Oil starvation at high rpm.

#1

I’ve noted some interesting behavior towards the end of long straightaways and it took me a while, and a few conversations with others, to figure out what is probably going on.

The symptom is that my oil temp, as measured on the driver’s side of the oil pan, is occasionally climbing up ~60deg rapidly near the end of RA’s back straight and RR’s straight.

My temp sensor is is about 1-1.5" up from the base of the pan. And the reason it’s showing OT go up all the sudden is that the sensor probe is coming uncovered. But that doesn’t mean that the oil pump pickup is coming uncovered because it’s about 1/4" from the pan’s base.

I think that what’s happening is that so much oil is going up to the top of the engine at high rpm, that it’s lowering the oil level in the pan. What’s unique about the RA back stretch and the RR front stretch is the amount of time that you spend at high rpm without a shift, brake or blip.

Consider what this means in terms of oil pressure. If the oil volume is going low because of large amounts of oil going to the head, than the oil’s flow restriction in the head is fairly low. That means that as you start worrying about what the low oil pressure in your motor might mean…you need to think about oil going to the head (cam journals and sprayer bar) as the possible culprit.

It also means that running a quart over is good idea, and not just for left turns.

#2

This seems to be a reasonable explanation for the temp spike you’ve been seeing.

Something that I found after pawing through my data from RA that might tend to support that theory is a drop in OP in T1, and only in T1. The engine has a Paul Poore pan and thus greater oil capacity than a standard pan. it also has an IJ crank scraper. Additionally, for readers that don’t know, the pan has baffles and one-way gates for better oil control. The drop in pressure is only to about 8psi/thousand rpm, so it isn’t worrisome and it lasts less that a second. It occurs just after the apex. I suspect that the combination of the run down the back straight followed by the front straight is stacking a lot of oil up in the head and high on the block.

I’ve not yet seen anything like this at any other track and at RA it only happens in T1. I’m not sure that one could even seen this with a standard pressure sensor as it it such a brief drop. I modified the sensor to improve it’s response time as I was concerned that it would miss transient events. it should have a response time 2-3 times faster that a stock VDO sensor.

#3

jlevie wrote:

Details?

#4

jlucas wrote:

[quote]jlevie wrote:

Details?[/quote]
OP sensors often have a tiny pinhole aperture. Drill it out a little.

#5

Ranger wrote:

Fixed it for you. :laugh:

Serious question: If the oil is pumped into the head faster than it can fall out, won’t that extra quart end up in the head anyway?

#6

Steve D wrote:

[quote]Ranger wrote:

Fixed it for you. :laugh:

Serious question: If the oil is pumped into the head faster than it can fall out, won’t that extra quart end up in the head anyway?[/quote]

Folks don’t spend a bunch of time on the Autobahn at redline. The average driver isn’t comfortable with their tach that high. But the Autobahn might not be a great comparison. Oil pumping up to the head would shortly reach an equilibrium with oil coming back down from the head. So steady state this isn’t an issue. But it does seem to temporarily be an issue.

Most folks go around 80-90mph on the unlimited portions of the Autobahn. And sadly, the amount of it that is speed unlimited goes down each year. For the 4yrs that I was there, not only was it pretty fun, but at 100mph you get to the girlfriend’s house or the ski slopes in a hurry.

The average person isn’t going to care that their oil volume was briefly reduced to 1" in the pan. Not when the oil pump is 1/4" from the pan. But that means that the oil level is about even with the top of that 3" sauce that makes up the pickup and screen. And that’s a low enough oil reserve to get my attention.

Re. extra quart in the head. Neg. The pan is the reservior. Extra oil is always in the pan until the oil level gets so high that it splashes on to the crank. When that occurs oil splashes everywhere, to include too much on the piston walls, which results in blue smoke and fouled pistons.

When I was trying to understand how I could be losing oil pressure for several minutes at a time with an Accusump but no scraper I experimented with adding too much oil. At 2.5qts over I had blue smoke and fouled plugs.

#7

Ranger wrote:

My head hurts. In your first post you advocate running a quart high because oil accumulates in the head at high RPM.

That last post says it all drops to the pan.

I shudder to think of the number of people who might lurk here and decide not to build a Spec E30 because they think the motors are finicky and poorly designed from the factory.

Dear Newbies - I am having my one and only motor refreshed after 2 1/2 years running the series with a crank scraper and oil up to ‘full’ on the dipstick. Stock oiling system FTW.

This was my original motor (freshened head, untouched bottom end) that carried us to 1st E30 in the 8 hour enduro, 4th in the sprint, 2nd in the Toy race, and ran all the DE1 sessions that weekend.

These cars are fine. Put in gas and go. Don’t believe the hype.:laugh:

#8

Agree with Steve that the stock setup is plenty reliable. Most SE30s aren’t probably even running crank scrapers or baffled pans. Keep it simple.

#9

I stated from the outset that I’m not describing a problem, it just struck me as interesting.

