Thread: Provent Question for Dr Ben.

Originally Posted by Dougal

Ben, I've got a quick provent question for you.

How much oil would it take to flood the provent when it's draining into the factory 4DB1T drain hole of approx 6mm?

Enough oil that it comes out the oulet hose in a manner that would suggest there is no air/oil seperator in the line. Is it enough that the engine is definitely rooted or just possibly rooted?

Mine floods out the top hose, but I never hooked it to the intake either, not sure, now I've taught myself TIG welding I will weld that nipple in place and see if it fixs it

TIG is great fun, I had a crack yesterday for the first real go in 5 years. I'd like to say the new intake pipe made everything better, but it seems to have made my blowby worse.
I took the turbo off and went for a spin without (bloody noisey), even then it's pushing oil out the vent hose, enough to coat everything near the exit in shiney blackness. This normally meets my turbo intake, I initially blamed the turbo for the oil.

The factory 4BD1T drain appears to be below oil level. Hooking up an air-pump makes gurgling noises. Is this a problem? Should I drill and tap a drain hole in the block or sump above the oil level?

No real interesting input but i wouldnt drill into the block it being cast iron it may effect grain structure and MAY cause a weak spot... then again as ive said before i could be talking crap like always
Can someone post a pick of a provent setup so i can see what its all about please ? i havnt seen one

I'm about to reverse the inlet and outlet hoses on my provent to acheive the following aims:
1. Let the oil from the breather go straight down the drain without passing through the filter.
2. Let the filter work to collect only the oil that doesn't go straight down the drain.
3. Get the outlet entry point as high as possible in the provent to minimise the amount of oil leaving the provent and entering the engine.
4. Postpone my engine rebuild until I have some other projects out the way.

So the question:
How is the pressure regulator on the original outlet pipe going to like this flow reversal?

I realise the inlet port won't be purely tangential any longer, but I can make some temporary mods to help that.

Right. My provent is now a Brovent (tm).

I have pulled the pressure regulating valve apart, removed the spring, plunger and diaphram which are replaced with aluminium blocking plugs. The cap has been RTV sealed back on as the original diaphragm was also the seal. A PVC deflector has been installed in the old regulator position to deflect the oiley air in tangentially.

Reinstalled with the original filter to see how it goes and it now goes like this.

Oiley air in the bottom has a tangential poke into the bottom centrifuge. Oil which centrifuges out goes straight down the drain. Oil which doesn't centrifuge out can get caught by the filter and drain down.
Clean air out the top is taken at a reverse spin to the air entering at the bottom. This stops any oil from spinning around the housing and taking the easy way out.

If this isn't enough, I'll be fitting a cone inside in place of (or supplmentary to a modifed) original filter to act as a second centrifuge.

Honestly I'm really disappointed with the provent as delivered. It has caused a serious oil consumption problem because it couldn't seperate air and oil at flows which I thought would have been well below design. This was sending litres per 100km of oil through my turbo and into the engine.
My old compact centrifuge actually worked better, it just wasn't big enough and let the crankcase pressurise under hard use. If this doesn't work out I'll be making another two stage centrifuge and binning the provent.

I'm also struggling to understand the design intent of taking clean air from the oiley side of the filter at such a low point. It didn't make sense to me originally, but I fitted it anyway.
The resulting oil consumption has led me to rebuild my turbo, burn half a bucket of oil (yes 10 litres) in 1500km and almost rebuild my engine.

I'll post the pics later.

Originally Posted by Dougal

Ben, I've got a quick provent question for you.

How much oil would it take to flood the provent when it's draining into the factory 4DB1T drain hole of approx 6mm?

Enough oil that it comes out the oulet hose in a manner that would suggest there is no air/oil seperator in the line. Is it enough that the engine is definitely rooted or just possibly rooted?

Hi Dougal. If I understand correctly, your original question was "how quickly can oil flow through the drain?"

I don't have an exact number for you, but you could calculate it yourself using the Energy Equation (Bernoulli + viscous losses).

It would depend if you have the one way valve in the drain line though. In this case drainage will only occur when pressure in the PV is greater than crankcase pressure - so when you shut down or idle the engine.

