NO FLAMES please

[Stlheadake]

OK dad and I were talking the other day, and got to waxing philosophically about diesel engines in trucks and their relatively recent rise in popularity. We did hit upon a question that we need other input on. I/we aren't dissing or slamming any brand of truck at all, just asking inquisitively, so keep that in mind!

Why are the PSD's so loud? The engine noise in those trucks is unbelievable. The Cummins engines had a reputation for their noise, but they have quieted down somewhat.

I'm curious to hear the new PSDs to see if they have gotten any quieter. I'm just curious if anyone can explain to me logically why the 'other' engines are so noisy?

[Tough Guy]

Lack of pilot injection, more timing advance.

The newer 7.3L PSD trucks are quieter than the pre 99 trucks. The 6.0L trucks are quieter than any 7.3L and the new 6.4L is rumored to be as quiet as the Dmax/Cummins.

The new quiet Diesels are a result of emissions, sales and technology.

Look at how much better they start in low temps and the power they can make!

Chris

[ronniejoe]

I don't know this for a fact, but I surmise that there is something peculiar acoustically about the geometry of the cylinder head on the older PSD's that amplified the combustion noise.

As TG said, timing plays a big roll in the noise as well.

[DmaxMaverick]

I think it's just the nature of the beast (the beast being Navistar). I don't know of any Navistar engine that's quiet, relative to other similar classed engines. They're just loud. Ford applications aside, Navistar's target applications place noise pretty far down the priority list. The medium duty market is very competitive, and they didn't pencil much R&D funding into N/V/H. They've always been that way. Compare a DT466 with an L10, or 3126.

Well....I said I didn't know of any quiet Navistars. That's not entirely true. There are a bunch of 03/04 6.0's that have been very quiet, even more quiet than Cummins or Duramax.

[Tough Guy]

The pre 99 7.3L trucks had single shot injectors more advanced timing (loud), in 98 they introduced the super duty and with it some changes to the 7.3L, one of them being split shot injectors and retarded the timing somewhat (not as loud)...which is similar to pilot injection, just not as effective. The 6.0 had pilot injection in the first model year of the 6.0L introduction but was disabled with newer software versions to correct other issues.

Chris

[Mark Rinker]

The first light duty diesel pickup I ever drove was a mid/late 90s Dodge/Cummins. That truck was so noisy that you couldn't hear the radio above the din.

It was a few years later that I drove my first 6.5 Chevy and thought that the noise level was acceptable for the power it put down.

Today, I regularly have people ride with me and not realize that the DMax is a diesel. I even had one guy tell me authoritatively "...no way this truck is NOT a diesel." I assured him it was :) and he had to see the fuel gauge on the dash before he believed me!!!

[More Power]

Speaking of Ford's new 6.4L PSD, I read in a recent Diesel Builder magazine that the cooling system utilizes a 40% larger radiator and that the water pump flow rate was doubled to 135 GPM (if I remember correctly) when compared to that used with the 6.0. They also mentioned two large EGR coolers.... which explains the cooling upgrades. ;)

Jim

[Stlheadake]

Thanks for the input. I surmised that sound levels were pretty far down the list for Navstar. And I have noticed that the Cummins has gotten much quieter in later model years. I just noted that the Fords (again this isn't a slam) are so much louder, and I wondered if anyone had heard or read anything about the sound levels on the new PSD.

[Bobo]

The Duramax has a high psi common rail system.....and the Cummins switched over to that when they got "quiet". The new 6.4 Powerstroke will have a common rail system on it. Expect it to be as quiet or quieter than the other two. Pilot injection plays a big role into the sound too. You need high fuel psi to burn diesel efficiently. If you add a pilot to a system that can't recover the psi in time to shoot the main injection event in at the proper psi, you get a quiet truck with horrible emissions and power. Since the powerstroke generates psi with oil on each injector, it has a difficult time recovering from pilot injection. With a common rail, the system can recover from multiple pilot injections and post injections without a problem. The electronics are being advanced to allow more and more of these events to occur. The Duramax had 2 events, pilot and main, in 01-05. They have the capability of 4 events in the new LBZ electronics. Using EFI Live, you can get your truck to sound more like a Powerstroke or an old Cummins by eliminating the pilot injection. It is kinda neat, but gets old fast. I like having a quiet motor!