Thread: Another Turbo Build! Questions

When I installed my provent I had serious oil consumption issues which I rectified by modifying the provent.
After a lot of musing I think I have a process by which the provent was trying to kill my engine.

The plumbing was to the factory sump drain (below oil level), to the intake pre-turbo and to the factory rocker cover breather.

The failure method is as below.

High boost raising the crankcase pressure.
High boost also dropping the pressure in the intake and in the provent.
Provent body is below atmospheric, sump is above atmospheric.
Oil is drawn up the provent drain, into the provent and partially or completely flooding the lower cone.
The breather flow through the provent (which in factory form is out the lower drain) is increased and this takes oil with it to the turbo which is misted and heads straight into the engine. A large amount of this oil also is centrifuged out into the intake tract and enters the engine in large gulps during or shortly after cornering.

The oil consumption was extreme enough that the engine ran on it's own oil at least half a dozen times. Including when my wife was driving it alone. Several times it produced enough smoke that vehicle was engulfed.

It is only because the 4BD1T is such a robust engine that it survived this treatment. It drank somewhere over 5 litres of oil in 2,500km. The worst run drank almost a litre of oil in 10km. There was no engine damage. I did rebuild and swap two turbos to try and isolate the problem.
Contrast this with Serge's 2.8L engine which drank a little oil through the intake from an overfill and cost him about $8k to rebuild.

Now this consumption was worst due to my usage. Corners, hills, 24psi boost and accelleration/braking combined to throw oil at the provent outlet. If I was driving at cruise (8-9psi) on a flat road the oil consumption would not be a problem. But I do not live in an area of long flat roads. I also like using full boost.

The permanent solution was to modify the provent to run the breather inlet into the lower port and the breather outlet from the top port. This keeps the air leaving the top as far from the oil as possible. Oil consumption since this mod has been insignificant.

It should be noted that the vacuum my turbo pulls at max boost is only halfway up the scale of the Donaldson Informer that I use to monitor air-filter performance. It takes around 2.5kPa (2.5% of an atmosphere) to draw/push oil up a 0.3m column.

Originally Posted by Dougal

When I installed my provent I had serious oil consumption issues which I rectified by modifying the provent.
After a lot of musing I think I have a process by which the provent was trying to kill my engine.

The plumbing was to the factory sump drain (below oil level), to the intake pre-turbo and to the factory rocker cover breather.

The failure method is as below.

High boost raising the crankcase pressure.
High boost also dropping the pressure in the intake and in the provent.
Provent body is below atmospheric, sump is above atmospheric.
Oil is drawn up the provent drain, into the provent and partially or completely flooding the lower cone.
The breather flow through the provent (which in factory form is out the lower drain) is increased and this takes oil with it to the turbo which is misted and heads straight into the engine. A large amount of this oil also is centrifuged out into the intake tract and enters the engine in large gulps during or shortly after cornering.

The oil consumption was extreme enough that the engine ran on it's own oil at least half a dozen times. Including when my wife was driving it alone. Several times it produced enough smoke that vehicle was engulfed.

It is only because the 4BD1T is such a robust engine that it survived this treatment. It drank somewhere over 5 litres of oil in 2,500km. The worst run drank almost a litre of oil in 10km. There was no engine damage. I did rebuild and swap two turbos to try and isolate the problem.
Contrast this with Serge's 2.8L engine which drank a little oil through the intake from an overfill and cost him about $8k to rebuild.

Now this consumption was worst due to my usage. Corners, hills, 24psi boost and accelleration/braking combined to throw oil at the provent outlet. If I was driving at cruise (8-9psi) on a flat road the oil consumption would not be a problem. But I do not live in an area of long flat roads. I also like using full boost.

The permanent solution was to modify the provent to run the breather inlet into the lower port and the breather outlet from the top port. This keeps the air leaving the top as far from the oil as possible. Oil consumption since this mod has been insignificant.

It should be noted that the vacuum my turbo pulls at max boost is only halfway up the scale of the Donaldson Informer that I use to monitor air-filter performance. It takes around 2.5kPa (2.5% of an atmosphere) to draw/push oil up a 0.3m column.

Dougal, The (air) outlet has a valve which shuts off airflow if the vacuum gets too high.

So your scenario shouldn't happen, and therefore I am highly dubious of your theory. Only if your filter is blocked could the DP across the filter get high enough to provide the pressure needed to suck up oil through the drain.

