Intake Resonance

[Will L.]

It was all based on engine intake/head design. Working at the fuel company we tested the tornados. My wifes main ride at the time was a Chrysler LHS. I put a tornado in that as part of the multi car testing and it actually dynoed up a few ponies (10 ish maybe) and got 1 (maybe 2) mpg better. Been too many years to remember the details and I try not to remember many Chryslers in my past...
The tornado actually did worse then stock in the GM vortex engines. Turns out the tornado created a similar vortex as their head and intake system! But it went the wrong way and cancelled out! We tried putting it in the other way to work with it and found GM maxed all gains in that area. Zero effect on stock 6.5 - Oh, the gm tbi pre vortex- it helped those something like 0.75 mpg hiway. Maybe 5 ponies or something.
I never tested the screened intakes.
We even had to test the magnets on fuel lines! Haha.

Seriously though and back on track,
So maybe painting with something like rhino lining’s new low texture stuff. It stops a lot of sound and would stop under hood heat from soaking in from the outside. If you form a good sound barrier on the outside of the intake system, then it’s just fighting the sound in the air.

 

[94DieselSub]

DEI self-adhesive heat reflective multilayered compsite damping sheet material at summit racing/jegs. Several members (maybe it was on that "place" forum) have reported good results with it even on their water/air CAC's.

There is also automotive/heat rated, water based spray-on sound dampening goo (lizardskin sound control) sold by the above outfits. Autosound installers use it.

 

[Husker6.5]

There's this. Sound deadening and heat reflective from the original manufacturer of automotive panel adhesive sound deadening products, Dynamat.

Dynamat.com | The Hoodliner for Automotive and Restoration

The Hoodliner is an under-the-hood acoustic foam effective at reducing the heat and noise from your engine, and protecting your vehicle’s finish.

www.dynamat.com

 

[schiker]

When I look at some sound-absorbing foam it's pyramid-shaped like an egg-crate.

I wonder if building a little deeper floor plenum and or airbox and have a pyramid-shaped mesh or grate in the bottom to help absorb the air and sound pulses and under it put a sound-absorbing material or paint like mentioned above?????

There are some interesting you tube videos of quieting generators by angling plywood to deflect sound into grass or ground. I think directing sound in better directions might be beneficial. I guess it is some of the reasons why most new cars have all that plastic cowling on top helps deflect some sound. A tiny bit of sound suppression might have been some added benefit of the 6.5 cover engine cowl probably most of us took off. Might could line or cover one of those with a good sound absorber to help.

As a side note I built a table over my air compressor and stacked a moving blanket on it and draped it over the side like a table cloth and it reduced air compressor noise in the shop a little. It's relatively cheap and gives me another shelf. Its easy to move away and service the air compressor.

 

[Husker6.5]

We would sandbag our small (5kW size) generators in the Army with a wall around them about 6" away and twice as high as the generator. Did a great job of killing the noise from them AND kept some idiot from tripping over them, too!

 

[Twisted Steel Performance]

My dually must be broken, I don't notice any annoying resonances unless the mother inlaw is talking...

 

[Husker6.5]

Installing a Flomaster Delta Flo muffler with a 3" inlet/outlet between the turbo and the intake would effectively kill any resonant frequencies without really affecting the CFM flow of the intake. It would look goofy as all hell under the hood and there are the fitment issues, which could be mitigated by using the shortest body muffler they make.

The Delta Flo works by internally reflecting the sound waves off of angled baffles in such a way that the sound waves cancel each other out while allowing the exhaust to flow through unimpeded.

 

[Twisted Steel Performance]

Here is a very good write up on how to eliminate drone and such, they talk about the exhaust side but it would directly transfer to the intake, GM knew this and did this with that tube most remove from the intake plumbing...

 

[Twisted Steel Performance]

In fact, my intake tube is long gone, I have looked for a replacement but haven't found one yet, if anyone has one I'd be interested in it....

 

[Husker6.5]

In fact, my intake tube is long gone, I have looked for a replacement but haven't found one yet, if anyone has one I'd be interested in it....

You mean that plastic closed tube that comes off of the intake elbow pre-turbo and juts over between the alternator and radiator on the K-47 airbox equipped motors?

 

[Twisted Steel Performance]

yes

 

[schiker]

I like how he does say its impossible to predetermine what will drone and what won't.

It obviously works per all the comments but what sorta bothers me about the math is each cylinder is at a different phase in time (something like you can't connect 2 non-inverter generators together) so the math seems like a bigger educated guess than implied. I guess you get the avg frequency of all the cylinders and that is what matters?

I would think some of it comes from No. x cylinder pulse sound waves collides with No. Y cylinder or maybe W cylinder on the rebound from end of exhaust manifold that creates a new resonance????? Then when you change the mass of air through engine you get more turbulence in manifolds and phase timing changes such that different sounds resonate????? Where now cylinders A,B&C resonate. But what matters is the overall RPM driving frequency?

