I'm about 1,000 miles into my 2006 C4S ownership. I'm puzzled about the exhaust note while engaging the clutch, and curious if anyone has any explanation.

When starting from a full stop in first gear, the exhaust note sounds very different from any other point in time. The car sits idling at just over 700 RPM and I give it a little boost to ~1,000 RPM as I release the clutch. During the portion of clutch pedal travel where the plates are engaging, the exhaust note deepens significantly and sounds much throatier/raspier. Very easy to notice with the windows open. Think Louis Armstrong.

After the engagement period ends, the tone returns to normal as the RPMs increase. Think Bobby Darin.

I don't believe anything's wrong. The clutch feels good. The engine idles beautifully and pulls hard all the way to redline. It's all stock exhaust (not PSE) and sounds great at all times - this "throaty-ness" I'm asking about doesn't sound bad at all, just different.

I can't explain it. The throttle opening is constant, but the load on the engine is obviously changing. If the engine load explained it, wouldn't I be able to duplicate the sound by just pressing on the pedal when rolling along slowly in first gear? (No throaty-ness when doing this, only when clutch is in the process of engaging...)

EDIT: It's the clutch pedal switch. See my response in post #23 for details.

 

Do a search for clutch pedal switch. It's easy to disable the switch (tape it with the plunger in) to see if it's the reason for the sound change.

 

+1

I feel with the switch disabled that the clutch engagement feels more linear and without the switch retarding the engine timing you don't get that engagement delay when trying to accelerate hard up through the gears too. IMO, no downside to defeating it.

 

FWIW - I'm a new 997.2 C2S owner (< 2,000 miles driven by me), and I've noticed the exact same thing. Very deep/raspy exhaust note when initially starting out. Very noticeable when parallel parkting, but I like it :-)

 

It's all normal. It's my favorite part of driving a 911!

 

Question about this... The engineers at Porsche don't do anything for "no reason". There is very little that is truly superfluous on these cars. So the delay switch is there for a reason, no? So when you say "no downside to defeating it", if that were the case, why is it there?

Sorry I'm not articulating this particularly well and I'm not disputing you necessarily -- I lack the technical knowledge to do that -- just trying to understand.

 

It's there to keep people who aren't good at modulating the clutch release and balancing the throttle from stalling the car - so if you're looking for a downside, that's it. On the .2 cars though I think it sometimes causes an error, but not on the .1s

 

Ah I see. When you say causes an error -- you mean its disabling causes the computer to show an error code?

 

I can tell you that my .1 does have clutch switch codes logged a couple of times when I've checked. There was no visible code on the dash or indication of a problem. The switch is still taped up so maybe the switch itself actually failed.

 

On the .2s, that's my understanding, but both my 997s are .1s, so no direct experience

 

@Petza914


so if I tape up the switch does this mean I no longer have to press the clutch to start the car ?

also as somebody that has been driving stick since I was 15 would I benefit from having it taped up ? Meaning will the driving experience be better - just wondering if I should do that

thanks

 

Yes, you'll still have to press the clutch to start the car and pressing the clutch will still disengage the cruise control if set and active. There must be a different switch somewhere for those other functions - it seems the only purpose for this particular one is to retard the timing as you're letting the clutch out. Yes, if you've been driving MT cars for years, I believe you'll much prefer the more direct feeling of bypassing this clutch switch. I first taped mine to test it, then when I was happy with the result, used one of those snap on splicing devices to permanently connect both wires, and reinstalled the switch into its holder.

 

awesome thanks for taking the time to reply to me

little project for tomorrow

 

(Ok, so I'm committing the cardinal sin of not searching first, but...) where is this switch? Easy to tape over to test...? There a DIY on this?

 

If it's anything like the 987's it's super easy to get to and takes a few minutes to tape over or remove completely. I took mine out and jumpered the connector.
Here is a picture on a p-9 thread: http://www.planet-9.com/987-cayman-a...tml#post286903