Turbo Oil Return

[nigelp]

Advice wanted please, regarding my turbo onto blacktop Zetec project.
Engine's out and gearbox being refurbed. Was planning to do the turbo
oil return similar to Jim's but ...... As my turbo is sitting near
the top of the engine, above and away from the crankase breather I
plan to keep the breather (adding a heat shield), is there any reason
why I can't weld an oil return pipe onto the breather? A 13mm oil
return seems insignificant compared to the size of the breather hole.
This would save me having to remove the sump, which is the two part
steel base and alloy unit, drill the block, machine the outlet etc.
Got into a dispute with the guy who sold me the turbo, he said 1.5mm
play in the shaft and two bolts broken in constituted perfect
condition, (the ad said perfect condition and no shaft play). E Bay
have just ruled in my favour and its going back. Now on the look out
for a turbo again.
Thanks.
Nigel

[Hamish Freeman]

Nigel,

The reason why turbo oil return is taken directly back to the sump is that
the oil flow levels are high and could a) swamp a breather and b) cause
frothing and ultimate "mayonnaise" build up in the crankcase. The design
criteria is straight forward - return the oil to the sump below the
stipulated oil level. This can if necessary be achieved using a tube but
keep it out of the breather as this should have some form of separation
system, depending upon the age of the engine.

In my experience on diesel turbo's over 40 years, 1.5 mm end float is
excessive, 0.5 mm probably being more realistic. High end float suggests
that the turbo has been run short of oil and consequently has worn out the
end float thrust bearings. Too long now since I sized a turbo to remember
the requisite oil flows - these should be available on line from the turbo
manufacturers - but bear in mind that the turbo is normally fed before the
pressure relief and will likely drop oil flow rate to the bearings.

Take care!

Hamish

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[nigelp]

Thanks Hamish. I'm a little puzzled as all the information I have
read including Garett's web site says the turbo oil return should be
above the oil line and as high as possible in the sump. I do agree
with yuor logic and explanation; the opposite logic seems to be that
the return is unimpeded and no wash up the return. Although I would
have thought it made little difference since p = h x density etc.
Having done some more research since my first post, my favoured route
is to make a plate to cover the breather hole and weld two oil unions
to it. One higher for the crankase breather and the second lower for
the turbo oil return, will also angle then in oppostie driections.
Will then take the higher one to an oil ctach tank. As the breather
hole is about 45mm diameter (haven't measured it exactly) I can't
imagine there being a problem, but would appreciate any input please.
Nigel

[Jim Hearne]

All the Ford turbos just seem to return the oil into the bottom of the
block, theres no tubes from there going down below the oil level.

One problem i've always had on the ZVH is oil being blown out of the
filter on the catch tank.
Even though it's got a separate drain drain pipe from the bottom going
back to the sump (above the oil level) i think the crankcase fumes
blowing up it stops the oil draining properly.
When the engine is out next i intend to take the catch tank drain pipe
back down to the sump below the oil level, this should stop the fumes
blowing up the wrong pipe.

Some sideways play in a turbo shaft is fairly normal as the bearings
have a fair bit of play in them when there's no oil going through them,
when there is oil pressure the shaft centralises on the oil. 1.5mm
sounds a bit much though.
There should be no in-out play on the shaft though.

Jim

[nigelp]

I'm slightly confused by the plumbing here. On your ZVH you drilled
the block to an 18mm hole and put in a separate line which I thought
was the breather going to your catch tank, I also thought the catch
tank had a line from the rocker cover breather. I thought the fumes
went out of the catch tank filter and the excess oil gathered in the
catch tank which had to periodically be drained off. I asume there is
no PCV in these lines. Confusion is that is the hole you drilled out
in the block to drain your catch tank or is the breather and the drain
is a different line? Do you vent any gases into the engine inlet or
plenum?
One thing I did notice on the Garrett web site is that the turbo
return should not be in an area that receives backwash from the
crankshaft. I think but haven't looked that the crankshaft views
directly onto the breather hole. I guess to solve my confusion, could
you please explain your connections to the catch tank Jim. I have
noticed on one web site an alum block to screw directly onto the block
in place of the breather to take the line to the catch tank.
Unfortunately I seem to have found lots of bits of info on this, but
nothing definitive. I am now trying to make the sum of all the parts
make a whole. As is usual with things like this there is also lots of
conflicting information around.
Thanks for the info on the turbo Jim and Hamish. I had always expected
some play for the reasons you mention and when guys say no play I am a
little sceptical, but this did appear excessive and as Hamish
mentioned I am a litle concerned by the flow to the turbo resulting in
an oil pressure drop. I am still to sort out where to take the flow
from as the Black top doesn't seem to have the additional hole you
mentioned in a previous post. It probably will end up coming from the
pressure sender unit hole - a task for next weekend!!
Thanks
Nigel

[Jim Hearne]

The CVH standard breather system has a outlet on the lower rear of the
block which is connected via a rubber pipe into one end of the rocker cover.
The other end of the CVH rocker cover goes to the crankcase breather
system (filter, back into the inlet manifold etc).

