986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post - Racers. Do you worry about oiling issues, or do you just drive?

The Radium King · 10-18-2017, 08:24 AM

from what i can glean, engines fail from extended g-force in one direction (depending on the car - different in rear vs mid-engined applications?). g-force due to sticky tires and/or long/banked turns.

it is not a pick-up, oil capacity or foaming problem, otherwise updated pickups, extended sumps, baffles, and accusumps would address.

it appears to be an oil pooling in the heads problem. indirect evidence? x51 and subsequent generation engines add additional head scavenge pumps. now, the oil pooling in the head reduces available oil, however as noted, increasing oil capacity doesn't solve the problem, so the issue is that the oil doesn't move once in the head in these high-g conditions, so doesn't cool and eventually breaks down and something fails.

so, there are additional scavenge pumps you can add (TTP sells a kit) or you can get a dry sump kit. the benefits of the dry sump noted below are not the increased capacity or the increased defoaming, but rather that the external scavenge pump draws from the heads as well as the sump. you note that an aos is not required with his kit - this is because *i think* he is using the aos vents on the heads to scavenge from (and also starts you down the thought path of how oil pooling in the heads is also tied to aos failures on the track ...).

i have a further sneaking suspicion, however. jake raby notes that his is not that impressed with the x51 heads, which leads me do believe that the additional scavenging in the heads is not the silver bullet. also noting that oiling failures do not all occur in the heads; they are also seen in the bottom end. what i am thinking is that oil pooling in the heads is creating sufficient back-pressure to trigger the spring-loaded pressure relief valve in the oil pump and, as a result, inhibiting oiling throughout the engine in extended high-g situations. my question would be if anyone has put a different spring in that thing - how does oil pressure behave at the track?

ps, this doesn't answer your question at all, but the thread got me thinking out loud so to speak.

10-18-2017, 08:24 AM	#12
The Radium King Registered User Join Date: Apr 2010 Location: Canada Posts: 3,121	from what i can glean, engines fail from extended g-force in one direction (depending on the car - different in rear vs mid-engined applications?). g-force due to sticky tires and/or long/banked turns. it is not a pick-up, oil capacity or foaming problem, otherwise updated pickups, extended sumps, baffles, and accusumps would address. it appears to be an oil pooling in the heads problem. indirect evidence? x51 and subsequent generation engines add additional head scavenge pumps. now, the oil pooling in the head reduces available oil, however as noted, increasing oil capacity doesn't solve the problem, so the issue is that the oil doesn't move once in the head in these high-g conditions, so doesn't cool and eventually breaks down and something fails. so, there are additional scavenge pumps you can add (TTP sells a kit) or you can get a dry sump kit. the benefits of the dry sump noted below are not the increased capacity or the increased defoaming, but rather that the external scavenge pump draws from the heads as well as the sump. you note that an aos is not required with his kit - this is because i think he is using the aos vents on the heads to scavenge from (and also starts you down the thought path of how oil pooling in the heads is also tied to aos failures on the track ...). i have a further sneaking suspicion, however. jake raby notes that his is not that impressed with the x51 heads, which leads me do believe that the additional scavenging in the heads is not the silver bullet. also noting that oiling failures do not all occur in the heads; they are also seen in the bottom end. what i am thinking is that oil pooling in the heads is creating sufficient back-pressure to trigger the spring-loaded pressure relief valve in the oil pump and, as a result, inhibiting oiling throughout the engine in extended high-g situations. my question would be if anyone has put a different spring in that thing - how does oil pressure behave at the track? ps, this doesn't answer your question at all, but the thread got me thinking out loud so to speak.