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Oil Filter Relocation for convenience and performance
- Thread starter Hohn
- Start date
I wonder if the OEM filters at the time had different efficiency … the one being on the "bypass" circuit being higher efficiency? Back then, it would probably be nearly impossible to get that kind of info
Did the OM say anything special about those filters and anything specific about changing them, like different change intervals, etc?
From what I've heard, engines using this type of thermostat for oil coolers will still have slower oil warm up in cold weather because it does not completely cut off the flow to the oil cooler.
For the GR86 in particular, you don't want to add much restriction, since those engines struggle to maintain good oil pressure at high rpm in the first place when the oil gets hot. Builders of those engines will go through the effort of drilling out or porting certain parts of the timing cover or block connections to pick up a few extra psi at the crankshaft.
So here's an idea for the GR86, but something similar should work on other engines. The engine has two common points for measuring oil pressure: the oil pressure switch just downstream of the oil filter, and a connection at the top of the block that taps into the crankshaft gallery. There's a substantial difference in oil pressure between these two points at higher rpm, as seen here.
If you were to run an oil line between those points, you would reduce restriction and increase oil pressure at the crankshaft. Add a filter in this line, and you'd have effective bypass filtration as well. You could relocate the oil pressure switch, or better yet, install an oil pressure sensor downstream of the bypass filter. This setup would not flow all that much oil through the bypass filter at low rpm/flow when there wouldn't be much of a pressure difference between those points.
Alternatively, you could use a sandwich adapter with a single outlet at the primary oil filter, and connect it to the bypass filter, then to oil pressure switch location or the crankshaft gallery location, maybe through a check valve. The sandwich adapter would add some restriction, but the bypass path would reduce restriction to compensate for this. You could do something similar with a thermostat to switch the flow path between the filters, but then you'd have to start worrying about restriction again.
This setup would send more oil through the bypass filter, especially if the downstream connection is to the crankshaft gallery. Flow and pressure to the engine should be improved over OEM as well.
Amazing fuel economy I bet.
If the left gauge is the one on a main gallery feeding the crankshaft (also located after the filter), then the approx 1 bar (1 bar = 14.5 PSI) pressure drop between just after the filter and that gallery location could be due to a restriction in that flow path even though it's a "main gallery". Or maybe the flow split-off somewhere before getting to that pressure point (?). Would have to see a schematic of that engine's oiling system to get a better idea.So here's an idea for the GR86, but something similar should work on other engines. The engine has two common points for measuring oil pressure: the oil pressure switch just downstream of the oil filter, and a connection at the top of the block that taps into the crankshaft gallery. There's a substantial difference in oil pressure between these two points at higher rpm, as seen here.
In the photo above, the main gallery pressure is 4.5 bars (65 PSI) at 6000 RPM with 10W-40 at 90C. Is this really causing a lack of lubrication on these engines? What's the proof of that (smoked bearings?), or are "racers" just wanting more oil pressure for the sake of having more oil pressure?
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I had to ask, as we were instructed not to ask.
I am sure i will not get a response.Here's a diagram. The flow does split off to one of the heads just after the oil filter, near the OEM pressure switch location. Point 12 would be where the crankshaft gallery pressure sensor would be located. Point 14 is the most obvious restriction, since the hole in the block is smaller than the piping on either side, introducing sharp-edged restrictions down to 11.5 mm diameter.
This hole is often drilled out to match the diameter of the piping on either side when an engine is rebuilt after it spins a rod bearing.
The recommended grade is 0W-20, and the oil can get a lot hotter than 90C. Rod bearing failures have been pretty common. Here's an example of how oil temperature/viscosity can affect oil pressure on the FA20 engine. Measurements were taken at the crankshaft gallery.
With thin oil, the oil pressure is lower at 7,000 rpm than it is at 4,000, and this engine will rev to 7,700. 5 to 6 psi per 1,000 rpm is going to be pretty marginal for the rod bearings at these revs.
It could be that the oil is getting so thin that the pump is no longer in pressure relief. The oil pump being driven at crankshaft speed at 7000+ rpm probably doesn't help with pump efficiency or cavitation either.
For some of the restrictions in the system, like Point 14 above, the dP will increase with the square of flow rate, so they'll have a more pronounced effect on oil pressure with thin oil and high flow rates.
For the FA24 engine in the newer BRZ/GR86, Subaru used a larger oil pump. It's smaller in diameter, but has a thicker rotor, which I'm thinking might help it perform better at higher revs. That engine is better at holding pressure to redline (but only if you don't corner too hard and starve the oil pickup).
dnewton3
Staff member
Fuel mileage was great. And they were very reliable.