However - I think it is a good idea on any 4x4 to install the check valve in the drain line to make sure the Provent cannot suck oil up the drain under any circumstances.

p.s. - I did mention to M+H that you had some issues and swapped your inlet and outlet. The PV 400 (up to 400 kW so larger) has both the inlet and outlet at the top.

Originally Posted by isuzurover

Dougal, The (air) outlet has a valve which shuts off airflow if the vacuum gets too high.

Yes it does, this is the valve I removed completely when modifying the provent.
I don't believe this valve was doing it's job at all. It's simply a spring with a rubber diaphragm which will close the inlet a little more when the intake gets below atmospheric.
But it cannot close completely, it's just there to modulate the flow. Blowby keeps it open.

It should be noted that this valve sits in a pocket which can't drain. Once oil has sloshed into there, the only way out is the hose to the intake.

Originally Posted by isuzurover

So your scenario shouldn't happen, and therefore I am highly dubious of your theory. Only if your filter is blocked could the DP across the filter get high enough to provide the pressure needed to suck up oil through the drain.

There are two pressures at play.
Intake depression and sump pressurisation. Around 1kpa suction exists on the intake, I know that. It's measured by the informer.
It's no problem at all to get the other 2+ kPa from the crankcase under high load.

If you don't think my theory is possible, I'm certainly willing to hear yours. The breather does not produce the amount of oil which flowed through the intake, the sump drain is the only other oil source.

Originally Posted by isuzurover

However - I think it is a good idea on any 4x4 to install the check valve in the drain line to make sure the Provent cannot suck oil up the drain under any circumstances.

In a continuous load situation (say towing against a strong head-wind for an hour or so) that would lead to all breather oil headed straight back into the inlet. Maybe not a problem for vehicles with internal oil seperators. But not good on a 4BD1T which requires an external seperator.

I think the provent needs a completely different set of install instructions for 4wd's. Firstly avoiding low mounting positions.

But the single biggest problem is the inlet and outlet on the provent are around the wrong way.
Replumbed to put the outlet on the top side where it takes filtered air it works perfectly.

Originally Posted by Dougal

... It's simply a spring with a rubber diaphragm which will close the inlet a little more when the intake gets below atmospheric.
But it cannot close completely, it's just there to modulate the flow. ...

From memory the valve closes (fully) when DP gets to -20 mBar. I assume you had > 25 cm of vertical separation between the bottom of the Provent and the sump connection? [ if not then there is your problem ]

The bottom line is that these things are designed for (and have been installed on) many, many TD engines up to 200 kW. Your issue was the first reported.

Originally Posted by isuzurover

From memory the valve closes (fully) when DP gets to -20 mBar. I assume you had > 25 cm of vertical separation between the bottom of the Provent and the sump connection? [ if not then there is your problem ]

The valve is between atmospheric and the pressure inside the provent cone. It can never close because the pressure in the provent never gets below atmospheric. It is always passing positively pressurised blowby from the breather.

1kPa suction at the air-filter which is a metre away isn't going to close it when I likely have several times that in the crank-case pushing oil up the drain.

I have 300mm vertical from sump drain tube to the provent plastic drain.

Originally Posted by isuzurover

The bottom line is that these things are designed for (and have been installed on) many, many TD engines up to 200 kW. Your issue was the first reported.

The fitments I have seen are all around 60-100kw. Most were also running a catch-can setup where there was no drain to pull oil up and the engine had enough air/oil seperation internally that the factory deemed an external seperator wasn't needed.
In short, these were setups which were didn't require a provent at all. So not much of a test really.

Since you are involved in these I thought you might be interested in the actual problem, the solutions and the potential for this (serious) problem to occur in other installations.

Are you? Right now I'm just hearing denial.

Originally Posted by Dougal

The valve is between atmospheric and the pressure inside the provent cone. It can never close because the pressure in the provent never gets below atmospheric. It is always passing positively pressurised blowby from the breather.

1kPa suction at the air-filter which is a metre away isn't going to close it when I likely have several times that in the crank-case pushing oil up the drain.

I have 300mm vertical from sump drain tube to the provent plastic drain.



The fitments I have seen are all around 60-100kw. Most were also running a catch-can setup where there was no drain to pull oil up and the engine had enough air/oil seperation internally that the factory deemed an external seperator wasn't needed.
In short, these were setups which were didn't require a provent at all. So not much of a test really.

