A couple weeks ago I started hearing a hissing, or shhhhh, sound as the turbo starts to kick in around 3K. Sometimes it's worse than others, and I've tried a lot of things to see if I can narrow down exactly when I'm noticing it most. I took it to the dealer yesterday, and 4 hours later they told me nothing was wrong...
I've been digging and researching this problem, and I'm not the only one it sounds like. The only difference seems to by my car is "ok" in the eyes of the dealer. I found a thread that linked to this vedeo:
That's EXACTLY what I hear. Mine just isn't quite that loud usually.
The car is bone stock except for a Cobb AP. When I got it, and after doing some data logging, I settled on the Stage 1 ACN91 HWG map (HWG probably due to my altitude being almost 5000 ft). I now have 8000 miles on it.
I decided to do a little diagnostics of my own hoping that it would help you guys help me get to the bottom of this:
My original data logs (when I originally tuned the car 4-5 mo ago) had a very clean boost curve that peaked at just under 15 and smoothly backed off to about 10. I didn't have time to drive out to BFE to get another set of logs, but I did use the monitoring on the AP to see if I could see anything. Sure enough, when I start at about 3K I hear the hissing sound. Right around 4K I hit almost 18psi boost, then it quickly backs off to 15, then gradually drops back to 10. It NEVER launched over 15 before this problem. I threw the "stock" map back on, tried the LWG and NWG maps and all of them are doing it.
One thing I think I noticed, but haven't verified, is that if I let the car sit for 10-15 min it's less pronounced. Then, after heating the turbo back up I think it gets louder. I got bombarded with texts and emails, so I decided to pull off the freeway and reply. After 10 min or so I ran back up the freeway onramp trying to get a hiss and it was either not there or much less pronounced. After a half mile of fooling around on the freeway it was a bit louder. Again, this hasn't been repeated multiple times, so may have been a coincidence...
Another thing I notice is if I'm full boost and I let of the gas I get a "squeak" noise. I'm almost positive this is just the stock blow off doing its job, but I wanted to throw it in here just in case it's related.
Environmentally, the temperatures have been getting cooler (it's September, go figure), but it's still been in the high 80's during the day, so I don't think that has anything to do with it. OAT doesn't seem to play a role, I hear it all the time.
I've tried all the gears to see if there's any difference. 1st is hard to tell because it's done with so quick. Plus the engine noise gets in the way, but I think I do hear it. 2nd I definitely notice. 3 and 4 it's there as well... and I can even get it in 5th at normal freeway speeds.
One of my first posts here was me wondering if I'd experienced a loss of power. This was very soon after I got the car, and I just dismissed it as me getting use to the power and how the car handled. This may very well still be the case, but it's one of those nagging thoughts that keeps me wondering if this problem "started" way back and has just progressively gotten worse. I just remember right after I got the car that when the turbo kicked in I felt like I was just along for the ride, especially up around 5K. Now when I'm running up an onramp it just doesn't feel the same. All of my data logs from the AP tell me that it was boosting normally and nothing was amiss. Very likely just my experience and perception, but I needed to put it in here.
I'm not a gear head (obviously), but I have done a little work on my cars in the past and generally pick things up very quickly. I really need to learn more about this car so I'm not running to the dealer ever time I hear a new noise. Being in the onsite IT business, I can't afford to be without my car for half a day, especially when they just tell me everything is fine and I'm imagining things. Can someone tell me what I can check and maybe some other troubleshooting steps I can do? Any pictures would be great!
Thanks a lot for all your help. I love this forum!