Initially i duplicated this system on the ZVH with the Zetec block.
As the Zetec block breather hole is behind the turbo i had to blank it
off and drill a new outlet on the rear of the block.
As you know.

Initially i connected the rocker cover outlet directly to a "catch tank"
that i created out of some stainless steel tube with a breather filter
on the top and several levels of steel mesh inside to hopefully collect
the oil.
I say catch tank but the idea was that the oil would drain back down the
breather pipe into the rocker cover and back to the sump.
This didn't work, to much oil seemed to sit in the pipe between the
cover and the tank.

I later modified the tank so it had 2 pipes, one still from the breather
in the rocker cover and the other now went downhill to Y piece in the
pipe between the block and the other end of the rocker cover.
The idea was that the new pipe on the lowest point of the tank now went
almost straight down so oil wouldn't be able to sit in it.
This is better but it still doesn't work, oil still gets blown out of
the catch tank filter after a while under boost.
I think because the crankcase fumes find it just as easy to go up the
drain pipe as they do through the breather pipe so they keep the oil up
in the tank.

Plan 3 is to remove the Y piece from the crankcase to rocker cover pipe
again and this time take the return from the catch tank down into the
sump below the oil level.
That way there can't be any fumes blowing back up that pipe.
I think i'll have to use a solid pipe up until block level as a rubber
pipe splitting there would empty the sump.

I don't feed anything back into the inlet, i blanked off the 2 holes in
the CVH manifold that used to do that.

You should have enough spare oil pressure to feed the turbo without
affecting the main oil pressure.

Jim

[nigelp]

Thanks for this. Out of curiosity where does your turbo oil return
goto. I am slightly worried now that keeping the oil return above the
sump may also impede the return and thinking about Hamish's advise to
take ythe turbo oil return below sump level.
Thanks

Nigel

[Jim Hearne]

Mine goes in just above the bottom of the block.
There was a cast boss in the block there with a thread in it, i just
drilled it out and fitted a pipe fitting.
It's about the same place as the return in the Escort and Fiesta turbos.
I think on Matthews Focus RS sump the return is into the top of the sump.

None have anything inside the engine to take the return below the oil level.

Jim

[Jim Hearne]

The Focus RS return is where the arrow is in the alloy section of the
sump in picture attached.
You may well find something here on the sump on your engine as the RS
was a blacktop Zetec.

Jim

On 07/02/2012 06:42, nigelp wrote:

[Steve Kodz]

That's quite high, but I'm assuming that's because the turbo in the Focus RS
is higher than on the CVH engined cars. The photo I've attached shows the
CVH block (Fiesta Turbo) which has the return at the bottom of the block.

Regards,
Steve
--
www.h4-turbo.co.uk
www.quantumowners.co.uk
www.quantumcars.co.uk
www.quantumkitcars.co.uk
www.quantumheritage.co.uk

[nigelp]

Thanks guys. Thought you'd cracked it Jim, so went to look and then
realised this is right where I've hacked away to get the starter in to
mate to the Type 9 box. Still thee are plenty of other bosses around
the alloy sump housing. Will have a look this weekend, but right now
I am leaning towards using the standard Zetec breather assy with a
turbo return boss welded on on the side where the separated oil runs
back into the sump. The aperture is so much larger than the turbo
return pipe, that I can't imagine it getting swamped, the flow from
the oil separating out from the breather can't be that great and there
is a guard on the breather to prevent splash from the crankshaft. I
may well put a contingency boss on the sump just in case!! The key
decision is whether to take the breather outlet to a catch tank, but
am not sure of the benefit. I guess if I do that though, it will
provide a more visible warning of any problems and I don't want the
risk of sending any oil through to the plenum!! Opinions always
welcome.

regards

Nigel

[nigelp]

Jim Steve, what ID do you have for the oil return pipe on the bosses?
Nigel

[jon jackson]

My MX5 turbo (HSK kit) blocks off the dip stick and uses the hole for the
return, on these engines the turbo is higher than the head.
Cheers Jon 2+2

regards

Nigel

--

[Matthew Wastell]

I'm not sure but I really would avoid putting into the front crank breather separator pcv. On boost that pressurises and will try to force oil/vapour back through the turbo if the vent part is blocked.

You also need to take the crank breather back BEFORE the turbo not after. On the fiesta zetec the return is to a sandwich plate between throttle and head, on boost that will pressurise and cause all sort of interesting issues (such as blowing all the oil out of the rocker breather!). On mine I have blanked the sandwich plate off. The front crank breather system is standard but connected to a stub pipe welded to the side of the inlet tubing directly after the air filter. My rocker cover is piped to an oil separator then air, however I will connect that to the air filter and t the crank breather in a quite a bit of oil 'crud' still gets through the pcv.

