oil back through intake

[natedogg]

hey guys,

general query here.

took my wizard apart in the weekend to get at broken manifold bolts.

noticed quite a bit of oil in the intake pipes. coming from a breather from the motor into the intake just after the airfilter.

question, is this here for a reason?? - to lube some of the intake/turbo or anything like that?

if i blocked it off and ran a catch can like on a petrol motor will i run into any problems?

any help appreciated.

also as a side note, why do diesel engines not run a factory blow off valve? surely with the high boost diesels typically run, it would prolong the life of a turbo by venting the excess boost when the throttle is closed? - can anyone shed some light on this for me? cheers.

Nathan

[doddzee]

My bighorn did the same thing, aparantly the bores go oval you get blow by and pressurise the crank forcing the oil out the breather located at the rear under the intercooler. I disposed of mine rather quickly when i found that out.

[natedogg]

oh, that dont sound good.

the motor is a superb runner though. no smoke or anything. i will probly keep it till it dies and rebuild it if that happens.

its a 3.1td not a 2.8td just incase that makes a difference

[doddzee]

Mine was a 3.1 as well. It got to the point where it started to run on and rev by itself as it started to run on its own oil. If it starts to run on id suggest you do something about it as they can keep reving till they self destruct.

It did blow quite a bit of smoke so yours could be different. Divert the breather into a bottle and go for a drive. If oil ends up in the bottle yours will have the same problem as mine did.

[natedogg]

ok, noted doddzee. thanks for that.

will see what happens, but generally the motor is in pretty good nick i think. I had a diesel mechanic look at it before buying it and he couldnt fault it (apart from the 2 broken manifold bolts)

[KiwiBacon]

Mine was a 3.1 as well. It got to the point where it started to run on and rev by itself as it started to run on its own oil. If it starts to run on id suggest you do something about it as they can keep reving till they self destruct.

I've had an engine so knackered it ran on it's own oil. It would only run hot enough to do that if run hard up a hill, then as soon as the engine cooled enough it would revert to running on diesel alone.

After all, once they get that knackered, they don't have the compression needed to burn cold oil. But load them up enough and they can.

[natedogg]

ok just to clarify, when i said "quite a bit of oil" i didnt mean it was overflowing with oil and when i pulled the clamps off, oil didnt run everywhere. i meant that there was the 'remains' of oil in there, i.e was quite greasy, and when wiping it with my fingers could tell it was oil.

so, i probly wouldnt harm anything by adding a catch can like on a petrol motor? can anyone confirm? i just want to make sure its not recirculated back into the intake in order to lubricate something.

[KiwiBacon]

ok just to clarify, when i said "quite a bit of oil" i didnt mean it was overflowing with oil and when i pulled the clamps off, oil didnt run everywhere. i meant that there was the 'remains' of oil in there, i.e was quite greasy, and when wiping it with my fingers could tell it was oil.

so, i probly wouldnt harm anything by adding a catch can like on a petrol motor? can anyone confirm? i just want to make sure its not recirculated back into the intake in order to lubricate something.

It's not there to lubricate anything. It's routed back in there for emissions controls (burn the crankcase fumes).
Doesn't sound like you've got excessive oil, but the engine will already have an oil trap built into the rocker cover. An external catch can as well is fine as long as it doesn't restrict the gas flow and pressurise the crankcase.
I'd keep the vent gasses heading back to the intake though. It's the cleanest place to run it.

[Dak]

also as a side note, why do diesel engines not run a factory blow off valve? surely with the high boost diesels typically run, it would prolong the life of a turbo by venting the excess boost when the throttle is closed? - can anyone shed some light on this for me? cheers.

You said it, what throttle?? A diesel doesn't have a throttle plate to close and stall the turbo, BOV's on diesel's don't do anything, a lot of people see a pop off valve on some factory diesel manifolds and think these are BOV's, they aren't, they are just an overboost pop off valve.

[tweake]

just check your not over filling it with oil.

some motors are worse than others for venting oil out the breather, even when new.
as far as blow by goes, take the rocker cover cap off and feal how much is gas is blowing out.
having said that a lot of older deisels that are well known for blowby run happly for years like that.

i would fit a decent catch can and just see how much oil is coming out.
the oil is not requred in the intake and it actually causes problems for ECU vechiles as the oil is unmetered fuel.

blow off valve? deisels don't have throttle butterflys so no need for a BOV. however they often have a butterfly used for EGR purposes. usually you don't have a lot of boost when thats been used and once you disable the butterfly you then have no need for a BOV.