 

[Quadstar Tuning LLC]

So, 4.10's at 75 - 80 mph. With OE tires that is 2,500 - 2,700 RPM's. Little wonder it is loud

Are the 4.10's for towing? Or bragging rights for off-the-line starts?

If the latter, 3.42's and a NV4500 will net about the same jump off the line. Bonus is that this combination will make the beast a LOT more quiet at the target cruising speeds

#1 : 2700 RPM isn't scary
#2 : We abhor the NV4500

One additional thought. Given that an open air box is under the hood, my vote is to first find a K47 box and see if that drops the sound enough. Make sure that the box's intake port has tubing to the fender, as without it IAT's above 200* F are likely when towing. (Don't ask how I know).

If the K47 works good enough, then you are past the brush fire and can decide whether any additional work is worth the effort.

We can't run the K47 with 4" inlet turbos. Even if you adapt it, it can't flow enough. We can, however, adapt the resonator tube into our 4" intakes and see how it goes.

 

[Quadstar Tuning LLC]

My dually must be broken, I don't notice any annoying resonances unless the mother inlaw is talking...

Seems like there's just as many people that say they have the problem as there are that say they don't. Honestly don't know the correlation or if some people's ears just don't pick up the frequency? Hard to say.

 

[Twisted Steel Performance]

Seems like there's just as many people that say they have the problem as there are that say they don't. Honestly don't know the correlation or if some people's ears just don't pick up the frequency? Hard to say.

Are you sure it's intake and not the exhaust drone you hear ?? I guess you are or you wouldn't be working towards the intake LOL....

 

[Rockabillyrat]

A drone is a frequency of pressure pulses. What if it has something to do with the stock 6.5 turbo exhaust system. It's the only v8 diesel with a side mount open system. The length between each bank to the turbo is different. And on top of that the drivers bank runs into the rear two cylinders on the passenger side. So the frequency of the pressure pulses reaching the turbo is "off balanced" for a lack of a better term. Turbo speed will actually fluctuate a 1k rpm or so as these pulses run through the turbine housing. What ever happens on the exhaust side will transfer to the compressor side. Air leaving the turbo and entering the intake will have a similar "off balanced" pulse because of the changes in turbo speed. Now I would think the Intake would create it's own pressure pulse due to the opening of the intake valves. But that will be a very balanced/even event unlike the off balanced exhaust pulse. Maybe these two pressure pulses create a unwanted drone when then come in contact?

 

[FellowTraveler]

@ak diesel driver,

Yep, me too!

But ironically, unlike the million variation of the bent sheetmetal "tornado" inserts seen on ebay. The screened gaskets at least had a shred of science behind them.

On a carbureted engines, intake manifold fuel dropout (fuel separation) did occur. It was detrimental to emissions and fuel economy. The screened intake gaskets would (in theory) brake down the precipitated large fuel droplets into a finer mist.

Also dealing with "wet runners" back then.

 

[FellowTraveler]

A drone is a frequency of pressure pulses. What if it has something to do with the stock 6.5 turbo exhaust system. It's the only v8 diesel with a side mount open system. The length between each bank to the turbo is different. And on top of that the drivers bank runs into the rear two cylinders on the passenger side. So the frequency of the pressure pulses reaching the turbo is "off balanced" for a lack of a better term. Turbo speed will actually fluctuate a 1k rpm or so as these pulses run through the turbine housing. What ever happens on the exhaust side will transfer to the compressor side. Air leaving the turbo and entering the intake will have a similar "off balanced" pulse because of the changes in turbo speed. Now I would think the Intake would create it's own pressure pulse due to the opening of the intake valves. But that will be a very balanced/even event unlike the off balanced exhaust pulse. Maybe these two pressure pulses create a unwanted drone when then come in contact?
View attachment 59119

Exacerbated by changing out to a larger x-over pipe when the rest well "just sux."

 

[Rockabillyrat]

I forgot to mention. I attended a NVH class a few years back. My local trainer showed us a app for your phone that is a great tool for diagnostics. You enter the vehicle information and drive the vehicle for 5 minutes. It will record any noise/vibrate frequency occurring in the vehicle. Mechanical components will have a certain frequency they will produce. Example: A 8 cylinder engine will fire 4 times per revolution. Or a CV axle has 3 ball bearing so it will have it's own frequency per revolution. The app can pick this up and is very accurate in telling you what part of the vehicle is responsible for the noise/vibration. It was very accurate according to the case studies he presented us. Might be worth a try.

 

[Quadstar Tuning LLC]

Exacerbated by changing out to a larger x-over pipe when the rest well "just sux."

One simple thing we haven't tried yet would be putting a stock double wall pipe x-over back on