Exhaust Controller Valve

In order to quiet down my new exhaust, I picked this up off eBay, almost ordered the 2.25″ one, so make sure you get the right size. The valve opens or closes at the touch of a button. You can have it full open, or full closed, or anywhere in between.

I did some tests with a Radioshack Decibel Meter (model 33-2055, the digital one). I compared the KO Racing T1 Exhaust with the Exhaust Valve Controller with and without the silencer, to a Greddy Power Extreme (known for being a pretty quiet exhaust) that has been modified with a block off plate where the drivers side muffler normally sits.

Here is the data from the test.

What I learned was that the valve controller dropped the noise about 2-3db on average throughout the rev range. One thing that interested me was that peak noise was at different RPM for different exhausts (for the T1 was about 5,000rpm, and 4,500 for the Greddy), and that levels drop of significantly by 7,000rpm. It didn’t matter which way the exhaust was setup, the decibel levels always dropped to 84 by 7,000rpm. What is happening is the exhaust note gets lower after 5,500rpm, and the engine noise crosses over while the exhaust noise is dropping. So by 7,000rpm you are only hearing the engine noise, no matter which exhaust was on the car. I never noticed that before, but now when I pay attention, that’s exactly what happens.

This fits in one of the switch holes next to the fog lights perfectly.


Fully closed in this pic, plenty of exhaust can still get by the sides of the valve, but the noise level is way lower. Power is down too, but just push the button, and power is back.

Closed here, but you can’t tell because it’s mostly all carbon black now.

The following was grabbed somewhere off the web. -Pat

Decibel (Loudness) Comparison Chart

Here are some interesting numbers, collected from a variety of sources, that help one to understand the volume levels of various sources and how they can affect our hearing.

Environmental Noise

Weakest sound heard 0dB
Normal conversation (3-5′) 60-70dB
Telephone dial tone 80dB
City Traffic (inside car) 85dB
Train whistle at 500′ 90dB
Subway train at 200′ 95dB
Level at which sustained exposure may result in hearing loss 90 – 95dB
Power mower 107dB
Power saw 110dB
Pain begins 125dB
Pneumatic riveter at 4′ 125dB
Jet engine at 100′ 140dB
Death of hearing tissue 180dB
Loudest sound possible 194dB
OSHA Daily Permissible Noise Level Exposure
Hours per day Sound level
8 90dB
6 92dB
4 95dB
3 97dB
2 100dB
1.5 102dB
1 105dB
.5 110dB
.25 or less 115dB
Perceptions of Increases in Decibel Level
Imperceptible Change 1dB
 Barely Perceptible Change 3dB
Clearly Noticeable Change 5dB
About Twice as Loud 10dB
About Four Times as Loud 20dB
Sound Levels of Music
Normal piano practice 60 -70dB
Fortissimo Singer, 3′ 70dB
Chamber music, small auditorium 75 – 85dB
Piano Fortissimo 84 – 103dB
Violin 82 – 92dB
Cello 85 -111dB
Oboe 95-112dB
Flute 92 -103dB
Piccolo 90 -106dB
Clarinet 85 – 114dB
French horn 90 – 106dB
Trombone 85 – 114dB
Tympani & bass drum 106dB
Walkman on 5/10 94dB
Symphonic music peak 120 – 137dB
Amplifier rock, 4-6′ 120dB
Rock music peak 150dB


  • One-third of the total power of a 75-piece orchestra comes from the bass drum.
  • High frequency sounds of 2-4,000 Hz are the most damaging. The uppermost octave of the piccolo is 2,048-4,096 Hz.
  • Aging causes gradual hearing loss, mostly in the high frequencies.
  • Speech reception is not seriously impaired until there is about 30 dB loss; by that time severe damage may have occurred.
  • Hypertension and various psychological difficulties can be related to noise exposure.
  • The incidence of hearing loss in classical musicians has been estimated at 4-43%, in rock musicians 13-30%.

Statistics for the Decibel (Loudness) Comparison Chart were taken from a study by Marshall Chasin , M.Sc., Aud(C), FAAA, Centre for Human Performance & Health, Ontario, Canada. There were some conflicting readings and, in many cases, authors did not specify at what distance the readings were taken or what the musician was actually playing. In general, when there were several readings, the higher one was chosen.

This documentation in no way replaces the Toyota MR2 Repair Manuals. The purpose of this content is only to provide supplementary information to fellow MR2 enthusiasts. Midship Runabout and its contributing authors will not be held responsible for any injury or damages that may occur as the result of practicing any of the methods or procedures described within this website. Article and photo submissions are property of the contributing author.

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