I hear a lot about penalty of vehicle height in Japan. How do you actually measure this?

The minimum ground clearance is the distance between the lowest part of the vehicle (such as a CAT, muffler shell, mid pipe, etc., but not accessories such as aero parts and mudguard) and ground surface. It is measured without any passenger in a vehicle. The allowable minimum ground clearance of the safety standard is 9cm, and all of HKS muffler series retain this 9cm clearance.
* The ground clearance is usually measured with the standard vehicle height. The vehicle height is lowered than the standard, the allowable minimum ground clearance may not be obtained.

Can I use inner silencer and still pass the safety standards?

HKS MUFFLERS passed noise regulation without using inner silencer.

How do you measure the proximity stationary noise level of exhaust?

Close noise of exhaust is measured in a certain condition of an engine at a certain RPM.

1. Set the sound measument device at a 0.5m from the exhaust tip of 45 degree.
2. The engine RPM for the measurement has to be 75% of what the engine can produce.
3. From the #2 situation, put the gas for 5 seconds with no pressure for RPM and release the pedal, and measure the sound while the RPM get to the idle RPM; the highest sound is the sound of the test result.

* This is the diagram of the tesing.

Set the muffler as shown here

For example, the max power of Lancer Evolution X is reached at 6,500rpm, so set the engine rpm to 4,875 which is the 75% of 6,500rpm.

Adjust the engine rpm to 4,875rpm, and start to measure the sound. After 5 seconds, take the foot off the accelerator, and finish measuring the sound when the engine rpm declined to idling.

Structure & Warranty

What's the difference between stock muffler and HKS muffler?

Stock mufflers are made not to have any problem and to have the efficient exhaust capability. HKS mufflers and pipe layout are designed to support the best performance of a car.
Also, the shell part of the stock vehicle is made to decrease the sound of exhaust gas, but HKS shell is designed for a cool and sporty sound.

What is the HKS warranty for the products?

HKS provides a warranty to the original purchaser of HKS exhaust systems against defects in materials and workmanship for a period of one year. The warranty is available only for vehicle specific exhaust systems. Metal catalyzers, front pipe, exhaust manifolds, and center pipes are not covered.
(For more details, please go to the product warranty site.)

I bought a muffler about 2 or 3 years ago. The sound of the muffler got bigger than before. Is it normal?

The muffler passes hot air; so over the years, due to the secular change in the long-termuse, the muffler sound may become bigger.
Muffler is a consumable product. That's why we are using the advantex glass wool for the best and long lasting mufflers.

What is a cylinder in the mid pipe of HKS MUFFLER series?

That's called a "SILENT CHAMBER (ex: ES WAGON 409)".
A stock car, mini van or wagon, tends to have a muffled sound when you change the muffler, and the silent chamber make this muffled sound go away.
As you can see below, this silent chamber can change the frequency and reduce the bad sound from the muffler.
We tested and analyzed each vehicle's sound and make the best silencer. However, by putting this chamber does not effect on the exhaust pressure and appearance of a car.

  • Silent chamber makes the reflection of the sound to delete the noise
  • However, the Silent chamber does not block the exhaust gas flow

For sport user

I have a NA car, and I am looking for a muffler that makes sounds like NA, does HKS have such a muffler?

The HKS SUPER SOUND MASTER MUFFLER is perfect for you. It creates a cool high pitch sound and has a quiet sound at a low pressure.

I changed the sport turbine kit, and I am looking for a muffler for my big powered car. But, I don't want a too loud muffler. Do you have such a muffler?

Yes we do. HKS SUPER TURBO MUFFLER has a low pressure and lower noise muffler.

I ofter go to circuit for driving. I want a ultimate muffler for a ultimate car driving. Does HKS has a perfect muffler for me?

The sport muffler that is made fully of titanium (one of the lightest muffler in the market) and ultimate straight design muffler HI-POWER SPEC R, HKS' top level muffler developed to attack in the circuit, is perfect for you.

I think it's very important to have a good performance muffler, but recently, the regulation becomes more strict, so I want a muffler with quiet sound and still has a good performance. Does HKS has such a muffler?

The SILENT HI-POWER as the name indicates, it is the muffler with quiet sound and still has performance power in a good balance.

I usually use my car to drive in a city, and I don't need a sport muffler, but I want a muffler with cool looking design and a good perforamnce.

LEGAMAX PREMIUM is the clean and stylish tip design muffler that are very cool and beautiful looking. It's a perfect for city drive by a normal vehicle.

I have a sports car and look for a exhaust system made fully with titanium, but it is very expensive. Is there an affordable lightweight exhaust system?

"Hi-Power SPEC-L" is recommended.

Pipe plate is 0.8mm thick, and silencer outer plate is only 0.5mm of SUS304 material. This super lightweight exhaust system is comparable to a full titanium made. Also, it has an efficient exhausting ability and cool sound. Only HKS can make this kind of high engineering exhausting parts.
*Subaru WRX Sti: The weight of this SPEC-L is only 10.5kg which is -53% of the 22.4kg stock exhaust system.
The lightweight exhaust system has many advantages such as better exhaust efficiency, acceleration/deceleration performance improvement, reduction in a brake load, more accurate turning traceability by reduced inertial weight reduction, etc. Replacing the exhaust system with this product changes the driving drastically.

For Mini Van & Wagon User

I have a mini van with the aeroparts and aluminum wheels. I am looking for a muffler that fits to my van, the sound is quiet, and the design is attractive. Do you have such a muffler?

LEGAMAX PREMIUM is what you need. It fits great for a van with the aero and aluminum wheels. And, of course, it has passed Safety Standards regulation for a sound level.

I want to change the muffler for my car. I want something with decent performance and looks good and affordable

We have exactly what you want! The LEGAL MUFFLER is what you are looking for. Its tip is designed for each vehicle, and it has a good feature for a low price.
* There is also LEGAL MUFFLER SPORT.