retlas

Hi guys

i am noticing a pretty loud clank when I hit the throttle from <1200 rpm

You can hear the sound at 10, 12 and 14 seconds in the below audio clip.

2007 997 4S

Any ideas?

https://www.dropbox.com/s/yfzqa2klk8...d%203.m4a?dl=0

groovzilla

I thought I also hear a slight similar sound at the 4 sec mark.
Almost sounds like the lag sound (valve tap) when you are in too low a gear and put stress on engine
Better qualified will give input I'm sure.

snaphappy

Does she burn oil?

Edit: after you figure out what the problem is you might want to consider switching to 5W oil if you’re running 0W. But don’t start with that. Leave everything like it is until you get it diagnosed. Smarter people than me will chime in shortly.

TheBruce

Do you live in California? If so its engine knock from the 91 octane, at least thats the best explanation I got.

I had a similar knock blipping the throttle below 2k rpm when I first got my car. I solved it by not blipping the throttle below 2k rpm anymore :-)

Petza914

Take a look at your motor and transmission mounts. Sounds like the initial torque of the motor when you hit the gas is causing it to contact something metallic, maybe a coolant pipe like those that fastened around the oil sump or something near an exhaust component.

retlas

Thanks for the reply, and nice ride. Mine's arctic silver as well.

retlas

A little, about 1L per 1,200 KM, which from what I understand, is normal.

retlas

Hmm, the local station only has 91 - but the Shell station has 93. It's a good idea and I will fill up the next time with 93 and see if it makes a difference - thank you.

retlas

Hi, I had thought something similar and just replaced the engine mounts as I had inspected and found about a 8mm drop on the right side of the engine. The new mount leveled things back up but didn't stop the noise.

TheBruce

Keep me posted if the 93 helps. That would put the mystery to bed, as @Petza914 's comment just put my OCD into overdrive :-)

Check out this post from 2008 where a lot of people reported similar thing. I resurrected it when I first got my car.

https://rennlist.com/forums/997-foru...e-knock-2.html

Petza914

I had another thought on this - is it only happening on cars with the factory airbox? I'm wondering if it is the Helmholz resonator in the airbox snapping shut upon throttle blip due to the immediate increase in air requirement from the quick throttle press. Someone with an automotive stethescope could put it on the resonator in their airbox while someone else blips the throttle and see what they learn.

I have never heard this in either of my 997.1 C2S cars and I'm wondering if that's because I don't run the stock airbox - the supercharged car has a Fabspeed J-Pipe intake and the other has the Evoms, which is what got me thinking about the resonator in the stock airbox.

TheBruce

No, as the C2 doesnt have the variables baffle in the resonator.

In mine its definitively a metallic sounding "clanking", as the OP described.

Petza914

Hmmm. OK