One of the biggest issues with diesel cars is their noise levels. Even the most refined diesel car is noisier than an average petrol car, and that’s something not all buyers are comfortable with. CarToq looks at ways in which you can reduce the noise emitted by a diesel car.
One of the biggest reasons for diesel engines being noisy is that they run on high compression and the fuel molecules in diesel fuel is much larger than petrol – hence producing more noise while the fuel ignites. Also as there’s no spark ignition in a diesel engine and the fuel self-ignites due to the heat generated during compression, it clatters when cold.
Here are some methods of reducing diesel engine noise by about 10 to 15 dB.
Use a synthetic engine oil instead of a regular mineral oil in the engine. Synthetic oils are about 4-5 times more expensive than regular oils for the engine, but they also are far superior with much better lubrication. Some synthetics have chemicals like PTFE (also known as Teflon) that coat all moving parts and reduce friction as well as noise in the engine. Also read: Synthetic oil vs mineral oil
In case you find adding synthetic oil is too expensive for your car, you can also add an oil additive to the vehicle which can perform a similar function of coating the moving parts with a very smooth coating that will reduce friction and noise to some degree. STP oil additive and Nulon are two such additives that work well with diesel cars. They will cost about Rs. 400-Rs.600 a can for one treatment.
One of the most effective ways of reducing diesel engine noise is to use damping material in all perceivable areas. There are brands like Dynamat that are quite expensive, but very effective in absorbing sound. Dynamat costs about Rs. 2,500 per sheet of 1 sq metre. A cheaper, but not so-effective fix is to use polyurethane yoga mats, commonly available in hardware stores.
You will need to fix this with the help of adhesive to the underside of the bonnet, along the sides of the engine bay and on and behind the firewall between the passenger cabin and engine bay. For additional effect, you can also paste this material inside the door pads and on the floor of the vehicle.
This can bring down sound quite a bit inside the cabin and make the vehicle quieter. Padding an average sedan will cost about Rs. 25,000 or so with high quality sound damping material.
Engine cover / shield
If your vehicle does not already have an engine cover or shield above the engine, you can get one fabricated with light-weight aluminium and pad the underside with sound damping material, with a reflective sheet covering it (to reduce heat build up). If you already have an engine shield, then add a layer of padding to it.
Underbody coating also plays a role in noise reduction to a minor extent. Thick underbody coating of 100-150 microns not only prevents the vehicle from rusting and damage from stones hitting the underside of the car, it also reduces the road noise and some engine noise that can be heard inside the cabin. Good underbody coating from companies such as 3M cost between Rs. 3,500 to Rs. 5,500 depending on the vehicle. Also read: Pros and cons of underbody coating of cars
If you really can’t afford any sound reduction techniques that are listed above, just get yourself a good music system. A music system can take the stress out of driving and your mind off the constant diesel clatter to a large extent. Decent music systems are available from Rs. 6,000 upwards. Also read: Guide to music systems for small cars.
Share any other sound reduction methods that you have experienced with the CarToq community.