2BWise

Instead of burying this in the nether regions of the "996 is a bad track car" thread I thought I'd restate and go more in depth with my post over there concerning wet sump oiling issues and possible driver associated oil starvation.

It is to be noted that all of this testing was carried out on a Honda F4i. Although it is not a Porsche motor, it is a wet sump design and other than specific values, the general information contained within will pertain to any wet sump motor.

Let's start off covering the use of oil pan baffling to prevent oil starvation. On the stock motor Honda did not provide any baffling. Being as motorcycles see mostly vertical forces due to cornering being done with the bike laid over there is very little concern for oil sloshing away from the pickup. Therefore, the initial setup for a four wheel vehicle included a flat aluminum plate mounted flat under the motor and on top of the oil pan. This plate had 1/2in holes drilled throughout with nearly half of the overall material removed. It should be noted that this motor has more of a tendancy to starve in right hand corners. This is due to the design of the case. With this setup around .5g the oil pressure began to drop. Then with any increase increase in cornering load the oil pressure would hit nearly zero, if not exactly zero.


The next baffle remove only about 20% of the material from the baffle and used both 1in and 1/2in holes strategically placed in such a manner that it would attempt to keep more of the oil from sloshing away from the pickup in right hand corners. It also incorporates baffling up in the case to slow the flow of oil from the pan. This time we see a slight difference in the process to oil starvation. Again at over .5g the motor begins to lose oil pressure, but it won't lose total pressure until over 1g. It is slightly better but any sustained loads over 1g, which are easily attained there is nearly complete starvation. Pressure does not get as close to zero as before, but there is still a very pronounced decrease in pressure.


The final comparison is with a baffle plate with nearly 15% cut way. Anything more than that and there were serious issues with getting oil back into the pan. Most importantly it can be seen that there is a definite difference in oil starvation and driver technique. I don't have time to explain it all at this point, but it should be pretty obvious that the right hand cornering loads and heavy braking are causing the reaction that becomes complete starvation.



All of this should be generally applicable to other vehicles (996 included ) depending on the engine design. Each will have its own tendancies to starve under certain loads. Also, we do know that we've been starving our engines for over 5 years, but until the last two cars, which have shown the ability to pull 1.8g, we haven't had any issues with motor failures. It tends to show that the motors have a point at which excessive force tends to wear them much quicker.

More later, I'm hungry!

2BWise

Now, depending on car setup and tires it may be very possible to exceed the range of the stock oiling system baffled or not. Once reaching this point there can be no guarantees to the life of the motor. It could last forever or could blow up in laps, but there is definitely a way to drive around it if you know the weaknesses of the system. As outlined above it is noticed that our motors tend to starved more often in right hand turns and consequently also under hard braking. The following two Motec plots show two different drivers on the same day, turning lap times within a second of each other. One of them is me, but I don't tell which. The only difference in this plots is that one was logged early in the morning with an ambient temperature of ~60 deg (black) and the other ~80 deg (red). The tires are very temperature sensitive and are quicker when the ambient/track temp is higher.



You can see that the black driver has two major transition periods that cause the severity of the pressure loss. He losses all pressure, but regains full pressure before losing it again. The red driver has a loss of pressure, but never to the point that there is less than 20 psi. Now, low pressure it bad, because its probably consuming large quantities of air, but it is better than total starvation.



This is just a sampling of the driver comparison, but shows that someone that is extremely smooth has a lesser likelihood of destroying a wet sumped motor.

Mark in Baltimore

Interesting data, but I'm not convinced that it should be generally applicable. Maybe it is. Maybe it isn't. Unfortunately, this data doesn't prove anything with regard to Porsche motors. Since the previous thread discussed 996's, then the specific application should be for 996's. Although I'm firmly in the camp that a dry sump is better than a wet one, logic and objectivity would dictate that using data from a Honda engine, and, if I'm reading it correctly, a motorcycle engine, at that, and generalizing it to wet sump Porsche motors is , um, fraught with problems. This would all have more relevance if the testing were done with a...996 motor.

Ray S

Interesting, but I don't see how it is relevant to Porsche wet sump motors. This is an entirely different motor. It has a different configuration, different baffle system, etc.

2BWise

I understand that there is a large difference from the Porsche motor, but it will have weakness with regard to the wet sump oiling. I'd be willing to bet that under certain, common, track driving conditions that there will be a point at which oiling becomes a serious issue. Not sure of any data out there, but the fact that companies are building baffling kits is telling me that there is a real issue with oil supply.

chris walrod

One must also factor in the fact that bikes can lean into a corner at relatively high angles whereas a car will stay relatively flat.