just bought an 06 base z 5 weeks ago. It now has about 1700 miles on it and I broke the car in like the manual states and Im still driving cautiously. Its my first rear drive car and I want it to last. My question is about "spark knock". Ive noticed that if I cruise at low rpm and in a higher gear and I then accelerate I hear a brief rapping sound coming from the engine as it winds up. My previous car was a gti vr6 and those german engines sound totally different and I dont recall anything sounding like this, but Im not sure I can say that its a sound Ive never heard in other cars. My owners manual states that you will hear a small amount of "knocking" upon acceleration or when the engine is under load and that this is a normal sound due to the engine timing and that it is a function of the engines efficiency. So, is this what Im hearing and is it really normal and is it something other owners hear too? I seem to go through a phase of over analysis of a car's sounds after I buy it in an attempt to learn its idiosyncracies. Is this just a difference in engine sound from german to japanese?

 

I dont think its engine knock because your n/a and stock. Unless you put 87 octane it still shouldnt knock that bad. It shouldnt be to the point where you can hear it, the ecu should retard timing in any knock situation. I suggest taking it to the dealer so they can check it out. Is your Z stock?

 

Yeah it's stock. It isn't a clunking sound it's more of a change in note and character of the engine sound and I hear it with the windows down on a quiet road and its brief upon acceleration. Oh and I only use 93 octane. It is only occasional like when the load on the engine is just so. The manual references something called spark knock.

 

check your oil level. I've seen some 06's having pro blems with oil consumption.

 

Why don't you downshift to accelerate like you should?

 

What RPM/gear/mph were you in when you heard this? You should'nt try to prolong engine life by under-reving it -- i.e driving 35 mph in 6th gear and at 1,300 rpm.

 

If it's really 93 octane you will never, ever knock with a stock engine. We have 91 octane in california and no one I know has problems with knocking.

If you're concerned, CHANGE GAS STATIONS. Sometimes gas stations can have bad gas.