I have a remote oil filter, after market oil cooler 3.5X as large as OEM, an Accusump, many feet of -10 line, and endless optimism. It all worked ok with the crankscraper, but now that i’m running the spare engine and it has no scraper, there’s been a lot of crazy oil pressure problems.
I have oil sensors all over the damned place. Friday I was able, for the first time, to really watch the gauges during left turns. Normally I’m watching the turns, but Friday was all about oil so I watched gauges. I could see the interplay between pressure at the pump, pressure at the Accusump, and pressure at the engine’s oil galley. It was pretty interesting. I watched the same gauge interaction lap after lap.
The oil pressure problems that I had at 2 other events in the past month were being repeated and I was trying to understand them. When my oil got good and hot, 3 left turns in a row left me without oil pressure for an incredibly long time. Accepting risk I idled the motor for 60secs and got no pressure. After turning the motor off for 5min and then restarting it, pressure was returned.
This same sequence repeated itself several times.
I went a quart over and things got a little better. Then I went 2 qts over and things got slightly better. But still, once the oil got hot, my oil pressure would go to 0 for a long minute.
Saturday morning I got up early and ripped out all my fabulous oil system plumbing, the product of many hours of labor 15 months ago. I threaded the oil filter directly on to the block like an E motor. Therefore I now had an oiling system entirely different. The length of oil path between pump and galley was only a couple inches and because of the filter’s backflow valve, if the pump when dry it could prime the whole system with about a teaspoon’s worth of oil.
And my oil pressure behaved completely differently. I could still see the pump go dry on almost all left turns, but the oil pressure recovered almost immed.
Sadly, the motor only lasted for about 15min and then failed. No compression in 5 cylinders. Leakdown indicates it’s leaking past the rings. Which is odd because they lubricate via “anti-wear”, not “constant flow” so it’s hard to understand how some interruptions in oil flow would have damaged them. But such is the price of science.
So after all of that, here’s my theory on oil pressure and elaborate oil systems.
The scraper is critical. The pump going dry in virtually every left turn was painfully obvious in the gauges.
The Accusump was doing it’s best, but the 3 successive left turns at CMP…1, 3 & 4 were totally overwhelming it.
The additional oil plumbing created by my -10 lines to the remote oil filter, oil cooler, and Accusump create a lot of oil system volume. Add to that, my oil cooler is far larger then OEM. Therefore when my oil system goes dry there is much more volume that the oil pump has to charge in order to bring pressure back up in the whole system. Our oil pump doesn’t pump that much oil. It’s kind of a fast dribble. I think that it’s incapable of quickly refilling so much oil plumbing volume.
So I’d kind of set up a perfect storm. No crankscraper in the spare motor meant constantly going dry. So much oil plumbing made the consequences of going dry far more severe then otherwise.
When I ran Saturday with all my oiling system ripped out and the oil filter directly on the block like an E motor, I could still see the oil pump drop to ~25psi on left turns, but the pressure came back up almost immed. The duration of the oil pressure drop was very brief. So when the pump goes dry and you have a short oil path, pressure is restored quickly. If you have a long oil path, not so quickly. If you have a long oil path and multiple “pump sucks air” in rapid succession, not even an Accusump will save you.
Lessons learned.
An Accusump is a bandaid. That’s obvious enough, but I thought that it was a really good bandaid. It might be more accurate to simply call it an “ok” bandaid. The real solution is not letting your oil pump suck air. Installing a scraper is a big step forward as is a better oil pan like the Poore pan. But I think that the best solution would be to install both. That’s what I’m doing.
There are folks that have been tracking their car for years with no scraper and have had no problems. That means that there’s aspects of this that still aren’t understood.
Because our oil pump is a pussy, remote oil filters and big oil coolers are a serious liability IF you have problems keeping your oil pump’s pickup submerged.
I got 14deg of cooling out of my big aftermarket oil cooler. I’d estimate that the OEM oil cooler is good for 6deg on it’s best day. I wonder if the oil cooler is worth the downsides of additional oiling complexity, plumbing volume, and weight? If our oil temp goes from 225deg to 230deg because of no oil cooling, is that a problem? There’s lots of performance cars that run hotter oil then that.
