Thinking about taking my 86 to an autocross before I get the full suite of oil control & cooling mods on the engine, how much overfill can I get away with to be extra sure the engine will not sing the song of its people? From searching around it looks like 0.25qt is safe but some people have reported sudden rapid oil burning at 0.5qt+ overfull. Also a lot of people reporting that dealerships have overfilled their engines by nearly 0.5qt...accidentally?
I think I hear some unfounded myths here.
Oil goes in reasonably thick but it gets hot as it's used. As it gets hotter it gets thinner. Until it's thinner than water more like gasoline.
As you step on the gas it all surges to the back of the pan. When you're braking it surges forward up into the timing chain cover. Same thing with corners.
Everything is OK until the oil pickup is un- covered. Then it doesn't suck oil. It sucks air.
Since air isn't a lubricant the bearings take a beating.
The idea is adding extra oil might give you a tiny bit more time before it's uncovered.
People worry that the conrods will hit the oil and splash oil around. Well so what? You think it isn't happening under hard cornering? Stopping? acceleration?
Want to be extra careful? Warm up the car properly before you rev up the car.
Not 100% sure about the Fx engines, but on the EJs and EAs, they would pump all the oil into the outside cylinder head, and on a long enough corner it would overpower the PCV system and cause detonation/Giant White Cloud on corner exit. I would think overfilling would make that significantly worse at the same time it solves oil pickup uncovering issues.
Autocross runs are pretty short and the same for the corners. I'd just top the oil up to the full line and double check it half way through your runs unless it's some sort of oddball event on a banked oval. I don't think oil temps will be a problem, likely a hard pull through the gears on the street will generate higher temps.
If the course design contains a 360 degree turn oil starvation is likely in many engines. I am not familiar enough with your engine to know how problematic oil starvation is, but over filling is unlikely to be much help.
Yeah being a boxer engine, the oil can not only escape the pan more easily but also collect in bad places more easily. I do always get engines at least close to full operating temperature before running them hard. The engine has a small oil catch can that could keep a few giant white clouds from making it to the intake, so I think I'll just go with the mild 0.25qt overfill.
FA20? I haven't heard of any oil starvation issues, even with heavily tracked cars. *Fuel* starvation is definitely a thing though (full gas tank helps).
Are you N/A? If so I think you will be fine. I tracked mine without an oil cooler for quite some time.
EDIT: Fresh oil change before & brakes of course would be most important IMO.
Yeah I know about the fuel starvation issue and will run a full tank, and get a fuel pickup trapdoor added in the future. The engine's still NA.
Based on what I read on ft86club, there is a possibility for oil cavitation with the stock pickup, not necessarily for oil starvation unless your engine is trying to inhale the silicone from the valve spring recall.
Fitting the fuel starvation door took me half an hour excluding the trip to the Hammer Store to get more needle nose pliers. It's a bit messy with the glue that holds down the cover over the fuel pump, but it's not that big a deal to fit. I'd just do this before your Auto-X - although from what I remember, the issue is mostly supposed to happen during long lefthanders on the track, so you might not ever encounter it during an Auto-X.
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