[rl968]

My car has been sitting since November and yesterday I did my first DE of the year. When I started the DE, the oil level was at the top of the line and this morning it was down to the quarter mark on the stick. I did 4 25 min sessions and my rpms were 5500-6000 touching rec line once or twice. Is this normal consumption. In prior events, there was little consumption so this seems a little unusual. There are no external leaks. Wondering if car burned a bit more because it had been sitting. No other issues.

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[tamathumper]

There is a thread on sitting cars burning more oil, and kind of an informal poll therein.

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[MB968]

How old was the oil. My wife's Subby uses little oil just after an oil change and progressively gets worse as the oil gets more miles on it.



Tamath. do you remember the majority of the comments from the above thread.

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[rl968]

Oil was change mid-year last year. I will change it before next de.

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[tamathumper]

If you search for "oil consumption sitting", they come up. Here y'go.



http://www.968forums.com/topic/2675-oil-...entry23181



http://www.968forums.com/topic/11782-oil...msearch__1

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[RS Barn]

All 944-951-968 consume oil when driving <acronym title='wide open throttle'>WOT</acronym> at DE's. Several reasons including blow by,

crank case pressure and oil seperator function. There are some ways to decrease issues but generally-just add oil

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[flash]

yeah - it's a pretty crappy design. the valve cover gets pumped full of oil at high rpms, and it makes its way down into the combustion chamber. the 928s are so bad that it can pump all of the oil out of the crankcase. there is a fix worked out, but it is pretty complicated.

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[Cloud9...68]

I wonder if this may explain why my car kept showing relatively high levels of "fuel dilution" in the oil analyses I had had done. The analyst told me this was very common in these engines, and that my levels weren't dramatically high for an engine of this type, but that he typically sees this. Maybe the oil that finds its way into the combustion chamber that doesn't get burned and makes its way back into the pan would have picked up some unburned gas along the way.

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[flash]

between that and the way they made the oil rings, i'm not surprised. pretty lame design. not intended for sustained high rpms. that may well be why they limited the redline. they might have figured out that going any higher created bigger oil problems.



again, this is likely one of those things that nobody will discover until more people are pushing the envelope. until now, it has been a pretty small group. now that the cars are dropping in value, we may find more people turning them into track cars, and finding more problems and they push the envelope more and more



one thing for sure is that burning oil will ruin a cat. given that the OEM cat is now NLA, this could create a large problem for those who have to undergo emissions testing, and are using the OEM cat.

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[Cloud9...68]

You're all welcome in advance for my acting as the latest in a line of guinea pigs by subjecting my car to the stresses of the track as its primary function once I get it all back together. I fit in the exact category Flash describes - I was going to sell the car, but when I saw how little it was worth in its current condition, and kept reading about how successful these cars can be on the track (witness the incredible string of results turned in by Pablo, Joel, Craig Woodman, Dubai944, Eric_OZ_2, Benspeeder, Eric Krause, Jim Child, and I'm sure Rlips in the very near future, plus I'm sure I've left off a few dozen), I decided to go the track car conversion route. Of course I'll keep everybody posted on things that go boing as a result <img src="/forum/images/smilies/968/ohmy.png" class="smilie" alt="" /> <img src="/forum/images/smilies/968/tongue.png" class="smilie" alt="" />



Good point about the impact of excessive oil consumption on the cat. Hmmm...

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[flash]

yeah - the problem here is one that makes me crazy. it always starts with "i don't have that problem" or "i haven't seen that problem". far too often people assume there is no problem, purely because they haven't seen it yet.



the reality is that the problem is there, and it just hasn't shown up yet. some of these things take years to show their ugly head. does that mean that you should ignore it, or not do something to cure it before it shows up?



some things won't matter in the long run, and you may destroy the car long before a problem shows up. this is really one of those things that you have to think about based on how you plan to use the car, what is involved in a fix and whether or not it is worth it to you, and lastly the odds of you seeing the problem in the time you will have and use the car.



for a track only car, emissions are not an issue, and you are probably able to remove the cat. for a street car, you can't. for a dual purpose car, you may just have to find another cat. it sort of depends on what you are willing to go through, what you are willing to give up with an alternate cat, and whether emissions testing is an issue for you.



as i said, there is a fix for the oil consumption cause, but it's pretty involved, and i don't have any empirical data on it yet

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[MB968]

[quote name='Cloud9...68' timestamp='1335108990' post='125888']

I wonder if this may explain why my car kept showing relatively high levels of "fuel dilution" in the oil analyses I had had done. The analyst told me this was very common in these engines, and that my levels weren't dramatically high for an engine of this type, but that he typically sees this. Maybe the oil that finds its way into the combustion chamber that doesn't get burned and makes its way back into the pan would have picked up some unburned gas along the way.

