Anyone else getting a loud ruuuuuushhhhhh sound out of the tailpipe after DPF and CAT/DOC removal??? I'm using the MBRP 4-inch turbo back system with only the MBRP muffler.

100% normal, no worries. The engine can actually breathe now.

Anyone else getting a loud ruuuuuushhhhhh sound out of the tailpipe after DPF and CAT/DOC removal??? I'm using the MBRP 4-inch turbo back system with only the MBRP muffler.

This is pretty typical on these trucks with the exhaust off. Those vanes are closed up pretty tight at idle. Opening them up gives the LB7 type idle if you're into that sort of thing :).

Nick

mine does the same thing, its weird at first. freaked me out that i had an exhaust leak

mine does the same thing, its weird at first. freaked me out that i had an exhaust leak
X2:D

This is pretty typical on these trucks with the exhaust off. Those vanes are closed up pretty tight at idle. Opening them up gives the LB7 type idle if you're into that sort of thing :).

Nick
So can you use EFI Live to eliminate this hissing?

So can you use EFI Live to eliminate this hissing?

at idle yes

at idle yes

Cool. I had an MBRP 4" on my 06 Dodge, and it had a hissing sound at idle too. Never really liked it. Good to know it can be changed.

i like the hissing personally, definately unique

the hiss will actually quiet down over time...well at least mine has...:D...and if you think its loud with the muffler, you need to get rid of it and take a listen...im running dual MBRP straightpipes and sounds like a 747!!!

So can you use EFI Live to eliminate this hissing?


Ahckk,, it sounds too cool to eliminate.... to me sounds like a jet turbine idling,, especially in high idle...

Ahckk,, it sounds too cool to eliminate.... to me sounds like a jet turbine idling,, especially in high idle...

I'm all about having turbo whistle and a loud exhaust, but when it's sittin' their idling, I'd rather just here the low rumble of the motor. Not something that sounds like an air leak.:D

The issue is the variable turbo vanes are appx 85% closed at idle per GM strategy, causing the exhaust rush past the mostly closed vanes, and many tuners do not touch vane position at idle in their strategies. Some have said you must open the vanes to around 50% to stop the hiss.

I wonder what drivability issues that might cause?

I wonder what drivability issues that might cause?

The EGR is the issue, it needs exhaust pressure to operate at idle. If you've tune the EGR out, you can open the vanes. If not, it's best to leave them up.

The vanes can change their position very quickly to bring boost up off idle and maintain driveablity.

Hope this helps,

Nick

The EGR is the issue, it needs exhaust pressure to operate at idle. If you've tune the EGR out, you can open the vanes. If not, it's best to leave them up.

The vanes can change their position very quickly to bring boost up off idle and maintain driveablity.

Hope this helps,

Nick

From my observations after 2 days with this setup, it seems to me that the vanes are open more at idle once the engine is warmed up... The hissing seems very loud on a cold start, and much less pronounced after coolant at 210*. Based on your experience, is this an accurate observation?

Thanks for the input

A friend of mine has a ford ps straight piped from turbo with 5". On a cold start-up the "hiss" almost hurts your ears. Not cool.

Mine actually cycles. When I start the truck it hisses then goes to a deep rumble then goes back to the hiss. It also does this when I stop at a light for any length of time.

I wonder if I put in my EGR blocker plate, and efi the vanes open, would that eliminate the need for the back pressure for the EGR?

I don't really care for the hiss, but it is funny to see peoples reaction.

JT

Mine actually cycles. When I start the truck it hisses then goes to a deep rumble then goes back to the hiss. It also does this when I stop at a light for any length of time. JT

this is exactly what mine does...wonder why it does that...