Delica Canada | Mitsubishi Van Club

Here we go, easy with pictures:

1. Whats this? 2. And what might be making it toss all this sludge up there?

I am not familiar with the diesel model L300 (I have USA 4G64 version), but I do have experience with turbo engines and it look like that is a emergency overboost 'pop-off valve'. It looks like there is some blow-by getting into the intake manifold and being ejected by the valve when it activates.

...yup, that would be the blow-off/ dump valve. Not for "emergency", just routine overcharge from the turbo. I included a caption that best descibes its purpose if interested. The oil is some blow-by from your PCV return.

“Back pressure caused by lifting off the throttle can cause the compressor of the turbo to stall. In extreme cases, the compressor can actually shatter. After a dump valve is fitted, you will notice an immediate change in feel to the car, especially after changing gear. This is because the turbo is kept spinning during closed-throttle conditions and is therefore able to provide full-boost quicker.”

To take advantage of the spin up lag a different/additional dump valves can reduce the pressure more rapidly and therefore decrease the load on the compressor thus decrease the spin up time for when you put you foot back down.

bionic wrote:...yup, that would be the blow-off/ dump valve. Not for "emergency", just routine overcharge from the turbo. I included a caption that best descibes its purpose if interested. The oil is some blow-by from your PCV return.

“Back pressure caused by lifting off the throttle can cause the compressor of the turbo to stall. In extreme cases, the compressor can actually shatter. After a dump valve is fitted, you will notice an immediate change in feel to the car, especially after changing gear. This is because the turbo is kept spinning during closed-throttle conditions and is therefore able to provide full-boost quicker.”

To take advantage of the spin up lag a different/additional dump valves can reduce the pressure more rapidly and therefore decrease the load on the compressor thus decrease the spin up time for when you put you foot back down.

Not quite. The above is only accurate for a petrol engine where the throttle is usually some kind of venturi valve which closes and then this can occur, on a diesel engine, there is no venturi, diesel engines like all the air they can get at all times, the throttle on a diesel only modulates the fuel input. It's not a dump valve, its an over boost/pop off valve, fitted for the emergency sistuation where the wastegate actuator valve fails, or operates out of spec, and the pressure in the manifold exceeds a certain amount. In our case around 14 or 15 psi IIRC. I t should not operate under normal conditions as the spring weakens and it starts to vent at lower psi.

There is no purpose to a dump valve on a diesel except for sound effects :D

Oh, and you need a new one! Or a secondhand one from a scrapper.

FalcoColumbarius wrote:AKA a wastegate. See: http://www.delica.ca/forum/turbo-wasteg ... -7786.html

Falco.

Not quite again The wastegate is quite near it though.

FWIW it looks like the top is missing from that, I bet it came apart and you have not much boost now, due to it constantly venting.

This little trick stops the valve from operating. however, I'd only use it with a boost gauge. It looks like a piece of yours is missing. If that's the case just blank it off!

Hm, lots to think about. Thanks all for the 'Help an engine noob' session.

That may be what causes the 'flitting' sound when under load (when I walk on it going up hill, or generally any time I put the pedal down with a vengeance.

So, I'm missing the top piece, can't remember ever noticing it being there or not being there. I had the turbo rebuilt at CVI last year, I think it looked like that at that time, (no top)

Time to take a closer look after seeing the vids (thanks Falco) and see what I'm actually missing, and where to get parts.

lrp374 wrote:This little trick stops the valve from operating. however, I'd only use it with a boost gauge. It looks like a piece of yours is missing. If that's the case just blank it off!

Bad idea, this can cause major damage if the wastegate fails. It can happen quick enough that you will not notice it on your boost gauge. It's like chaining the emergency exit doors shut, and saying you'll keep an eye on it. It should be fixed properly.
Jason

On closer inspection......

Quick and dirty EGR blanking? I think I need to get someone to take a look at it. I'm (barely) mediocre at wrenching and this van is my only transportation.
Looks like there's a pretty good leak, and I can't tell from visual inspection exactly where its coming from.
Just gotta find a good shop in Kamloops now, anyone got a suggestion?

Yeah thats an attempt to stop the EGR opening, it should work too, assuming that the egr isnt cruddy inside and sticking open.

As for the pop off valve, since there are parts missing from it, just get another, it screws into the manifold, and you just need to get another, one from a van being parted out will be better than what you have.

It should never open under normal driving conditions with a working wastegate actuator.

It's there for when bad things might happen, you dont want to clamp it shut either.

yojimbo is absolutely correct, should have re-read my response before posting..it should have wrote "actuator dump" not "blow-off"...

