Diesel Engine Noise
 

Hi Guys,
I have been searching in this forums and can't find anything related to my question. This is my first diesel car and while I was not that excited about the diesel engine rattleing at accelaration, I was sold on the gas economy. Again this diesel noise is only at the start of the acceleration and then it goes away. A few months have passed already and still can't fully get used to the diesel noise and some friends make theri wises comments/jokes..."I think the fedex/ups guy is coming, oh no it your car.."WEV
Surprisingly the 335d is a lot quieter than the X5 diesel, why ? Don't know. Another interesting fact is that in the mornings, the car is very smooth and the diesel noise at acceleration is barely noticeable. Once it warms up the noise its back. This make me to believe that it seems a sensor/ pump or what ever it is, it's closed or not activated. :dunno: has anyone figured it out ?

1. "diesel noise" posts make me crazy...especially when it is driven by "what other people think/say to me"...

2. The changing noise with warm up is likely due to oil viscosity, and not a problem with your car.

3. The 335d has a different sound controls, components, damping panels, etc.

To your comments :
1- I Don't care what others are saying, just brought up the comment in order to reflect how noisy it is.
2-That is a possibly a fact but I think there is something else there that is not fully opne, stopped or something. I understand there are 2 fuel pumps in this car as opposed to the 335d.

3-another known point, but asking if anyone has fiddle with the possibility of reducing the noise some way some how :cool:

For me the car drives fantastic and love my x5 35d. I haven't gotten any issues with it. The only one thing that annoys me a bit is that engine clatter at acceleration. I love BMWs and love to play with them )driving and mechanically ;-) ) .. but this is one have no clue where to start..

Let me start it for you, you got yourself a DIESEL (which makes that DIESEL noise) case closed.

Did you not test drive it before hand? I did, that's why I am in the 35i. ;)

You know I have to agree with King and Ard on this one. I have a 2011 35d and while I notice a little of the diesel sound upon acceleration I also know it is MUCH quieter compared to other diesel vehicles. I knew what to expect when I test drove it and fell in love with that sound and it hasn't changed since I took delivery. I am not sure what you expected but I sure got what I expected which is a great running vehicle with kick @ss get up and go that looks great.

It is a little hard to decipher what you mean when you say "engine clatter". Is there a measurement you can provide??

You will always have additional noise with the diesel, and there isn't a way to get rid of it (except, as others have said, buy a gasoline engine instead). The noise is much less than with older generations of diesels due to the multiple injection events and better managed combustion process.

I would be interested, however, in whether it has changed while you have owned the vehicle. If not, then there is not much to do about it. You can tolerate it (thinking always about the fuel economy), or you can celebrate it (imagining that you are driving a heavy truck). Both approaches have been described here by different posters, and posters who are fans of the diesel tend to fall into one of those two camps.

If it has changed, I would look into the fuel quality I was buying (cetane number) and see if different fuels from different suppliers had any impact on the noise upon acceleration. The cetaine rating describes how the diesel ignites, and low cetane numbers will increase engine noise. Not all diesel fuel is the same. Cetane isn't the same as octane rating, but it is somewhat similar in concept.

I don't think there is any significant difference between the 335d and X5 35d in North America since they both use the M57 engine. If you are comparing a new model (overseas) of the 335d, then you could be comparing the newer N57 engine to the older M57 engine, and I would expect them to have different sound levels.

Oddly enough I've noticed mine getting louder and thought it was because of the colder temps we suddenly had. But then reading JCL's post it made sense to me because I had been getting my diesel at the cut rate truck stop for months and thought I was losing my mind. My last tank I went to my local Chevron (it was .05 cents a gallon more) and now it doesn't seem so noisy to me.

Overall when I'm tootling down the road I like the sound of my diesel. At first I didn't, but it has grown on me. Sure there is something slick about a gas BMW engine spinning up (my old 4.4i V8 for instance)... I actually had a friend riding with me to go skiing this weekend and after the trip when I got diesel she said 'this is a diesel?... I wouldn't have known"....so go figure.

I didn't drive an X35d before I bought it, my only experience was with a 335d and there is a difference between the 2 in sound. But happy I chose the torque monster over a 35i.

Are you comparing the noise from outside? 335d is lighter and lower, so with all other thing equal it will be quieter - less energy needed for acceleration, and the source of the noise is positioned lower relative to your ears.

I can't comment on inside noise of 335d as I've never driven it, but i suspect X5 is quieter due to better soundproofing.

