Exhaust note changes pitch at idle - Ford Powerstroke Diesel Forum
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Old 04-27-2011, 06:11 AM
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Exhaust note changes pitch at idle

Has anyone noticed this on their truck?

At idle about 10 seconds or so after starting the truck it will get a deeper exhaust note for about 2 seconds then it goes back to normal, let it sit another 30 seconds and it does it again. Its not like clock work so it isn't always xx seconds of idling and it cycles. It does this w/ the AC on or off.

I read the truck has a warm up feature of the turbo that makes it get up to opperation temp faster but it wasn't clear exactly how that worked. It also seems to do this if the truck is as operating temp.

I've got a magnaflow exhaust on mine so it may magnify it over what a stock one would sound like.
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Old 04-27-2011, 06:32 AM
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VGT

From what Ive read that is the sound your hearing is the exhaust backpressure changing, the VGT moving to the full closed and full open position while at idle. Its suppost to try and help the unison ring from sticking... Maybe someone can correct me but that sounds like whats going on.
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Old 04-27-2011, 06:32 AM
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Thats just the turbo vanes cycling. Completely normal, it keeps the turbo from sticking during idling. Here's a video of mine, mine may sound a bit different since I have an '03 turbo:

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Old 04-27-2011, 06:51 AM
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Turbo cycle. Its your strat. My friends truck does it, mine doesnt. Wasnt noticable unil stright piped.
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Old 04-27-2011, 06:55 AM
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ok, thanks guys.

I love this truck so far and I'm trying not to be paranoid about any issues it may develop. Lately every sound has me turning down the radio and saying "whats that, where did it come from, why, etc..." better to ask than keep the radio up and head up my.....
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Old 04-27-2011, 12:40 PM
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Yep it is just part of the VXCF9 strategy to keep the turbo vanes from sticking. Completely normal.
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Old 04-27-2011, 12:56 PM
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yea normal and i kinda like it. the looks you get from people when your standing near it and the vanes change.
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Old 04-27-2011, 01:05 PM
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When the warm-up feature kicks on, you will know it. The idle goes up a few hundred RPM and stays there until you tap the brakes.
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Old 04-27-2011, 01:40 PM
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Thanks, wondered about that on mine. If you need some real noise break the clamp on the output of the turbo at about 20 psi boos. Did that yesterday pulling 8k up I5 into Portland
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Old 04-27-2011, 01:44 PM
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Quote:
Originally Posted by BigTang View Post
ok, thanks guys.

I love this truck so far and I'm trying not to be paranoid about any issues it may develop. Lately every sound has me turning down the radio and saying "whats that, where did it come from, why, etc..." better to ask than keep the radio up and head up my.....
Thats how I was when I first bought my truck. It was my first diesel and every noise i heard that seemed odd I'd call my dad and he'd tell me to just drive the ******* thing and quit worrying. He's been driving diesels for as long as I've been around anyways.
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