Steve, this is a transient condition. Your comments make it sound like you are oriented on the equilibrium state of sustained high rpm.

In order to visualize it a person has to imagine a lot of oil being pumped out of the pan (the reservior) and being pumped up to the head. Then, a few seconds later, it starts coming back down. But the rate that it comes down is linked to the rate it was going up a couple seconds ago.

It’s that time delay between increased flow going up, and increased flow coming down, that is the best explanation for the oil reservior going low.

Re. scaring off newbies. IMO newbies are generally surprised at how much help they receive from SpecE30.com. The conjecture in this thread is just one addition to the community’s body of knowledge. Nothing scary here.

Your frequent role poking holes in ideas and playing the foil is a service too. It helps to flesh out the conjecture and leads to community brainstorming.

The more I talk to race oriented engine builders, the more surprised I am at just how long our engines last. I put >100hrs on my car each year. The engine builders I’ve talked to say that would mean an engine rebuild each year. I can’t accept that it’s necessary for me to rebuild my engine each year, but its darn interesting that those smart guys think I should.

Kishg, I’d bet that most folks are running a scraper and/or have a baffled pan. The data that shows the consequences of doing neither is pretty complete, even if there are a few folks that have accumulated a fair # of hours with neither.

#10

Ranger wrote:

Every time I visit a dealership they think I need a new car, too. :laugh: But I think they might be right. 100 hours should be enough abuse on the top end at least, no?

Scraper and stock pan here.

#11

I ran engine number 1 for an entire season of SE30 and that included doing the 8hour enduro race.

It is also worth noting that my debut race included the oil pressure relief dealio “blowing an O-ring” and I pumped the entire contents of my non-baffled, non-crankscaper pan down the front straight at Roebling. For which I was charged $300 worth of oil dry (I got to keep the final 1/4 bag full).

The oil pressure light came on a little before the entrance of turn 1. Since I didn’t notice the exxon valdez behind me since were still on formation / pit exit and I had been having electrical gauge issues (thought the flickering light was just that) as well I probably ran the car for nearly a minute before I turned it off by the corner worker station.

That motor served me well until I wanted a hopped up .20 over. That didn’t work out so well and lesson learned we did a very basic stock rebuild on engine 1A. At last count I think it just finished its 3rd 8 hour race? And still pulls strong. I did break down and install the crankscraper.

I’ve posted this several times but I’ll do it again. You can see here is a log of all channels on a STACK dash including Oil Pressure and Temp, using just rough guide OP never dumps below 40 during a lap. Except at the entrance to 10a, but that is commensurate with Engine Speed (RPM)since I have the bad habit of holding the clutch in while I brake. You can see for the most part it holds to the 10psi / 1000 RPM rule.

http://dtomracing.com/photos/Stack%20All%20Channels.jpg

Ranger - this isn’t to dissuade you from your observations or accumulation of knowledge but more as a counter point to any new soul that may get the impression that they need a F1 engine builder on speed dial with this cars.

#12

My dataset agrees with Paul Poore’s stable, and with the data collected by the Pro3 guys supported by TCMotorsports. There’s a couple others, but I forget who.

Your data, and the anecdotal evidence of engines that have run for likely several hundred track hours with no scraper nor baffle is completely at odds with that.

And that’s all cool. I want to understand what is going on. And often the way to get there is for folks to point out how I’m wrong. The process of figuring something out can easily involve some early and not-quite-right conclusions. Often the way to really understand what is going on is to figure out why the data seems to contradict each other.

Let me bounce this thought off of you. Based on some conversations with engine builders re. the degree of strain on DD motors vs. race motors, here’s what might be a good low budget, yet high performance solution…

A newbie builds a car, puts a scraper in it and has the head done. After 1-200hrs of track time buy a motor from some kid parting his car out for $3-400, put your head on it and put it in the car. This assumes that the 1-200 track hours has hammered out the cast piston’s ring grooves.

Every other engine have your head re-done.

This would give you a primo head and bottom end solution, and the newbie could swap engines in his garage in a single long hard day.

One of the points that was made to me is that the average DD engine has a tired head and an entirely serviceable bottom end.

#13

Ranger wrote:

[quote]My dataset agrees with Paul Poore’s stable, and with the data collected by the Pro3 guys supported by TCMotorsports. There’s a couple others, but I forget who.

Your data, and the anecdotal evidence of engines that have run for likely several hundred track hours with no scraper nor baffle is completely at odds with that.
[/quote]
I think this has a lot to do with how fast the driver is, the lateral Gs the driver pulls in turns and that particular car. Slower (maybe newbie) drivers may have less issues then faster more experianced drivers.

Here is my experience. I bought my car built. I asked about oil starvation (car had no scrapper and stock pan) and puking oil out of the trans. Both issues that come up in SE30 land for some. The builder / shop owner / driver said he never had any issues. I believe him and the car was clean and dry underneath. I took it to a DE for a shake down and it puked tons of gear oil and I noticed a drop in oil pressure in hard left and turns. It was obvious.