[natedogg]

also as a side note, why do diesel engines not run a factory blow off valve? surely with the high boost diesels typically run, it would prolong the life of a turbo by venting the excess boost when the throttle is closed? - can anyone shed some light on this for me? cheers.

You said it, what throttle?? A diesel doesn't have a throttle plate to close and stall the turbo, BOV's on diesel's don't do anything, a lot of people see a pop off valve on some factory diesel manifolds and think these are BOV's, they aren't, they are just an overboost pop off valve.

Ah I see, thanks for clearing that one up or me

[IcedJohnno]

also as a side note, why do diesel engines not run a factory blow off valve? surely with the high boost diesels typically run, it would prolong the life of a turbo by venting the excess boost when the throttle is closed? - can anyone shed some light on this for me? cheers.

You said it, what throttle?? A diesel doesn't have a throttle plate to close and stall the turbo, BOV's on diesel's don't do anything, a lot of people see a pop off valve on some factory diesel manifolds and think these are BOV's, they aren't, they are just an overboost pop off valve.

You are not quite correct here Dak.
My 1KZ-TE does have a throttle butterfly and the engine does run vacuum when the throttle is closed. So the turbo does stall.

Why have the butterfly? I am told it is for quieting purposes but no one knowledgeable has ever confirmed this for me. These are questions that I have pondered as well.

[tweake]

You are not quite correct here Dak.
My 1KZ-TE does have a throttle butterfly and the engine does run vacuum when the throttle is closed. So the turbo does stall.

Why have the butterfly? I am told it is for quieting purposes but no one knowledgeable has ever confirmed this for me. These are questions that I have pondered as well.

read my post above.

you have vac because EGR is blocked. vac in a diesel is not a good thing. you really need to disable the buterfly. even just disabling the solinoid operated part (ball bearing in vac line) will improve things.

[natedogg]

just check your not over filling it with oil.

some motors are worse than others for venting oil out the breather, even when new.
as far as blow by goes, take the rocker cover cap off and feal how much is gas is blowing out.
having said that a lot of older deisels that are well known for blowby run happly for years like that.

i would fit a decent catch can and just see how much oil is coming out.
the oil is not requred in the intake and it actually causes problems for ECU vechiles as the oil is unmetered fuel.

blow off valve? deisels don't have throttle butterflys so no need for a BOV. however they often have a butterfly used for EGR purposes. usually you don't have a lot of boost when thats been used and once you disable the butterfly you then have no need for a BOV.

thanks tweake,

i will most probly fit a catch can and do as you say, measure the oil coming out. my isuzu has the electonic injection system so, assuming this has an ecu (im a complete noob when it comes to diesels) i'll hopefully be better off without the oil in the intake.

oh and im making up some flanges to block off the EGR and block off the EGR vacuum hoses as well.

[3VILC]

My old bighorn was the same, and indeed the EGR valves are well known for sticking or leaking allowing excess crap into the intake so once you plug those up should help a bit. Mine didnt blow terribly excessive blowby out the breather either, a little but it didnt spit any oil unless you really gave it snot, nothing unto be expected from a motor over 350ks anyway

[KiwiBacon]

Why have the butterfly? I am told it is for quieting purposes but no one knowledgeable has ever confirmed this for me. These are questions that I have pondered as well.

It's for emissions (NOx).
Because it's a high compression engine, which is also turbocharged the part load pressures/temps are high enough to create a lot of nitrous oxides (that brown crap that blankets Christchurch).
Throttling the intake reduces the in cylinder pressures and excess oxygen which gets converted to NOx gasses.

My nissan YD22 has a throttle plate, but it's simply switched on/off by a vacuum actuator for the EGR. Can't see it when I'm driving, but I suspect it's just pulsed when needed.
Being a direct injection engine with lower compression ratio the NOx emissions aren't as big an issue.

[Dr Rocket]

I had the same problem on my Terrano TD27t, I fiitted an old plastic bottle inline so that the hose from the rocker cover went through the cap and almost to the bottom of the bottle, then I ran another hose from the side of the bottle near the top to the original spot on the intake pipe. This catches the oil but does not pressurise the system and works well.

[tweake]

It's for emissions (NOx).
Because it's a high compression engine, which is also turbocharged the part load pressures/temps are high enough to create a lot of nitrous oxides (that brown crap that blankets Christchurch).
Throttling the intake reduces the in cylinder pressures and excess oxygen which gets converted to NOx gasses.

