Exhaust With High Flow PSP Downpipes

[PinnacleBuilt]

if you're trying to eliminate drone you need to attenuate that frequency range. Have you use a spectrum analyzer to identify the hertz of the drone?

That's a great starting point.

Understanding how loud and at what frequencies then you can address that specifically via a Helmholtz resonator or a j-pipe.

The downpipes with the oe exhaust have almost zero drone... but the cold starts are loud and part throttle inputs are loud.

I added resonators to calm down the cold starts and db's above 3k rpm.

Once you have a snap shot of what the magnitude of the frequency range while you’re experiencing drone you can build a resonator to attenuate those peaks

The RED is the oe exhaust with psp downpipes.
Peak at cruising is 73 db’s at 52hz. oe is 67db's for reference.

That is relatively quiet and hard to perceive over road and tire noise.

You need this same snapshot to solve your drone.

 

[PinnacleBuilt]

I haven’t but I will start there if my next iteration doesn’t get me the desired results. What’s the size of the resonators you used ?

download a db meter or spectrum analyzer on your phone, lots of free versions out there. Then go cruise at your drone RPM and get a snapshot. I can help you design a resonator to fix your drone.

My vehicle doesn't have drone but didn't before resonators either... The oe valves are there for drone no other reason. Once you remove the valves you are chasing drone.

Mufflers in general attenuate all frequencies but do a better job on the higher end of the range. Sub 100hz you're going to have to have chambered mufflers to get rid of it and that is no bueno for flow.

I've run 36" long 7" diameter straight through mufflers trying to eliminate drone... Doesn't work.. I've been deep down this road before on multiple platforms.

"We" really need to understand how loud your drone is to address it properly.

 

[PinnacleBuilt]

View attachment 32990
Once you have a snap shot of what the magnitude of the frequency range while you’re experiencing drone you can build a resonator to attenuate those peaks

The RED is the oe exhaust with psp downpipes.
Peak at cruising is 73 db’s at 52hz. oe is 67db's for reference.

That is relatively quiet and hard to perceive over road and tire noise.

You need this same snapshot to solve your drone.

On my vehicle the circled area is what I've been "chasing"

That is under throttle and an almost 90db peak at 175-ish hz is what I would describe as unpleasant.

Soooo I added resonators to tame that down.
with the addition of 2 pairs of resonators the vehicle is now quieter than completely stock at cruising hwy speeds 70-ish mph. It also pulled down the nasty peak at 175hz but the 225hz is still there just lower magnitude. You can see how some frequencies are not impacted at all under throttle ie 120-130hz, zero impact.. 50-70hz got louder under throttle...

 

[rpr]

The oe valves are there for drone no other reason. Once you remove the valves you are chasing drone.

This is all very interesting. Can you clarify why/how the OE valves address drone? I can’t wrap my head around the science behind this.

I can see how the OE valves might contribute to the bwaaaps (or wet farts as some call them) on gear shifts as they’re likely momentarily closing and then fully opening during gear shifts. Even if that’s not the intended purpose of the OE valves, it (arguably) sounds like that’s what’s happening.

I can say that with my MRT Trail Rated exhaust and my OE valves removed I don’t get any highway drone at all. There’s a very slight drone in the low 2K range with mild acceleration which was annoying in the 1st 1K miles or so, but even that has diminished.

Thanks for the detailed posts, very informative.

 

[PinnacleBuilt]

This is all very interesting. Can you clarify why/how the OE valves address drone? I can’t wrap my head around the science behind this.

I can see how the OE valves might contribute to the bwaaaps (or wet farts as some call them) on gear shifts as they’re likely momentarily closing and then fully opening during gear shifts. Even if that’s not the intended purpose of the OE valves, it (arguably) sounds like that’s what’s happening.

I can say that with my MRT Trail Rated exhaust and my OE valves removed I don’t get any highway drone at all. There’s a very slight drone in the low 2K range with mild acceleration which was annoying in the 1st 1K miles or so, but even that has diminished.

Thanks for the detailed posts, very informative.

The bigger the hole, the louder she goes!

wet fart sounds are from timing and fuel. retard the timing and add fuel during shifts. viola burbles..

Side note: this is why they are melting cats.

 

[Jramos44]

download a db meter or spectrum analyzer on your phone, lots of free versions out there. Then go cruise at your drone RPM and get a snapshot. I can help you design a resonator to fix your drone.

