Scotty II w/ hole cut turbine whine

[rweis]

Cut the hole in the firewall for the end of the Scotty II. I don't want to just "cover it unless you need it" because when I need it towing it will be there.



The whine is fairly significant unloaded cruise and really significant when accelerating hard. Tried A/C on and off, outside vent on and off to see if there was a setting that was acceptable. Nothing I tried helped.



I thinking something like a fitting into the 4 1/2 hole that would make the turbo pull air from the vent to the left (left looking from front to back). Something like a 4 1/2" PVC coupling with large holes drilled in it positioned so the solid side is to the centerline of the truck and the holes are to the outside.



Has anyone worked on getting the trubine whine out of the air intake system with a Scotty II?



Thanks



Bob Weis

 

[JBlock]

Try Sound Proofing the cowl inside

I saw a picture of the 4. 5 inch hole in the cowl. Stop by a Heat and Air Conditioning shop and see if you can get a few scrap pieces of sound black mat face insulation, it usually 1 inch thick. it installed with a rubber like cement on stick clips, the insulation, then finally a speed washer ,



The stick clips. glue down first then the installation then the speed washer hold in place. I have considering doing mine that way when I cut the hole.



the material is designed to aborsb sound it might just be the ticket.



you might try contacting both STA



http://www.atpwrap.com/home.htmhttp://www.atpwrap.com



or GSI



http://www.soundstop.com/index.htm

 

[illflem]

I never got around to trying it, got used to the noise first, but thought that building a "dam" in-between the area of the cowl where the Scotty sucks and the vent intake sucks would help. My thought was to use waxed cardboard for "forms" and aerosol foam insulation for the dam. Scott said he was going to experiment with this idea, never heard anything more though. The whine on mine is less in the Recric position on the climate control.

 

[scotty1]

I never got to this as I have had a pile of other things ahead of it.

I did try a 'dam' in the cowl made of ABS plastic, but it never helped a bit.

On the site it does state that the Scotty II will change the sound in the cab and goes on to mention that some individuals are more sensitive to the sound then others.

 

[rweis]

Not questioning that there would be increased sound at all. That is clearly stated on the web site.



Exactely where does the intake vent suck? It must be toward the center from the windshield corner but where?



Just trying to see what the choices are.



One approach so far: I ordered a set of ear plugs that block frequencies out of the normal human speech range and specifically designed to cut out high pitch industrial environment sounds.



I can do ear plugs just like we did in the USAF, and actually made by the same company and probably is just the civilian version.



I'll let you know how it turns out.



Bob Weis

 

[scotty1]

The vents take the air from a large inlet in the center. I placed the ABS divider to the right of that if you are in the cab. I sealed it with silicone and it was also a double wall piece shaped for the cowl and made of 1/4" ABS. Total thickness of the divider was one inch. Never made a difference.

 

[satmike]

I made a dam out of balsa wood and fiberglassed over it and silaconed it in. I also put dynamat and GSI foam in the holes where the vent gets air from and it actually helped quite a bit. I have much less whine now

 

[JBlock]

Scotty1

Scotty



Great Product, You might want to swing by and stop at a Local Heating and air conditioning shop and check out the Acoustical lining for Fan Plenum and ducts.



I work in the insulation trade some 15 years ago and it is effective, I lined my return air ducts to the central air condition in the house and quiet down fan noise coming from the basement a lot. Since your dealing with High frequency noise, there a good chance you can find something that will absorb the wine off the turbo.



See my other post above for some contacts, if you want to discuss it. I know, it can be done. I work oversea and just have not had the time.



JB

 

[rweis]

Totally agree the Scotty II is a GREAT Product. Very provable results with EGT gauges. Does its job well!



One thing that might make a difference is the kind of turbo we each have. Mine is a KSB1B.



My first approach is high frequency ear plugs ordered today ($8. 90 includes shipping).



My second approach is going to be to address the sound waves comming from the end of the air filter cone. The sound waves from the turbo have to come out there and my reasoning is if they hit sound absorbing material before they hit anything else it should absorbe most of them.



Therefore I am going to concentrate on the air intake area where the sound should hit first.



The ear plugs should work until I experiment with "catching" the sound comming out of the cone shroud. I am going to try to not let the sound touch any metal, so it is not transmitted mechanically rather than accoustically.



Should be an interesting experiment path.



ps:Scotty



Was there ever an idea to line the fiberglass shroud with anything for sound suppression? Do you think it may disrupt the air flow too much? Something like a canvas lining?



What about a prefilter sock over the AFE? would that have any sound deadening effect?



thanks



Bob Weis

 

[JBlock]

INlet silencer

A while back there was a product being kick around called an inlet straighten vanes, the idea was to increase boost. As I recall if also seem to cut the noise.

 

[rubberneck]

I also have a B1 turbo. These things whistle pretty loud as is. I put the scotty2 in and it lasted exactly 2 days, just couldn't take the noise. Now it is sitting on the workbench. If you guys come up with a solution let me know.

 

[rweis]

Did you put the B1 on the shelf, or the Scotty II on the shelf?



My ear plugs have not come yet. They are designed to cut out pitches above the human voice range. I think they will be very effective against the compressor blades sound waves.



I keep thinking about the way sound waves propagate. They are reflective, they are absorbative, they are directable.



