is very easy to stall (I've been driving sticks for over 50 years) and it feels very flat in first gear just starting out. Both demo cars I drove also felt sluggish in first just after the clutch was fully engaged. I do not slip the clutch much at all in any gear and most especially not in first.

I'll let you all know how it goes.

Today, as promised, I removed the clutch switch and taped the plunger in the compressed position, just as it is when the clutch pedal is fully let out.

I immediately, on starting to back out of the garage, noticed a change. The car almost stalled! For the first couple of shifts from first gear it was difficult to get rolling without more RPMs than before. But after a while I could adapt to this behavior and get rolling from a standstill smoothly. I did notice that the car seemed to have more power after clutch engagement at low RPM in first gear. I don't know if this is because of the switch mod or because I was starting off with higher RPM. I do know that the dead feeling I mentioned before was gone, I think.

Overall I am not sure if this mod is beneficial or not. With the mod in you must drive the car as it it has a very light flywheel and low torque at low RPM. Some people may like that, I don't. On the other hand, I do like the feeling that the power is right there in first gear at low RPM after the clutch is fully engaged.

Now, is this all just my imagination? I did this test before fooling with the clutch switch.

Car in netrual, bring RPMs up to about 1000 and hold. Push in clutch and observe the RPMs drop to about 800 and hold steady. Let clutch out and RPMs go back to 1000. So something is really happening to the engine when you use the clutch. Strangely, when I tried this same test with the switch taped shut, I could not hold the RPMs steady. The engine would hunt between 900 and 1000 RPM. Strange.

So where from here? I think I'll leave the mod in for a while and accumulate more miles.

Just for reference:

08 CS
93 octane fuel
Just 200 miles on the clock
Less than a week old

As a very new Porsche owner, I have now put 1600 miles on my 08 CS, the idea of mods on a new vehicle is IMO a little extreme. Some mods are less extreme than others...this mod is very simple and very reversable...so I did it.

As most of you, I have driven many vehicles and I have confidence in being able to drive a manual trans high-performance car like a gentleman when the wife is in the car and driving it hard when she is not. The Cayman was a little difficult to get used to...I would say that I am still getting use to the idea of a null zone in the clutch before it engages.

My dad tought me many years ago that a little clutch slip in ratio with throttle is equal to a smooth transition. The more racing technique, the less slip required.

Backing out of garages, starting uphill, or just low RPM manuevering is touchy in the CS. The CS didn't really appreciate that until I performed this mod. I must say BRAVO!!! Have yet to stall or feel the hesitation on my driveway which is on a good angle. Many Thanks!!!!

PS. I used bus wire to jump the leads. Great thread.

__________________
Do more of that which adds value to your life and less of that which adds little or no value...

Should this thread be in the Mods section?

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Do more of that which adds value to your life and less of that which adds little or no value...