diesel versus gasoline

[franksolich]

I was talking with the local grocer this morning, while picking up another half-bushel of oranges (which fortuitiously are rather cheap right now), when he commented about a pick-up truck driving down the main street, something to the effect that it had a diesel engine.

Now, a particular chip on my shoulder--which can be both ugly and charming at the same time--is that, as a deaf person, I'm constantly perplexed that hearing people seem to know a great deal more about things than I do (despite all my college education), and I'm always trying to figure out how hearing people know these things, so I can use them too.

I asked the grocer how he knew this pick-up truck had a diesel engine.

"By the way its engine sounds," he said.

Then another customer came in, needing attention, and being a nice guy, I took my leave, although I was still mystified.  Motor vehicles running on diesel have a different sound than motor vehicles running on gasoline?

Now, normally, one can detect what a vehicle is running on, simply by odor, and as Nebraska has the freshest, the cleanest, the purest, air in the world, Nebraskans tend to have very good nostrils, with the ability to immediately discern even the most subtle of differences in scents.  By smell alone, a Nebraskan can even detect the difference between a vehicle running on regular gasoline, another vehicle running on 10% ethanol gasoline, and a third vehicle running on one of these "super" gasoline blends.

It never occurred to me that a diesel-powered truck (a civilian vehicle, remember, not one of these big semi-trucks) would sound any differently from a gasoline-powered truck.

I assume a diesel engine has a louder and clumsier sound than a gasoline engine.

Right, or not? 

[Carl]

Yes,a diesel engine has a different sound.

The gasoline charge is spark ignighted under a relatively low compression ratio in the range of 9:1.
The diesel has a compression ratio of in the range of 16:1 (both can vary a bit).
That results in compression pressures of around 400 psi at cranking speed.
This raises the temperature of the air high enough to ignight the fuel charge that is injected in a very high pressure 2500-4000 psi at the injector.

Diesel has more BTUs/gallon then gasoline so the resulting expansion under the higher compression/combustion pressures causes the diesel engine to have something of a deeper sound.
They also run slower because of the heavier,larger parts required to handle the dreater stresses imposed by the differing ignition methods.

Valve timing is probably different as the piston is much closer to the valves at TDC so clearance is an issue,the differing cam profiles and overlaps probably also lend to a deeper,more knocking sound.

[Chris_]

MUI modern diesels are as quiet as their gasoline brethren.
 

[Chris_]

MUI modern diesels are as quiet as their gasoline brethren.
 

With the new electric injectors, there's no noise compared to the old mechanical ones.  Nothing sounds worse than an old diesel with mechanical injectors that needs a tune-up.  You'd think it was dropping parts every time it moved.  

[Chris_]

MUI modern diesels are as quiet as their gasoline brethren.
 

With the new electric injectors, there's no noise compared to the old mechanical ones.  Nothing sounds worse than an old diesel with mechanical injectors that needs a tune-up.  You'd think it was dropping parts every time it moved.   

I had one that parked right under my apartment in the 70s -- one of those gawdawful VW Diesel Rabbits.  Every morning at 6:30 am -- clackity, clackity, clackity.

[Chris_]

Diesels are great if you want gas mileage and torque.  I'd like to get one myself... those diesel Rabbits get 50 miles per gallon.  Problem is, by 2015 diesels are required to meet the same emissions standards as gasoline cars which is going to wipe out any MPG advantage that diesels have.  The new ULSD engines already have reduced MPG ratings from the low-sulfur models (pre-2006).

[Carl]

Diesels are great if you want gas mileage and torque. 

Smoke too.

[Miss Mia]

I drive a diesel.  It does sound different than a gas.  It's not a loud vehicle, by any means, it's not the diesel of the 70s.  But It's a distinct sound of a diesel vs gasoline engines. 

Plus, it's a lot more fun to drive.  Torque rocks!

[franksolich]

I drive a diesel.  It does sound different than a gas.  It's not a loud vehicle, by any means, it's not the diesel of the 70s.  But It's a distinct sound of a diesel vs gasoline engines. 

Plus, it's a lot more fun to drive.  Torque rocks!

But am I correct in assuming that a diesel engine has a clumsier and heavier sound than a gasoline engine?

Sort of a clunk-clog-clunk-clog as compared with a vrsssssh?

[Miss Mia]

I drive a diesel.  It does sound different than a gas.  It's not a loud vehicle, by any means, it's not the diesel of the 70s.  But It's a distinct sound of a diesel vs gasoline engines. 

Plus, it's a lot more fun to drive.  Torque rocks!

But am I correct in assuming that a diesel engine has a clumsier and heavier sound than a gasoline engine?

Sort of a clunk-clog-clunk-clog as compared with a vrsssssh?

Yes, but it's not really loud Frank.  Gas engines on the whole are quieter.  It's a noticeable difference, to where if they're moving vehicles at the dealership you can instantaneously tell if it's a gas or diesel. 

I'll be hard pressed going back to a gas engine.  When my car's been in the shop, I've driven gas vehicles and, well, it's just not the same. 

[Lacarnut]

I drive a diesel.  It does sound different than a gas.  It's not a loud vehicle, by any means, it's not the diesel of the 70s.  But It's a distinct sound of a diesel vs gasoline engines. 

Plus, it's a lot more fun to drive.  Torque rocks!

But am I correct in assuming that a diesel engine has a clumsier and heavier sound than a gasoline engine?

Sort of a clunk-clog-clunk-clog as compared with a vrsssssh?

My ex brother-in-law purchased GM first attempt at a diesel. That Caddy sounded like a cement mixer going down a gravel road when it first started up. That was back in the 70's. During that time frame I used to go with him and his wife to see LSU play basketball and watch Pistol Pete Marivich. I would kid him and his wife about the noise that thing would make. It was loud and you could feel the vibration of that thing when he started it up. To add insult to injury, I would kid his wife about it being a pimpmobile. It was pink and his wife picked the color out. He worked for GM so he would buy a new one every year and sell the old one. That was one car he was glad to get rid of. Today's diesels are not loud but they do have a raspier sound than a gasoline car.

[vftb]

If you really want to get picky, if you're familiar with diesels you can actually tell the difference between manufacturers (I'm speaking specifically of pickups).  I drive a 7.3 litter Ford Powerstroke and can tell the difference between that and the newer 6.4's, and I can hear a Dodge a mile away.  The GMC Duramax has it's own distinct sound also. 

[Chris_]

Diesel’s second coming
Will Americans finally warm to diesel cars?

The catalytic crackers used by oil refineries in America are optimised to produce as much petrol as possible—typically about 50% of every barrel. Diesel accounts for only 15% of the rest, with the balance used to produce heating oil, jet fuel, heavy fuel, liquid petroleum gas, asphalt and other products.

Refineries in Europe and elsewhere tend to use hydrocrackers that produce 25% petrol and 25% diesel. They would like to produce more diesel than they currently do, but that would mean producing even more petrol than they need. At present, they export their surplus to America.

So, if America switched to diesel cars in a big way, the Europeans would be even more awash in unwanted petrol than they are today, and might have to dump it elsewhere or even idle some refinery capacity. Either way, the global price of diesel would soar still further.

Meanwhile, back at the pump in America, diesel currently costs 20% more per gallon than regular petrol. When that premium reaches 35%, the difference in fuel efficiency will equal the difference in price—and there will be no economic reason to make the switch. Some reckon that day is only a few years away.

[Chris_]

Up until the last few years, diesels sounded like this: