F1technical.net

Dry Sump = negative pressure under the pistons.
And no one is sneaking oil past the rings any more than what naturally makes it past during operation. Doing so is counter to an efficienct engine.

Do these power units have oil squirters for the pistons? These are usually threaded into the block with a banjo bolt, the bolt contains a check valve as well.

drysump still has a breather to the air intake right? Any oil fumes would leave the sump through that breather i presume.

NL_Fer wrote: ↑

20 Apr 2018, 21:53

drysump still has a breather to the air intake right? Any oil fumes would leave the sump through that breather i presume.

Used to in previous seasons although with a slightly different mechanism.

On normal wet sump road cars there is a breather that is run to the intake through a check valve.

On most dry sump engines the oil is scavenged through the bottom of the block and sent to an oil tank which separates the air out, the air is then sent to the intake.

For 2018, the crankcase gases have to be sent overboard (not allowed into the intake), hence the smoking from the Ferrari at low load/rpm.

godlameroso wrote: ↑

20 Apr 2018, 21:03

Do these power units have oil squirters for the pistons? These are usually threaded into the block with a banjo bolt, the bolt contains a check valve as well.

Of course they must have, otherwise the pistons would melt right away.

On road engines the check valve is there to stop the oil from short-circuiting through the squirt jet and starving the bearings at low engine speed.

In an F1 however the oil system is actually sized based on the squirt jet pressure requirement which far exceeds the bearing requirement. I don't have the data handy atm but I recall 20 bar required for nozzles and only 8-9 bar required for main and big end bearings.

Interesting most high performance road cars have oil pressure ~5.5 - 6.6 bar peak.

There's a few high revving road motors that around around the 10bar area.

I've seen around 7.5bar at 8400 rpm with manifold pressure approaching 2 bar on my car. That's with the stock oil squirters retained and an external oil cooler.

But 20 bar. Holy Moly lol. I can't wait for more info on these motors to come out. Might be the best thing when these PUs get binned. I've actually come to really enjoy them. They sounded pretty bad at first but they are getting better and the tech is amazing.

pro stock 1100HP = zero weight oil; 3 bar (45psi) pressure; 2thou mains and BE's

PhillipM wrote: ↑

22 Apr 2018, 01:49

There's a few high revving road motors that around around the 10bar area.

Some German horizontally opposed engines? S53 and S65 engines that need those ridiculous viscosity numbers on the oil(15w-60)?

Alright, found the cossie numbers (RET):

TJ V10: 8.5 bar
CA V8: 7.5-8 bar
HK (inline 4 turbo developed before they decided on current V6 turbos - had a separate oil curcuit for the squirt jets) 20 bar!

They reckon the CA would have needed more than 20 bar had it had a split circuit.

Why is the compression ratio limited at 1:18 ? This insane even for NA engines, do these engine have a Miller/Atkinson cycle?

They could, but just as well not. I wonder if anyone is running 18:1.

I know CR is swept volume, but what happens with super/turbo charging?
For instance, easy numbers, if a cylinder is 10:1, and the charge is increased to 1.5 does the CR then become 15:1?
It does seem obvious, but the 'stipulated' swept volume stays the same.

(Ignore valve overlap etc)

No, that's the difference between static and dynamic compression.