OEM Exhaust flaps

[RamFan]

Yes I was just under the truck hitting on the exhaust and I’m sure the rattle I hear at idle is those flaps.

Chris

 

[MurphNH]

Yes I was just under the truck hitting on the exhaust and I’m sure the rattle I hear at idle is those flaps.

Chris

You take a picture that you can post?

 

[tbolts10]

Yes I was just under the truck hitting on the exhaust and I’m sure the rattle I hear at idle is those flaps.

Chris

Yep I hear them rattle too.

 

[RamFan]

You take a picture that you can post?

I can tomorrow sure

 

[BilletRHO]

What's the function of these flaps? There's no exhaust mode changes right? You can tell I don't have my truck yet.

 

[MurphNH]

Not sure on the rho but on the GMC they were to try and stop the helicopter sound when it dropped cylinders

 

[Cautionary Tale]

What's the function of these flaps? There's no exhaust mode changes right? You can tell I don't have my truck yet.

I haven't made it to exhaust day on mine yet (a ways off) but is it possible the flaps have serve a back pressure or some other pressure function? I've not had flaps in an exhaust on anything before, that I'm aware of so my mind goes to manufacturing not spending money on extra fab for zero purpose.

@Dcchris311 That's some PURDY welding there! Excited to see the finish and hear it roar. Any plans to take for testing after to put some science down on your work of art?

 

[Eighty]

Perhaps those flaps serve to increase back pressure when the turbos need extra power?

 

[tbolts10]

They are solely there to reduce noise when the engine is at lower operating speeds. They open variably according to flow - higher flow ie WOT, they are wide open. Low flow ie driving on the highway they are closed for noise reduction.

 

[BilletRHO]

I haven't made it to exhaust day on mine yet (a ways off) but is it possible the flaps have serve a back pressure or some other pressure function? I've not had flaps in an exhaust on anything before, that I'm aware of so my mind goes to manufacturing not spending money on extra fab for zero purpose.

@Dcchris311 That's some PURDY welding there! Excited to see the finish and hear it roar. Any plans to take for testing after to put some science down on your work of art?

I used to have an 05 Saleen mustang that came with butterfly valves in the exhaust. After a few thousand miles they would begin to rattle so they had a recall to replace the muffler without the flap.

 

[Dcchris311]

They are solely there to reduce noise when the engine is at lower operating speeds. They open variably according to flow - higher flow ie WOT, they are wide open. Low flow ie driving on the highway they are closed for noise reduction.

100% on the money.

100% on the money.

Perhaps those flaps serve to increase back pressure when the turbos need extra power?

No, the less back pressure the better the turbos perform. I actually hear my turbos spool up a bit quicker and a couple hundred rpms lower now. There's an article behind the myth of back pressure and turbo engines. WHILE it's not about flaps, it more about exhaust diameter. They dyno'd a Supra with a 3", 4" and 5" exhaust and the 5" made the most power because it was less restrictive/back pressure.

 

[Silver RHO]

100% on the money.

100% on the money.

No, the less back pressure the better the turbos perform. I actually hear my turbos spool up a bit quicker and a couple hundred rpms lower now. There's an article behind the myth of back pressure and turbo engines. WHILE it's not about flaps, it more about exhaust diameter. They dyno'd a Supra with a 3", 4" and 5" exhaust and the 5" made the most power because it was less restrictive/back pressure.

Are you going to do a video of your exhaust sound? Excited to hear what that sounds like.

 

[Dcchris311]

Are you going to do a video of your exhaust sound? Excited to hear what that sounds like.

Yeah, ill make a video once I get off work. I moved my truck to the top floor of our parking structure so that it gets a nice cold start.

 

[Dcchris311]

Here's a small clip of the exhaust. I messed up the recording—I didn’t realize the second wireless mic was also connected, so you’ll hear some interior sound mixed in. I also didn’t account for the tailgate being aluminum, so I couldn’t attach the magnetic mic, and the placement ended up a bit too close to the exhaust. I’ll record another clip either tonight or in the morning.

I’m also considering a different setup: running a Y-pipe into a 4" muffled expansion chamber, then back into a 3" Y-pipe to connect to the OEM system.

 

[RHOfan]

Here's a small clip of the exhaust. I messed up the recording—I didn’t realize the second wireless mic was also connected, so you’ll hear some interior sound mixed in. I also didn’t account for the tailgate being aluminum, so I couldn’t attach the magnetic mic, and the placement ended up a bit too close to the exhaust. I’ll record another clip either tonight or in the morning.

I’m also considering a different setup: running a Y-pipe into a 4" muffled expansion chamber, then back into a 3" Y-pipe to connect to the OEM system.

Definitely added some “growl”.

Looking forward to hearing your other set-ups, if you go that route.

 

[tbolts10]

Here's a small clip of the exhaust. I messed up the recording—I didn’t realize the second wireless mic was also connected, so you’ll hear some interior sound mixed in. I also didn’t account for the tailgate being aluminum, so I couldn’t attach the magnetic mic, and the placement ended up a bit too close to the exhaust. I’ll record another clip either tonight or in the morning.

I’m also considering a different setup: running a Y-pipe into a 4" muffled expansion chamber, then back into a 3" Y-pipe to connect to the OEM system.

Sounds damn good to me. What are you hoping to accomplish with the Y pipe setup?

 

[Dcchris311]

I've made another video with the mics placed in a better location. You still get a bit of road noise but that's unavoidable while driving. This is still my original setup. Please let me know what you guys think about it. The is an external mic set up, no interior sound clips were made.

 

[Ctech-Review]

Does anyone know the point of the flaps? I have a metallic sound coming from my exhause and i think i have pin pointed it to these being somewhat loose and rattling

This valve is a passive valve vs an active valve like we see on the Raptor. Point of this is to reduce sound at idle or under partial throttle. This works in conjunction with the RFP patches that are welded onto the exhaust tail pipes.

 

[tbolts10]

I've made another video with the mics placed in a better location. You still get a bit of road noise but that's unavoidable while driving. This is still my original setup. Please let me know what you guys think about it. The is an external mic set up, no interior sound clips were made.

I think it sounds great. How's the volume inside while cruising? Any drone?

 

[sheepoppa]

I think it sounds great. How's the volume inside while cruising? Any drone?

damn, that sounds really good