The Dry Sump Thread

[JakeLehmkuhl]

Moved from the balance shaft thread:

http://evo-tech.net/forums/showthread.php?t=125

This was such good information it needed its own topic. Awesome conversation guys. Great to see great minds conversing.

Carry on here :) - admin



Dry sumps (sealed system) won't pull a crankcase vacuum on a turbo car under boost. 3 guesses why.

Interesting. Do tell, because I've seen up to 22inches of vac on previous systems on my Chevy's. None were turbo's but a couple were supercharged.

[JakeLehmkuhl]

Hmm, thinking about this depending on how much you'll pressurize your crank case under load the scavenge may not keep up? It's easy enough to add extra stages of scavenge with that thought though. You have me stumped on this one Mr Wookie :) But then again you're a far smarter man than I.

[The Wookie]

Hint- If you completely separate the turbo oil supply and scavenge setup from the engine crankcase then it works like it would on an N/A or supercharged car.

[JakeLehmkuhl]

Because you'll pressurize the crank case from the turbo oil return. So is it safe to run a scavenge to the turbo?

[The Wookie]

Safe? yes. It won't pull a vacuum though. You'd need to run a separate pressure and scavenge stage and tank for the turbo only, and it will need to be heavily vented.

[JakeLehmkuhl]

Interesting. Ok, well even with the slight vac setback I can't see a single reason why a dry sump isn't superior in every single way to the factory setup. Obviously taking into account cost in the short run versus cost in the long run.

[Kiggly]

You can easily make a much worse dry sump setup than a wet sump. I've been involved in two 4G63 dry sump engines, one of which intended to reuse the factory oil pump. This is the setup that makes the most sense. The other setup was a reverse rotation engine, so it couldn't use the factory pump. I also did pump sizing, plumbing, and testing on one particular US production dry sump engine (I think most people can guess which one).

The only saving grace with a dry sump engine is you can be sloppy and add a bunch of capacity. That capacity gives the oil time to de-aerate enough that the quality might not be crap. Your best bet is to still keep the oil pickup(s) wet and not have too much over-capacity on the scavenge stages because all that does is add air. Dry sump isn't god's gift to oil systems.

If you can get a wet sump to work, it is a better solution. It is lighter and there are less parts to fail.

I've been involved with two road race engines that tried to pull crankcase vacuum. One wasn't able to because of too much blowby at WOT (at 1% leakdown). The other one had a centrifugal air separator and I believe was able to pull a little vacuum. It was also a factory-internal racing program with a couple million annual engine program budget.

Chewie is talking about piston ring seals on the turbo shaft with maybe 30-50psi on one side. They can move a lot of air.

Kevin

[The Wookie]

Chewie is talking about piston ring seals on the turbo shaft with maybe 30-50psi on one side. They can move a lot of air.

Kevin

Yessir.

BTW the 10 character response minimum sux.

[JakeLehmkuhl]

You can easily make a much worse dry sump setup than a wet sump. I've been involved in two 4G63 dry sump engines, one of which intended to reuse the factory oil pump. This is the setup that makes the most sense. The other setup was a reverse rotation engine, so it couldn't use the factory pump. I also did pump sizing, plumbing, and testing on one particular US production dry sump engine (I think most people can guess which one).

The only saving grace with a dry sump engine is you can be sloppy and add a bunch of capacity. That capacity gives the oil time to de-aerate enough that the quality might not be crap. Your best bet is to still keep the oil pickup(s) wet and not have too much over-capacity on the scavenge stages because all that does is add air. Dry sump isn't god's gift to oil systems.

If you can get a wet sump to work, it is a better solution. It is lighter and there are less parts to fail.

I've been involved with two road race engines that tried to pull crankcase vacuum. One wasn't able to because of too much blowby at WOT (at 1% leakdown). The other one had a centrifugal air separator and I believe was able to pull a little vacuum. It was also a factory-internal racing program with a couple million annual engine program budget.

Chewie is talking about piston ring seals on the turbo shaft with maybe 30-50psi on one side. They can move a lot of air.

Kevin



While you make some *very* good points I still think that a dry sump is the right way to go. Our front cases are a piss poor argument for a wet sump. And running a small amount of extra weight to make sure that my engine is never without oil on the road course is worth it to me. Especially since I can choose where most of that weight sits. I can't uncover a pickup. I gain ground clearance which is huge for me (I'm sure you can guess what I'm up to). And honestly I don't think that our front cases will live for long at 13k. And it doesn't break my heart to run a large tank. When done right I honestly believe that a dry sump on a 4G will far surpass the factory wet sump setup.

[The Wookie]

Jake you don't have to justify to us why you want it, but implementing one properly is a lot more difficult than it at first seems.

I haven't heard of any sportsman level road race EVO's having issues with oil pressure on the road courses around here, although I can imagine at some point they will. Recently had a lightly instrumented local EVO9 out on Hoosiers at MSR and it pulls 1.1g's consistently with peaks in the 1.2g range, no issues. Now DSM's on the other hand, well that's another story.

Personally, until someone takes the plunge and casts a pan with built-in main/lower block girdling and other features that kills several gophers with one shot (oh, say new front cover with fuel pump drive, vacuum/scavenge pump for turbo built into the gear reduction for the pump section, etc.) I ain't particularly interested.

[JakeLehmkuhl]

The girdle isn't an issue so much for me since I don't use 6 bolts. Never really been a fan of one. I have logs of oil pressure dips. Quite significant ones. Especially since the head likes to hold oil. Too much in suspension and not enough on the pickup is a recipe for disaster. This 13k engine is a whole other beast I think. The implementation is going to be a pain sure, but I have someone by far smarter than I working on it so I have faith. Once it's worked out well enough I think that it's a godsend.

[OldSixBolt]

The girdle isn't an issue so much for me since I don't use 6 bolts. Never really been a fan of one. I have logs of oil pressure dips. Quite significant ones. Especially since the head likes to hold oil. Too much in suspension and not enough on the pickup is a recipe for disaster.

Jake, can you elaborate on this more a bit? Your saying that the 6 bolt block and head combination apposed to the 7 bolt stuff is more prone to drop pressure? Where in the head do they hold oil, and in comparison to a 7 bolt casting? And are you also contributing the pressure differences to the different oiling setup as far as oil gallerys?

[JakeLehmkuhl]

No. I'm saying I don't like the 6 bolts. That's just a self supporting statement. The rest is information from my 7 bolt. That's all :)

[Marco]

7 bolts have 1 more extra bolt to hold on the flywheel! :)

[Public Enema]

7 bolts have 1 more extra bolt to hold on the flywheel! :)

For the WIW category, does brent rau run a 6 bolt or 7 bolt?

[Marco]

Brent's car runs a 6 bolt, It used to run a 7 bolt, I used to run a 7 bolt. But it just became too difficult to get 7 bolt parts at the time we were racing and we switched over to 6 bolts. Common historical misconceptions were that 7 bolts couldn't hold power back in the day, yet I put down 723hp in 2000 and shut everybody up. Brent had already switched to a 6 bolt by then in the AWD.
I then finally switched over to a 6 bolt sometime in 2001 when I built the 2.4L stroker after we made the whole 1g in a 2g swap popular.
If I could do it again, I would use 7 bolts, that extra bolt would sure help keep the flywheel on :)

[KDeiwert]

...If I could do it again, I would use 7 bolts, that extra bolt would sure help keep the flywheel on :)

Get out your stick welder!