Very good point. Scroll up a few posts.

The "10 psi per 100 hp" is more of an upper limit than a lower limit.

 

so i guess 50-60 psi at WOT no matter how much power you make!

 

Damn...... you guys are hard to please.

 

For reference....

At the Engine Masters this year hose guys were running 650-700hp 410 cube small blocks a max 6500rpm and from what I saw on the data screens during the contest. (not like the crappy coverage they give it now) The top 6 motors normally ran a 50-60 psi oil pressure.

I've seen some numbers from Cup motors that suggest a oil pressure in the 30-40's and not for the plate motors, someone mentioned 28 psi for those. Now that's low for 450hp motors!

Bret

 

What Bret noted at the engine masters event is probably a very good guide as the people within the contest have both scientific information and practical experience to back it up.

Think the biggest problem here is lack of recent research data regarding oil pressure/ wear and or failures at certain pressures/viscosities. Sure something like this exists either within the automotive manufacturers or the oil manufacturers. Probably even submitted and presented at one of the SAE meetings. But that would be a good place to get a good answer.

I’d bet the farm NASCAR has a handle on this to the T for their engines, but you know how those guys like to share their secrets with everyone.

My belief…… is current thoughts on oil pressure are more folklore, rumors and urban legends than based in science. With the newer super oils and trend by automotive manufacturers to go to lower viscosities the old golden rule: “10 psi for every 1000 rpm” is no longer applicable. Honestly think you don’t need as much oil pressure as is commonly considered as “safe and effective.”

An argument can be made for using slightly thicker oil if you’re going to use NO2. Top fuel uses 70 weight oil with thickeners to absorb the hit on the bearings and perhaps the same can be said for nitrous.

Personally, I’d go with what everyone knows works and use your idle pressure and higher rpm pressure as the guide as to what weight oil to use.

 

The thinner the weight is the more apt at higher RPMs to become blowby
Going too thick and as example a 20w50 costs 7 HP.

Use Mobil I sync and what I do as per Mobil I race engineering is mix 50/50 ratio of 5w30 and 20w50 gives you a 10w40.
I have done it this way on my race engines for many years with no downside and is exactly how Mobil I did it with my GM/Mobil I Snakeskinner ZR-1 that ran 24 hour races and worked just fine.

 

I would imagine that the bearing clearances matched the 10W-40 oil and high oil temps that you saw as well in 24 hour endurance races.

Bret

 

Let me chime in by saying I'm not an expert here, but here is my experience with Mobil 1 10W30. Idle is right around 30-35 hot, and at WOT it goes up to 50 psi and hovers there until 6000 rpm.

Sounds just about what you are looking for, but my mods are significantly different than yours. After reading about Mobil 1 5w30, it seems to be pretty thin at operating temperatures.

In any case, go with a synthetic oil. There is NO reason to use good 'ol dino oil, except possible for the first few thousand miles. I just had my valvetrain apart, and after 70,000 miles the parts looked fantastic. Granted, they should look great with only 70,000 miles. I've been using Mobil 1 10W30 since about 4000 miles. The first 4000 miles were with dino Valvoline 10W30.

Dan

 

Are you sure oil helps blow by? blowby ussually happens when the compression rings can't take it and then the other rings also let the cylinder pressure go through the rings, what difference does it make if you have thicker oil or not? It doesn't I don't think, thicker oil will help if you're ring clearances are sloppy and you don't want to burn oil by getting oil through the rings into the CC, but not the other way around.

 

Nothing technical to add here just a daily observation.....

30 deg temps up here and the LS1 in my car just got a new oil change.

45-50psi at 1000-1500rpm with 0W-30 Castrol Syntec in the motor.

Maxes out at around 60-70psi

In the summer i've seen as low as 35 psi when the oil is hot, same thing in OldSStrokers C5 running 5W-30 Mobil 1.

Bret