Life is Good Racing

Just how low does your oil pressure drop to? and how high?

Thanks,

Steve

Cobra4B

When it's uber hot... before my oil cooler I'd see high 30's at full boobie at 280+ oil temps.

After my oil cooler I was in the high 40's

Now I have a hivh volume LS4 oil pump.... haven't been on track w/ it yet, but I see 74 at WOT w/ 214ish oil temp.

Aardwolf

Mine has the same pressures driving to the track as on the track.

Red Gump

I wonder about this too. my idle pressure is 50+ but under load it was dropping to 36psi. is that normal?

davidfarmer

it only takes around 20psi to maintain stable bearings, but more is better.

Slalom4me

Please fill out your profile, this will help when there isn't enough info
in a post to base an answer on.

After hunting through his past posts, I determined that Steve Rea is
interested in oil pressures for a GEN III LS series engine.
My experience is with the earlier GEN I or traditional SBC. With
a Moroso pump that has anti-cavitation grooves, pressures will
spike to 60+ psi. Hot idle pressure is below 20 psi.

I subscribe to the '10 psi per 1000 rpm' rule of thumb. For my series
of engine, after market pumps are frequently sold with bypass springs
that result in pressure of 80+. Too much, IMO.

.

Life is Good Racing

Thanks for sharing what your oil pressures have been. It's about what I expected.

Slalom, yes I have a hybrid of Porsche and Covette endurance race car. Sometimes it's nice to ask a simple question to get simple answers . From there, I can sometimes figure out the rest without bothering other people. Good idea though to fill out my profile for future reference on posts.

The issue was that my datalogger shows just one point in the course where the oil pressure drops to about 8-9psi. Other than that, it was about 30-60psi or so. Interestingly, the drop isn't even in mid corner as I expected. I am using a custom oil pan to fit my Porsche 944 turbo chassis, and it has trap doors in it, so thought I'd be protected from oil starvation issues.

The drop comes on a very short straight section that immediately follows a long, steady sweeper. It also appears that it could be dropping in the brake zone. The box in the oil pan that has the trap doors is relatively small, so I'm thinking that possibly there is oil trapped in it which is used during the long sweeper, then when we go from the steady turn into braking, the oil swooshes to the front of the pan on the side, avoiding the inlet doors to the oil pick-up box, thus causing the low oil pressure.

I'm going to try to look if I have data from past tracks to see if it happened there too, as well as contact the maker of the oil pan.

It could be a good push to do what I should be sure to do anyways for a 25 hour endurance race...get a dry sump installed! I guess the air jacks will have to wait a bit .

Steve

Slalom4me

What duration of time does the D/A log indicate low oil pressure?

If the situation is infrequent and short enough in duration, then an
accumulator with a pressurestat-operated electric valve like the
Accusump & EPC Valve might be a less expensive solution to the issue.

Even if you still decided to eventually switch to a dry sump, the
accumulator & pressure-controlled valve can be added now with
very little re-engineering. This would buy time for this season and
permit you make pan mods or switch to the dry sump over the winter.

.

Procrastination Racing

If you are dropping to 8-9 psi, then you had better check bearings. You still didn't mention what the engine is or what has been done. If you are running the small block common from 1969 to 1985, then you are probably running .002-.003 clearances. Probably 60 psi is good enough, as too high just wastes power, but you should never let it get below 30 when running. Idle is different.

If your clearances are more, then you may need more pressure, or at least more volume to prevent pressure drop.

Yes, if you are building to road race for 25 hours, then get the dry sump. You need to keep oil in the bearings at pressure the whole time, without the drops to 10 psi and under in corners or braking.

The drop is from oil starvation, and that isn't strictly from lateral G forces, but a combination of lateral G forces and the inability of the engine to refill the sump for the oil pickup. The low pressure indicates where the sump has become empty or nearly empty, and you were probably pumping a lot of air.

While it may be nice to have air jacks to save 30 seconds or a minute in a pit stop, it will be meaningless when the engine seizes at hour 11.

Mojave

He isn't running a Gen 1 SBC, he is using an LS based Gen III.

Life is Good Racing

It just shows a downward spike one time in the same spot each lap.
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Yes, it is a 2001 camaro ls1 engine. Stock internals with a lightened flywheel and Exedy 2 disc clutch.
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Agreed on the 30 second savings vs. finishing the race!


My thoughts are to do any engine mods at the same time, so that I only have to dyno-tune the car once. So if I'm going to dry sump it, I'll also look into possible mild cam, engine rebuild or even pick up a friend's fresh LS2 with forged internals. I'll have to do some budgetting and figuring then will start work likely in August. We have a 3 month layoff after a July 7th race, so it'll be a good time.

Thanks.

Slalom4me

But for how many seconds?

I ask because the accumulator has finite capacity and a non-linear
rate of discharge, while engine health at any given RPM depends on
a minimum GPM of oil flow.

If the reserve offered by an accumulator exceeds the worst-case
engine demand (with a suitable cushion), it would seem to solve the
problem without the cost, complexity, weight, HP loss and maintenance
of a drysump.

.

Life is Good Racing

I don't know the exact time off hand of the downward spike, but it's really just that, a spike. So I expect it's a second or two. I'll have to look into the accusump, though I figure a dry-sump can't hurt.

Am I wrong in understanding that with the dry sump you actually gain about 15 hp, due to less drag on the crank? I like simplicity, but this might be one I need to suck up and get.

Slalom4me

My vote is that a wet sump with an efficient system of scrappers,
trays, kickouts and a really deep sump will produce more HP on
a dyno than the same package fitted with a multi-stage dry sump.

The wetsump only has one 'stage' and no need for additional pumping
pressure to compensate for pressure drops thorugh the external
plumbing. It relies on gravity for return feed whereas the dry sump
uses extra HP-consuming stages for scavenging.

My view is that the principal advantages of a dry sump are that it
enables the absolute minimum crank-ground clearance, helps ensure oil
is always available for the pressure stage(s) and provides an external
tank where entrained air has a chance to separate before the oil is
recirculated to the bearings.

Whatever this costs in HP is more than compensated for in terms of
greater durability.

.