Turbo Noise Question
 

Hi All:
Just a question regarding the turbo on my 1985 300TD. I am used to the turbo sound from big trucks spooling up (Volunteer Firefighter),
but was wondering if the following is normal for a MB.

At around 2000 rpm with throttle you can feel the turbo kick in On release of the throttle there is a prominent whistling sound until the engine drops back to around 2000 rpm.
I do not hear it spooling up. Is this a normal sound on deceleration? :confused:
Thanks in advance for your replies.
Ron

Sounds like you might have a gasket leak.........mine doesn't make that sound.

Is this a california car?
 

I posted a similar question yesterday. On CA cars there was an emissions device called an air recirculation valve. It dumps pressurized air from the intake manifold back into the intake tube. Mine whistles like crazy while backing off on the accelerator on reaching cruising speed. Loose connections in the intake tubing makes the whistle much louder.

I am plugging the vacuum line that actuates it when I get home. The general consensus on this forum is that this will either increase turbo lag a bit a highway speeds, or perhaps improve performance a bit, depending on whose opinions you believe.

See the following threads for some more info:
http://www.peachparts.com/shopforum/diesel-discussion/111196-300sd-intermittant-squeal-engine-pass-side.html?highlight=air+recirculation+valve
http://www.peachparts.com/shopforum/diesel-discussion/112210-turbo-vacuum-line.html?highlight=air+recirculation+valve
http://www.peachparts.com/shopforum/diesel-discussion/44354-air-recirculation-valve-turbo.html?highlight=air+recirculation+valve

If you can feel a prominent turbo kick, then you may want to tweaking your alda. earch using the keywords "alda adjustment" and tweak the alda according to the instructions you find. You will probably get a big enough increase in low end power.that you no longer notice the turbo kicking in.

Check your air recirculation valve
 

I posted a similar question yesterday. On CA cars there was an emissions device called an air recirculation valve. It dumps pressurized air from the intake manifold back into the intake tube. Mine whistles like crazy while backing off on the accelerator on reaching cruising speed. Loose connections in the intake tubing makes the whistle much louder. The valve is located behind the flex hose that feeds air to the air filter housing.

I am plugging the vacuum line that actuates the ARV on my car when I get home tonight and see how performance is affected. The general consensus from the threads I have read is that this will either increase turbo lag a bit at highway speeds or perhaps improve performance a bit, depending on whose opinions you believe.

See the following threads for some more info. One of them has a picture of the ARV with a blue vacuum line attached to it:
http://www.peachparts.com/shopforum/diesel-discussion/111196-300sd-intermittant-squeal-engine-pass-side.html?highlight=air+recirculation+valve
http://www.peachparts.com/shopforum/diesel-discussion/112210-turbo-vacuum-line.html?highlight=air+recirculation+valve
http://www.peachparts.com/shopforum/diesel-discussion/44354-air-recirculation-valve-turbo.html?highlight=air+recirculation+valve

If you can feel a prominent turbo kick, then you may want to consider tweaking your alda to richen your mixture at low rpm's, if you have not already done so. Search using the keywords "alda adjustment" and adjust the alda according to the instructions you find. You will probably get a big enough increase in low end power that you no longer notice the turbo kicking in. :D

Oops...
 

Sorry for the double post.

Press "edit" in lower right hand corner of post.

Select "delete"

Press "delete this post".

Ray, Thanks for the information and thread links. I will check those items tomorrow.
I considered tweaking the ADLA after reading about it, but a diesel mechanic friend of mine recommended I not touch it.
His concern is raising the fuel mixture will increase the exhaust temperature and potential turbo damage due to the higher temperature.
Best wishes, Ron

It's normal. If you replace the stock air filter setup with the "High performance" model that's been discussed lately, it will become much more noticable.

