Oil changes and soot

[Jens]

Today I did an oil/filter change on my truck. It had roughly 150 engine hours since the last change (8000 km). The oil was black yes ... but when I spilled a little bit there was a whole bunch of 'golden' in the spot. In other words, it wasn't a situation of blacker than black type stuff. In contrast, when I did oil changes for Thumper at 200 hrs, the oil is BLACK. We are talking black hole black, blacker than black (and also a bit more viscous but that could be because it is 30 wt oil compared to 10-30 in the truck).
Anyway, the point is this ..... one is an 8 cylinder diesel and one is a two cylinder diesel. The oil in the 8 cylinder unit, comparatively speaking to the 2 cylinder unit, is virtually new.
Besides possibly getting some (minor) veg oil leakage into the sump of Thumper, what determines how cruddy the oil is.
Volume is comparable, but besides the truck engine having 4 times the cylinders, it also has probably at least twice the crank revolutions in a given oil change interval. This would suggest that the listeroid produces a HUGE amount more crud than the modern engine .... more than a factor of ten even when one is being optimistic!!!
Two questions come to mind ...... why is there such a huge difference in crud factor and what are other peoples oil changes like in their listeroids. Is the old oil really really black or is it comparable to changing oil in a modern diesel engine ?

Comments ?

BTW, I believe recommended oil changes are 250 hrs in the singles and 500 hrs in the twins. As I said, I change at 200 hrs and even that seems hard on the engine .... 100 - 150 hrs seems more reasonable but it is a matter of testing to see what the oil looks like.

[Crumpite]

The first thing that comes to mind is that your truck has continuous filtration, the Lister doesn't...

Enough to make a difference ?

Older diesels seem to have more soot in the exhaust than modern lean burning engines too.

I remember the first time I saw the dipstick in an older diesel car - it was much blacker that any used oil I'd seen to date.

Excellent question !
Crumpite.

[Crofter]

More piston ring blowby, much lower injector pressures so more carbon and products of combustion wind up in the oil.

[cschuerm]

Jens, just a data point for you:
I've had several Dodge trucks with Cummins engines.  They turn the oil absolutely BLACK within 100 miles.  They've done it since new.  Both of my listeroid twins do turn the oil pretty black, but over maybe a 50-100 hour period.  I'm pretty sure it's just micro fine soot from blowby.  I can tell you that on aircraft engines, that has a huge impact on oil.  I've owned many and by the time the engines start to get up in hours, they grunge up the oil pretty quickly even though they're running fine and cylinder compressions still measure to almost new limits.  After overhaul, the oil stays like honey all they way to oil change time.

Chris

[mobile_bob]

the following is my opinion only, based on my experience building all sorts of diesel engines over many years

two things lead to the problems of black oil

1. the injection system is relatively low pressure,and the idi design along with alternate fuels lead to in adequate atomization
and an incomplete burn which all work together to produce more particulate matter, and

2. crankcase pressure which is a byproduct of cylinder leakage (blowby)
more blowby allows much more of the PM (see #1 above) to end up down in the crankcase.
all piston rings are not created equal, all liners are not created equal, and certainly the rms crosshatch is likely just adequate
for the engine to run, with no consideration given to blackening of the oil.

we can't do much about #1 above, save for making sure the injector is in good condition and popoff pressure set properly, and
to use decent fuels which usually favor pump diesel over alternate fuels.

this leaves us with #2 above, and in my opinion there is much that can be done to improve this problem,

we can improve the surface finish/crosshatch to a much better surface with a bead hone, and we can clean the liner properly at rebuild
so that there is no residual grit left behind,
we can make sure the ring end gap is correct and also the groove clearance is within spec,

aside for that, the breakin procedure is in my opinion the single most neglected consideration of not only these engines, but quite frankly nearly all
rebuilt diesel engines.

we have to get the engine up to temp as quickly as possible, followed by applying more
and more load, in steps while monitoring crankcase blowby

we increase load while monitoring blowby, and at each increase in load we might expect an increase in blowby, but
not a dramatic increase,
if there is a small increase in blowby we simply continue to run the engine at that load until the blowby recedes, this indicates
the rings are seating,
then we add more load and watch for a small increase in blowby, run at that level until the blowby recedes and then
continue ramping up in steps to full rated load, where we continue to run until the blowby recedes,

the engine is then properly broken in.

if at any point in the stepping up of load we see a larger than expected increase in blowby we simply reduce the load
and continue to run there until it recedes.

in my opinion there is nothing better for making a good engine that building it properly, cleanly and then break it in properly

shortcuts always lead to less than spectacular results, unless you just get lucky.

if i were to build a listeroid, i would set it up to monitor blowby, and have a stepped load bank to bring up the load
in perhaps 750watt increments, i would also have it connected to a cooling system that would allow it to come up to temperature
within no more than 5 minutes of startup, running at 750watts.

cold engines, running at no or low load, for long much longer than about 20 minutes, generally will never break in properly, and the problem
only gets worse with poor finishes and poor assembly practices.

back in the early 80's i could routinely build 3406 cats that would run 8000 miles to a gallon of oil (they hold 11 gallons)
as compared to new 3406 cats that generally could do no better than 4000 miles to the gallon of oil.

the only difference between the new engine and the rebuild, was attention to detail, cylinder finish, cleanliness of the build (perhaps)
and the breakin procedures. Cat would sell 3406 engines to the oem truck manufactures that were only ran long enough at the factory
to assure they would run, they like other engine manufactures would not spend the time to do a proper breakin.

also, all of the 2 stroke detroit diesels (53,71,92 and 149 series) could effectively be ruined if allowed to run without a load for more than
20 minutes after a rebuild, and if you did so, you would have an engine that would forever blow oil out the airbox drains all over the ground
those engine's were very finicky about the breakin procedures.

fwiw

bob g

[rl71459]

Guys

I think this is on topic.... As Bob described engine building it reminded me of my experiances with engine building (gas automotive). While Drag Racing we would do anything we could afford to make more power!

