concerned about a sound I hear

Today I started noticing a sound I have not noticed before. Maybe it has always been there, but after 1000 miles I think I would have noticed it sooner. Let me describe the sound and under what conditions I hear it. I would appreciate it if others would try to recreate what I describe and see if you hear the same sound. I shift through a number of gears and reach a desired speed and gear level. Lets say 40 miles per hour and in fourth gear. I take my foot off the throttle and coast. If I then press abruptly on the throttle, there is a sound that comes from the engine right behind me that is similar to the sound of a shot from a can of hair spray. Then the engine accelerates. If I press on the throttle gently, the shot of spray is not heard. But if I gun the throttle, I hear the shot of spray sound. This same sound can occure if coasting in any gear, so long as it is punched while coasting and with the rpm's above 2000. Maybe this is normal, and part of the injection system. If so, it would be comforting to know this. If any of you out there have the time to check this out, I would be grateful. I did not post this in the compaint forum since it may be normal and therefore would be an fyi and not a complaint. Thanks in advance for your feedback.

kmns, I have not heard that sound, but I will try to create as you suggest. I will let you know! Russ

Thanks Russ, I appreciate it.

I believe this sound is normal and has been discussed on the forum before, although i don't remember which thread. The sound is a bit like a woosh as airrushesinto intake maifold. It's pretty easy to hear if you listen for it. The 2 Caymen's i test drove as well as mine make the same sound.

Thanks Attila, I'm just surprised I never noticed it before. I wonder why it only makes that sound when you pop the throttle as you coast and not as you pop it right after a shift. It will be interesting to see how many others hear it now that it has been addressed again.

I noticed the exact same sound on the demo and personal CS

I haven't heard that noise; but I think 40MPH in 4th gear and punching it isn't right. That sure sounds like a 2nd to 3rd gear speed. When you mash on the gas, it throws lots of fuel in, so the whoosh is probably the air volume rushing to catch up. But if you aren't at or above 4K, I think that squeezing the throttle is the proper go approach.

It is possible that know KMNS has mentioned it, we might hear it as well. If it wasn't still pouring rain I would be out there now driving it. Think it is wet here, how about 2 inches in one hour where it is usually dry! (and still coming down hard). Russ

fmarshall, Interesting analysis. I agree that normaly if one is at 40mph and 'needs' to punch it, the proper way would be to donwshift and punch. Cruising in a 40pmh zone in 4th gear, however, is not unusal, and usually you would squeeze the thorttle if you wanted to go a little faster. (by squeezing the throttle I assume you mean slowly applying throttle rather than punching it) The whoosh sound however is something I only recently noticed, and maybe the reason is that I probably had not punched the throttle before at a low end rpm. Having done so, for whatever reason, I heard the whoosh sound. I then tried punching while in second and third gear and heard it in those gears as well and at different speeds. I used the 4th gear and 40mph as a guestimate of one instance when the whoshe sound was heard when punching. Since I first heard the whoosh sound I have tried punching it in several different gears and various rpm's, and it always makes the whoosh sound when punched. I hope it's normal, but it's the first time I have ever heard an engine make that sound following a punch of a throttle. The good news is that there is no apparant hesitation or drop in performance. One more reason why I thought it might be a normal engine sound on the Cayman S . Given that others have heard it I tend to think it is normal, unless many others report that they don't hear it in their cars. Thanks again for your analysis.

Russ, You are a real trooper. Thanks for your concern and intentions. I agree, though, that you should leave your baby out of the weather and check this out after it clears up./fckeditor/editor/images/smiley/MWPX/thanks.gif

Its strange that I found this topic this morning because I heard that sound for the first time as well! With it only happening when youpunch the throttle, I wonder if its the injectors shooting in extra air/fuel?

Are you sure that this isn't the sound of air being sucked in through one of the side vents into the engine? the vents are their for that reason! but if it's not then let us know. I've heard that air sucking sound firstly in November on my test drive and played with it a little and thought it was kinda' cool. There is a cackling sound that comes from the engine sometimes (rarely) when I put my foot down but I think that's different.

I played that sound on a test drive and believe it is just one of the musical instruments - another part of the symphony of sounds this engine is capable of producing. My dealer with me actually pointed it out and said it is something you should hear especially after the engine has been broken in a bit. I believe he told me at the time that it had to do with the variable intake manifold working properly under the load of a quick acceleration. I'll have to ask him again, but he was well aware of it from attending a dealer launch training event where they drove several cars at all speeds.

follow link below: http://www.planet-9.com/topic.asp?TOPIC_ID=1952&FORUM_ID=1&CAT_ID=1&Topic_Title=Scratchy+injector+sound+with+quick+acceleration&Forum_Title=Cayman+Chat it's normal

unpollo2, Thanks for the link back to a February discussion of various sounds. That link touched on this but it also covered several other sounds, including bibrations and backfire type sounds. This sound is a subtle sound that is consistent with punching the gas pedal when it is completely in the up position. Today I tried the gas pedal punch at various speeds, rpms, and gears. From 2nd gear on up to 6th the results are always the same, and regardles of rpm's. If you let up on the gas pedal completely, and then quickly punch it, you hear a whoosh (air spray like) sound just before any other normal sounds. If you gently press on the gas pedal, just slightly, and then punch it, you do not hear this sound. It's almost as if something disingages if the gas pedal is fully extended and when engaged suddenly causes the whoosh. Apply small pressure first and then punch, and there is no whoosh. It appears that many are hearing this sound and so maybe it is normal. It just seems strange that I never heard it before over the first 2 months plus. It would be interesting if anyone writes in and says they do not hear this sound at all when following this punch process as described. If that happens, then maybe it is an issue associated with a series of vins.

