0W20 load bearing capability in race block

[Belgian1979]

Another question : at idle I saw the pressure go up with the 5w30. With the 5w30 it was 40-45 psi where with the 10w40 it was around 25-30. How does this figure into the story. As for the temperatures. Yes the oil is cooler with 5w30

 

[ac_tc]

If i understand you correct, you have a lowering oil pressure at top end speed.(?) And you experience lower idle pressure with thicker oil! -I would look for restrictions or leaks on the inlet side of the pump.

 

[Belgian1979]

Yes, exactly : lowering oil pressure at high speed, higher oil pressure with thinner oil.

 

[Clevy]

Originally Posted By: Belgian1979

Another question : at idle I saw the pressure go up with the 5w30. With the 5w30 it was 40-45 psi where with the 10w40 it was around 25-30. How does this figure into the story. As for the temperatures. Yes the oil is cooler with 5w30

If the oil is cooler with 5w-30 wouldn't that mean its thinning less which may increase pressure,however a 15-20 pound difference can't be right. There wouldn't be that big a spread between 5w-20 to sae60

 

[Clevy]

Originally Posted By: Belgian1979

Yes, exactly : lowering oil pressure at high speed, higher oil pressure with thinner oil.

Higher oil pressure with thinner oil at more rpm. K. Where is the pressure sensor taking the readings. A thinner oil may show higher pressure at elevated rpms if the sensor was after the filter,and the thinner oil passed through the filter faster increasing pressure vs a thicker lube that was more restricted by the filter.

 

[Belgian1979]

Filter is before the OP sensor. The filter is the last thing before the oil goes into the block. The OP is on the inlet of the block. OP was also higher at idle as stated.

 

[KrisZ]

Looks like the oil pump is in by-pass mode with thicker oil pretty much all the time. You can only cram so much oil into the system before the back pressure starts to spike.

 

[MolaKule]

Originally Posted By: A_Harman

Originally Posted By: MolaKule

I base this on Cameron's first order equation of frictional forces within bearings: Ff = pi^2 X u X Db^2 X Lb X N)/h' where; u is oil viscosity, Db is bearing diameter, Lb is bearing length, N is RPM or shaft rotational speed h' is mean radial clearance.

What is this equation calculating? Torque loss in a bearing as a function of bearing dimensions and viscosity? There is a right parenthesis in there, where should the left parenthesis be? (Hate to be nitpicking on that.) Also, is the pi^2 term correct?

It should also have said, "I base this on Cameron's paper of the Petroff first order equation for frictional forces within a bearing." The equation should have a parenthesis on the left side as in: Ff = (pi^2 X u X Db^2 X Lb X N)/h' It is Petroff's equation for the frictional forces within a bearing. u is dynamic viscosity. It is derived by modeling the oil flow within a bearing as a "Couette" flow, or du/dr = (pi X Db X N)/h' therefore, Ff = A X u X du/dr = (pi X Db X Lb) X (pi X Db X N)/h' = (pi^2 X u X Db^2 X Lb X N)/h'.

 

[Shannow]

Originally Posted By: jrustles

Now for the good stuff, let's focus on the bearings. The mains get fed right off the main gallery, pressure drop is minimal. What about the rods? Well, the only way they can be fed is through the crankshaft. The oil passages in the crankshaft are a pressure drop nightmare. Not only does the feed have to enter a constantly rotating orifice at the main bearing, which is already leaking volume from it's clearance, but the already pressure-dropped feed into the crankshaft via the mains must again find it's way through small, angularly drilled passages within the crank. Getting to the rod bearing orifice, we now have seen the ultimate pressure drop in an engine, compared to what we see on the gauge.

Your long and detailed post was very good, just one nuance that I'd like to add about the big end lubrication... Because the big end is spinning, it's trying to sling its oil out from the centreline of the crank, needing pressure to force the oil "uphill" to the crank centreline, when the "centrifugal force" then slings it towards the bearing.

 

[MolaKule]

For cross-drilled crankshafts, that is the case, but for non-cross-drilled crankshafts, splash lubrication and wide groove bearings are the norm for conrod bearing lubrication. Cross-drilled Crankshaft pictures

 

[Shannow]

Oil still has to go from the periphery to the centre of the main before passing towards the big end. Cross drilling takes high pressure oil and wastes it to the low pressure side. Calculated 2.45" diameter main at 628 rad/s, density 0.9, only a couple of kpa, so not as big an effect as I thought.

 

[Clevy]

Originally Posted By: Shannow

Oil still has to go from the periphery to the centre of the main before passing towards the big end. Cross drilling takes high pressure oil and wastes it to the low pressure side. Calculated 2.45" diameter main at 628 rad/s, density 0.9, only a couple of kpa, so not as big an effect as I thought.

Bitog We really are blessed to have these kinds of minds posting here. Molekule,Shannow Thank you forgive me if my absorption rate is slow but count on it being absorbed.

 

[Garak]

Originally Posted By: MolaKule

The equation should have a parenthesis on the left side as in:

Or get rid of the right parenthesis, since it's not necessary anyhow, or use a negative exponent just to be quirky. You chemists and engineers, sigh.

