Oil Cloud - How Worried Should I Be?

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rb1971

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On the fourth drive of my project car on the highway, downshifted from 4th to 3rd ending up at about 6k RPM or just above this morning. Probably the highest revs the engine has seen since it was laid up 4 years ago now.

All the operational characteristics were great, but saw a big dark (oil?) cloud in the rearview. Biggest one I've seen since starting the car a couple of months ago.

Drove the three miles home and parked it. Ran absolutely fine all the way home, no overheat on water or oil temp. Checked oil and added a small amount.

Should I be worried about this? Anything else I should check before I have a big issue? Or is this just one of those things when you hit a high RPM that an engine hasn't seen for years. The engine was babied for weeks before being started, hand cranked, several oil changes etc.
 
rb1971 said:
On the fourth drive of my project car on the highway, downshifted from 4th to 3rd ending up at about 6k RPM or just above this morning. Probably the highest revs the engine has seen since it was laid up 4 years ago now.

All the operational characteristics were great, but saw a big dark (oil?) cloud in the rearview. Biggest one I've seen since starting the car a couple of months ago.

Drove the three miles home and parked it. Ran absolutely fine all the way home, .QUOTE]

hi

as far as i know a dark cloud, would not be oil, that usually is a white-blue cloud

if it is dark and considering which kind of circumstances you were in, what yo told us, is more likely to be a mix of unburned fuel and particles than any other thing

check your car regularly, liquids, temperature, etc, and consider a more progressive wake up for your sleeping beauty

regards
Click to expand...
 
What purpose served to spin your engine to 6 grand?--

For an engine that has been "resting" for several years your test at high RPM and down shift is very dicey practice, hardly a prudent way to waken your engine after sleeping for a long time.

A more prudent way is to thoroughly warm it up to operating temparature and take it for a 100 mile run with RPM ranging from 3000-5000 in your initial run--perhaps liken it to a break-in run--rather than a break 'em run. JMHS
 
I don't want to give anyone the wrong impression. We've been pretty careful re the wakeup procedure generally. Before even getting on the road, the engine was pretty carefully run up, with additional systems (cooling, electric, etc.) added one at a time. I've made several trips in the 50-75 miles range and already been up to Napa. Perhaps I have the wrong impression by saying the "fourth" trip- this was the fourth long highway trip, not the fourth trip of any kind.

The engine has been running a bit rich, so I think deQuincey is probably right about the fuel burn-off. Also, there are a lot of new parts (air intake, headers and exhaust system) that might contribute to that.

Clearly should have given more facts. :)
 
There is just no reason to take that engine to 6k rpm....none.
You left the torque and hp curves way behind and you are begging for a blown engine.
 
my bad- I apologize to you. I was stuck on the idea it was a m30.

Enjoy!

Don
 
6K rpm is just not part of the power curve.
Especially when on the down shift.
The cloud of smoke was a visible sign. A slightly slower wake up during this period may help with longevity. Change the oil sooner than normal also, when good and warm. I changed my oil/filter after 1k miles when doing my wake up from hibernation. No rpm over 5k during acceleration during wake up.
You do not know the PO's maintenance schedule and there are always more contaminants than you would expect.
When you KNOW everything is right, then wind it up.

reno
 
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steve in reno said:
6K rpm is just not part of the power curve.
Especially when on the down shift.
The cloud of smoke was a visible sign. A slightly slower wake up during this period may help with longevity. Change the oil sooner than normal also, when good and warm. I changed my oil/filter after 1k miles when doing my wake up from hibernation. No rpm over 5k during acceleration during wake up.
You do not know the PO's maintenance schedule and there are always more contaminants than you would expect.
When you KNOW everything is right, then wind it up.

reno
Click to expand...

Steve- thanks! We've got an oil change planned at the 1-month interval (i.e. next weekend) regardless of mileage. Back when I was into old US iron I used to do that just to be sure. However, the motor in my car doesn't really have a PO. (My understanding is that it was built as a racing motor for a guy that races CSLs - but then either the rules of the vintage motorsports org he was in, or his read of them changed so that he couldn't use a later motor. As far as I know he's now running a fully-built carb'd CS motor, with the original CSL motor sitting on a shelf somewhere.) I think that 6k is part of the torque curve on the S38, but agree it's high before you know everything is perfect.

In fact, I will freely admit that I didn't expect to put it up to 6k this morning. Chalk it up to poor understanding of the gear ratios to date. Twenty years ago I would have also said "youthful exuberance" but I don't think really applies anymore.
 
Oh, and thanks for the advice to everybody. After letting the car sit for 6 hours, I checked everything (oil was perfect, as was coolant, etc.), looked at everything and fired her up. Not even an instant of roughness, and went out and put a lazy 10 miles on the car on the highway just to be sure. Runs like a top. I used to say my M5 was the best car I ever owned, but this one might take its place.
 
S38- 7200. But as everyone says be careful. Tachs can be quite inaccurate and you don't have a knock sensor/ rev/ timing limiter to pull it back for you.

The stock mapping causes overfueling (lean signal) just where you said it did. BMW did it for longevity and noise.(pesky engineers) Unless you custom map (+20HP) BY SOMEONE WHO KNOWS, it was born to run that way.

Now that's not to say you shouldn't check some things because it can also be caused or symtomatic of other issues. You're basically first looking for lean conditions being sent to the ecu. Exhaust leaks first. O2 next, especially ground.(Change it to wideband or pin the ecu and read the voltage). Then sensors.

But remember- that baby was born to run that way.:-D
 
61porsche said:
S38- 7200. But as everyone says be careful. Tachs can be quite inaccurate and you don't have a knock sensor/ rev/ timing limiter to pull it back for you.

The stock mapping causes overfueling (lean signal) just where you said it did. BMW did it for longevity and noise.(pesky engineers) Unless you custom map (+20HP) BY SOMEONE WHO KNOWS, it was born to run that way.

Now that's not to say you shouldn't check some things because it can also be caused or symtomatic of other issues. You're basically first looking for lean conditions being sent to the ecu. Exhaust leaks first. O2 next, especially ground.(Change it to wideband or pin the ecu and read the voltage). Then sensors.

But remember- that baby was born to run that way.:-D
Click to expand...

Thanks. I wonder if the fact that I'm running Split Second (with a Dinan chip) changes things? In any event, given that I am running revised headers down to a reasonably unrestricted exhaust, if it was over fueling I would expect to get a cloud. (This could also explain why I get some fuel on the ground behind the exhaust on start.)

Given this is a brand new exhaust system (that we have checked multiple times), and new O2, it might just be the way it works, but I will communicate this on to my mechanic and ask him to take a look.
 
Dinan chips are famous for running rich- quit speculating and use a wideband to know what your a/f ratios are at idle, cruise and WOT.
 
I don't know anything about S38s, but if this were an M30, I would expect the oil cloud came from worn valve guide seals.
 
Dinans tend to run rich as Don pointed out. Add the Split (mainly used for boost) and if the maps are off; that would do what you've described.

Wideband+1. The only sure way to tune FI or serious carbs.$200 bucks ( inc. a meter) and you know nearly as much as a dyno on a bad hair day. Idle, mid, and WOT. Stupid little things like fuel pressure get much easier to find and correct.

Split has logging or it's an extra for under a $100. I just don't know much more about split since it's a piggy back system than stand alone, but I'll do my best to help.

You need a tuner; a very good one familiar with S38s.

But remember, S38s were meant to run rich from the factory. Play with it too much by advancing and leaning it up and it's going to get noisey and run hotter. It's basically a 80's race engine detuned for street.
 
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