Mitsubishi Delica Diesel PCV question

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simon84
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Mitsubishi Delica Diesel PCV question

Post by simon84 » Tue Sep 17, 2019 10:32 pm

So I have a 1995 Mitsubishi Delica 2.8 turbo diesel and I have a question about the PCV venting to atmosphere.
All you Americans may well be scratching your heads and the handful of Canadian from the west coast likely know what this vehicle actually is.
FYI, it's a JDM right hand drive import that you can't have in the US (until it's 25 years old).

I've asked this on the delica.ca forum but the people on there are sometimes not as helpful as the great people on here.
So the question is, what's the point of venting the PCV to atmosphere. I assume it's to improve mileage and performance. And I assume that the downside is the small amount of oil that goes down the pipe and into the air and on the road.
I looked online and installing a catch can seems to be reasonable option to recover some oil. If I install one then should I vent that to atmosphere or send the blow by gas into the intak?. Not so familiar with turbos and intercoolers so don't want to screw it up.

Thanks
Driver: 87 Tercel SR5, white, 4ac, weber carb (aka the Tercedes)
Road Tripper:95 Mitsubishi Delica L400 2.8L Turbo Diesel
Motorbike: 94 Kawasaki Ninja ZX6
Project Car:Red 68 Plymouth Sport Fury III
Previous Tercel:Orange 84 Tercel 4wd (aka the pumpkin)

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Mark
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Re: Mitsubishi Delica Diesel PCV question

Post by Mark » Tue Sep 17, 2019 11:08 pm

Yep, lots of Delicas here on Vancouver Island. So I assume right now, your PCV valve vents to the intake and you're wondering if you can disconnect it and vent it to atmosphere? In my opinion, the small amount of gases and oil vapour venting through this tube into the intake doesn't noticeably affect engine performance. The benefit of leaving it connected is that the vacuum in the intake creates a positive flow that "sucks" these gases out of the crankcase. If these gases (and more importantly, the water in the exhaust gas) aren't properly sucked out constantly, the engine oil might get contaminated and not last as long. I think in the old days when the crankcase would vent to atmosphere, it was through a tube under the car. When driving at speed, the lower pressure created under the vehicle would act as a vacuum, drawing out the gasses from the crankcase. At a stop or lower speeds, this vacuum effect didn't happen. I experimented with a catch can on my Tercel years ago. I put the can between the PCV valve and the intake. It collected maybe 2 cc of oil a month. It was a bit of a pain checking it and emptying it so I eventually stopped using it. I didn't notice any difference in performance, fuel economy and valve cleanliness with or without the catch can.

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Re: Mitsubishi Delica Diesel PCV question

Post by Mark » Tue Sep 17, 2019 11:23 pm

I just remembered that your van is a turbo. I don't know if there is a problem with pcv oil fouling the turbo blades, which would reduce its efficiency. Personally, I doubt it would be much of an issue otherwise everyone's turbos would be fouled and degraded within a month or two of buying their vehicle.

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Re: Mitsubishi Delica Diesel PCV question

Post by Petros » Tue Sep 17, 2019 11:41 pm

you youngsters don't know anything <smirk>.

when I first started working on cars many did not have a PVC valve, including the first two cars I owned. the PVC is to recycle fuel vapor blow by so it does not allow unburnt hydro carbons into the air. there should not be much oil vapor and it should not collect oil droplets. Vapors only. it was one of the first emissions control devices mandated by federal law.

You have to ventilate the crank case because the small amount of leakage past the piston rings will build pressure up in the crank case, and eventually blow out seals, contaminate the motor oil and do all kinds of problems. so they used to just vent it to outside the engine, "BC" (before smog). Some old timers clained it caused the spark plugs to foul, but after many many decades of having PVC required on cars, it is clear, that is not the reason they foul (if they did at all).

It would run fine with it vented to the atmosphere, if you are not concerned about the tiny amount of blow by that you vent to the Canadian forests, that is what was done on cars older than about 1965. Or if you rig it up like other cars, to suck air from the air cleaner, and than draw it through the crank case, and into the intake manifold, it likely would not harm a thing either. It needs a one way check valve in the system.
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Re: Mitsubishi Delica Diesel PCV question

Post by The Professor » Wed Sep 18, 2019 8:14 am

Mark wrote:
Tue Sep 17, 2019 11:08 pm
In my opinion, the small amount of gases and oil vapour venting through this tube into the intake doesn't noticeably affect engine performance. The benefit of leaving it connected is that the vacuum in the intake creates a positive flow that "sucks" these gases out of the crankcase. If these gases (and more importantly, the water in the exhaust gas) aren't properly sucked out constantly, the engine oil might get contaminated and not last as long.
I agree 100%. Not only is venting to the atmosphere irresponsible and bad for the environment, you'll be removing a system that prolongs the life of your engine. The vapors collected by this system contain fuel that, if allowed to mix with your oil long term, will dilute it. Most people delete or modify the PCV system in the name of increased performance with the idea that oil and blow-by vapors reduce the octane rating of the intake charge. The reality of the situation is that on a turbocharged car, the PCV is only open under vacuum, thus, when you're making power under load with positive inlet pressure, the PCV is closed and not venting blow-by vapor to the engine inlet.

Catch cans are a waste of money and venting to the atmosphere is a sorry alternative. Keep the system intact, maintain it and enjoy cleaner air and water.
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Re: Mitsubishi Delica Diesel PCV question

Post by simon84 » Wed Sep 18, 2019 9:37 pm

Thanks for the info. I knew that folks on here would be knowledgable and helpful.
No word from delica.ca yet.

