Should I be able to hear the turbo spooling? - Page 3 - PeachParts Mercedes-Benz Forum

katja · #31 09-29-2006, 03:31 PM

Nice to see a thread about this. I thought I was just me. I've wondered for years why I couldn't hear the turbo whine on Mercedes turbodiesels, but can hear it easily on a Cummins, PowerStroke, Duramax or TDI. On a Sprinter or new CDI, one can barely hear the engine, but the turbo whine is quite noticeable.
It seems like the exhaust setup has the most to do with not being able to hear the whine, although I know if I really listen close I can hear it a little even on a stock 300SD. The ONLY time I've ever really noticed the sound of the turbo was on a 300SD in poor condition with a rusted out, partially missing exhaust. I thought it sounded great though.

I'm impressed how much my 240D quieted down with new exhaust, new engine mounts, valve adjustment, replacing the oil bath air filter system (had been converted to a foam one), and 20% biodiesel. Maybe with a new underhood pad, better insulation under the dash & maybe some dynamat in the interior, it will be as quiet as a new CDI...lol....

TheDon · #32 09-29-2006, 03:40 PM

Quote:

Originally Posted by Shorebilly

Howdy again,

When you folks speak of 'Blow Off"......are you referring to what I know as Turbocharger surge......???

When a turbocharger if well loaded, and then the load is removed from the engine.....the Turbo will "bark".....sometimes sounds like a gunshot on large turbos......large like bigger than your auto.....20,000 HP MAN/B&W

Anyhow...that noise is actually the Turbo (compressor side) blade tips breaking the sound barrier......as the hot exhaust, hottest under load, spools up the turbo on the turbine side.....and the load is dropped, fuel rack closes...Engine RPM drops......charge air ceases to flow, air flow stagnates, momentarilly at compressor.......thus turbo becomes unloaded rapidly.....and it spins up fasrer.......blade tips break sound barrier........

Just thought y'all might be interested.....

SB

cooool... i find it so interesting that the tip of the blade is moving faster than the center....i do know why... but its soo cool.. i frign need to build my jet engine using a car turbocharger.... the blade tip reaches speeds faster than .9 mach

85chedeng300D · #33 09-29-2006, 08:22 PM

Is the gasser's blow-off valve similar to the MB diesel's air recirculation valve except that MB's suck the air again to the intake instead of dumping it to the outside atmosphere just like the Dodge Neon SRT4's and the Chrysler PT Turbo's?

#34 09-29-2006, 08:37 PM

On 2006 Jetta TDI you can hear it when it kicks in you not only hear it but feel it when it takes off down the road..One fine car runs like hell 45 to 50 mpg. on 75% wvo 25% diesel. LOVE IT..

PanzerSD · #35 09-29-2006, 11:15 PM

All I can hear when I accelerate is my turbo

my exhaust terminates just below the rear seat

When I had JUST my downpipe I could hear the turbo from idle, it sounded like a big truck

Flyin4now · #36 10-09-2006, 12:28 PM

After reading this whole thread, I'm wondering if what I hear from my 85 300D is what you guys are referring to. Some of you are calling it a whine, while others refer to it as spooling up. Mine makes more of what I would call a shrieking noise, and usually does so just after an upshift. It almost sounds a little like a high pitched squealing belt. I notice I have to change pressure on the pedal in order to make it go away. Is this normal?

Thanks

PanzerSD · #37 10-09-2006, 02:17 PM

Quote:

Originally Posted by Flyin4now

After reading this whole thread, I'm wondering if what I hear from my 85 300D is what you guys are referring to. Some of you are calling it a whine, while others refer to it as spooling up. Mine makes more of what I would call a shrieking noise, and usually does so just after an upshift. It almost sounds a little like a high pitched squealing belt. I notice I have to change pressure on the pedal in order to make it go away. Is this normal?

Thanks

I know that sound, I had it in my '80 SD for a long time. it turned out to be an exhaust leak in the flex pipe. one of the rings in the flex pipe had broken, allowing the whole assembly to rotate when held in my hand, and the looseness of the two pieces resonates when theres alot of exhaust flowing thru it, much like the reed on a clarinet or saxaphone...very irritating and if you can hear it in the car, it's 40x louder outside the car.
Also, it could be a manifold gasket leak producing the same sound, but it's much more likely to be an exhaust pipe issue. Real turbo spool up should sound like a nice hissing whistle sound...it can't be mistaken for anything else other than a turbo...

Check your flex pipe and other exhaust joints for black spots...

2.5Turbo · #38 10-09-2006, 02:35 PM

That's what I would guess. Mine had a leak on the manifold gasket between the turbo and the manifold. A couple nuts went missing and a gap opened up. It sounded like somebody was strangling a rat under there.

Flyin4now · #39 10-09-2006, 09:13 PM

Thanks for the tips! I'll check out the flex pipe tomorrow.

Hit Man X · #40 10-10-2006, 03:43 AM

The Garrett on my SD is louder than the KKK on my other stuff (SDL, 745is, etc). You can BARELY hear the KKKs

DubMutant · #41 10-10-2006, 04:12 PM

After a 250 mile round trip this weekend from W.Mass to RI and back, I can definately say I hear the turbo. It is a distinct sound, mine is soft but if I listen I can hear it alright. If I drop the tranny into 3 and stuff the pedal and then when I an up to about 4500 rpm or so dump it into D I can hear the blowoff.
If I just stuff the pedal in D from a dead stop I can hear it spool also, so I know everything works alright.

2.5Turbo · #42 10-10-2006, 08:58 PM

Quote:

Originally Posted by DubMutant

If I drop the tranny into 3 and stuff the pedal and then when I an up to about 4500 rpm or so dump it into D I can hear the blowoff.

I don't know what you're hearing, but unless you put one on there, you're not hearing a blowoff valve. Diesels have absolutely no need for one.

85chedeng300D · #43 10-10-2006, 09:50 PM

Quote:

Originally Posted by 2.5Turbo

I don't know what you're hearing, but unless you put one on there, you're not hearing a blowoff valve. Diesels have absolutely no need for one.

he might be referring to the air recirculating valve. mine does have one, and i can hear the the high pitched turbo whistle or whine everytime it opens up from time to time on varying rpms when tranny is shifting gears.
that's what i am asking on post # 33 of this thread. i know diesel don't really need it but, are those recirculating valve for MB Diesels are the equivalent of the blow-off valves for the gas-ricers except that MB Diesels recirculate the excess air and those aftermarket blow-off valves for tuners just dumps it out of the atmosphere?

PatricdeBoer · #44 10-10-2006, 10:29 PM

I can hear it if I am accelerating next to a wall or K rail on the freeway with the windows down.

Flyin4now · #45 12-03-2006, 12:39 AM

Well, I was able to tighten the aft coupling on the flex pipe a couple of turns, but after a drive today, it still gives me the shrieking noise. I haven't driven the car for about a month, dash pulled, waiting on parts, and work and family getting in the way of working on the car. I have not noticed any black spots on any exhaust surfaces. So, my question is: How do I determine where this high-pitched squeal is coming from?