Sounds like you're hearing the same thing I do. Dealer says it's normal. Perhaps, according to specs, nothing is wrong, but it sure sounds to me like to electronics are unable to keep up and is therefore far from normal... Everyone should try the following and note the response: With the engine warm at any speed and in any gear - even standing still with the parking brake set - with the accel pedal not depressed at all, floor the throttle as quickly as you can. Don't begin by pressing lightly and then quicken as you get into it, jam the pedal to the floor in one swift motion. Unless you've got a tiptronic, you'll hear a quarter second pause as the engine sucks air before the electronics and the fuel rail catch up and start to produce power.

friedman_japan, Your instructions are right on the money and reflect my exact experience. The quarter second whoosh is always there. I would love to have many of our members write in and see if this is consistent with all cars regardless of build date, and then begin to disect this as normal or not. And if normal, what exacltly is it, and why. Sometimes normal is not the same as 'by design'. What if it is an issue that simply exists in all cars. I would not call that normal. I would call it a recall candidate. Unless, of course a good explanation is provided. Maybe we should look into whether Boxters also have this sound, and if not why? A 911 's engine is not right behind your ear, but it is relatively close. Do they have this sound, and if not why? What if all the cars had a squeek. Would that then be 'normal'?

I went to my dealer to have them investigate this issue. They also initially thought the sound was very unusual. To try and narrow down the issue, we tried three other Cayma's in their inventory - 2 manual and 1 tiptronic. The manual (same as mine) cars exhibited the exact same issue, the tiptronic had a hint of the problem but it was massively less apparant. The dealer contacted Porsche Japan HQ and after two days came back telling me that the 'noise' was a normal part of emissions controls. I found this one a bit hard to swallow as the tiptronic didn't really have the same issue. Would be very interesting to test a few Boxsters to see if they display the same issue.

The noise I heard did not sound like a problem to me at all, and I began to listen for it as an additional indicator of the shift/power ratio that I was applying. Perhaps you are hearing a different sound, and I hope to get the chance to try to produce what you are describing again soon when my car comes.

Like I said back in that thread in Jan/Feb I feel it is perfectly normal and is purely an induction noise as air is rapidly sucked into the engine when you bang on the accelerator. I hate to have to use stupid similes, but it's the difference between opening a bottle of coke quickly, or slowely. If you open it quick you get the rush of gas escaping rapidly making that whooshing noise. If you open it slowly, you get a faint hiss. Someone here must be able to tell us that it is a definate induction noise caused by the blah-blah-widget-valve expanding as the thingy extends when the transition of the flex-tronic fluggaltoid hits a critical ratio of coefficient energisation............... Isn't it the just the variable inlet manifold (thing) expanding or contracting as the throttle is pressed, and it just does it quicker the faster you press the peddle down? I'm sure it's fine, and even if it isn't, it sounds great, and I don't want it to not be there. Jack

>>Someone here must be able to tell us that it is a definate induction noise caused by the blah-blah-widget-valve expanding as the thingy extends when the transition of the flex-tronic fluggaltoid hits a critical ratio of coefficient energisation............... Isn't it the just the variable inlet manifold (thing) expanding or contracting as the throttle is pressed, and it just does it quicker the faster you press the peddle down? I'm sure it's fine, and even if it isn't, it sounds great, and I don't want it to not be there. Jack<< . It's called 'air scavenging' at my company. We've been making large industrial engines for over 100 years - and if you think the 'whoosh' is loud on a 300 HP unit you should hear what it sounds like on a 9,000 HP unit with a 16' bore and 16' stroke, when you 'step on the gas'. In the airline industry there is also a phenomenon called 'crosswind vacuum'. The engine will make a 'poping' noise as the induction air is being disrupted by air flow that is tangential which disrupts the incoming stream. I've only heard it twice on an airplane (and I fly well over 100K miles each year) and both times only when on the tarmac. If you ever hear it you will be 'very alarmed' as it is loud (and quickly followed by the pilot on the intercom telling you its normal).. Paul

Are you with S&S (GE). I have worked with the folks for years.

Cooper. S&S is a competitor of ours. Paul

So Case closed? Everyone happy with Devos explination? Jack

Sorry to be a pain, but if it's normal why didn't I hear it in a Boxster or a 997S that I drove recently? Why is it so much less pronounced in the Cayman w/Tiptronic? I would care less about the sounds if it didn't come with a lag in power - it does.

Does a Boxster have the same air box configuration and manifold? A 997 air inlet is not 6 inches from your left ear. \throttle response on a Tip, I would have thought, would be programmed very different to a manual box car. And I don't know what you mean about lag in power. If you stamp on the throttle the car has to suck in air, burn it, and transmit power to the the wheels, all things that take time. I don't know for sure, but these are some guesses from me to some of those questions. Jack