Hi Guys,

I have a mostly stock truck. the only thing thats not stock is the exhaust. When i first test drove it, it had a straight pipe. We could hear this whistle. At the time i thought it was just noise from the pipe. Well, now that i have a 86108M Nelson (the one with the baffles) the whistle is still there. Its about the same pitch as a person whistleing (as in not super high freq, like a turbo whistle), and it tied to RPM. It seems to start in a little over 1500 rpm under load and is still noticable to about 1900 RPM. It either goes away after that or just is overpowered by other engine or wind noises. Also, it doesn't seem to be as loud when at the same RPM, but going down a hill...but is still present.

I did look briefly last night at the air intake and filter area and everything seem solid and tight.

So....anybody have any idea what it could be??

Thanks in advance!

 

Sounds like it would be turbo noise to me. Although my stock turbo whistles, I really heard it out of the exhaust when I had II's Silver64 turbo. Are you sure you have stock turbo?

 

I suppose its possible, but I would very seriously doubt its an aftermarket turbo. I talked to the previous owner and he said that he was "eventually going to do a chip" but didn't have the money.

So a turbo whistle can still be lower pitch?

 

Without hearing it I'd just be guessing. Is the truck running ok? How many miles on her? Did you get underneath and give a decent inspection, check the exhaust hangers, etc. Too many variables.

 

Silencer MIA?

 

yup, truck seems to be running ok, though I MIGHT start to think there is an injector issue starting. It vibrates my butt a little at idle....more than my old 12v did a few years ago.....its got 86k miles. I did look it over when i bought it....it was a new pipe when the previous owner straight piped it, so no holes there that could be singing. As far as hangers go, i know there are at least 2...lol. I'll ahve to crawl under again tomorrow to check to see where they are all located.

Yeah, I understand its pretty subjective....."whistle" can be many things! I dunno if you have a sine wave generator, but its probably between 800-1000 hz depending on the RPM. (sound guy in me coming out...lol)

A removed silencer wouldn't really fit that tone, but its worth a look!! How can i verify this? is there an easy way to tell?

Thanks again guys!

 

Take your intake off and look in the front of the turbo. If you see a conicle metal disc and almost no turbo vains, your ring is in place. My guess is if a guy were to straight pipe it, he might as well pull the silencer. He wasn't worried about noise!