My nissan YD22 has a throttle plate, but it's simply switched on/off by a vacuum actuator for the EGR. Can't see it when I'm driving, but I suspect it's just pulsed when needed.
Being a direct injection engine with lower compression ratio the NOx emissions aren't as big an issue.

yes/no. it is for emmissions.

the butterfly is part of the egr system. it throttles the intake so it can draw in more EGR to replace the air. the lack of air plus the lower peak flame temp due to the egr reduces nox emissions.

low compression usually means big boost ( YD is proberly 15psi for the early ones and even more for the varable turbo ones) more boost = more air = more nox, so its a big issue on modern diesels.
you will proberly find the butterfly on the YD is most likly on from just off idle to about 3000rpm. (i don't know the yd22 so i can't say for sure)

[KiwiBacon]

low compression usually means big boost ( YD is proberly 15psi for the early ones and even more for the varable turbo ones) more boost = more air = more nox, so its a big issue on modern diesels.
you will proberly find the butterfly on the YD is most likly on from just off idle to about 3000rpm. (i don't know the yd22 so i can't say for sure)

Remember toyota was using throttle plates in their diesels long before they had EGR.
It works with EGR but that's not the only reason.

My YD22 is non turbo, I can't find any specs on the compression of it, but it's rare for a direct injection diesel to have a CR higher than about 18 even when non-turbo.
Indirect injection engines often to go to 22 but have to to regain the efficiency and starting issues they lose through the prechamber.

Many truck makers are now using excess air/boost to control NOx. If they can cram enough air in the cylinder and keep temps low enough, then not much NOx can form.

[tweake]

those Toyota throttle plates was for load control rather than emissions. most of those motors that I've seen are of the age where no emissions controls where required at all. not sure about some that had a petrol like throttle butterfly and had another butterfly which control the injector pump. something I'll have to look into as we have an old forklift with that sort of setup.

compression......good question. there are so few modern DI atmo motors these days. I've seen some info on the atmo ZD30 and it mentioned having same compression that the turbo version which i find strange. however correct info has been hard to find on that version (many report it as having 100kw+ !)

IF they keep flame temp down enough by using high amounts of EGR then minimal nox will be form regardless of the amount of air used. hence the use of cooled EGR to increase the amount of EGR drawn in. i guess that cooled EGR would allow more room for air compared to hot EGR.

[KiwiBacon]

i guess that cooled EGR would allow more room for air compared to hot EGR.

Industrial engines are about the only modern non turbo diesels. Isuzu do two very similar 2.2L 4 cyl's, one direct injection, the other indirect.
Indirect has a small fuel consumption penalty. Direct compression is 18.8, indirect is 21.5
http://www.isuzu.co.jp/world/product/in ... spe02.html

Come to think of it, they're very similar to my YD22, valve train and rev range being the biggest differences.

Hot egr was probably to blame for the rash of engine failures around the time it was introduced. All good when things are working fine. But if the valve has a spaz and lets hot egr into a cylinder at high load then you're in for a melt-down.
The EGR coolers started appearing after that.

[tweake]

Hot egr was probably to blame for the rash of engine failures around the time it was introduced. All good when things are working fine. But if the valve has a spaz and lets hot egr into a cylinder at high load then you're in for a melt-down.
The EGR coolers started appearing after that.

hot egr has been around for a while. i don't know with commerical engines but in toyota small engines i think it came out late 80's proberly 88 or so. cooled egr hasn't come out untill the D4 (tho has been out earlier with other manafactures and even in big rigs).
cooled egr didn't come out due to any problems with hot egr, its simply made so they can shove more egr into a motor. the denser it is the less volume you have to flow to get the % of egr thats required. makes it a bit easier to get large amounts when there is only a small pressure difference between exhaust and inlet.

[rayndeb]

On my old 2h it was getting to the end of its life .. It was leaving the oil residue in the inlet aswell.I put a catch can on it with a good breather and it cleared up within a few days .. It ran bloody good (as good as a 2h can) after that too.. it didnt smoke as much either..

[dazza85]

Lots of Isuzu's that I have seen have had catch cans of one sort or another added.
My newly rebuilt 2.8 puts out a little when it's working hard ...
I have got a can from a friend that makes them that has a drain on the bottom that is connected to a nipple that is added to the dipstick tube so that the recovered oil ends up back in the sump.