Why our LS-powered Nissan 350Z needed a dry-sump system

Our V8-powered Nissan 350Z has been too quiet lately. Sure, it’s still loud when it’s running–really, really loud–but after two back-to-back podiums in NASA’s TTU class, it hasn’t been running much.

[Surprise podium finish for our 350Z’s competition debut]

Instead, it’s been parked in the back corner of the shop, hooked to a battery tender with a tank full of fuel stabilizer. Why? Because it’s still missing one key ingredient: oil pressure.

We’ve run a giant oil accumulator for years, as accumulators are great, easy fixes for protecting an engine against intermittent oil pressure loss–like from a dry oil pickup in corners.

But looking at the data logs from Roebling Road, our LS wasn’t leaning on its accumulator only intermittently. Instead, it was leaning on its accumulator for seconds at a time, drying out its oil pickup and relying solely on stored accumulator pressure through almost every single corner.

The writing on the wall was clear: Keep running the car without changes, and we’d be building a new engine before much longer.

So how do we fix it? Well, there are a few options.

The first and easiest? Just make the car slower. Pull off some aero bits, switch to slower tires, ruin the suspension setup Andy Hollis so expertly helped us dial in, and perhaps the car’s cornering loads would decrease enough to keep our engine happy.

Yeah, sorry, but no way. When has slowing your race car ever been the right answer?

So let’s move on to option two, which we’ll call the Band-Aids. Basically, were there any tricks left in the book to keep our wet-sump engine happy? We could try a bigger, baffled pan that holds more oil, a fancier PCV system and a big accumulator.

[Video: Are oil catch cans the best solution for PCV system issues?]

And we know we could try those things because the car already has them all, and they’re just not enough. Even with 10 quarts of oil, there’s simply not enough staying where it needs to stay.

There’s only one real option left, and it’s the same option you’ll find on most serious LS-powered race cars in the world: the dry sump. It’s finally time to convert the 350Z.

[Installing a dry sump onto our Corvette’s LS3 engine]

Welcome to the next few months of our life and the next few thousand dollars out of our wallet, but at the end is the promised land: an LS with perfect oil pressure no matter what conditions it’s subjected to.

First, though, we should cover the basics. What exactly is a dry sump?

In a normal engine, the oiling system is fairly simple: An internal oil pump sucks up the oil from a pan at the bottom of the engine. After being pumped up through the pickup tube and then through the engine’s various passages, clearances and bearings, the oil falls back down through the engine, landing in the pan. Then the ride starts all over again. Think “goldfish pond fountain” and you’ve got the basic idea.

Go racing, though, and this system can fall apart in a few ways. First, there’s a big, wide pan of oil, so heavy cornering, acceleration or braking loads can push the oil away from the oil pump’s pickup.

Second, you’re relying on the engine’s internal pump, which the manufacturer designed for a specific operating window. That window probably wasn’t “8000 rpm on track for 20 minutes at a time.”

And third, because there’s only one pickup, it can’t suck up oil that might be trapped in other places in the engine, like the heads on our LS in hard corners.

In theory, a dry sump fixes these issues. Rather than use the oil pan as your oil reservoir, an external tank–usually a tall, skinny one–is used, meaning oil slosh becomes a non-issue. This external tank allows more oil to be carried, too.

Once oil falls back down to the pan, it’s instantly sucked out and put back in the big tank, creating a “dry sump.” Oil from the tank is then pressurized and pumped into the engine by either the stock internal pump or an external pump that can be sized and driven for specific race conditions.

And because the acts of recovering oil and pressurizing it are separated, you can technically have as many oil pickups as you’d like–think two or three or even four little pumps pulling oil from different areas and adding it back to the big tank, meaning the pressure pump has a constant supply of oil to use for your engine.

To go back to our analogy: We’d been racing with a goldfish pond when we really needed to plumb a swimming pool.

Which is why we didn’t design our dry-sump system ourselves. Instead, we called a company that does it all day, every day: Peterson Fluid Systems.

And after an hour or so of chatting and a few questionnaires asking about our engine, our racing, our goals and yes, our credit card number, we received a giant box of dry-sump parts.

Photography Credit: Tom Suddard

But what did we order and why? And could we have just done this project with junkyard parts instead? Over the next few updates, we’ll take a deep dive into how and why we landed on this parts list and how you can convert your own car to a dry sump. Post your questions below, and we’ll do our best to answer them in future updates.

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