What's that hissing sound?

[CStansbury]

When I am pulling down the steep road to my house in 2nd gear and I get to the bottom of the hill the truck is making a hissing or whooshing sound from the turbo side of the engine. That's not the only time it does it, just an example. Anytime I have downshifted, the engine is braking, and am driving slowly it does it. Is it the wastegate exhausting excess boost or what? It's kind of a cool sound, like I've got air brakes or something

 

[RabidRam]

I was gonna guess exhaust brake. But chances are you'd know if you had one of those on your truck or not. If it's when you are going DOWN hill (not on the go peddle), then I don't think it would be wastegate related because (from what I understand, which, isn't that much) the wastegate has more to do with a build up of boost... not a lack of it. But hey, I'm a 2nd gen guy, so what the heck do I know anyways? I'm just bored at work and tryin' to kill some time (but don't tell anybody).



Dave

 

[CStansbury]

Thanks for the quick reply Dave. No, no exhaust brake yet, that's on the wish list. The reason I was thinking wastegate is if I am in second going down a steep hill, I can give it gas and then let off and make it hiss every time. I'm sure I'm not the only one this happens to, but I'm clueless as this is my first CTD. All my other diesels have been NA so I don't know some of the unique sounds. We'll get it figured out eventually

 

[RabidRam]

It's probably just good ole turbo whistle. You're a lot more likely to hear it when you back off the go peddle quickly (i. e. shifting a manual or the situation that you described).



Have you straight-piped your truck? If you like that hiss or whooshing sound, you can make it a HECK of a lot louder by putting on an aftermarket air filter (BHAF/AFE/K&N/etc... ), "misplacing" the cat and muffler, and taking the silencer ring out of the turbo. Then you'll hear it pretty much whenever you darn well please. Or you could put on twin turbos



Enjoy the music,



Dave

 

[CStansbury]

Well, I listened to it some more today. It's not as easy to get it to do it as I had mentioned previously. Reall, it's not so much a hissing sound as it is a buzzing, whirring, or whizzing sound. Kinda like a high frequency mechanical buzzing sound. Maybe the fuel pump? I'm sure it's not turbo whistle. I may seem very concerned about the sound, but I'm not. I don't think anything is wrong with it, I'm just curious.