What in a diesel engine makes it sound the way it does compared to a gasoline engine?

 

I think its the very high compression of the engine, but not sure on that. You gotta admit though, a nice FE with dual exhaust and headers sounds so much better then a diesel.

 

High compression has some to do with it plus the way it fires by injecting the fuel into the combustion chamber as it is coming up to max compression.

 

My BIL, who used to be an engineer for Cummins (worked on the '03 Dodge TD), says the extra noise is from the valve train. It must be that the extra-high compression helps them to "slap shut" harder or something like that.

Jason

 

I've always thought it was the fuel pump. My grand-dad had an old Oliver tractor with a diesel engine that was the smoothest running diesel I've ever heard. Absolutely NO rattles. Couldn't tell it from a gas burner. I've also heard that Rolls Royce makes a quiet diesel. I figure it's possible to make them quiet but cheaper not to.

 

It's the TIMING of the valve train. Listen to a hopped up diesel compared to a stocker. When the 6.9IH came out in the Fords it was fairly quiet, as were the pre-powerstroke non turboed 7.3s. With the advanced timing and boost the valves basically SLAM shut from the compression. Also the explosion of the hot hyper-compressed air meeting with the cooler fuel doesn't help any.

 

my 7.3 -6.9 rig sounded like a gas when you got on it. idle was a different story. Idle drove me crazy I always wondering if the thing was missing or not(later on I cracked the 7.3 Idi block and it was missing). It never seemed like I lost any power just sounded werid at Idle.

 

Not to mention the fact it isn't a spark ignited explosion, but a compression ignited one...

Injector noise has a fair bit to do with it as well - thats the main noise from the 7.3 PSD
And most diesels for that matter.

 

I know I know

Diesels work by sponaneous combustion. The fuel is squirted into the cylinder, and the pressure from the piston moving up "squeezes" it and increases the temperature for combustion to occur. On the older diesels, some of the fuel ignites before the piston has completed the up cycle, causing the characteristic diesel "clatter."

The recent diesels use a high pressure fuel delivery system (1200 lbs+ sq/in). They can inject a small amount of fuel on the pistons up cycle, then inject the primary amount towards the end of the upcycle- eliminating most of the traditional diesel noise. They also burn cleaner- which was the real reason for the switch.