Here is a reasonable explanation of the "actuator dump" on a diesel. ATTN: FALCO

Dump valves and wastegates are different:

Waste gate is on the exhaust side and opens at a predetermined boost pressure to bypass some of the exhaust gas and hence limit the boost pressure and turbine speed. Dump valve is fitted in the air side between the turbo and inlet manifold (or on it in our case) and opens when the throttle is shut to vent the air and stop the turbo stalling, as has been said. There is little point in having a dump valve on a diesel engine because you don't have a throttle and aren't therefore in danger of closing off the inlet manifold suddenly at high boost pressures, and stalling the turbo.
What we do have is in effect is a "blow-off" of sorts...but one with a primary function of use only under extreme over pressurization...

yojimbo wrote:

bionic wrote:...yup, that would be the blow-off/ dump valve. Not for "emergency", just routine overcharge from the turbo. I included a caption that best descibes its purpose if interested. The oil is some blow-by from your PCV return.

“Back pressure caused by lifting off the throttle can cause the compressor of the turbo to stall. In extreme cases, the compressor can actually shatter. After a dump valve is fitted, you will notice an immediate change in feel to the car, especially after changing gear. This is because the turbo is kept spinning during closed-throttle conditions and is therefore able to provide full-boost quicker.”

To take advantage of the spin up lag a different/additional dump valves can reduce the pressure more rapidly and therefore decrease the load on the compressor thus decrease the spin up time for when you put you foot back down.

Not quite. The above is only accurate for a petrol engine where the throttle is usually some kind of venturi valve which closes and then this can occur, on a diesel engine, there is no venturi, diesel engines like all the air they can get at all times, the throttle on a diesel only modulates the fuel input. It's not a dump valve, its an over boost/pop off valve, fitted for the emergency sistuation where the wastegate actuator valve fails, or operates out of spec, and the pressure in the manifold exceeds a certain amount. In our case around 14 or 15 psi IIRC. I t should not operate under normal conditions as the spring weakens and it starts to vent at lower psi.

There is no purpose to a dump valve on a diesel except for sound effects :D

Oh, and you need a new one! Or a secondhand one from a scrapper.

This is the same in gas cars; the factory puts on one for emergency over boost not for turbo performance.

Yokohama wrote:

yojimbo wrote:

bionic wrote:...yup, that would be the blow-off/ dump valve. Not for "emergency", just routine overcharge from the turbo. I included a caption that best descibes its purpose if interested. The oil is some blow-by from your PCV return.

“Back pressure caused by lifting off the throttle can cause the compressor of the turbo to stall. In extreme cases, the compressor can actually shatter. After a dump valve is fitted, you will notice an immediate change in feel to the car, especially after changing gear. This is because the turbo is kept spinning during closed-throttle conditions and is therefore able to provide full-boost quicker.”

To take advantage of the spin up lag a different/additional dump valves can reduce the pressure more rapidly and therefore decrease the load on the compressor thus decrease the spin up time for when you put you foot back down.

Not quite. The above is only accurate for a petrol engine where the throttle is usually some kind of venturi valve which closes and then this can occur, on a diesel engine, there is no venturi, diesel engines like all the air they can get at all times, the throttle on a diesel only modulates the fuel input. It's not a dump valve, its an over boost/pop off valve, fitted for the emergency sistuation where the wastegate actuator valve fails, or operates out of spec, and the pressure in the manifold exceeds a certain amount. In our case around 14 or 15 psi IIRC. I t should not operate under normal conditions as the spring weakens and it starts to vent at lower psi.

There is no purpose to a dump valve on a diesel except for sound effects :D

Oh, and you need a new one! Or a secondhand one from a scrapper.

This is the same in gas cars; the factory puts on one for emergency over boost not for turbo performance.

No, yojimbo is correct. In gas motors the blow off is resposible for overpressure and has an VALVE which is constantly in use during the compression/decompression cycle to preven compressor stalling. On a diesel, its primary function is to relieve intake pressure in the event the wastegate malfunctions.

yojimbo wrote:Yeah thats an attempt to stop the EGR opening, it should work too, assuming that the egr isnt cruddy inside and sticking open.

As for the pop off valve, since there are parts missing from it, just get another, it screws into the manifold, and you just need to get another, one from a van being parted out will be better than what you have.

It should never open under normal driving conditions with a working wastegate actuator.

It's there for when bad things might happen, you dont want to clamp it shut either.

Sounds like that's where I should start looking. Also had a quick chat with a few shops on the coast, one agreed, the other wanted to sell me a new turbo....