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Old 10-10-2007, 05:51 PM
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Richard Hudgins Richard Hudgins is offline
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Join Date: Jun 1999
Location: Fallbrook, CA USA, CA
Cobra Make, Engine: Porsche 928 S4
Posts: 739
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Vector1,

The oil tank has been used and it works quite well. It is not the first dry sump tank that I have designed and I considered all the normal tank issues such de-aeration, clean venting, pickup coverage, and packaging.

Note: packaging is really very critical for a dry sump tank. The oil level in the tank needs to be as low as possible relative to the crank center line to avoid back filling of the oil pan through the pump when the engine is off. I have seen many tanks where this was not considered and it caused main seal leaks while sitting and in the worse case oil starvation on startup as most of the oil had drained back into the engine and the pickup in the tank was exposed. At startup no pressure until the scavenge pumps put some back into the tank. And the result is most often bearing failure from this short bit of time without pressure.

It has been used with a single stage pressure/4 stage scavenge pump with the scavenge out going through a 25 micron filter>through the cooler>back to the the tank. Note: going through the cooler also partially de-aerates the oil

In track testing of the chassis with this setup the unit saw steady state 1.6g cornering on a skid-pad for durations of 2>3 minutes with no oil pressure issues and >2 hours of endurance running at Willow Springs with lateral spikes of 2.9g and deceleration rates of 2g with no problems.

The only problem that occurred was loss of the oil cap due to improper latching (By me) and all this did was make a bit of a mess of the right side outer footbox area.

Of course we did have to spend about 30 minutes trying to find the cap as it came off in turn one and went a bit of a distance out into the desert and we did not have a spare.

After this incident the cap was installed and latched correctly and we also installed a safety chain to avoid wandering through the desert looking down for shiny bits.

The center divider is sheet with drain cutouts as shown. This allows a controlled drainback and de-aerates the oil.

Fabrication is actually quite simple and most any decent fab shop can make one up.

Mounting is done with a couple of bolt in clamps that are not shown on that drawing. The initial installation really should be done prior to engine install due to hose routing etc.

Ride height is measured from the bottom of the front lower crossmember (the one where the dampers are mounted) and the rear is measured from the rearmost part of the fuel cell surround. (The very last bit of metal rearward.)

Note: It is very important that the correct rake is maintained when setting ride height. The front must be .75 in. lower than the rear. If the front is 4 inches the rear must be at least 4.75. (Note: for road use 5in. front and 5.75in. rear is recommended minimums)

Also per John's discussion on pans. With a proper Road Race wet sump we have not seen any problems either.

There are many benefits of a dry sump system and one major one on the JBL is the bottom of the center tunnel can then be skinned per the design and subsequent interference drag is much reduced and some under-body negative pressure is developed. Note: you must run the small Tilton bell-housing as well.
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Richard Hudgins
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