[/quote]



Because you run much lower A/F ratios when racing, there is available unburned fuel in the combustion chamber. The rings won't necessarily do a very good job of keeping the fuel from getting past them, and the next time the piston goes up, the oil from below can pick up some of the unburned fuel. When I first put the aftermarket ECU on my Mazda engine, I had it running very rich by design to minimize any risk of detonation. I wanted to creap up on the correct fuel settings from the rich side. I must have started below 10:1, my oil very quickly took on a distinctive fuel smell.



As to why it might be worse on our engines under any conditions, could have to do with the way the cylinder walls are created. Microscopically I suspect the rings only touch an exposed aggregate of silica in the aluminum. This could lead to a lot of space on a micro level that could allow the fuel an even easier track to get past the rings.

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[Eric_Oz_S2]

Mine has always used a bit on the track. I notice that if I keep the revs down it uses less, but when really pushed with sustained 6000+ rpm it tends to use oil at an alarming rate. With the supercharger it is even worse. I used to loose maybe 0.2 litres in 5 to 6 laps. Recently at Bathurst (in a 30km session/6 laps) it used 0.5 litres. I suspect a lot of it is going into the intake through the AOS. I think this may partly be due to old AOS o rings and leaks at the AOS limiting its ability to reduce crankcase pressure.



I'm going to put an oil catch can in and also a vent for the camshaft cover (routed to the catch can with the crankcase) to see if this helps - or at least see how much is being blown through the intake.

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[MB968]

Catch can seems like a good way to tell how much is being taken in the intake. And I see a strong movement of the forced induction cars to the use of a catch can. If I remember correctly isn't it to keep the oil being taken in via the intake from increasing liklihood of detonation.

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[flash]

if you don't route the vacuum right, you will pressurize the crankcase and blow oil where you don't want it - been there done that



the cam cover does fill up. porting it and evacuating it back to the crank case is the fix, but it's pretty involved in order to get it right.



the valve stem seals are a culprit too.



hopefully you haven't over-boosted the engine, bent a rod, and are now scraping your oil rings down to the point where you are passing oil. that's what happened to me. it was completely unnoticeable in power and operation. it began by just using oil. then, after a few thousand miles, it finally started smoking when i was on it. upon tearing it down, it was painfully evident what had happened.

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[Eric_Oz_S2]

Well in a 2000 km road trip it didn't use a drop of oil. So I think that is a sign the rods are OK.

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[RS Barn]

I use the Lindsey catch can on my turbo which runs at 10.8:1 afr. I get 4 onces of water and gas in container after 30 minutes on track. My turbo which was built by Michael Mount doesn't use any oil....Zero

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[flash]

probably apples and oranges, but way back when i was running the mgs i had an engine that i thought was not burning oil, but turned out that because we ran it so fat, it was actually pumping fuel into the oil. if we waited long enough, we found the oil in the crankcase had a large portion of fuel mixed in. we were just checking the dipstick and thinking it was not burning oil. we were very wrong. an oil analysis showed us just how wrong. was not pretty. explained the ring wear though. as soon as we leaned it out to something more reasonable, we saw a pretty big change. lol - then we had to resolve the oil consumption issue, then the oiling issue, then..............



it will be interesting to see how the new engine does on oil. after hearing about some disturbing things about redline, and how it may have contributed to the cylinder wear, i am switching to amsoil. i'd run torco, but it's too hard to get.

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[RS Barn]

Both my Turbo and FireHawk have different bore materials and Nascar style ring packages. The pistons are also ported to put pressure behind the rings to increase seal. No cylinder wear on turbo with Redline

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[flash]

total seal rings are nice when you can use them. i've used them quite a bit over the years in cast iron blocks. they don't last, but they do work. pretty hard to use them in our engine though and expect any life. the alusil in our block is a very real pain in the butt. you could nicasil, though it is expensive, but it works better, but apparently not with total seal. dry sleeves, which do work with total seal, move around too much, and wet sleeves on an open deck design are a bad idea for a high revving motor, according to those who have done them. even darton recommended against it. i just went through this decision process on my motor. i was all set to send my motor to darton, and somewhat excited about the idea of really going big, but then i spoke at length to people who had tried it, and found it to be a very bad idea for me. it made me just about crazy though.



as for redline, it seems there is quite a long list of front engine cylinder wear issues with redline. i'm compiling that information now. i was very surprised, and very disappointed when i heard it, as i had heard nothing but good things about it up to that point. we'll see just how objective the information is as soon as i finish getting it all together.

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