You are reading a single comment by @Dammit and its replies.
Click here to read the full conversation.
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
@Dammit
Here's the oil circuit for the M96:
What's going on there is that the engine has three sumps - one per head (as this is a flat/boxer engine) and one central/crankcase sump.
Each head has a scavenge pump that feeds back to the central sump via a swirl pot.
The central sump has the oil pickup, drawn on by the engines oil pump, which is driven by the (infamous) IMS (intermediate shaft).
Porsche, for the X51 performance version of the X51 introduced a dual stage head scavenge pump - literally stacking another stage on top of the standard one, with both driven by a common shaft, itself driven by the exhaust cam. The second stage scavenges the other end of the head from the first stage, in order to prevent oil pooling under braking that is not returned to the central sump.
The X51 package also has a higher gated baffle in the central sump to (try!) to keep the oil pickup submerged during high-G.
Despite this, the M96 can still encounter oil starvation on the track - the pickup is uncovered and oil supply stutters, and whilst this may not be immediately fatal it dramatically shortens the life of the engine.
I am considering the following:
If you'll forgive the deeply amateur diagram, what is going on is:
Each head has a dual-stage scavenge, evacuating oil from either end of the heads. The oil is not being returned to the central sump - it's going to the dry sump tank, which features a centrifugal de-foaming path for the oil.
The original oil pump is now drawing oil from the central sump which is going straight into the dry sump tank. It's been turned into a scavenge pump, basically - hence my question earlier today.
A new oil pump is stacked on top of the original oil pump, both driven by the IMS. I'd need to make a new cover plate for the oil pump for this. This new pump takes de-foamed oil from the dry-sump tank and routes it into the oil filter, and thence the block/existing oil galleries.
The engine would have five scavenge pumps, four in the heads and one in the central sump for the main bearings and piston oil squirters.
It would have one pressure pump/oil pump, added by modifying the standard oil pump to add a second stage.
What say you LFGSS- insanity? Or would this work?