Small-Block Chevy Oil Testing

[Ramblejam]

Food for thought:
"It bears emphasizing that oil flow (while more difficult to measure) is actually more important than pressure in terms of engine life. Oil flow with some pressure behind it is far superior to low oil volume with lots of pressure behind it."

http://www.hotrod.com/how-to/engine/ccrp-0911-small-block-chevy-oil-pumps/

 

[Kool1]

I agree with you. A high volume oil pump is more important than a high pressure oil pump.

 

[BrocLuno]

They got 3.6 HP difference between the straight 30 and the 0W-20 as they approached 6,000 RPM - if I'm reading this correctly...

They do fall into the trap of flow. Bearings take what they take and flow is equal to the side leakage. Thinner oils leak faster and so need more flow to replenish. The pumps are doing the same amount of work, it's the downstream parts that are tossing the oil off faster ...

But, I did get a new idea (?), install and BBC pump on a SBC - cool. I build motors that drool internally. Extra oiling points in the motor like directly onto the distributor gears, lifter gallery plugs drilled to squirt on the timing chain, etc.

BBC pumps are stronger physically and some of the newest "light weight" pumps have been breaking off their single bolt mounts. BBC pumps, not so much

 

[The_Eric]

Originally Posted By: BrocLuno
They got 3.6 HP difference between the straight 30 and the 0W-20 as they approached 6,000 RPM - if I'm reading this correctly...

They do fall into the trap of flow. Bearings take what they take and flow is equal to the side leakage. Thinner oils leak faster and so need more flow to replenish. The pumps are doing the same amount of work, it's the downstream parts that are tossing the oil off faster ...

But, I did get a new idea (?), install and BBC pump on a SBC - cool. I build motors that drool internally. Extra oiling points in the motor like directly onto the distributor gears, lifter gallery plugs drilled to squirt on the timing chain, etc.

BBC pumps are stronger physically and some of the newest "light weight" pumps have been breaking off their single bolt mounts. BBC pumps, not so much

Not new at all. In fact, Melling has a pump that is made to do just that- the M99HVS. It's been around for at least 20 years.

 

[novadude]

Originally Posted By: The_Eric


Not new at all. In fact, Melling has a pump that is made to do just that- the M99HVS. It's been around for at least 20 years.


A whole lot more than 20 years. I recall seeing mention of BBC pumps on SBCs in the old "How to Hot Rod Small Block Chevys" book from the 1970s.

 

[novadude]

One more thing....

BrocLuno... if you take this to the Team Chevelle forums, we'll get 12 more pages of "20W-50 with a big slug of ZDDP additive is the best" posts. LOL

 

[BrocLuno]

It may have been around, I just never considered it. I will on my next SBC... I just always made do with std HV pumps. Prolly cause I don't read all that much in the trade rags and such ...

I'll keep it away from the Chevelles forums ...

I'll let someone else open that can of worms

 

[Shannow]

Suggestions that I've read over the yeas (never built an SBC, but read and read) was that the bigger tooth count on the BBC reduced pulsations, and that (along with "anti cavitation") grooves in the casing reduced spark scatter.

Reducing "pulsations" in the bulk oil flow is silly in concept, as the flex in the filter casing would act as an accumulator for the tiny "deltaV", and the bearings etc. would never see it...and if they DID, it wouldn't matter a jot.

Looking at the pics, they tapped the pressure side of the pump at the oil filter mounting plate, and remote mounted a filter and flow metering.

So the pump relief is still functioning, and is the clear differentiation on "flow" between the oils. If they measured the pump inlet flow, they would be identical...it's postiive displacement.

As per Broc Luno's post, the difference is that on the thicker oils, the bearings actually need LESS oil...they draw less oil off the galleries, and the pump is providing flow against that, which results in oil pressure rising, the relief flowing, and LESS oil reaching the engine.

Less oil reaches the engine because the engine is signalling that it needs less.

In the Case of Broc's engines with additional squirters and sprays, the increased pressure is actually flowing more oil to these points, as they rely on pressure to deliver volumes of oil.

Sooooo....

* Oil pumps supply oil to the engine.

* If the engine requires less flow, the oil pressure rises to reach an equilibrium, and if it can't the relief flows, and diverts that volume elsewhere.