I have to see how to take the air grid off the windshield. Then I think build a dam concept has merit, but a dam to minimize the waves getting to the air intakes and another one at the air intakes to make sure they take on air from straight ahead.



I'm playing with an idea in my mind of puting a 90* PVC elbow in at the Scotty II air intake channel pointing toward the outside so the waves will be directed away from the passenger compartment.



Not sure what effect it will have on the air in, but it will be better than sealing the firewall back up and making it draw from the side fender opening.



I am also waiting on Scotty1 to see if they ever looked at puting a fabric liner in the fiberglass shroud.



Maybe a fabric liner and a aFe prefilter would do the trick.



I have some RV roof patch which is a 1/16" thick rubber with a strong adhesive backing. Comes in rolls 4" wide. Waterproof. Might make a good sound deadener for the air intake channel. Just line the whole thing. Maybe liner the Scotty II AND the air intake channel.



Lots of ideas, have to have the time to test them. This is nothing more than sound management and I just know there is an answer. My B1 and Scotty II stay, the sound waves don't!



My concern with my wife is she only is in the truck when we go camping. The boost will be higher with the load of the 5er, the compressor supersonic shockwave gets louder and higher pitch as the boost goes up, not a conducive combination to good maritial relations, lol.



How is the B1 with the standard air box? if that is the combination you are using.



Bob Weis

 

[RustyJC]

Here's a Thought

Guys,



Here's something to mull over in your quests to quiet the turbo noise. The stock rubber inlet elbow that attaches to the turbo violates one of the basic industrial engine manufacturer's application rules that's been around for 50 years. Our turbocharged engines require one of the following:



1. Intake piping must have a straight run that's a minimum of 5 pipe diameters long leading into the turbocharger. As an example, for a 3. 5" inlet, that would be 17. 5" of straight pipe required.



2. If that isn't possible, a properly designed set of turning vanes are required in the bend closest to the turbocharger inlet.



I'll guarantee you that the stock rubber inlet elbow is producing turbulent flow at the suction side of the turbo impeller. The impeller is trying to pump (compress) turbulent air - not good for efficiency or noise.



Like I said - just something you might want to consider.



Rusty

 

[rweis]

Interesting,



I wonder if you used a smooth pipe like a 3 1/2 " (if the compressor inlet is 3 1/2", I have no idea, haven't measured it) exhaust pipe bent to a specific bend instead of the corregated rubber to get the air in. 17. 5" straight pipe would be kind of hard to fit in there with a filter I would think.



The exhaust pipe bender folks bend the 4" to go over the rear axle and I bet the bend radius is not much different to get it around to the air box or Scotty II.



Rusty, what do you think? You have more knowledge on this than I do, I'm guessing.



On high perf aircraft we did have vanes to guide the air into the compressor inlets properly.



Bob

 

[RustyJC]

Bob,



It's the 180* bend right at the turbo inlet that's the primary problem - pipe smoothness really wouldn't make that much difference as long as that blasted bend is present. I've eyeballed this on my truck, and I don't know if you could run the inlet piping out under the passenger side battery box or not before making the 180* bend (a bad thing, but probably necessary) and coming back to the filter.



Assuming the inlet piping must conform to the stock geometry, if I had the time and welding equipment, I might play with some exhaust piping by having it bent, then splitting it open longitudinally and fabricating and welding in some turning vanes before welding the halves back together. Might be a good "cottage industry" project for someone.



Rusty

 

[rweis]

Fix the problem, not bandaid the problem. Better approach!



What to do in the mean time though?, especially for us that don't have serious machanical ability. Earplugs are cheap, lol.



Bob

 

[RustyJC]

Either earplugs or don't penetrate the firewall, I guess. That's why I'm still running the BHAF on mine. Not the optimum solution, but since we tow a large 5th wheel, listening to the whistle and whine for days on end is not an acceptable solution for us, either.



Edit: By the way, cleaning up the inlet airflow would likely help, not totally eliminate, the noise problem. Unfortunately, centrifugal compressors generate high frequency noise even under the best of circumstances. The nature of the beast!



Rusty

 

[JBlock]

Snorkel

When I was in Austrilia everone ran snorkels that ran alond side the A pillar.



COuld someone adapt this to the scotty,



JB

 

[rweis]

I went down to my local RV dealer and got a roll of rubber roof tape. 9" wide 54" long and EXTREMELY sticky adhesive on the backing. I am going to line the inside and outside of the Scotty II, and the air inlet area by the hood with this rubber tape to see if I can deaden some of the sound waves, or absorbe some portion of them.



Second action will be to put in a rubber 90* elbow in the cowl opening pointing to the outside side, side of the air inlet area to direct the sound waves away from the cab and the fresh air inlet area.



Anyone know how to take the air inlet plastic covering off? I will dive into the T. O. at home, but could use some advice if anyone has done that.



Will let you know how it goes.



I do not have a db meter, just SOP expermentation, and a wife.



Bob Weis

 

[satmike]

The plastic air inlet is easy. There are 5 plastic torx type nuts, screw them out. Windshield wipers next, lift wipers off windsheild. There is a little lock pin use a screwdriver to pull it up and the wipers will stay about 3" off the windsheild then wiggle them a little and they will come right off, Lift the plastic piece a couple of inches and take off washer tube at the joint and lift the piece out and that's it

Good luck Mike

PS My dam and dynamat and foam do really work pretty good. I wish I would have taken a picture when it was apart, I didn't oh well