Strange exhaust noise

[3cans]

Just replaced exhaust from down pipe back with MBRP 4" on a 2008 LMM. Installed a 50hp tow/economy tune (DPF Delete) and have a very strange continuous hissing sound. Once, when I started the truck and walked to the tailpipe, the sound changed to a "normal" low rumble for about 2 seconds and then went back to a hiss. Any ideas?

[camcojb]

Just replaced exhaust from down pipe back with MBRP 4" on a 2008 LMM. Installed a 50hp tow/economy tune (DPF Delete) and have a very strange continuous hissing sound. Once, when I started the truck and walked to the tailpipe, the sound changed to a "normal" low rumble for about 2 seconds and then went back to a hiss. Any ideas?

yes, it's the vane position on the turbo, totally normal. You can make it go away at idle in the tune by changing the vane position numbers. The "normal" sound is the computer testing and altering the vane position briefly.

http://forum.efilive.com/showthread....=vane+position
Jody

[3cans]

Thanks for the info. I just got off the phone with Rob and he said the exact same thing. I was only worried because my '01 and '04 never sounded like that when I replaced them with Banks exhaust and the edge.

[LBZoom]

Yeah, only happens with the VVT turbos on the LLY and newer trucks, mine does it too

[wildonwheels]

Also> only change 600-1000 rpm and up to 15 mm3.. You want the 300rpm area OE, otherwise you'll get the 'shut-off buzz'...

[bballer182]

Also> only change 600-1000 rpm and up to 15 mm3.. You want the 300rpm area OE, otherwise you'll get the 'shut-off buzz'...

Actually that has been discovered and fixed with one of the newest updates. It contains a new table B1501 "EGR performance testing" Disabling it will get rid of the noise regardless of the vane position.

[wildonwheels]

Actually that has been discovered and fixed with one of the newest updates. It contains a new table B1501 "EGR performance testing" Disabling it will get rid of the noise regardless of the vane position.

Thanx.. Just did the update, looks like I was one behind..

Btw; what does the EGR control have to do with the turbo-vane position checking and hunting around??..

I've had my vane's set at 0 in 600-1000rpm to 15mm3 for the past year and still get the vane hunt when warming up or first minute of warm starts.
Even with the vane's at OE spec I get the vane position hunt.

I have a no muffler, straight 4" turbo-back system so, I can hear any slight change..

[bballer182]

It's the ECM learning 0% and 100% positions. happens at every startup. Totally normal and you DO want it to happen.