With no exhaust on my TD, I can VERY clearly hear the garrett/KKK turbos spool up/down. The Garrett makes a very loud WOOSH, like a gasser blow-off valve, when the pedel is released at high boost (8-13psi). The KKK turbo makes a high-pitch wistle-whine when crusing at low boost (2-5psi) and decelerating. Both have a nice sucking whine at full 13.5psi. :D

I've heard that this sound is much more noticeable on the 85's.... mine does the same thing.

I hear the turbo kick in on my 85, and not on the 83.

That occured last year on my SDL. It is still there, although much more subdued than before.

Well, I don't have to be on the accelerator. At 2400 - 2600 there is a whistle, much like a tea-kettle just beginning to boil. It's always there, but more prominent under pressure.

I don't care enough to inspect it. It is not annoying, just piqued my thoughts of interest at the time.

I plugged the ARV vac. line on my '85 300sd over the weekend
 

The post-acceleration whistle is gone. Interestingly enough, I do not notice the turbo spooling up on my car at all. But whistle from the ARV was very noticeable on my car. Good riddance. I hated that noise. I noticed no change in performance with the ARV disabled, whatever that's worth.

As far as ALDA adjustment is concerned:

I don't know if high EGT's are a problem with alda adjustment. I have not read anything about that in any of the many alda-related posts that you will find on this forum. I do know that by backing out my alda screw one turn, I realized a very noticeable increase in off-idle performance. Prior to adjustment my car was very sluggish on pulling out into traffic. I nearly floored it most of the time. When the rpm's climbed up to 2500, the car would suddenly leap forward. Now I just ease the accelerator down a bit and the car accelerates in a smooth, linear fashion. I find it hard to believe that that is not how MB designed the car to behave.

My gas mileage for the first tankful after the adjustment was 23 mpg, about what EPA estimated for the car when it was new. Nearly all of my driving was around town, so the alda adjustment was playing some role in the mixture I was burning much of the time. My conclusion is that on average I am burning about the same amount of fuel now as the original owner did when the car was new. Based on that somewhat simplistic reasoning, abnormally elevated EGT's due to alda tweaking should not be a problem for me. Please note that I have my fingers crossed here, but I now grin everytime I press the accelerator :)

Perhaps some of the forum members with EGT guages installed can provide some before/after data on EGT's with changes alda screw (Hint...). It would be really interesting to be able to relate some the subjective observations about performance increases, increases in smoking (or not), etc., which are discussed endlessly in alda-related threads, with **real live numbers**.

Please understand that maximum EGT, in the approximate range of 1150°F., will only occur during full boost and maximum fuel conditions. The adjustment of the ALDA, which affects the feel of the vehicle in low power conditions, will have no effect on the EGT. Maximum fuel is governed by the full load screw in the IP. The ALDA cannot affect this.

The only thing that the ALDA does is to add more fuel when you press down slightly with your right foot. You can do the same thing if you just press down further with your right foot. The vehicle "feels" more responsive because you need less pedal to get it to move.

I have just developed the "whistle" also although my car is an '82 with a Garrett turbo. As far as I can tell I dont have an ARV on that year, It is a Cal. model. I cant imagine a blown gasket would make that sound. I was thinking the impeller was contacting the compressor housing at a certain rpm. Anyways its driving me nuts!

Thank you all for your replies. :) I do have the full emission package, not sure if it is Ca or if all 1985s adopted this system to meet federal standards. Since the "Whistle" is not a fault (I checked for leaks, etc.), I will leave well enough alone. I kinda like it.
As to the ADLA. Since it only effects the low rpm range prior to boost, I may give it a tweak for *****s and giggles. (Oops, wrong country).

Thanks,
Ron Young

Stable:
1973 Jag Series 3 E type V12
1976 Triumph TR6
1985 MB 300TD wagon
2000 Volvo C70 (wife's ride)
2003 Ram 2500 Cummings Diesel (towing truck)
2004 Ram 2500 Hemi (Work Truck, 9 MPG, reason I bought the 300TD)