Just to clarify, it has been piped from the PCV to underneath the car and vents to atmosphere. I'm keen to set it up properly and I want to make sure I do it right so as not to foul up the intercooler or the turbo.
I will try to find out how the stock set up looks. Then I can also see if there's any effect on mileage or anything else.
Driver: 87 Tercel SR5, white, 4ac, weber carb (aka the Tercedes)
Road Tripper:95 Mitsubishi Delica L400 2.8L Turbo Diesel
Motorbike: 94 Kawasaki Ninja ZX6
Project Car:Red 68 Plymouth Sport Fury III
Previous Tercel:Orange 84 Tercel 4wd (aka the pumpkin)

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Re: Mitsubishi Delica Diesel PCV question

Post by The Professor » Thu Sep 19, 2019 7:53 am

simon84 wrote:
Wed Sep 18, 2019 9:37 pm
I'm keen to set it up properly and I want to make sure I do it right so as not to foul up the intercooler or the turbo. I will try to find out how the stock set up looks.
That is another reason people ditch the PCV system, to prevent oil film from building on the inside of the intercooler. However, if you're accumulating a significant amount of oil (enough to pool and pour out of the IC when removed) then there are larger issues lurking.
1975 Subaru SuperStar wagon
1984 Subaru Turbo-Traction wagon & Turbo-Traction hardtop
1987 Subaru RX 3-door, x2
1987 Subaru RX Type-RA 3-door
1987 Toyota Tercel SR5 wagon
1999 Subaru Forester S
2002 Subaru WRX sedan
2019 Subaru Outback 2.5i Limited

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Re: Mitsubishi Delica Diesel PCV question

Post by simon84 » Thu Sep 19, 2019 3:18 pm

That's why I am considering a catch can. So I can see how much oil is coming through the PCV.

I'm also curious if the blow by gasses are mostly fuel vapors or exhaust gas. Or both?

My delica has 165000 km and I've been doing oil changes every 5000km since I got it with only 70000km on it. It's been running quite well and I'd like to keep it that way. I just had some servicing done (trans flush, new brakes, valve cover gasket). It's coming due for some other new parts as well (sway bar linkage, ball joints etc).
Driver: 87 Tercel SR5, white, 4ac, weber carb (aka the Tercedes)
Road Tripper:95 Mitsubishi Delica L400 2.8L Turbo Diesel
Motorbike: 94 Kawasaki Ninja ZX6
Project Car:Red 68 Plymouth Sport Fury III
Previous Tercel:Orange 84 Tercel 4wd (aka the pumpkin)

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Re: Mitsubishi Delica Diesel PCV question

Post by Petros » Thu Sep 19, 2019 8:51 pm

simon84 wrote:
Thu Sep 19, 2019 3:18 pm
That's why I am considering a catch can. So I can see how much oil is coming through the PCV.
if it runs well there should not be much oil in the catch can. when the rings and cylinder walls are worn enough to decrease power and burn lots of oil, you may be getting more oil vapor since both exhaust and partly burned combustion gasses will be leaking past the rings into the crank case, pressuring the crank case and allowing more oil droplets to get caught up in the PVC system.

I have never felt the need for a catch can on any car I owned (even high mileage ones that ran good), except when the engine was in bad need of a tear down and rebuild. I was trying to make an engine on its last legs last a little longer, I improvised a catch can out of a one gallon oil jug. Each day I would put the oil from the catch jug back into the engine. Needless to say, it would eventually fail to run at all not long after that happened.

I bought a cool looking anodized red aluminum catch can to eventually put on my 4age swap Tercel, just for fun. they do not cost much, I think I paid about $20 on an Ebay store. if nothing else it would dress up the engine bay.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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Re: Mitsubishi Delica Diesel PCV question

Post by simon84 » Fri Sep 20, 2019 8:52 pm

Yeah, I'm going to find out exactly how they plumb in the PCV and I'm going to improvise a catch can and then I can see how much oil builds up. It will be cool to see if it's only a little bit and if it changes over time.
I will report back here with more info when I get it sorted out.

Thanks everyone for the input. I knew I'd get some good response.
Got one reply on Delica.ca with some similar info.
Driver: 87 Tercel SR5, white, 4ac, weber carb (aka the Tercedes)
Road Tripper:95 Mitsubishi Delica L400 2.8L Turbo Diesel
Motorbike: 94 Kawasaki Ninja ZX6
Project Car:Red 68 Plymouth Sport Fury III
Previous Tercel:Orange 84 Tercel 4wd (aka the pumpkin)

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Re: Mitsubishi Delica Diesel PCV question

Post by The Professor » Mon Sep 23, 2019 8:12 am

Just make sure you check it at every fuel stop. Nothing like a nice, fresh coating of oil under your hood to ruin an weekend.
1975 Subaru SuperStar wagon
1984 Subaru Turbo-Traction wagon & Turbo-Traction hardtop
1987 Subaru RX 3-door, x2
1987 Subaru RX Type-RA 3-door
1987 Toyota Tercel SR5 wagon
1999 Subaru Forester S
2002 Subaru WRX sedan
2019 Subaru Outback 2.5i Limited

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simon84
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Re: Mitsubishi Delica Diesel PCV question

Post by simon84 » Mon Sep 23, 2019 10:09 am

Yeah, I know about that. When I had it serviced recently & there did the valve cover gasket, they did not te-connect the pcv hose and it made a small mess in the engine bay. Some extra rust protection for that area, I guess.
Driver: 87 Tercel SR5, white, 4ac, weber carb (aka the Tercedes)
Road Tripper:95 Mitsubishi Delica L400 2.8L Turbo Diesel
Motorbike: 94 Kawasaki Ninja ZX6
Project Car:Red 68 Plymouth Sport Fury III
Previous Tercel:Orange 84 Tercel 4wd (aka the pumpkin)

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