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New 320i engine idling noise

30526 Views 24 Replies 11 Participants Last post by  The X Men
Is it just my hearing or do the new 4 cylinders sound like diesels at idle?
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Yes, it sounds like a diesel. What you're hearing are the high-pressure fuel injectors...
Is it just my hearing or do the new 4 cylinders sound like diesels at idle?
Then why doesnt the 335 sound like that?
Yes, it sounds like a diesel. What you're hearing are the high-pressure fuel injectors...
Is the 335i a direct injection twin turbo like the new 328i N20 engine?
Then why doesnt the 335 sound like that?
yes. direct injection twin scroll turbo.
Is the 335i a direct injection twin turbo like the new 328i N20 engine?
Also, the noise goes away after the engine is warmed up, which leads me to believe the noise is from piston slapping.
Piston slapping...? Come on .I am sure I heard one ticking like a diesel however...I looked at the bafge and ir said 320i ....I was expecting 320d
Also, the noise goes away after the engine is warmed up, which leads me to believe the noise is from piston slapping.
No, That noise that happens at cold start is the cold start light off used to heat up the catalytic and lower cold start emissions. It's caused from the way the cam timing is requested during cold start and likely a portion of the combustion event actually going out the exhaust valves to heat up the pre-cat.
This is speculation on my part, but educated speculation based on my knowledge of emissions control systems.
I asked in a forum about it when I first got my 328i, as my sales consultant didn't inform me of this "feature", and knew that if it was normal then it was emissions related.

Once I get an OBDII reader that works for my 328i I'll record cam positions, timing and 02s to show how this process physically works.

I can't believe there aren't any BMW videos or technical briefs that explain this feature..

It's a real neat detail that HAS to have people returning their cars to the dealer for warranty issues in the fist 90 days of ownership for no reason.

There are a few SAE docs on cold start cam timing, but not any that I have seen that specifically say BMW uses it.
Yes, the N20 is built similarly to the 3.1 liter GM piston slap king. I am sure F30 drivers will be reporting rods being driven through engine blocks in the next year.

Come on...
Also, the noise goes away after the engine is warmed up, which leads me to believe the noise is from piston slapping.
you should see his other posts...
Yes, the N20 is built similarly to the 3.1 liter GM piston slap king. I am sure F30 drivers will be reporting rods being driven through engine blocks in the next year.

Come on...
car and driver noted the same thing:
And when a 328i pulls up, a pronounced ticking from the injectors also gives away its identity. BMW tried hard to suppress the N20's diesel-like injector noise with an acoustic cover and a thick rubber pad on top of the engine, but it remains somewhat noticeable.​

i hear the same ticking from my N54 only if i have the hood open and the engine cover removed.

my guess would be that the placement of the injectors in the head and the amount/material surrounding them is influencing how loud the injector noise is. based on what i've seen of the N20's head vs the N55/N54, the injectors on the N20 have less of the block around them.
If the noise is due to less of the block around the injector, then why does the injector quiet down after the engine is warmed up?

my guess would be that the placement of the injectors in the head and the amount/material surrounding them is influencing how loud the injector noise is. based on what i've seen of the N20's head vs the N55/N54, the injectors on the N20 have less of the block around them.
i hear the same ticking from my N54 only if i have the hood open and the engine cover removed.
Do you always drive with the engine cover removed, hood open and your head inside your engine? If not, then your N54's noise is not the same as the F30's.
OMG! How do I unsubscribe from this discussion...
yes, i do!

might i ask how you have an N20 in a 2011 328i? the OP says nothing about the noise going away once warmed up. if you have an N20 2011 328i.....

just remember folks, its "piston slap"
If the noise is due to less of the block around the injector, then why does the injector quiet down after the engine is warmed up?

Do you always drive with the engine cover removed, hood open and your head inside your engine? If not, then your N54's noise is not the same as the F30's.
Ignorance is bliss I guess.
yes, i do!

might i ask how you have an N20 in a 2011 328i? the OP says nothing about the noise going away once warmed up. if you have an N20 2011 328i.....

just remember folks, its "piston slap"
As the engine warms, the combustion chamber longitudinally expands, eliminating cold op piston slap. Interestingly, circumference slightly constricts, maintaining constant cylinder volume. Special piston rings have been developed as part of R&D which has its roots in Nikasil development.

The efficiency of cold op slap is now undisputed, after much research and a covert test program re: 2006+ 3 series engines. Hardened contact areas with micro-crystalline elasticity are proprietary BMW innovations they are not yet ready to detail - the wheels of patent protection grind slowly. There is more to this technology to be revealed!

Engine tic'g, or engineered 'piston slap' is increasingly important to emissions control and is expected to be a feature and benefit in all internal combustion engines within 5 years.
the OP says nothing about the noise going away once warmed up. if you have an N20.....

just remember folks, its "piston slap"
As engineers continues to design lower and lower friction engines and ultra short skirt pistons, piston slap will become a more common engineering issue.

A lot of early Toyota 3.5L V6 engine had the piston slap. Toyota maintain that the psiton slap noise during warm up will not harm the engine. So far, they are correct.

I am not saying the N20's cold engine noise is definitely from piston slap, but it is certainly a possibility we should consider.
I have heard a second one today idling like a diesel! Unbelieavable. What is the point of designing a turbochaged 4, if its gonna sound like your turbocharged 4 diesel, which is stronger and more torquey???
Gone is the time when even the 2.0L came with 6 cylinders...
As already noted, direct injection is noisy. The fuel rail pressure is 30 to 40 times greater than port fuel injection. The sound is the injectors opening and closing, controlling the release of extremely high pressure fuel. My guess is it is a bit noisier at idle as this is a lean burn condition.

I have no idea why the 328 is noisier than the 335.
Does it still sound like a diesel when warmed up? Most reports say no. And a comparable diesel is slower and doesn't rev as nicely. It has more torque but for those who don't want a low redline and like to wring out our cars, a diesel is a no go. 0-60 is almost 2 seconds slower than the N20 engine by the way.
I have heard a second one today idling like a diesel! Unbelieavable. What is the point of designing a turbochaged 4, if its gonna sound like your turbocharged 4 diesel, which is stronger and more torquey???
Gone is the time when even the 2.0L came with 6 cylinders...
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