E300TD - whistle/scream on low boost
 

Hi all,

I seem to have a whistle or scream on lower boost, nothing at higher boost though, it only happens when gently accelerating eg pulling away from some traffic lights.

The pipe from the rocker cover that feeds into the inlet pipe to the turbo isn't sealed properly at one end - the connector is damaged on the engine end, could this cause the noise as the turbo sucks the additional air in?

I am also thinking that there might be a vacuum bleed off pipe somewhere which is venting and making the odd noise, then again it might be a boost leak but would seem odd if its only on low boost.

I have checked the turbo and thats 100% solid, no shaft play at all and spins freely so I am thinking perhaps a vac line somewhere making a noise?

That pipe is the crankcase ventilation, it is supposed to relieve blow by and return it to the intake. In the old days that would have been vented to the atmosphere. Blow by is laden with hydrocarbons and so it is a pollutant. So now it has to be directed into the intake to be burnt again.

That leaking fitting is certainly suspect.

I will look into trying to sort out that crankcase, it makes sense for it to make noise if its open like that, will see if there is a way I can vent it temporarily to diagnose.

I believe this issue is actually the boost solenoid failing, it still boosts but removing the vac line to the wastegate actuator stops the noise (but would only run the low spring boost.

As the EGR uses the identical solenoid I am going to swap them over, I believe the solenoid also pulses to maintain a certain pressure on the turbo, its been doing that for the last 235k miles so my thought is that its slightly tired now!

I will be installing a manual boost controller at some point but would be looking to use that as a VNT/VGT controller when I go for a turbo upgrade in a year or so time.

Removing the vac line to the wastegate transducer will cut boost too so don't be fooled. Try swapping transducers from left to right, the EGR and wastegate units are interchangeable.

I'd smoke test it to look for leaks.

Thats exactly what I did, the boost was cut but I needed to test drive it around to check for the noise which had then gone.

I heard that the EGR and turbo solenoids were interchangeable so I will be swapping them over during the weekend.

I also have a mechanical boost gauge coming so I will get that plumbed in to see what the boost levels are like. I will also be using the vac line (probably the same one feeding the MAP sensor) with a manual boost controller instead soon.

Does anyone know what the wastegate spring pressure is on the stock turbo?

There's just a light weight return spring in the wastegate that actually tried to open it. The Vacuum is what holds it closed and keeps boost up. You have to maintain the ECU controlled boost because when the car reaches highway speed and levels out, the ECU will release pressure on the wastegate to lower boost and back pressure for best economy.

If the ECU doesn't see the corresponding drop in boost pressure, you will get a code.

So, in short, you can't run a traditional bleed off type boost controller on this car.

Ah I see, so the turbo is actually controlled via vacuum only rather than boost?

Seems quite an interesting way to control the turbo - would this setup work on a VNT/VGT turbo though as I always thought that the solenoid would be simply modulating the boost to the wastegate - might look into swapping out the actuator to be default closed rather than default open.

Is this the same setup as all of the other cars that use the K14 turbo or is it a Mercedes only actuator being used?

What would the code mean to the running of the rest of the engine? Would it need to see a drop in boost at the MAP sensor or would it simply be happy that the boost solenoid is still plugged in?

Edit:

Just reading up on this a bit more, I thought that all turbo actuators ran off boost rather than vacuum - lean something new everyday!

I guess it also means that its a bit easier to run a VNG/VGT turbo by simply plugging the stock vacuum line in as before.

With regards to the bleed manual boost controller, I can see how that now wouldn't work on this setup - might be able to use it on another part of the vacuum system though maybe on the MAP sensor or the vac line to the transducer.

The problem is this car is too smart for its own good...if you are trying to do modifications.

If the car throws a code it goes into limp mode, this restricts fueling and transmission shifting.

If you are trying to experiment the best platform for that is a 124, later 124s have the OM606 but it is mechanically controlled. 210s were the first drive by wire Diesels.

You probably have a much greater selection over there, we only got one 124 with OM606 (and it was n/a) in 1995 before the switch to W210 in 1996. 96 and 97 were n/a, we got the turbo for 98 and 99. Never got the CDI engines in a 210 here, had to wait for the 211 in 2005.

I have the EGR delete and bypass done on my car, but if the car does not start successfully (including forgetting to glow) then it throws P0400 and goes into limp mode. For this reason I have a cheap OBDII reader that stays in the glove box.

I've always thought a VGT would be a virtual direct swap since the controller would follow almost the same profile as the vacuum wastegate control.

As far as I know, this is the only car that runs vaccum controlled wastegate.

I have experimented the bejezzus out of this car. If you have a question about what works or not, ask away. I may be able to save you some time.

In the U.S. 124s, the OM603 (1987s) used a simple pressure waste gate
The OM602 (1990-1993) and the OM606 (1995) used the vacuum waste gate

There is a popular thread on this forum for converting the vacuum waste gate to the pressure waste gate. But as Evan says, this won't work on the OM606.962 on the W210 due to it throwing codes when the boost does not change when commanded by the ECU.

http://www.peachparts.com/shopforum/diesel-discussion/212097-wastegate-actuator-swap-om602-962-a.html

Thanks for the info guys, I actually don't have an issue with the way the boost is controlled, just need to figure out how everything works. I know on a previous car I was using an electronic boost controller which ensured that boost was reached as quick as possible with careful wastegate control - this seems to be standard on my car.

I am not adverse to ECU tuning and remapping, I am specifically not going for a mechanical OM603 pump but will be getting a stock electronically controlled pump uprated instead to maintain all of the stock functions.

The car is indeed drive by wire, however there is a throttle cable which is connected to a throttle sensor in the engine bay - the signals of this can be tweaked.

To be honest simply swapping over to a VGT/VNT turbo will be the preferred option anyway - looking at a Holset HE series rather than the usual HX35/40 etc as then I can have boost throughout the rev range.

I just need to work out how best to initially adjust the sensors to read slightly differently for the ECU to then use a different part of the map. I know there has been work around increasing the max fueling on the stock pump as well as resistor mods - basically I just need to make the ECU think its injecting less fuel than it actually is.

I don't really see it as an issue but more of a challenge, the car is quite clever even though it is using an engine which is mechanical.

Now that I have sorted out the MAF issue and hopefully will sort out the boost transducer issue over the weekend the car will actually accelerate quite well with stock settings. After all it was the fastest diesel produced when it came out!

I will do the swap over soon and give everyone an update, I bought the OM606.962 engine and there just happened to also be a car attached to it - just need to make that part work with the engine!

Here's a couple helpful hints:

The ECU is pretty smart but it's focused in a couple narrow areas, mainly for emission control. In other areas, it's a non-issue.

The ECU cares about:

1. Does the MAF decrease when I open EGR?
2. Does boost decrease when I release the wastegate?
3. Does the boost remain under ~30 PSI absolute?
4. Are the cylinders putting out the same amount of power? (No misfire)
5. Is the fuel rack where I told it to be?

All of the above being satisfied, the ECU does not care about:

1. How much fuel is being injected into the cylinder.

Thank you so much for your help on this and letting me know which parts of the system are sensitive to change.

It looks like I could perhaps tweak a few of the readings from various sensors to run it as I would like it. Although if I bolt on a larger turbo then even though it might be set to 1 bar of boost, its going to be flowing more air than the stock turbo!

I will swap over that wastegate transducer with the EGR one to see what difference that makes, I am guessing as the transducer on the turbo side has been in constant use vs the EGR side which hasn't as much it will be good to see the difference.