With all of the tapping, gurgling, pinging/tinking, growling, knocks, etc., the PSD has got to be the most musical diesel I've driven. At first I was concerned with the noises and asked a guy we know who's only owned 7.3s and he laughed about it saying they're all normal. It seems like all these different noises pertain to throttle, idle, RPMs, etc.

With a standard, during a deceleration w/o brakes, but in gear just letting it slow... At first it's a quiet exhaust sound and the motor is quiet. Then towards lower RPMs, the motor kicks in and sounds identical to when you lightly press on the gas to maintain speed. What is that? What is the motor doing? Then when you want to accelerate more, the sound is much louder and sounds busier. Is the changing noise related to the fuel consumption and valves?

Is there a link that explains what's going on when these different noises come up?

 

Are we not lucky to have the 7.3 sing to us. I love the song. I even have a more manly sound coming from mine with the turbo and injectors.

When you don't here all the singing, then something is wrong.

 

Autos and manuals do the same thing on decel. The PCM commands the injectors off "zero pulsewidth" to save fuel when coming to a stop. Basically the engine just becomes a big air pump.

The noise is a combination of injector poppets, compression ignition, and the timing of that ignition. Powerstroke injectors are much more complicated than injectors you find on Cummins and Dmaxs, with more internal moving parts. Our injectors are pressurized by high oil pressure. So you have both a fuel rail and an oil rail feeding injectors. That's one of the reasons why they are so noisy and make a different racket than other diesels.

 

I changed my oil from using dino to syn yesterday and I cannot beleive the difference in sound the engine makes. It is much quieter

 

I'm no expert but I am going to do my best here.

The motor will sound similar when you are hitting similar RPMS...whether you are slowing or accelerating. The higher the RPM, the louder the motor, the more fuel your injectors are pushing through..the more compressed air enters the chamber and the faster your pistons are hitting.

Remember here are the 4 strokes of a diesel engine:

Intake stroke -- The intake valve opens up, letting in air and moving the piston down. *
Compression stroke -- The piston moves back up and compresses the air.
Combustion stroke -- As the piston reaches the top, fuel is injected at just the right moment and ignited, forcing the piston back down.
Exhaust stroke -- The piston moves back to the top, pushing out the exhaust created from the combustion out of the exhaust valve.

Of course depending on the RPM of the motor, various strokes slow down or speed up..and the motor will sound different.

Our trucks also tend to have what they call "injector cackle", especially on the #8 cylinder. That may lead to some of the noises you are hearing.

Some of these trucks have very audible turbos. When I first got my truck I was perplexed by the turbo flutter I was hearing at low RPM. You'd need someone more knowledgeable than me to explain how a turbo works..just know they make all different kinds of noises based on the demand (or lack of demand) for them.

 

OH also..lets not forget about the EBPV. Thats a cool sound too.

 

Good stuff. The EBPV noise had me concentrating to replicate the noise one night. Then I read about it on here after I got back.

 

My gasser friends give me crap about my noisy truck all the time, but it's music to my ears

 

A turbo is basically a compressor that is run off exhaust gasses. There is a compressor side and a turbine side. As the exhaust leaves the engine it is routed past the turbine, causing it to spin. If you give it more fuel the gasses get hotter and move out of the engine faster, causing the turbo to spin faster. As the turbine side spins faster it causes the compressor side to spin faster (both sides are connected by a shaft, center section, shaft, and vane assemblies are called the cartridge sometimes) making boost.

With more boost the engine can handle more fuel, and with more fuel the turbine spins faster causing more boost untill the turbo or injector capacity is reached.

 

Begin :

Question: My turbo makes a fluttery sound, a noise I can only describe as a loud hummingbird sound...usually at low RPM just cruising around town at 35-40 mph, in high gear.

It was once explained to me that the sound I was hearing was exhaust pressure being pulled back INTO the turbo and hitting back side of the turbine wheel/compressor. I guess going from high RPM and into low RPM causes a pressure void..and the noise is air flow hitting the wheel on the opposite side.

Does that make sense?

End

 

Makes sense Lisa... and I like the new sig quote

 

Thanks. That was hilarious. Best quote I've seen in a long time. I can always count on you to say some funny $h*t!

 

That flutter noise is normal. It is the exhaust moving through the turbine at low speeds. The turbo is spinning to some degeree all the time (not the high speeds when under load), and the exhaust pulses are being broken up by the turbine. This happens because the exhaust pulses from the engine have different travel length and hit the turbine at the same time causing a press spike.

 

Thanks for that explanation gmm.

I've come to really enjoy the noise.