At first I thought this guy must have been full of crap but how did he get the car so clean. Then I registered the lap timer on My Laps and noticed this driver was way slow compared to many. I actually raced against this car and driver at VIR in a Drive Gear rental car a few years back.

It was clear by the lap times in that race weekend I was faster then the previous owner. The only mod I made to the car after purchase before shake down was to add gauges. So I had issues and he did not. Only thing that comes to mind to explain why I had some issues and he did not was, he was full of crap (but I still think he was not) or I drive the car a bit faster and get some of the issue noted above.

So two drivers in the same car may have different experiences with some of these issues based on the drivers and how they drive.

You do if it your first time in that situation with a rental. I logged over 45 minutes 500 RMP shy of redline in an Opel a while back. About 110 or 120MPH in that car I think. It held together for the rest of the two weeks I was in Germany with many more shorter trips to top speed. Probably can’t string that long a drive at top speed today though. It was a blast and I really wondered if it would hold together and it did.

#14

The slow driver is sure to be one variable, but there’s going to be lots of variables. Jim’s fast, and his various codrivers were faster.

#15

The engine in my car has been there since 1987 without a crank scraper!! It has done well over 200 on track hours. I don’t plan on removing it until it goes bang!! When that happens I will probably rebuilt the head and slap it on the block out of my parts car. Rinse and repeat!! I do have a leaky oil pan gasket so I will probably add a scraper this off season when I fix the leak.

My theory on engines!! An engine that is well put together will stay together, while engines that are poorly put together go bang before they should. So if you come across an engine that is well put together don’t F**k with it!!!

Greg

#16

I fully agree with Greg. I will take my chances with my 200k mile BMW factory built M20 till it blows up before going with a fresh rebuild that could have been built wrong. I ran 6 DE weekends last year with no crank scraper and just made sure my oil was always a little over full on the dip stick. With that being said, I still enjoy the threads talking about oil starvation.

#17

Steve D wrote:

[quote]Dear Newbies - I am having my one and only motor refreshed after 2 1/2 years running the series with a crank scraper and oil up to ‘full’ on the dipstick. Stock oiling system FTW.
[/quote]

I’m running an original motor, had 145000 on the clock when I started racing. It has done 4 seasons, although I only did 1 race weekend last year. I am somewhat lucky in that it makes just over 150. In my experience most older engines seem to be in the high 140 range. I run a crank scraper and probably a 1/4 quart overfill. Motor was only just opened for the first time this off season for a valve adjustment. Haven’t asked the mechanic how out of spec they were.

#18

the question i’d ask is what did skeen have on his motor? :stuck_out_tongue:

I’m not disagreeing with the data re scrapers/baffled pans. I run a PP pan (no scraper) myself but I don’t think the data is conclusive that they are mandatory either.

#19

kishg wrote:

[quote]the question i’d ask is what did skeen have on his motor? :stuck_out_tongue:
[/quote]

Before his rebuild in 07 at Nationals (I think he came 3rd) he had 148-151 hp and 146-150 trq depending on the dyno run. It was his first time at Mid Ohio also. After his rebuild I vaguely remember it being around 155-156 in 2008 but certainly nothing outrageous.

#20

There are lots of great points being made in this thread. Some people like to wrench on things and some people like to drive; I like to do both. My first engine was an overbored build by other than me that had ring failure at ~30 hours; this engine only made 142 HP. It made great oil pressure until the end, but when I took it apart, there were two rod bearings that were near failure. They were coated bearings but it was clear they had experienced oil starvation; I did have a crankscraper installed for all 30 hours and oil pan baffle for the last 4 hours. My current engine is a well used junk yard motor that only makes 143 HP and really bad oil pressure (3 psi at idle). STP helps with the pressure, but it clearly has a weak oil pump and/or excessive clearance at the rod bearings.

BMW definitely builds a great motor, but they do wear out. The weak point is the rod bearings; according to metric mechanic, the main bearings almost never fail. Main bearing failure would require extended running with no oil pressure, but the rod bearings will fail with short duration oil starvation very quickly. IMHO, if you have a good BMW bottom end you are better off not monkeying with it. Not that a good engine builder can’t build an equal motor, but you are taking a risk any time you wrench on your car. A good oil pan baffle/crank scraper combo is good insurance that your good bottom end will in fact stay good. If your bottom end sucks, which both of my do, you have no choice but to rebuild or buy another motor which may or may not be in good condition.

I like to do things myself and understand how things work. This is why I’m a mechanical engineer and do ALL of the work on my race car. Scott and I are going to build our own motors next weekend (see metric mechanic thread). I certainly could just buy another used motor or take the one out of my DD and refresh the head, but I’d rather “learn” how to build a good motor from some of the best engine builders in the US. You know they do ship BMW motors to customers in Germany and as far as Australia. I figure by the end of the weekend I’ll have a good motor that will last a few years, have an idea how to rebuild this motor when it’s time, and there is no way I’d risk my hard work and $ on an inadequate oiling solution.