Clay

Hi.

So I've put a little over 2000 miles on my 997C2S since I started driving it a little over a month ago.

I always match revs when down shifting any standard transmission vehicle and when I blip the throttle on the 997, it sounds like I'm getting some engine knock just for a second....but I'm not sure because i think there are some clicking sounds in there too. Been doing this since day one.

Anyone else hear things comparable to this when blipping the throttle?
Could it be something other than knock/detonation?

I've used 93 octane since taking delivery.
Car performs great and no engine knock detectable anywhere else....ever.

Thanks!

gweedo911

My C2 does the same; only when blipping the throttle. I'm not to worried about it.

Frino

Have never heard the referenced engine knock when blipping. 93 octane since new.

speed doc

I've heard it on throttle blip too. It's not all the time, but it does occur.

Dr_KarlB

Yes i hear this too.
Sounds like the same sound you get when trying to start at too low revs.
If i "blip" a bit slower i dont get the sound so bad.

lig

The same thing has always bothered me. Blip - knock - revs. More at low rpms than high though.

Edgy01

This isn't something that you encounter at such engine speeds. You shouldn't be encountering any knocking with 93 octane. The only place I encounter it is at low RPMs when starting out.

Likemystoppie?

Hmmm this is a new one...........I've never noticed it.

Da Hapa

I've also heard this a few times on my 2008.

The powers that be here in CA (CARB) don't allow for 93 octane to be sold in S. CA. So we're limited to 91 octane.

I have tried mixing a gallon or two of 100 octane with 15 or so gallons of 91 octane and didn't hear the knock. But that's a limited sample set since I don't always hear the knock.

Gundo

I get the same sort of thing every once in a while and only run 93 Octane

I actually tried dumping some octane booster in the tank, and it seemed to help.

997, esq

I've heard the same thing. Has been bugging me. Glad I am not alone.

ADias

I've never noticed that in my 996 C4, but I've noticed that in other cars here in CA using 91. I wonder if that phenomenon is a by-product of the anti-knocking process getting confused.

Clay

Good point.

Now that I think about it....it's much worse when blipping agressivly when the rev's are below 3000.... Like cruising in 5th or 6th at 60mph then blipping for a downshift to 3rd to use some engin braking for the stoplight ahead...compared to a downshift to 4th from 5th or 6th for acceleration at 70-75 mph.

Guess I'll be less aggressive when the rev's are low.

Thanks all!

axhoaxho

Thanks guys for bringing up this subject.... for the longest time I thought it was just my car. And yes, my car does this blip-knock thing since it was brand new, and I do live in California with the 91 octane gas.

With best regards,
- Alex, 07 997S.

Moderato

Why do I want to spend twice the cost of an M3 to get a car with the engine in the trunk that knocks when I rev-match?

Edit - OK, so I was in a bad mood when I wrote that but still......the engine knocks when you rev-match, WTH?