A not-crazy-loud catback exhaust that keeps the OEM valve?

[suicidaleggroll]

Keep in mind there are two HKS exhausts, the dual muffler and the super turbo. I have the super turbo, there is quite a large difference in sound with the valve open versus closed. Valve closed sounds similar to the stock exhaust in sport mode, with the valve open it's quite a bit louder. Not WTFRACECAR loud, but a good increase, I'm happy with it. There's a small amount of drone at 2k RPM in sport mode, zero drone in normal.

https://www.hks-power.co.jp/en/product_db/muffler/db/21365
https://www.hks-power.co.jp/en/product_db/muffler/db/21559

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[decodeddiesel]

Keep in mind there are two HKS exhausts, the dual muffler and the super turbo. I have the super turbo, there is quite a large difference in sound with the valve open versus closed. Valve closed sounds similar to the stock exhaust in sport mode, with the valve open it's quite a bit louder. Not WTFRACECAR loud, but a good increase, I'm happy with it. There's a small amount of drone at 2k RPM in sport mode, zero drone in normal.

https://www.hks-power.co.jp/en/product_db/muffler/db/21365
https://www.hks-power.co.jp/en/product_db/muffler/db/21559

The twin muffler version is also significantly louder with the value open. I'm not sure why the OP refuses to believe that.

OP, it sounds like you've already made your decision.

 

[suicidaleggroll]

Okay riddle me this about the HKS setup because it's been brought up repeatedly - maybe I'm just looking at pictures and not seeing what's going on. It looks to me an awful lot like the piping is the exact same after the Y on both the valved and non-valved side.

Just because the left side muffler and the right side muffler look the same on the outside, that doesn't mean they're the same on the inside.

 

[Spart]

Keep in mind there are two HKS exhausts, the dual muffler and the super turbo. I have the super turbo, there is quite a large difference in sound with the valve open versus closed. Valve closed sounds similar to the stock exhaust in sport mode, with the valve open it's quite a bit louder. Not WTFRACECAR loud, but a good increase, I'm happy with it. There's a small amount of drone at 2k RPM in sport mode, zero drone in normal.

https://www.hks-power.co.jp/en/product_db/muffler/db/21365
https://www.hks-power.co.jp/en/product_db/muffler/db/21559

That is good intel, thank you.

 

[decodeddiesel]

Just because the left side muffler and the right side muffler look the same on the outside, that doesn't mean they're the same on the inside.

I'm really on the fence between the super turbo version and the twin muffler myself. The super turbo seems more difficult to source, and I've heard it a little quieter with the valve closed which is a good thing in my world. I've only heard the twin muffler version on a dyno IRL, and it was a gorgeous racket lol.

They both fit under the Versus Diffuser which is my main criteria.

 

[Spart]

The twin muffler version is also significantly louder with the value open. I'm not sure why the OP refuses to believe that.

OP, it sounds like you've already made your decision.

I just think we're not on the same wavelength when we use the word "significant."

Particularly in regards to the HKS dual muffler exhaust you're talking about, I can't ignore what I'm seeing and hearing in this video:




They show a decibel meter about two feet from the car and at a constant 3000 RPM in neutral, it's making ~90.8dBA with the valve closed and ~93.0dBA with it open. At 5000 RPM, it's making about 102.4dBA valve closed and ~108.1dBA valve open.

I'll ignore the peak measurements they make revving, because without a better decibel meter set to hold on peak, the numbers you see rolling around are useless.

That being said, ten decibels is what it takes for humans to perceive a doubling in sound. The differences I'm seeing here are 2.2dB and 5.7dB.

That to me doesn't sound "significant" the way I'm used to thinking about "significant" differences with valved exhaust.

 

[decodeddiesel]

I hope you understand that without specialized recording equipment it's difficult if not impossible to capture the actual sound of an exhaust in a video. The software in that camera no doubt clipped, filtered, compressed, and otherwise altered the actual sound of the exhaust to weigh it for human ears and speakers. I won't even get into the effects the speakers (or headphones) you're listening to the clip on will have on the actual sound.

As far as the sound meter, when you say 10dB is what it takes to "double" the intensity of sound you're literally talking about a sound that has a 100% greater sound pressure level. That's a HUGE increase. Decibels are a logarithmic base 10 scale, not a linear scale. A 5.7 dB increase is very significant and absolutely detectable to the human ear.

Keep in mind too that revving the car in neutral with no load on the engine is not a very accurate depiction of how the exhaust will sound in real life.

 

[Spart]

I hope you understand that without specialized recording equipment it's difficult if not impossible to capture the actual sound of an exhaust in a video. The software in that camera no doubt clipped, filtered, compressed, and otherwise altered the actual sound of the exhaust to weigh it for human ears and speakers. I won't even get into the effects the speakers (or headphones) you're listening to the clip on will have on the actual sound.