This post is about finding new things about 1 particular personal observation. At iddle i can hear the diesel engine, at cruising I can hear the diesel engine and that doesn't bother me. I know it is a diesel and it will sound that way always .Yes I did test drive the car and noticed the engine rattle/clatter at the beginning of the acceleration. Even knowing that particular noise i went ahead and acquired the car. The fuel efficiency of this car is awesome despite my heavy foot :D(better gas mileage than my 335i) and power is great! Fill up is every 2 weeks :thumbup: and would not changes it for a 35i

Again I'm not disappointing about the x5 35d nor I don't like it. I love the dam SAV..
BUT, There is always someone that knows something you don't know ;)

Facts I know :
1- When cold the engine will be louder
2- X5 35d% has an extra fuel pump (high pressure) as oppose to their siblings that may contribute to this extra noise
3- 335d has a lower stance thus reducing the noise travel

Anyway thanks for all your comments. :thumbup:

The cetane level makes a substantial difference. My dad was b*tching about the same thing. Then I introduced him to the concept of higher cetane diesel fuel, which is available at some locations but it varies by state. Once we started putting in premium diesel fuel (45-47+ cetane), the clattering went away, and the engine output is both smoother and quieter especially along the highway. This has proved consistent over many months and tankfuls of varying types of diesel fuel.

In Europe, under DIN EN590 the minimum cetane level of diesel sold is 51 and thus most diesel engines including the BMW ones are designed to provide optimum performance at that level. In the US, the minimum and most common cetane number is 40; modern diesel engines will compensate for that and the behaviour is what you're experiencing. Labeling laws vary by state. My dad lives in VA: Law requires the cetane to be posted and thus, one can distinguish the difference.

Long story short: what you're experience is a result of the lower cetane diesel. The fix? Find premium diesel, which may not be available in your state. If that's the case, well, you're SOL.

Or you can additize your own fuel...which despite being verboten by BMW may be some owners' only option to using high cetane fuel...

Right, similar in that octane and cetane are both "good" for gasoline and diesel engines respectively, but for opposite reasons. High octane = large ignition delay to avoid pre-detonation. High cetane = short ignition delay to start the burn early for more complete combustion...longer burn duration...less bang.

I'll chime in here. I just got my 2012 X5 35d and I am very happy so far. The "rattle" you hear off idle is actually timing rattle and pretty common on most HPCR diesels. I own Left Coast Diesel, and we do everything from oil changes to competition builds on diesel pickups. My other truck is a 675rwhp 2004 Ram diesel and it does this pretty badly with the larger injectors and programming I have in it.. anyway, as timing is increased, especially at low rpm/high load condition (like off idle or tip-in at cruise) you will get some rattle as the rpms increase to match the timing in the map.
Hope this helps some.

Welcome. Impressive what you guys are getting out of those trucks. Real trucks. ;) I watched some dyno runs that Ken Imler in sacto was running.. CRAZY power.

(FYI HPCR = High Pressure Common Rail)

I look forward to the day folks are under the hood of these DMEs, and you can change maps, etc...after the warranties are done!

Yeah, its pretty nuts. Our sled puller is daily driven and makes 906HP (1800approx TQ, our dynojet flatlines TQ at 1500, but Cummins are generally 2:1) on a single charger with no NOS or anything.
We are just starting to get into the DMEs for the Cummins (using EFI Live) and the results have been pretty impressive so far, but we have a LOT to learn. I imagine, in typical BMW fashion, that our DMEs are pretty complicated.

Yeah. Getting in is the trick.

But Dinan can sell a tune for $1895

dollars.

:wow:

Yeah..not a dinan fan. Too much for not enough

Sent from my DROID RAZR using Tapatalk

Agree on cetane definition

I consider octane rating to be a measure of resistance to detonation, not timing delay, since timing is set by ignition.

How do the transmissions last? My brother sold a Ram after experiencing automatic transmission failures, it couldn't take stock torque levels. Went back and bought a manual version.

We build them in house. Runs about $5500 to build one like mine. Billet input, triple disc converter,constant pressure valve body. Etc.
They are junk stock

Sent from my DROID RAZR using Tapatalk

True, I was just comparing the two to highlight the fact that they are polar opposites. Timing is also controlled in a diesel not necessarily by fuel properties, but by injection timing.
I know that you knew the difference, but I have seen several people refer to octane and cetane as being analogous and wanted to dispel any confusion...:thumbup: