I installed my BD twins about 18 months ago and got tired of the turbo whistling through the AFE air filter. I guess I’m getting old, but after studying the silencer ring used in the HX35 that was stock in my truck, it seems that by providing a smooth transition into the turbo the whistle could be reduced.

The BD twins use 2 Schwitzer S300 turbos with the bottom turbo a little larger than the top. Taking some measurements of the bottom turbo I came up with an idea that seems to work well. The aluminum transition is modeled after a bell used in a horn like a trumpet. Not having any aerodynamics background, this seemed like a logical starting point. The only difference is the airflow is backwards from a horn.

I chucked up a piece of aluminum plate on a lathe cut the shape in the pictures below. Being worried about the aluminum piece contacting the compressor blades I tapped three radial holes for setscrews to hold the bell in place. Then I started to worry about the setscrews working loose and taking out the turbo so I used some Loctite to prevent that.

The turbo noise is just barely audible. I think there is more whistle from the exhaust now. Go easy on me. Not everyone can tolerate a high-pitched whistle for hours on end.

 

Looks awesome! I put on an Amsoil Nanofilter, and the turbo whistle is definitely annoying. I have a new (to me) HX35 to replace my little HY, and the snap ring is there. I am going to put my silencer ring back in place.

 

That looks like a high-quality job

I'm sure you also improved the compressor efficiency slightly too, as that's one of the purposes of silencer rings in the Holsets.

 

You will now have to give back your official diesel head plaque.

 

Well done sir.

 

I want one!

 

I could only stand my silencer ring out for one week, it went back in yesterday. Now i'm thinking about building a foam box around my K&N head shield to quiet down that whistle. I'm only 25 but i like to talk on the phone once in a while.

 

Heat Shield Box, any ideas? Sorry to hijack... but it seems the topic at hand is to quiet down the system.

 

Hm.... Very Nice!

I wonder if it would work on an s400. Could you have machined a lip on the ring that was flush with the outer casing wall of the intake so that it could not be possible to slide in? I am thinking like a socket fit.

Jim

 

Nice job on the velocity stack. Hopefully with twins it won't bark as easy as on a single.

Actually the silncer ring is just that; silencer. As with most mufflers it REDUCES the efficiency. The ring blocks the Map Width Enhancement (MWE) slots.

 

What are MWE slots, and what do they do? Other than whistle louder, I saw zero benefit from removing my silencer ring, over driving around with it in.

 

Slots/holes cut in the compressor housing around the inducer. Map is the efficiency range of a turbo charger compressor for mass flow & pressure deltas. The slots widen the band and reduces surges & barks.

 

I was also concerned about barking, because the silencer shown in this thread completely blocks the MWE slots.

I know the silencer ring blocks the MWE slots, but the MWE slots decrease compressor efficiency in exchange for a much wider map (according to www.turbobygarrett.com)

Based on how the silencer ring looks, it appears to me that it would direct air toward the impeller and "straighten" the flow, much like a TAG but less effective. However, this is only what I've been told and have gathered from looking at the silencer ring; I have no aerodynamic experience or education.

 

Good points. Maybe effectiveness is a better term than efficiency?

Buddy of mine made a velocity stack. He said it barked very easy. I was too chicken to try it.
I did use a TAG all last year. I saw no performance gains, but it sure quieted the whistle from the BHAF. Pulled the tag and went back to stock box with new Amsoil filter

 

if you have a turbo that is in a surge-prone application, that type of sliencer ring will really amplify the surging problem.

if not, this will work fine. but there's a reason those turbos are designed with those slots, and there's a reason that dodge's silencer rings still allow some air to bypass them