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jerkylips 08-06-2012 03:47 PM

general question about diesels
this may be a dumb question, but I've tried to research online & still haven't really found a concise answer..

There is a lot of discussion of "new" diesels and "clean diesel" - references to the vw jettas, the grand cherokee that's on it's way to the US, etc. "they aren't loud & stinky like the old ones", etc.

Yet, I can go to the dealership & buy a new chevy with a duramax diesel or a dodge with a cummins, and they're still fairly noisy and fairly "stinky".

So what are the fundamental differences? I know that the VM Motori diesel is referred to as "common rail diesel" but I don't really know what that means.

I'm just curious why some are clean/quiet/"you wouldn't even know it's a diesel", and some are exactly what you would think of when you think of a diesel..

mav383 08-06-2012 04:10 PM

Really any newer "auto" diesel is clean diesel. It all has to do with the emissions standards that were put in place in 2006. biggest change comes from the fuel used, which is why diesel fuel is now more expensive. Second is buy adding emissions devices, like the dpf or diesel particulate filter or other newer devices. As far as noise goes that's just on how they make the car around it. My crd wk was quiet untill I took off the many covers it had to silence the valvetrain, also helps that the size of the engine is fairly small next to a cummins or duramax. However the downfall is poor fuel economy. The DPF puts more strain on the already restrictive stock exhaust on these newer diesels. Many cummins owners see as much as 10-15mpg increase by deleteing the dpf, with little to no major changes to the stuff comming from the tailpipe. Yes you can still make a newer diesel smoke, but you really have to try.

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curio 08-07-2012 02:12 AM

Re: general question about diesels
Common Rail means that the injectors are fed by a common pipe ("rail") wich constantly holds the pressure needed.
New iesel engines are not comparable to old ones, the CR technique allows injections with multiple squirts (up to 8) resulting in a better fuel economy, smoother engine run and better emissions, sometimes even allowing to reach the highest emssion standards without DPFs. The VM Motori Diesel engiine is one of the most sophisticated on the market, comparable to those of mercedes and the Volkswagen group.
Cummins and duramax are more "industrial style" engines.
Usually you may notice thats a diesel only after startup, once running its sometimes diffcult to distinguish from a gas driven engine. The RPM range is not as big, but this is easily compensated by the much better torque.
In Europe almost all SUVs as well as the top of the lne Limos of Mercedes, Audi and BMW are diesel powered, the big gas engines are mainly produced for the export cars (and for people with prejudices against diesel engines :))
Happy Day


jerkylips 08-07-2012 11:23 AM

Re: general question about diesels
thanks for the replies - it sounds like it's more fine tuning & modern technology rather than a completely different design?

MAXGroup 08-07-2012 01:28 PM

Re: general question about diesels

Originally Posted by jerkylips (Post 666994)
thanks for the replies - it sounds like it's more fine tuning & modern technology rather than a completely different design?

You are abselutly right, the basic 4 stroke diesel engine has been the same for a 100 years.
Last real revolution was the 2 stroke supercharged / turbo diesel engine that was invented around world war 2......

However those 'fine tunes' make a world of difference. I recently had an MB sprinter for a year and the performance of that little diesel on the big van was amazing I towed well over the recommendation and only felt it in breaking :-)

BobT 08-23-2012 10:11 PM

Re: general question about diesels
If you sat in a WK2 diesel and drove it, you would never know it was a diesel. With the push in the back and the effortless way it gets to the speed limit you might think it is a V8. From outside, the engine noise might give it away as a diesel but most people wouldn't notice. There is no smoke. My tail pipes are perfectly clean.

jerkylips 08-24-2012 09:43 AM

Re: general question about diesels

Originally Posted by BobT (Post 674524)
My tail pipes are perfectly clean.

but what about the jeep? :lol:

BobT 08-25-2012 12:21 AM

Re: general question about diesels

Originally Posted by jerkylips (Post 674644)
but what about the jeep? :lol:

The jeep is filthy. I find it hard to get excited about washing cars. :detailer:

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