Since you are involved in these I thought you might be interested in the actual problem, the solutions and the potential for this (serious) problem to occur in other installations.

Are you? Right now I'm just hearing denial.

Dougal - this is getting silly.

As I said before - I passed on your (previous) comments to M+H (Head of PV R&D) - how is that denial?
I have no input into housing design - my involvement is optimising the media/elements.

There are many thousands (millions) of these things sold worldwide - aftermarket and OEM, and yours was the first report of such issues.

I have personally fitted Provents to TD5 engines with the drain plumbed into the sump (via one-way valve) with no issues.

Again - Where is the denial?

I am led to believe, based on the above, that your problem was due to mounting the PV too low down in the engine bay and not using a one-way valve in the drain - which as I said I would reccommend for any 4x4 install.

Emotive BS such as "killing your engine" is counterproductive.

p.s. - I went and checked in the lab. The outlet does close completely if the DP between the upstream side of the filter element and the outlet is sufficient.

Originally Posted by isuzurover

Dougal - this is getting silly.

As I said before - I passed on your (previous) comments to M+H (Head of PV R&D) - how is that denial?
I have no input into housing design - my involvement is optimising the media/elements.

There are many thousands (millions) of these things sold worldwide - aftermarket and OEM, and yours was the first report of such issues.

I have personally fitted Provents to TD5 engines with the drain plumbed into the sump (via one-way valve) with no issues.

Again - Where is the denial?

I am led to believe, based on the above, that your problem was due to mounting the PV too low down in the engine bay and not using a one-way valve in the drain - which as I said I would reccommend for any 4x4 install.

Emotive BS such as "killing your engine" is counterproductive.

p.s. - I went and checked in the lab. The outlet does close completely if the DP between the upstream side of the filter element and the outlet is sufficient.

There is nothing emotive about "killing my engine". If you have ever witnessed an engine inhaling half a cup of oil from the intake, then you will understand. I continue to be amazed that my engine survived this. It didn't happen just once.
Left hand turns (or indeed slopes) would cause the oil which sucked from the provent into the intake and accumulated in the intake piping to enter the intake manifold all at once.
The engine would start hammering and run at ~2,500rpm on the oil. The exhaust created a smoke screen thick enough to hide the road behind. This would take 10-15 seconds to stop.

My provent was installed according to the instructions, I am reading them again now. The check valve is only for those running a drain above the sump oil level. I cannot find any minimum drain height in the documentation.

You've stated above you were highly dubious of my theory and that you can get the valve to close in lab conditions. Yet how can a valve close when it has a relatively constant flowrate opposing it? The pressure (indeed crankcase pressure) will continue to build until that valve is forced open. The only question is. Will it be air or oil pushing it open?

If you have a lab setup running, I suggest you apply some pressure to the drain, watch the oil get pushed up the tube into the cone while air is being pumped from inlet to outlet and see what happens.
If the valve from the provent outlet is strangling the flow, then crankcase pressure rises, the oil level in the drain tube rises with pressure until the pressure is enough to force the valve (aka pressure regulator) open enough to match the flowrate and reach stable operation. At this point your crank-case pressure is higher than it would be without the valve.

In a nutshell, if you don't have a crankcase pressure problem, that valve on the outlet could be causing one.

I see the provents as having two major design flaws.
1. The inlet and outlet are the wrong way around.
2. The pressure regulating valve is counter productive.

By removing the valve and swapping the inlet and outlet around it works perfectly fine. With the additional benefit that the filter is handling a lot less oil.
Why couldn't Mann-Hummel have done this?

Hi All,

Bush65 - I'm going to use a Dawes valve from 3-bar Racing. Expecting it next week as they forgot to mail it over two weeks ago when I ordered it

I haven't made much progress in the last couple of days, had to go to work. But I did manage to mount my filter assembly today. I tried finding a service line (steel line to cooler) for the bypass filter housing but nothing, not even available from Isuzu anymore, apparently. I'll tackle that tomorrow, might have to use rubber in the short term.

I attached a couple pics below, oil bypass and oil return. I didn't have many options for the return so I poked a hole in the sump like a normal person!

I realized last week whilst thinking about something off topic that my engineer, if he notices, might not like my crank vent afterall, its a 92' model. I'll start hunting for a turbo rocker cover and vent system next week

Cheers, Tristan