If none of that makes sense I can draw you a small diagram.

M

[Matthew Wastell]

In general a separator is not needed from the crank pcv unless you want to get very anal about oil vapour/ residue build up in the air system. I will change mine to this setup at some point.

You will need a desperate on the rocker vent though.

I can get 10-20ml of oil here on a fast run!

M

On 7 Feb 2012, at 22:18, nigelp <nige...@tiscali.co.uk> wrote:

[nigelp]

The bit thats puzzling me, and I tend to agree with your reasoning
Matt, is that the positive pressure is prevalent in all the crank
area, not just the breather, so wherever I return to there is going to
be positive pressure trying to blow the oil back, including below the
oil level. As the crank ventilation 'box' has a return to sump side
to it and the cross sectional area of the opening is 3.1sq cm vs 1.327
sq cm for a 13mm return line from turbo, it surely should take the
flow OK. The only bit I am puzzling over is the internal construction
and shape of the crankcase vent 'box.' Has anyone ever ripped one of
these apart or have a drawing??

I don't understand what you mean by this statement 'You also need to
take the crank breather back BEFORE the turbo not after.' Perhaps I'm
missing something.

Thanks for all the inputs - intend to sort it this weekend. The
meassge is seeming like 'cover all bases.''

Nigel

[nigelp]

Decision made, going to use the boss behind the one indicated on Jim's
photo. Plan is to take the sump off, jig and drill it at work to 19mm
and tap for a 1/2 BSP union, it will be close on wall thickness for
the boss, but is just about achieveable. On the photo shown; was that
drilled out for a push in connector? Next question is what internal
diameter does the return bore need to be? I was planning on abouit
13mm, but some sites indicate 15mm, which is hard to achieve unless I
make a hybrid push in connector, what have you guys used?

Nigel

[Matthew Wastell]

The crank is always pressurised however when you are on boost this increases, therefore more pressure than an na. Normally this breather connects to the engine side of the throttle which in general is always below atmospheric pressure. On boost this goes into positive preasure which could be too high to allow the crank to vent via the inlet tract. You will therefore end up venting the easiest way possible which would probably be out of the rocker cover.

To avoid this you MUST connect the crank breather to a non positive pressure system, to the airfilter is ideal, however again the PCV is designed for an NA so you may get more oil being chucked up (it happens on an NA as well but most people don't care bout the tiny amount of oil deposits).

You also need to take care of the increased pressure that will be in the rocker cover. Normally that is connected to the airfilter. If you don't mind oil in your inlet then go ahead however I recommend an oil sep.

My oil sep has no oil return, I just empty it every year or so. It's a good indication how much oil I need to put back in!

Matthew

[nigelp]

Thanks Matthew, I think we are at cross purposes. I understand all
that and how the system works, I am talking about the oil return pipe
from the turbo which mustn't cause any back presure to the trubo
bearings not a drain from the separator. My question was about the
diameter of the turbo oil return, larger turbos seem to be about 15mm
and smaller ones 12.5mm, sop was wondering what you guys had.
Nigel

[Jim Hearne]

The turbo drain on the Fiesta RST is a braided hose and only about
8-10mm bore so 13mm should be plenty.
Thats about the size of the internal hole on the Escort RST as well.

Jim

[Matthew Wastell]

Hi Nigel,

I was responding on your point,

" I don't understand what you mean by this statement 'You also need to
take the crank breather back BEFORE the turbo not after.' Perhaps I'm
missing something."

What I was at least thinking I was trying to say was that you ought to
modify the standard crank breather and change where the fumes go to... on
the NA engine it connects to the manifold sandwich plate, you don't want
that when you turbo charge.

All my replies are about the breather system, not the turbo oil system. (I
think!)

Hope that helps.
Matthew

-----Original Message-----
From: quantu...@googlegroups.com [mailto:quantu...@googlegroups.com]
On Behalf Of nigelp
Sent: 12 February 2012 08:48
To: Quantum Owners Group

Subject: [Quantum Owners] Re: Turbo Oil Return

--

[nigelp]

Just taken the sump apart ready for machining the oil drain. I can't
get a 1/2 BSP thread in the boss (same place as Jim's RS Turbo photo)
so will have to go for 3/8 BSP, but am a little concerned about the
reduced diameter. On the picture you posted Jim it shows a smooth hole
- how was the pipe fastened in, is it just a press fit and any loctite
used? If I use the press fit route, should be able to manage about
11/ 12mm for the return. Am also going to weld a spare return with
blank at the top of the steel bottom sump as a contingency for any
future needs!!
Thanks

Nigel

[Jim Hearne]

The hole had an internal O ring groove.
The end of the return pipe had a lug on the side with a hole in it, and
a small screw went through it into the sump to hold it in.

Jim