* The oil pressure is therefore an artifact of that balancing act.

* OEMs oversize the oil pump so that as the engine wears there's reserve oil supply there to make up for the increased leakage.

* the differences in power have S.F.A. to do with oil pump drive power, it's friction in the bearings and piston skirts primarily that makes up the 3.6hp...the oil pump drive power change between 60 and 80 psi is akin in power loss to turning on the headlights.

* The reduction in drag comes at the expense of minimum oil film thickness (MOFT).

Read more on flow and MOFT, and viscosity here

 

[BrocLuno]

Yeah, I wondered about the plumbing too. To make a completely valid test(s), you'd need to block the in-pump relief and the filter boss relief ... Then your external plumbing would see all conditions.

So with in-pump reliefs in place for all pumps, that's what you see in the tests. The spring rates and differences come into play at some points...

The pulse issue and spark scatter is maybe real for high pressure pumps as they are driven by the distributor drive and any pulses the pump generates will feed directly back to the distributor. So, yeah I can seem the higher tooth count making some small difference to the spark stability ...

 

[The_Eric]

Originally Posted By: novadude
Originally Posted By: The_Eric


Not new at all. In fact, Melling has a pump that is made to do just that- the M99HVS. It's been around for at least 20 years.


A whole lot more than 20 years. I recall seeing mention of BBC pumps on SBCs in the old "How to Hot Rod Small Block Chevys" book from the 1970s.


Putting the BBC pump on the SBC definitely isn't new as you've stated- but I was referring to the M99HVS pump that bolts straight on the SBC, using the SBC driveshaft. Previously you had to do something with the driveshaft- I can't remember, maybe cut down a BBC shaft to fit...

 

[Shannow]

OK, another day on, time to explain the flow thing...and maybe the horsepower thing.

Here's a test on an actual engine, where they could externally tap into the number 4 main bearing of an engine, and feed that oil from a constant pressure tank at varying engine revs. They could change the viscosity and measure the time that it took for 250ml (1 cup) to flow through the bearing.

This was in the early days of high shear viscometry where they were trying to work out why (say) 10W 40 didn't provide any where near the wear protection that an SAE 40 offered....they discovered that there's a thing called HTHS, where the oil "thins" with increasing speed as the polymeric VIIs get stretched out...chart on the left shows almost perfect correlation of flow rate to High Shear viscosity...in this case called the "apparent" viscosity.

The LHS chart shows the Kinemtatic viscosity of 9.2 doesn't fit the line, while it has an apparent viscosity of 6.7...which fits the line.

If it was a monograde, it would fit the line, as the low shear and high shear viscosity are the same...no VIIs to stretch out.

So clearly, the lower viscosity oils have a higher flow rate through the bearings (they also have a lower oil film thickness, as per the link I included past post.

 

[Shannow]

Now have a look at the chart on the right...

Both of those are 10W50 "multigrades", a grade which can only (reasonably) get made through polymeric viscosity index improvers.

The upper one has a higher shear stability polymer, starting off as a well and truly 50 at low RPM (shear rates), and dropping into 40 territory at high shear rates...drop the RPM, and it should come back...that's temporary shear...if it doesn't come back, that's permanent shear.

The lower one is a much less shear stable polymer, dropping down to the low 30 grades at high revs.

It's this behaviour that got them investigating the issue...that these oils weren't offering the same protection as their "40" or "50" would suggest.

Look at M1 0W50 race oil...it's solidly a 50 in kinematic viscosity, but HTHS is 3.8, same protection as Mobil's 0W40...Mobil's 20W50 V-Twin has an HTHS of 6.2...60+% thicker in the bearings.

That provides greater resistance to wear, but saps a little power and economy.

Schaeffer COULD have had an HTHS down to 3.7 on their 20W50...maybe not likely, but we don't know...and their SAE30 was likely 3.5 or thereabouts...AND they averaged the HP over a span of RPM.

It's possible (and I'm not claiming it as an fact) that as HP is torque times RPM that the SAE30 sapped a little more torque at the top end...possible.

The different parts of an engine hit the high shear rates at different RPM points, so will have different points at which they start dropping their affect on torque.

 

[Shannow]

And just for BrocLuno, because I'm a nice guy in a sharing mood...