In my last 5 years or so involved in racing there was such a buzz about power to be had by running what was then new "Gapless Rings" That I tried them.... The difference was amazing! Noted power increase...
But long before you noticed that you could easily see the reduction in blowby out the breathers!

I tried 2 different brands/designs and both seemed the same. One brand had an overlapping ring end design.. somewhat like automatic transmission sealing rings.

The other was a 3 piece style very similar to a typical oil ring arrangment.

Does anyone use this type of ring in a diesel engine?

Rob

[bschwartz]

Bob G,

You said "we can't do much about #1 above, save for making sure the injector is in good condition and popoff pressure set properly, and to use decent fuels which usually favor pump diesel over alternate fuels."

I read an article somewhere (for the life of me I can't remember where) that tested injector pressure changes in spraying veg oil.  The higher the pressure was set within reason, the better the spray pattern.

Could the pop pressure be increased on a listeroid injector to help improve spray pattern, and therefore decrease soot?

If so, could it be done at home in a simple manor such as adding shims or something?  I've never worked with injectors, so any info including "don't do it" would be appreciated.

[mobile_bob]

i would connect the breather to an old freon tank, or similar with a matching outlet on the other side
this is used as a surge tank to dampen the pulses, my books actually show two such tanks hooked in series with
each other.

then connect a T in the outlet and connect a water tube manometer (home made) to the center leg of the T

you might need to put a small choke on the outlet leg to get a reading.

the exact reading is not important, but a relative reading is what is useful.

the 3 stone hones are ok, but a bead hone just works so nicely and provides an excellent finish that i have found to
enable the rings to seat quickly too.

not sure why this is the case, other than the advertised hype about plateau or whatever, it works so i never questioned why.

otherwise the procedure is the same, get the crosshatch somewhere close to 45 degree's, and then follow up with cleaning with ATF
and white paper towels until the towels come back with no signs or gray color (only red on the white paper towel tells you that all the
grit and metal is gone), then hot soapy water, dry well, and lube with whatever you like.

the cleaning thing i am convinced has a very high value in the outcome of your rebuild. any grit no matter how small gets caught in the rings
and the ring lands and ends up making an excellent lapping compound accelerating the wear to the cylinder.

bob g

[Randybee1]

Bob,

"the 3 stone hones are ok, but a bead hone just works so nicely and provides an excellent finish that i have found to
enable the rings to seat quickly too."

I also use  bead hones when I rebuild gas engines. What grit # do you recommend for a diesel? and does it depend on what type of rings you are using, such as moly or chrome?.. Randy B

[mobile_bob]

i don't recall what grit i used, but if memory serves me it was either a 180 or 220 grit,
am thinking likely it was the 220 grit

we always used the oem rings, most of which were at least a stainless allow for  the top ring
and some used all stainless alloys while others used iron secondary rings.

for the indian or chinese engine's i would probably use a 220 grit bead hone myself, running at 500rpm
and lubed with ATF.

Bschwartz:

one could certainly crank up the injector pressure setting to get a better pattern and/or better atomization, but
it probably isn't going to change things much, and it might aggravate the cam/idler gear issues with the listeroid.

but i don't know for a fact whether this is the case or not.

bob g

[billswan]

Bob G,

You said "we can't do much about #1 above, save for making sure the injector is in good condition and popoff pressure set properly, and to use decent fuels which usually favor pump diesel over alternate fuels."

I read an article somewhere (for the life of me I can't remember where) that tested injector pressure changes in spraying veg oil.  The higher the pressure was set within reason, the better the spray pattern.

Could the pop pressure be increased on a listeroid injector to help improve spray pattern, and therefore decrease soot?

If so, could it be done at home in a simple manor such as adding shims or something?  I've never worked with injectors, so any info including "don't do it" would be appreciated.

Well that is one of the things I am planing on, obtaining a couple of new injectors and trying to up the pressure to try to break up the fuel better. I know it is probably a futile challenge and will probably just kill the injector line and or pump but I just have to try. Of course where will I ever find the TIME, am about a year behind on where I was planing on being.

Billswan

[Crofter]

There are ring and cylinder liner materials that have a lower coefficent of friction and better wear characteristics than plain cast iron. Narrower rings with higher ring tension can be run that provide much better sealing and will "seat in" on a much finer cylinder surface. Too coarse of cross hatch allows gasses and solids to sneak past the rings especially on wide low pressure rings. I have seen cylinders that still showed deep cross hatching after many hours running and that is not good for keeping oil clean or sealing. The proper surface and operating conditions is important to prevent initial glazing but it is specific to the ring and cylinder materials.

Gas pressure above and behind the ring is a great part of what exerts ring force outward on the cylinder but on multi ring setups each lower ring is in the pressure shadow of the ones above, therefore initial ring tension is of greater sealing importance. Bobs reference to applying load in stages while watching blowby during break in probably has to do with the rings not all sharing the load the same because of the pressure shading effect. Ring land side and rear clearance that is affected by carbon buildup (polymerized veg oil deposits?) likely interferes with pressure transfer and load sharing.

[Geno]

I raised my injector pop pressure to around 1800 psi 1500+ hours ago. Everything is still working well. I haven't looked at my cam lobe or disassembled the IP in a while. I should do it soon. I'm seeing more carbon buildup on my injector tip than I'd like recently. I did check pop pressure today and it was right where I set it. The idler looked fine. It's the original cast iron one as well.

Thanks, Geno