Hi all,

Working on a dry sump system. How thick would you recommend making the plate that goes in place of the oil pan be? Also, what material is best?

 

I built mine out of 6061 and 1/2". Be warned it's not going to be cheap, even for just materials...

 

Thanks. Yeah last week I got a 5/8" 14"x14" piece of aluminum for something else, definitely pricey.

Might as well turn this into a DIY thread. Any thoughts on a pump? Is it possible to use the stock pump, or do I have to go external?

 

You'll have to either build a front cover and run it off the eccentric shaft or go external. Each has an advantage. We're almost finished with our billet oil pan. IMO dry sump should only be done if class rules require it...

 

I'm doing it so I can run a large custom engine. I'll disclose details if it ever runs (but having said that you can probably guess what it is).

I've read that the stock pump can be used but a scavenge pump will be needed as well. Any chance you know why it can't act as the scavenger itself. All external pumps do both.

I'm fine with modifying the front cover. I just need to better understand how to do it.

 

I should make you buy me a drink and I'll talk your ear off lol. Technically you could use the fd pump to be the scavenge pump to the remote mounted tank but you'll need to machine "veins" on the dry sump plate to a catch basin right below the factory oil pickup. This is all more complicated than needed and in reality a proper external dry sump pump would be best.

I hope you know what you're getting into. The real dry sump pumps are $$$. You're better off buying an old drysump or get a kit from an aftermarket manufacture.

IMO again, wet sump is more than adequate as long as class rules require dry sump. I like this talk of you going with a custom engine, you're surely addicted to complication haha.

 

As long as we're on the topic, how well would oil cooling work by plumbing the scavenge pump to the oil coolers, essentially running at at very little oil pressure? The oil would have a fair amount of trapped air in it, which would lower cooling capacity. However, the pressure pump would go straight to the engine, reducing the pressure drop across the coolers.
On the external pumps with the built-in pressure regulator, this means the regulator pressure would be equal to engine oil pressure, not cooler feed line pressure.
On a dual pass cooler such as the venerable stock FC design, the pressure drop across the cooler is very high, measured upwards of 30 psi.
Caroll Smith talks at length of this in "Prepare to win", and states that he prefers to place it on the pressure line. He doesn't give any data or real reason as to why.

I have only ever placed it on the pressure line.


To answer the original question, I typically use 3/8" Al.

 

If you're going to address oil pressure issues switch over to the FD regulator. Typically oil volume is the only problem with rotary's. Porting the passages and having the FD oil regulator is more than enough.

I wouldn't plumb the scavenge the oil right over to the oil coolers. There's such a thing as having oil "too cool." Not only do you lose out on lubrication properties of proper temperature oil but you will also have power loss with it being cold/cool.

If you're having high pressure drop on an oil cooler I wouldn't try to figure out how to work with that design. I would switch to a better oil cooler in itself. You'll not only have a lower drop but a more efficient core that's perfectly clean.

 

Thanks Lance, once I get a little further along I might just take you up on that offer and buy you some beer haha.

And yes, for some reason i do like to complicate things haha.

 

The external dry sump pump I have experience with has an adjustable regulator built into it. I use dual external oil filters and cut the oil pedestal off of the rear iron, and tap a -AN fitting into the oil passage.
This allows for use of superior oil filters, allows for higher than 105 psi oil pressure, and has a lower pressure drop measured across it.

well, obviously you would still make use of a oil temperature thermostat; theres no reason not to.
Àlso, plumbing into the scavenge line should theoretically cool the oil less, since there should be a fair amount of entrapped air in the oil.
Plumbing the coolers on the scavenge allows for less plumbing, the regulator to adjust to engine pressure, and a lower peak pumping pressure, which should cause less of a parasytic power drag to the engine.

The stock coolers are extremely efficient at moderating oil tempreatures, better so than many of the aftermarket coolers.
Its pretty tough to tell a person to "change to an aftermarket cooler", when published pressure drops at any given viscoisty and temperature is not available, and vary rarely is core efficiency printed. How can it be a given that anything aftermarket will cool as well and have a lower pressure drop without then buying and testing?
Rick Engman stated in "how to modify you RX-7" that few oil coolers are better designed than the second gen oil cooler, a (while somewhat dated) book edited by Jim Downing.

 

Thanks for the info. Can we play "post your dry sump pictures"?

 

External have multiple pumps all driven off the same shaft.

You need a second pump for the scavenge to move the oil to the tank. Basicsly the second pump on a wet sump setup is gravity. To get away with one pump you would need a completely closed system, I.e. your coolant system.

 

You know that external belt driven pumps have multiple suction/scavenge ports and multiple outlet pressure lines. No need for "multiple" pumps ever if you guy a belt driven one.

 

Every one I've seen has been a stack of separate pumps. Putting six pumps on a single input shaft doesn't make it one pump. The scavenge and the pressure pumps are separated from each other by reservoirs, one being the sump pan and the other being the oil tank.

Unless you get rid of the reservoirs you will have to use more than one pump.

 

I'm not sure exactly what you're saying. There are pumps that can take care of picking up oil, putting it into a remote tank and then pressurizing it and sending it to your motor/oil pressure valve.

Check this out http://aviaid.com/pdfs/cat05.pdf Page 3 has an excellent diagram...

 

Page 3's diagram is great. Thanks.

What is the need for a custom front cover if I can just tap the sump plate for a scavenge line and add bungs to each iron for the oil feed (the modification where oil gets pumped from the top of each iron into the bearings)

Kind of seems like the front cover is the most difficult/expensive part of a dry sump system. Or is the modified front cover only necessary when trying to keep the stock oil pump?

 

We're actually saying the same thing about the dry sump stuff you're posting. What I was specifically trying to say about pumps like that is they're actually multiple pumps attached to each other. The scavenge and the pressure sides of those pumps are separate from each other as far as the oil is concerned, however for packaging they are all stacked together and driven off the same input shaft.

Overall my point was that the reason why you can't have a full dry sump setup only using the stock oil pump because it's not setup anything like an aftermarket dry sump pump.

 

If you're using the stock pump to still be the pressure circuit and you tie into the stock pickup from the dry sump tank then you won't need to modify the front plate. I couldn't find it but I know somebody on here machined oil pathways into the bottom plate that replaced the pan.

The front plate from the mazda comp kits has a combined pressure and scavenge pump in the front plate so that you won't have to run a separate scavenge pump like you would if you kept the above mentioned setup.

 

Ok. Thanks.

Is it possible to run an external pump (scavenge and pressure combined like the NASCAR ones) but retain the stock oil pressure regulator? Or should I just go external everything?

 

Factory regulator is perfectly fine as long as it can keep up with the oil pump volume... Check with the pump manufacture for GPH!