My vehicle doesn't have drone but didn't before resonators either... The oe valves are there for drone no other reason. Once you remove the valves you are chasing drone.

Mufflers in general attenuate all frequencies but do a better job on the higher end of the range. Sub 100hz you're going to have to have chambered mufflers to get rid of it and that is no bueno for flow.

I've run 36" long 7" diameter straight through mufflers trying to eliminate drone... Doesn't work.. I've been deep down this road before on multiple platforms.

"We" really need to understand how loud your drone is to address it properly.

Can you tell from the screenshot where the peaks of the frequencies are from what I could tell while driving it’s all lower frequencies.

 

[Jramos44]

The bigger the hole, the louder she goes!

wet fart sounds are from timing and fuel. retard the timing and add fuel during shifts. viola burbles..

Side note: this is why they are melting cats.

Do you think these would work ?

https://www.goapr.com/products/exhaust_systems/universal_components/mufflers_and_resonators/parts/MUH0015

 

[PinnacleBuilt]

Can you tell from the screenshot where the peaks of the frequencies are from what I could tell while driving it’s all lower frequencies.

Can you change the settings so its not in large blocks like that.

Also what us the db on the left

 

[Jramos44]

Can you change the settings so its not in large blocks like that.

Also what us the db on the left

I don’t like this app , which do you use ? I’ll download it and do another run.

 

[PinnacleBuilt]

This is what I use

Settings

 

[Jramos44]

Can you change the settings so its not in large blocks like that.

Also what us the db on the left

I deleted the app so I don’t have the last files but this is a better picture.

 

[Jramos44]

This is what I use
View attachment 33014
Settings
View attachment 33015

I narrowed it down the frequency is definitely low 100s 100-120 but mostly around 110 on the freeway DB is 81

 

[PinnacleBuilt]

In

I narrowed it down the frequency is definitely low 100s 100-120 but mostly around 110 on the freeway DB is 81

that’s a nasty peak

A helmholtz resonator will dial that way down

I would put them back by the spare tire because of packaging and exhaust gas temperatures are much lower effecting the speed of sound.

You need a 4” x 10.75” pipe / chamber capped off on one end and a 2” elbow on the other that connects to the tail pipe section that has a 5” CLR

 

[Jramos44]

In

that’s a nasty peak

A helmholtz resonator will dial that way down

I would put them back by the spare tire because of packaging and exhaust gas temperatures are much lower effecting the speed of sound.

You need a 4” x 10.75” pipe / chamber capped off on one end and a 2” elbow on the other that connects to the tail pipe section that has a 5” CLR
View attachment 33029

Can you make them for me ? Or know anyone who can ?

 

[PinnacleBuilt]

Can you make them for me ? Or know anyone who can ?

Should be super easy to fab up for an exhaust or fab shop
Flowmaster for reference

 

[Jramos44]

Should be super easy to fab up for an exhaust or fab shop
Flowmaster for reference
View attachment 33045

10-4 thanks for the help bro, if you ever decide to make a cat back to go with the downpipes put me on the list !

 

[Jramos44]

If anyone in California wants a custom MBRP exhaust, let me know. I picked up and installed the stock exhaust today. It’s very nice to have quiet. Cold starts again.

 

[mghtymous21]

If anyone in California wants a custom MBRP exhaust, let me know. I picked up and installed the stock exhaust today. It’s very nice to have quiet. Cold starts again.

You sir are a better neighbor than me. I back the truck up to the garage door just to try and make the cold starts louder

 

[Jramos44]

You sir are a better neighbor than me. I back the truck up to the garage door just to try and make the cold starts louder

lol that’s hilarious my neighbors are far and I don’t care much about them. The issue is I have a 5 and 2 year old and I would prefer not to wake them early and start my wife’s day at 5am. It would ruin my day when I get home hahah.

 

[mghtymous21]

lol that’s hilarious my neighbors are far and I don’t care much about them. The issue is I have a 5 and 2 year old and I would prefer not to wake them early and start my wife’s day at 5am. It would ruin my day when I get home hahah.

I have 2 five year olds and a 2 year old. Fortunately for me they all sleep like rocks. I wish my ex wife was here. I'd love to wake her up every chance I got. She's a demon

But all my neighbors are pretty chill. Only have one that's a problem. His name is Lauren and he drives a Tesla. I'll let you do the math