Minimum Safe Oil Pan Depth
 

In an effort to reduce the amount of hacking I have to do/pay to be done to the firewall/transmission I want to try to lower the motor as much as possible without eating into the ground clearance too much. With that in mind I have taken a closer look at the oil pan in the 20b, FD, and RX8. Here is what I have found. All measurements were taken from the deepest point.

RX8: 45mm -RX8 forum member

RX7: 85mm -Rotary News article stating that the RX8 pan is 40mm shallower than the FD pan.

20B: 101mm. -Measured by RotorMtr's father at the deepest point. He said 'about' 4" so I don't have a lot of faith in this number. If someone can confirm I'd appreciate it. Otherwise I'll have the engine builder verify it later this week

If the above info is correct the RX8 oil pan is less than 1/2 the depth of the 20b pan. Is there any reason the 20b pan cannot be reduced to 45-50mm while still having an adaquate safety margin for oil slosh under high Gs? Bear in mind that the stock 20b pan does not cover the length of the block (see attached pics).

20b stock, 20b oil feed line route, rx8 stock (black) RX8 Greddy (silver-what is that black thing in the pan???), RX8 bottom view.

Two words sir DRY SUMP. Then your all good to go!

Oh yeah, deepest point in the pan is 102mm so he's pretty close.

my dad says "father knows best" (hes standing over my shoulder :wink: ). actually he was pretty close... maybe i should let HIM install my motor :biggrin: -heath

I believe the rx8 has a partial dry sump. It's oil pan doesnt hold much, but it has an external resiviore (sp?), and the whole oil system holds around 8 quarts.

Is it just me or does it look as if the RX8 oilpan would fit on the older 13B's?

This is of particular interest to me as I am about to embark on swapping the Cosmo 13B-RE into the RX8 and had not heard of this external oil reservoir.

The black thing in the oilpan is some kind of baffle, and there is also an electrical device (you can see it as the small round silver thing) which uses a connector from the outside of the pan. Not sure what that is yet, my guess would be some kind of oil level sensor.

UPDATE: turns out there is no external reservoir, at lease there is no mention of it in the lubrication section of the service manual. The black thing in the oilpan is indeed the baffle, and the electrical switch is indeed the oil level warning switch.

Thanks for posting the diagram Hakeem. Do you happen to have a shot of the oil pickup coming off the block?

Yes, somewhere. I installed the Greddy pan recently and took some shots of the progress. I believe the extra oil capacity is something to do with the oil coolers and the lines which would mean that the depth of the oilpan is literally the engines main oil supply.

Minimum is zero depth, at least thats what I have :)

https://www.rx7club.com/forum/attach...chmentid=35735

I've seen pictures of yours before, very nice :)

It's definitely interesting to note though that the RX8 is able to function on such a shallow oilpan depth. I am hoping that I can modify my Greddy pan slightly on the Cosmo engine and get the engine down as low as the Renesis used to sit.

Sorry for hijacking the 20B forum with my RX8 monstrosity, but it seems most of the interesting theoretical discussion takes place in here!

I spoke to Roger again today about the pan. He is starting to backpedal on 45mm being adaquate for use on the track. He is going to take a closer look at it and get back to me.

Dave,

Unfortunately going from 45mm to zero (really more like 10mm) costs another $3,000 :o. The other benefit to using a dry sump is that the oil system then has the capacity to safely go over 8000rpms for sustained time.

For whatever it's worth, I ran my bone-stock RX8 (had the Greddy pan and some Defi gauges) at the California Speedway infield course a couple of weekends back and had no problems with oil pressure or oil temperature for the duration. I probably got in about 10 sessions and ambient was about 85 degrees.

An RX8 forum member was nice enough to send me this pictures.

Notice How far toward the front of the motor and pan the pickup point is. The RX8 pickup appears to feed from under the front rotor while the 20b pickup feeds from under the intermediate. There also appears to be a slight backstop to the pickup that may slow the movement of oil to the rear of the motor during acceleration. I still can't figure out how the giant black 'baffle' that is bolted to the bottom of the pan works