Why do Diesels Whistle? (And Make it Louder!)

The distinct whistle between the smoke and rumble of the exhaust along with the roar of a diesel engine is really what completes the intimidating manly appeal of a diesel! But being uncertain of exactly what causes a diesel to whistle had to find out. Is it from the turbocharger or is the exhaust? Or maybe some other part of the car that causes it.

Chrome turbo – photo by Danny Sleeuwenhoek

Why do diesels whistle?

The whistling in a diesel comes from the turbocharger. The turbocharger spinning at high speeds causes the air to pulse at a high frequency and creates a whistle. There are a few other things that can cause a whistle such as an exhaust leak and alterations to mimic or make the whistle louder.

There are a few tricks to create a better whistle and a few ways you can diagnose where the whistle is coming from if you think it may be something other than your turbo charger. I will cover a few ways to make the whistle louder with things like a turbo upgrade, foil delete, or a straight exhaust.

Turbo Charged Diesel Whistle

Without a turbocharger or supercharger, a diesel engine will not whistle.

Diesels are turbocharged very often because they are often used in applications where lots of pulling power is required and this is often at low rpm. At low rpm a turbo charger creates a significant boost in efficiency and are a huge benefit to diesel engines. Check out my other article for a more in depth read

Why Diesel Engine Cars More Commonly Use a Turbo.

If a diesel has a turbo but does not produce much of a whistle, there are a few things that diesel owners can do to introduce or enhance the whistle of their diesel.

Turbo with Straight Exhaust

The main reason for a diesel whistle to be louder on one truck over another is the exhaust system. A leak in the exhaust will cause a whistle but also a straight exhaust (with no muffler) will enhance the whistle from the turbocharger. Hey louder exhaust muffler or removing the muffler all together will drastically boost the whistle from your diesel.

The straight exhaust allows for the whistle to be heard because it becomes like whistling into a tuba. The whistle will travel straight from the turbo out the exhaust and let that turbo sing without muffling it!

Removing your muffler all together will most likely be against some noise laws in place so some opt for an exhaust cutout that allows the muffler to be bypassed on demand.

Another solution is to swap mufflers to just be less restrictive.

Whistle Not Coming From Turbo

If a new whistle has developed or a whistle that does not sound like it is coming from the turbo, it is most likely an exhaust leak.

An exhaust leak before the diesel will cause are pressure to be lost at the turbo and forced out the leak, whistling.

An exhaust leak that is whistling can be best located by removing the belt that powers the turbo charger. This way you will know that the whistle is still happening even when the turbo charger is not spinning up.

There are a few ways to locate the precise location of an exhaust leak.

Simply moving your hand close to the exhaust pipe to feel for leaking air is the quickest way to find an exhaust leak. Pouring a mixture of soapy water over the exhaust pipe is the next best way to find a leak.

Don’t burn yourself and do this when the car is cold!

Making My Diesel Whistle Louder

Make that whistle louder! With your powerful mean turbo diesel truck, now all you need is to make it sound as mean as it truly is.

Unfortunately, car manufacturers are getting better and better at reducing in-cab noise and quieting down our turbos that just want to be set free and SINGGG!

Whistle From Turbo Exhaust

If the whistle from your diesel has already become louder than normal, it is most likely from an exhaust leak. If the exhaust leaks before the turbo then it will whistle from seeping out the exhaust pipes.

An exhaust leak although it may make for a great whistle must be fixed because if the exhaust is leaking before the turbo, the turbo will be less able to spin up with a loss in exhaust pressure.

This means less power which is no bueno and not worth the cool extra whistle.

Upgrading Diesel Turbo Charger for a Louder Whistle

Upgrading the turbocharger will no doubt improve the sound of the turbo. It does not always have to be a bigger turbo. By simply replacing the guts of the turbo you can achieve a much better sound and louder whistle!

For those considering a turbo charger upgrade kit, they are a fairly simple DIY project and you’ll be pleasantly surprised to know there is a decent selection of turbo charger kits on Amazon.

dieselorings.com seems to have the best deals around on pricing for turbo components.

Foil Delete

A foil delete is a modification – actually a part removal from your existing turbo system that reduces items in place to quiet down the turbo noise and will cause the turbo noise to be louder.

A foil delete is simply removing the insulating foil in place around the tube leading up to the intercooler. Removing this will cause better resonation of the whistle. Be aware that this was installed to reduce noise in the cab so if you remove it you know what to expect!

Upgraded Intake

Turbo Intake – Photo by Dylan Gillis on Unsplash

An upgraded intake system has a similar effect to a straight exhaust. It provides less in the way of the singing whistle of the turbo to escape. An aftermarket air filter will make the whistle of the turbo louder.

This is one of the simpler upgrades and will increase the noise less than a straight exhaust but is probably just the whistle boost that your turbo needs.

Creating the Whistle Without a Turbo Charger

A solution for many lack the true power and pride of having a turbo charged diesel is to install a whistle tip in the tail pipe of the exhaust.

Could be a fun gag gift or something to install for a few laughs.

But really, if you want your diesel to whistle, begin your research on a kit for a turbo and start saving!

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