eric523

I wouldn't think the oil temp is really causing that pressure drop. It happens in the first few laps of a session just the same as the last.

I don't have any indication that I'm losing power due to what you describe on the dyno nor the track. Much harder to tell on the track though. The later M.97 motors suffer from aeration problems from what I hear and I know of some guys running the earlier swirl pots in their motors to try and combat this.

eric523

I ran 20-50 in my previous motor, the 2.5L, but still had similar pressure drops in the hard braking and tight corners. Didn't experience the drops on the banking but I also was 20+mph slower and running without aero.

Byprodriver

Jake swears by the Joe Gibbs DT40 oil, might be worth a try...

TrackDays247.com

Great thread. Seen a few kaBLooies at the track with these cars, pretty sad.....

Macster

The engine may not be losing any power because the aerated oil only gets ingested under braking/sharp turns when you may not be on the gas as hard and thus not making max demand of the engine. Also, a bit of air in the oil doesn't really cause the valves any trouble because rpms are lower and the valves follow the cam lobe ok.

If the engine were seeing a big drop off in pressure while running WOT down the straight I think the engine would hand grenade before you would notice a drop off in power.

OTOH, I've never seen it but the techs who have driven the new cars with the DFI engine and its variable pressure pump tell me initially when the throttle is nailed oil pressure shoots up but rapidly falls as the DME can safely dial back oil pressure. The techs tell me the oil level can drop to 3 bar at higher but steady rpms when in the older cars/engines at the same rpms under the same conditions the oil pressure would be >4 bar.

eric523

That's where you lost me I guess. I described earlier that I am getting drops to 25psi under WOT at 160+mph when running about 6800RPM in 6th gear through the banking. No braking combined with cornering G's there.

Cars in the body shop right now so I'm going off of memory and not the exact dash data.

Macster

Even though you are not in the sharper turns when the oil pressure drops, still at 160mph even on a banked turn there is considerable g force and I have to point out for a longer period of time.

Could still be aerated oil.

The high rpms with the scavenge pumps just whips the oil into a froth and this overwhelms the swirl pots' ability to remove this air. Then because of the high rpms the oil budget is up -- more oil is in suspension under the camshaft covers and in the area of the crankshaft and in the heads the scavenge pumps are not as efficient as they should be -- which means the oil level drops in the reservoir.

The level is down and then add to this the g-forces from the high speed banked turn moves the oil away from the center of the reservoir and towards the outside wall of the reservoir (do not forget too that all that oil under the camshaft covers is either being forced against the underside of the camshaft cover on teh side of the engine that is on the outside of the turn and forced against the top of the head of the side that is in the inside of the turn all of which just means there is less oil in the reservoir during this high speed banked turn.

The oil level over the pump intake drops and while the intake is not sucking air it is pulling in oil that has not had enough time after leaving the swirl pots to lose some of its air on its own.

(I've watched large equipment oil systems working and one can see the oil level is not quite flat above where the oil pump intake is. Also, the return line puts the oil back in the tank and a considerable amount of this oil flows over and is obviously back in the pump. This is helped I believe by the return oil now being warmed and flowing on top of and over the colder oil in the tank.)

Anyhow, better air/oil separation coupled with better baffling to combat oil moving away from the pick up area along with a larger (deeper) oil supply would be my thoughts on addressing this.

The engines may change but the oil problems remain the same. Getting the oil removed once it has done its job, removing the air it picks up, cooling it, and the oil back in the reservoir and keeping the oil around the pick up given the high rpms and sustained g forces encountered on the track.

I note too the engine has a rather shallow oil reservoir driven by the need to place the engine low in the car and yet not reduce ground clearance too much which of course just contributes to oiling problem.

J richard

There is a direct correlary of angle and G forces, its how Porsche designs its dynamic test rigs for the engines. At 1 lateral G it is equivilent to tipping a running motor at a 45 degree angle to give you an idea of oil flow and how it would pool in all the wrong spots. At 2G you would have the motor up at 60 degrees, you can exterpolate for something in the 1.5 G range. This is way outside of the test rigs that Porsche uses, they go up to about 30 degrees judging from videos. A sustained corner would quickly drain an accusump, just about the only thing to do is a dry sump. Better oil would help but if you have no pressure it's a matter of time.

Dan951Man

This belongs here

I don't think my 944 motor could survive this very long

Flat6 Innovations

We don't just swear by it, we developed it. Joe Gibbs worked along side us and honed the formulation specifically for the M96 engine. We only use DT40 in our street engines after a 300 mile break in on Joe Gibbs BR.

That said, DT40 is NOT a track oil. It is developed with a anti wear/ detergent package and viscosity index that's optimized for street engines.

Track service with the M96 has proven Joe Gibbs XP9 is the most optimum oil for track use. We also developed this oil with Gibbs and used several DE/ Spec Boxster and Grand Am engines to gain our data coupled to our lab tests in my dyno cell. From original conception when the base oil was just called "980" the XP9 has proven to maintain viscosity when other oils lose viscosity. We have seen 10-12% gains in oil pressures at 300F with this oil over anything else tested against it and those are monumental numbers that mean life and death for an M96 on the track.

I see more scattered M96 engines in a month than others will see in a lifetime. We know exactly what kills these engines and how to avoid it.

gfl

We can see three problems here with high oil temps:

1. lubrication film breakdown
2. indication of metal fatigue, only indirectly related to oil temp
3. the original issue of high G and starvation ( separate issue)

I'm a simple guy. #3 requires a scavenger pump. #2 would surprise me. #1 - the only direct oil temp related issue, requires a higher viscosity oil that maintains hydrodynamic lubrication under the high temps. 260 is auite do-able with modern lubricants so long as you ignore Porsche's recomendations......

Correct me.

G.

Flat6 Innovations

260F is fine as long as the oil has the viscosity index to maintain film strength, and pressure at that temperature.

Most don't.