It sounds in your case as if you may be flooding the element, which can cause reentrainment of large droplets, causing the problems you are experiencing. You must have a LOT of blowby to be doing this!

Originally Posted by Dougal

Right. My provent is now a Brovent (tm).

I have pulled the pressure regulating valve apart, removed the spring, plunger and diaphram which are replaced with aluminium blocking plugs. The cap has been RTV sealed back on as the original diaphragm was also the seal. A PVC deflector has been installed in the old regulator position to deflect the oiley air in tangentially.

Reinstalled with the original filter to see how it goes and it now goes like this.

All the housings we use for research have had the valves sealed up with marine sikaflex - however the flow direction is the same. The valve in the cap vents to atmosphere at 50 mBar (which was the main thing we didn't want in the lab). Can't remember the pressure to close the outlet, however as we drive our system with a vacuum pump we didn't want that closing up either.

Honestly I'm really disappointed with the provent as delivered. It has caused a serious oil consumption problem because it couldn't seperate air and oil at flows which I thought would have been well below design. This was sending litres per 100km of oil through my turbo and into the engine.
My old compact centrifuge actually worked better, it just wasn't big enough and let the crankcase pressurise under hard use. If this doesn't work out I'll be making another two stage centrifuge and binning the provent.

I'm also struggling to understand the design intent of taking clean air from the oiley side of the filter at such a low point. It didn't make sense to me originally, but I fitted it anyway.
The resulting oil consumption has led me to rebuild my turbo, burn half a bucket of oil (yes 10 litres) in 1500km and almost rebuild my engine.

I'll post the pics later.

I can't answer why it was done like that. My guess would be packaging or to get around existing patents. That said, the PV system works really well on my 4BD1/T I have never had any problems with oil carryover. It sounds like your engine is really breathing heavily. I assume you have a Provent 200? They are designed, and used industrially on engines up to 200 kW.

Having airflow in the same direction as drainage/gravity will make the filter drain better. In your case, airflow and gravitational forces are fighting each other. However, if you have so much liquid oil (or "wall flow" as it is termed in industry) coming out your tappet cover, then it may work better.

Just make sure that you don't get reverse flow (e.g. offroad) - oil coming up the drain.


Look forward to the pics.

Pictures.

Here is where the provent sits in the rangie engine bay. This was the only practical place that didn't intrude on a possible future air/water intercooler position. If the tangent ports were coming out in the other direction it would have made fitment much easier.


Provent on the bench.


Pressure regulating valve parts. This valve just unclips in two stages, first unclip the cover to expose the spring, unwind the spring from the plunger, unclip the cap and then the plunger and diaphragm come off the other side.
From the bottom of the picture, cover, cap with spring, plunger and diaphragm.


I turned up two aluminium pieces to block the holes in the cap left by removing the plunger and diaphragm, it could have been done in one piece.


The real crux came for this thing last week. What happened was I tig welded up a new intake pipe (can be seen feeding the intake manifold in the first picture) and re-routed the lines out of the provent to the turbo intake. These used to go up and over the cross-over tube (hence gravity was returning oil along this pipe), but new was close to level. The result was oil coming up the clean air line from the provent at a rate it never had before.
The vehicle was generating a smoke-screen of oil, it was like a 2 stroke running on 25% oil. This was when it ate 1 litre of oil in 20km.

This is why I've spent my whole holiday weekend looking for the reason why. It wasn't until I went for a drive without the turbo and saw the oil spraying out of the provent that I realised just what the cause was. Unfortunately the provent fitment coincided with a few other changes (like oil type) so it took a while to nail down the exact cause.

I've only driven the vehicle 1-2km since the provent mod, but already the smoke screen has gone and the exhaust is pretty much clear. It will take a decent run to get the rest of the oil out of the system.

Other things that made the problem worse, hill climbing offroad and acceleration tilts any oil in the bottom to the outlet vent. When I stripped the provent for these pictures the regulating valve area was full of oil. This can't drain out, it can only go to the engine via the vent tube. Fitting the provent the other way around will give you the same problem going downhill or braking.

10km test run. It's running clear, still some hot oil smell and white/blue smoke if it's revved hard stationary against a dark background. But I think that'll improve.

I feel like I've dodged a bullet.