Part of my daily routine is a three mile walk through active suburban neighborhoods with numerous stop signs. One of my many cognitive issues is a hyper awareness of car sounds around me. As cars pull away from stop signs, I often, without looking, try to guess engine cylinders, type, brand, etc. It's weird, I know. But I remember not long ago when a turbocharged engine was always identifiable by the whistle/whine from the crazy fast spinning turbine. Newer turbo gas engines seem to have eliminated this sound. (Ford EcoBoost engines are still reliable whistlers, however.) And, we don't count the slammed WRXs with aftermarket whistle/blow-off gizmos.

I started to wonder if this was due to turbo design or manufacturer packaging: intake silencers, etc. So, I started reading about turbocharger engineering and... wow, no foolin', these things are interesting as hell. So, while the concept behind turbocharging is straightforward, the engineering most definitely is not. Even if you don't normally give a second thought to how things work, I'm betting you'd find this technology fascinating.

From what I've read so far, using the science of Computational Fluid Dynamics, aerodynamists were able to design turbine tips that create a whistle that's now above audible range. So, if you're someone who would be bothered by this sound (I'm not), thank the smart people at Mitsubishi Heavy Industries for making a turbo that goes about its ridiculous business in a quiet manner.

 

Amazing! Thanks for posting this. I am not quite as interested in the "engine" sounds as you, but have for years often tried to guess what engine I was listening to...often with poor results.

Whats also amazing, is Mitsubishi. They are so talented in so many areas, just not vehicle marketing! At least in the US.

 

The car sound thing goes back to childhood days. When GM divisions made their own engines, I was able to "hear" an Oldsmobile or a Cadillac. I could "hear" a Chrysler product starting. Not a marketable skill, unfortunately.

The turbo sound was distinctive too, and not hearing it in most newer cars, including ours, was a curiosity.

 

Yes, Chrysler starters were definitely different (and different sounding) than Ford or GM products.

 

With the windows down, you can absolutely hear the turbo spooling up in the RDX. No, it's not like a big single turbo Supra spooling up, but that likely has to due with everything you mentioned along with the size of the turbo.

 

Hmmm, interesting. I've never heard it, but never really mashed it with the window open. In casual driving, inside and out, it's been completely silent to me. I'll listen more closely.

 

So I guess future e-cars will broadcast "pedestrian alert noise". I wonder what that's gonna be like.

 

Mitsubishi, an old and diverse company. They made the Yamato during WW 2, the largest battleship ever built. They build planes and rockets and wind generators and so much more. Cars were a a very small part of their overall business empire and that is good thing. There trucks have done much better than their attempts at main stream autos. All that truck work helped with their turbo's. .

 

With the windows up, I can't hear a thing. I'm sure there's some active noise canceling going on in the cabin. Once I put the windows down and I accelerate, I can definitely hear the turbo spooling. It's not overly obnoxious ... just a faint, but noticeable, intake noise that's pleasant sounding IMO.

 

I did notice a 'swoosh' sound when I stepped on the accelerator last time I drove the RDX. Was worried initially, but figured it is probably the turbo. It sounded like gas escaping from a puncture in a rubber hose.

I have never heard it before, maybe the ANC was misbehaving, my windows were up.

 

A turbo impeller/compressor spins at VERY high rotation speeds: 100k+ RPM. The tips of the impeller often exceed the speed of sound. It's been typical for the vanes to create a whistle similar to a boiling teapot. This sound varies under load. It's a sound that most owners don't fully understand, or appreciate, and engineers have taken steps to minimize it. I have not heard it at all on the RDX, but at least one other has. Younger ears, perhaps.

 

Many manufacturers go to great lengths to ensure that the occupants of their cars cannot hear turbo spooling noises. On my Audi, for example, there's a "turbo muffler" built into the turbo inlet pipe, right below the turbochargers. The sole purpose of this thing is to silence the turbochargers. I like hearing my turbo spooling, so I removed it and replaced it with "turbo muffler delete", which is basically just an open aluminum pipe that bolts into place of the OEM turbo muffler.

Now I can hear my turbo, but it's still very subtle. If I really wanted to hear it, I could swap to an aftermarket intake that doesn't have a contained filter. That works on pretty much any modern turbo engine.

 

I was lurking around in a Volvo owners group and was mildly amused by the displeasure and concern about the whistle. More than a few indignant comments from unhappy owners who took the car back for repair and were told the sound was normal. I can understand why manufacturers would try to hide it.

 

Back in 87 I owned a Mazda RX-7 Turbo II and it whistled, I thought it was cool. But I was a lot younger then.......

 

I don't mind hearing the sounds machines make doing their work... within reason.

Anyone familiar with the Vietnam era "deuce and a half" know that as the standard for OEM turbo whistle.

 

FWIW, the Yamato was a total failure. Their G4M was mostly a failure, with some big upsides, but much bigger downsides.

Their real accomplishment was the Mitsubishi A6M, the Zero.

 

Probably had leaky valve seals and smoked a lot too!

 

I remember it well. The turbo whistle, the smell of diesel and napalm all in one.