I understand all of that. I will call attention to Borla here, because they do (or did) a great job with their videos, clearly using a discrete recorder with a fixed gain. I wish all exhaust reviews were done this way, but people just don't understand how much work the ADC+software/firmware in their cameras is doing just to get recordings that don't all sound way too quiet or way too loud. It renders almost all of their work making the review useless. With the way Borla does/did them, it's easy to tell in the audio playback the differences in sound level, if not the absolute sound level. They haven't put out a video of their Supra exhaust unfortunately.

I have an audio recording of my old GT350's exhaust at full chat recorded with fixed gain and no clipping. It's exquisite on a good sound system.

As far as the sound meter, when you say 10dB is what it takes to "double" the intensity of sound you're literally talking about a sound that has a 100% greater sound pressure level. That's a HUGE increase. Decibels are a logarithmic base 10 scale, not a linear scale. A 5.7 dB increase is very significant and absolutely detectable to the human ear.

I didn't say a 10dB increase doubles the intensity of a sound.

A 10dB increase is actually ten times the sound. 3dB is approximately twice the sound.

What I said was, "ten decibels is what it takes for humans to perceive a doubling in sound."

I have done work in A/V production and sound system design, I'm pretty well versed in the concepts.

Let's talk in absolute terms: an exhaust for a Supra that only exhibits a 5.7dB difference between loud and quiet modes is either too loud for me on quiet mode, or not loud enough for me on loud mode. Fair?

 

[razorlab]

I'm really on the fence between the super turbo version and the twin muffler myself. The super turbo seems more difficult to source, and I've heard it a little quieter with the valve closed which is a good thing in my world. I've only heard the twin muffler version on a dyno IRL, and it was a gorgeous racket lol.

They both fit under the Versus Diffuser which is my main criteria.

Just be mindful of Lime Rock's sound restrictions.

 

[Tersine]

Have you looked at the FI Exhaust? They replace the stock downpipe, but it should give you a good idea of the valves open/closed.



Skip to 8:00 mins

 

[decodeddiesel]

Just be mindful of Lime Rock's sound restrictions.

That's literally my other criteria for exhaust selection. Must fit with Verus Diffuser, must meet LRP sound requirements.

That said, spending $2500 on an exhaust is not on my priority list.

 

[decodeddiesel]

I understand all of that. I will call attention to Borla here, because they do (or did) a great job with their videos, clearly using a discrete recorder with a fixed gain. I wish all exhaust reviews were done this way, but people just don't understand how much work the ADC+software/firmware in their cameras is doing just to get recordings that don't all sound way too quiet or way too loud. It renders almost all of their work making the review useless. With the way Borla does/did them, it's easy to tell in the audio playback the differences in sound level, if not the absolute sound level. They haven't put out a video of their Supra exhaust unfortunately.

I have an audio recording of my old GT350's exhaust at full chat recorded with fixed gain and no clipping. It's exquisite on a good sound system.



I didn't say a 10dB increase doubles the intensity of a sound.

A 10dB increase is actually ten times the sound. 3dB is approximately twice the sound.

What I said was, "ten decibels is what it takes for humans to perceive a doubling in sound."

I have done work in A/V production and sound system design, I'm pretty well versed in the concepts.

Let's talk in absolute terms: an exhaust for a Supra that only exhibits a 5.7dB difference between loud and quiet modes is either too loud for me on quiet mode, or not loud enough for me on loud mode. Fair?

If I insulted your intelligence I sincerely apologize. Clearly you know your stuff.

I am a mechanical engineer and I've worked on sound attenuation devices for supersonic gas flow.

Check out the Magnaflow. It might give you what you're looking for.

https://www.magnaflow.com/products/...od-series-cat-back-performance-exhaust-system

 

[Janice]

The manual gearbox is actually smaller than the auto, so one wouldn't think it's a clearance issue, but you're right in terms of them clearly stating it doesn't fit the MT. Bummer.

Is this an issue with all aftermarket exhaust on the MT?

 

[NitroYellowMKV]

They don't list this on their website: https://www.shsautosport.com/products/A90-A91-c140962772

Can't really find any info on it or pictures.

Not retail available on the site yet, but you can get it through me, shoot me a message I’ll send over a bunch of photos and videos I took of the install the other day. Honestly super happy with it, the full straight was fun but got old quick

 

[Decimari]

I’m biased towards the magnaflow Xmod cause I have it but it’s a good modular exhaust. You want it quieter? Put both mufflers on, you want a loud unmuffled side that opens when you’re in sport mode? You can do that, want it all straight pipe all the time? You can do that too. It has a JPIPE/heinholtz resonator that gets rid of drone, i haven’t driven in any other exhaust modded supra but the drone is minimal at highway speeds.

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