 

[CATERHAM]

Originally Posted By: MolaKule

2. Keep the same HF oilpump and use a racing oil 5W20. That oll should have the highest HTHS you can find, about >= 1000 ppm of phos/zinc, > 200 ppm of moly, and the highest VI. 3. Use an oil cooler in front of the radiator to moderate the engine's oil temperature. This will keep the viscosity more stable.

Or instead of a 5W-20 with the highest HTHSV, a 0W/5W-30 with a lowish HTHSV which amounts to the same thing. That said there are very few oils that would fit the bill and most will involve a certain degree of blending. Here are three suggestions: Red Line has their 0W-20 (HTHSV 2.9cP, 172 VI) but you may want to add 10% or more of RL 0W-40 to boost the HTHSV to 3.0cP+ which will give you a 0W-30. Millers CFS 0W-30 (HTHSV 2.9cP). Again may want to add 10% of CFS 5W-40 to raise the HTHSV to about 3.1cP. Motul 300V 0W-20 (HTHSV 2.7cP, 166 VI). A bit on the light side so I'd suggest blending in a third (33%) of 300V 0W-40 to make a 0W-30 with a 3.1cP HTHSV.

 

[Belgian1979]

Another update to this. I was suggested contacting Schumann oil pumps. They make specialty pumps for these engines but based on the Original design, which my pump is by the way. Anyway, I explained the problem and they suggested a HV pump (which seems to be a requirement with my engine) but with a 2 mods, one of them being a ball in the bypass instead of the plunger and the second (which is the more important) a full bypass to the pan instead of the inlet. I talked to them some more about the second aspect. They said the problem with these pumps is that in a high bypass situation the bypass oil stream tends to backup into the inlet pipe, in essence restricting the inlet and inducing cavitation. With all that has been said so far I'm going to try the external bypass and putting the internal bypass out of the picture.

 

[CATERHAM]

Originally Posted By: Belgian1979

Another update to this. I was suggested contacting Schumann oil pumps. They make specialty pumps for these engines but based on the Original design, which my pump is by the way. Anyway, I explained the problem and they suggested a HV pump (which seems to be a requirement with my engine) but with a 2 mods, one of them being a ball in the bypass instead of the plunger and the second (which is the more important) a full bypass to the pan instead of the inlet. I talked to them some more about the second aspect. They said the problem with these pumps is that in a high bypass situation the bypass oil stream tends to backup into the inlet pipe, in essence restricting the inlet and inducing cavitation. With all that has been said so far I'm going to try the external bypass and putting the internal bypass out of the picture.

That's all well and good, but remember what Shannow has said, running in "bypass is bad" for a number of reasons and if don't run an oil that is overly heavy you don't need to run in by-pass ever. What's more important in an oil pump is having a by-pass setting that is well above the oil pressure you run at normal hot operating temp's. For example I use my oil OP gauge as a variable red line during warm-up; I never rev' the engine higher than the by-pass point until the oil has warmed up enough to allow maximum rev's without the OP rising high enough to reach the by-pass point. Running a light high VI 0W/5W-30 oil in your Chevy engine, that will be an easy practice to follow.

 

[Belgian1979]

Caterham, I already run 5W30 at the moment as explained earlier. If I go this route I would set the external bypass at 70 and leave the internal at 75 psi. The oil pump would not get to 75 anymore basically rendering the internal bypass out of operation. The only negative I see is that it has the potential of creating a larger pressure drop over the pickup/inlet tube and possible enhancing cavitation. If the last would be in play, the net effect would be that I would see the pressure start dropping at an earlier rpm point. The part I intend on installing is this http://www.petersonfluidsys.com/pump_acc.html an external relief valve. Maybe I'm wrong about this, but it's worthwhile investigating.

 

[MolaKule]

Originally Posted By: Garak

Originally Posted By: MolaKule

The equation should have a parenthesis on the left side as in:

Or get rid of the right parenthesis, since it's not necessary anyhow, or use a negative exponent just to be quirky. You chemists and engineers, sigh.

The parenthesis is to group the numerator terms and make it more readable, since we do not have an equation editor available to us here at BITOG.

 

[MolaKule]

Quote:

They said the problem with these pumps is that in a high bypass situation the bypass oil stream tends to backup into the inlet pipe, in essence restricting the inlet and inducing cavitation.

I don't understand this statement. Do they mean the level of the oil in the pickup tube is or would be higher? If that is the case, then a higher higher level of oil in the pickup tube would effectively contribute to a lower "head," and that should assist the pump which should lower the potential of a cavitation event. A lower head can certainly contribute to cavitation. If your strainer or pickup pump is short and as low as possible, just above the pan bottom, that should be ok. While adding a Peterson Remote relief valve will give you more control over bypass pressure, the dumping of this bypass stream into the sump will just increase air entrainment.

 

[Garak]

Originally Posted By: MolaKule

The parenthesis is to group the numerator terms and make it more readable, since we do not have an equation editor available to us here at BITOG.

Bah, humbug. Well, you could have used an equation editor, and exported the equation to an image, and linked it to your message. That wouldn't have been much of a hassle at all, right?