I've just figured something out.. this may come off as a dumb comment/question, but oh well.

I noticed when I first drive my car after quite a few hours (when it's had a chance to really cool down), especially if it's cold outside, that my HKS sounds absolutely amazing for about 2 minutes. Then it sounds normal.
By "absolutely amazing", I mean there is a much deeper, unbelievably mean sound when I accelerate. But it seriously lasts for no more than a minute or two.
I believe that is because it's cold, and after a minute it gets warm again.

So, my silly question is: if anyone knows what I'm talking about, would there be a way to mod the exhaust so it always sounds that good?

 

If you're talking about when your engine is cold, its cuz the idle is higher. In which case you should not be accellerating hard while the engine is cold. I don't even drive my car when its cold, I always let it warm up.

 

+1 I let it warm up like my bike to normal operating temps before I leave for the day.

 

I always let my car sit and idle until it warms up and even then i don't bring it above 2500rpms for a mile or two.

 

I've noticed that too.

 

Why does the idle being higher completely change the sound of the car?

 

The sound your car makes is in direct relation to the amount of air going in and out of your engine. Since what you are hearing is the sound of the air coming out. So opening the throttle more, increasing the idle, increasing the air flow, changes the way it sounds.

 

Dingo isn't referring to the sound at idle. My RX-7 (w/ Apexi N1) had a more aggressive note throughout the entire powerband when it was cold as well. My guess is that the sound deadening material in the resonators and mufflers takes some exhaust flow (heat) to heat it up. Until the packing in the muffler is at operating temperature, you're going to hear more resonance in the exhaust.

So, to answer your question: what can you do to make it sound like that all the time? Well, since you have the HKS exhaust, can't you tune the exhaust tone using the the tuning canisters that are on top of the primary canisters? Another possibility would be to weld straight piping in place of the resonators after the H pipe. That'll probably have an adverse affect on the noise in the car though so be forewarned...

These guys are right about letting the idle settle out before ripping away on the engine too. Going full throttle while the metals and liquids in your engine are still cool can lead to premature wear and cracking.

 

Citrus - thanks, I think you may be right.
When cold, it sounds like a whole different exhaust. MUCH deeper, sounds as if the exhaust air is more contained or something. Wait, I don't that made any sense.. ahh.
Anyway, tuning canisters? I know of those two canisters right above the exits of the exhaust, didn't realize they were meant for tuning the sound of the exhaust.. can anyone go into detail about this? I'm about to go home during winter break, and I have my local shop there that I trust.

 

well it doesn't get above 40 here for the next couple months so i will let you know when it gets warmer if my car sounds different.....

 

ok side question.... there has been debate if it is good to let the car "warm up".... basicly just sit at idle vs drive really gently at start up. one of the reasons is because at idle the engine is not turning fast enough to get oil everywhere cause the oil has more viscosity (since it is cold) so it isn't lubicating the parts it should. by just driving below 2500rpm or lower at startup, the oil will spread around more thus less wear. what do u guys think?

 

I'd go by what the owner's manual recommends, which is...

< someone go look it up >

Personally, I don't idle my car until warm, I drive gently until temp comes up. General automotive rule of thumb is don't rip on a cold engine or things will crack, warp, etc. over time. As long as you follow that, whether you idle or not shouldn't make a difference between a non-turbo engine that lasts 150k vs 200k.

 

My greddy exhaust gets louder when it's hot. The tone sorta changes a bit.

 

Really? Mine gets smoother and quieter- like stock until WOT.

 

Do you have tp's? I also have a custom h-pipe built into the system.

 

Oh maybe that's why. Mine is just the standard Y system, no TP's. I'm sure your's sounds great.

 

It may have to do with the engine being cold. Of course we know cold air is more dense. More oxygen packed into a small space = more power. The HKS might just amplify this sound. After a few minutes heat soak sets in and you've lost a bit of throttle response.

 

With the standard x-pipe, if you install tp's you will hear a weird sound coming from the exhaust. It took me a long time of investigating to figure out it was the x-pipe that was creating that noise.

You would have to either cut that middle portion and install another x-pipe that isn't as sharp, or install a h-pipe.

 

i wonder how long our engines generally lasts for....