But they were s-l-o-o-o-o-o-o-o-o-o-w-w-w-w-w-w-w-w-w-w to accelerate.
And man, were they noisy at idle, at redline and everywhere in between.
There were one-year trial lease vehicles; an attempt by Ford to test the marketplace. Didn't last long, as you would expect.
I think it is cool. It was a machine or as Johnny Cash might say, a moshine.
dnewton3
Staff member
Not that I recall, but I wasn't really into Beta data at the time and BITOG didn't exist then.
IIRC, the BP filter was done every other FF change??? It's been almost 40 years ago ...
I ran Rotella 15w-40; don't recall the sump volume.
dnewton3
Staff member
I wanna say (old memory here) it was like 25mpg around town and close to 40mpg on the highway. Remember, the speed limits in most places were 55mph back then.
Yep, sure do. I wonder how much of an EPA MPG impact that would have today if people weren't trying to travel at 90 on the interstate. My guess is MPGs would increase dramatically.
Thanks ... that gives a decent layout of the oiling system. I'm wondering if point 14 was a purposeful flow restriction "orifice" placed there to provide some flow control to the journal bearings, and to help balance the flow in the oiling system as a whole. When point 14 is drilled out, how does the dP between point 15 right after the filter and point 12 compare? And how does it change the Pressure vs RPM of different oils as graphed in the chart below?Here's a diagram. The flow does split off to one of the heads just after the oil filter, near the OEM pressure switch location. Point 12 would be where the crankshaft gallery pressure sensor would be located. Point 14 is the most obvious restriction, since the hole in the block is smaller than the piping on either side, introducing sharp-edged restrictions down to 11.5 mm diameter.
This hole is often drilled out to match the diameter of the piping on either side when an engine is rebuilt after it spins a rod bearing.
Yeah, the RPM vs Pressure curves are a bit puzzling. For instance, the 0W-20 @ 185F curve is right in there with the other 3 lower curves up to 4000 RPM, so that means the viscosity is probably pretty close for all 4 of those oils, so it seems they would all track each other pretty close out to 7000 RPM, but the 0W-20 @ 185F keeps climbing while the other 3 roll-off after 4000 RPM. As above, it would have also been good info if both points 15 and 12 were measured to help give a more complete picture. It could be that the lower pressure at point 12 at higher RPM with the oils that roll-off after 4000 RPM has something to do with the journal bearing side leakage and how the oils were shearing at higher RPM. If the pressure at point 15 didn't roll-over like at point 12 over the RPM range, then that could give some good info to explain the phenomena, and could give information to determine of the oil pump was falling on it's face with certain hotter and thinner oils in those conditions.The recommended grade is 0W-20, and the oil can get a lot hotter than 90C. Rod bearing failures have been pretty common. Here's an example of how oil temperature/viscosity can affect oil pressure on the FA20 engine. Measurements were taken at the crankshaft gallery.
With thin oil, the oil pressure is lower at 7,000 rpm than it is at 4,000, and this engine will rev to 7,700. 5 to 6 psi per 1,000 rpm is going to be pretty marginal for the rod bearings at these revs.
It could be that the oil is getting so thin that the pump is no longer in pressure relief. The oil pump being driven at crankshaft speed at 7000+ rpm probably doesn't help with pump efficiency or cavitation either.
With thinner oil, the pressure in the main gallery from the filter feeding point 14 will also be lower, which will decrease the feed pressure at point 14, and also have an effect on the dP across the point 14 restriction. So the dP effect across point 14 from thinner oil may not be much. Would have to run different flow vs dP vs viscosity conditions through a delta-p calculator model for point 14 to see how it would behave.
Subaru must have made the change for reason. Yeah, those pesky cornering G-forces starving the oil pick-up aren't a good thing.
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I'm trying to make sense of this.
I'll throw something out there that might surprise you. You might be witnessing the effect of crank deflection. This may explain why the engines struggle to keep oil pressure at higher RPM with lower viscosity and why they fail rod bearings.
The FA20 crank has very little journal overlap, which is a huge contributor to crank stiffness. It also seems to have the journal centerlines pretty close together, there's very little space (and beef) between journals.
As a data point, contrast that crank with the Honda K20c1 (civic Type R), noting the massive thick web area between journals as well as how much more material there is around the crank journals themselves:
Perhaps instead of asking where "the restriction" is, it's more useful to ask why the oil flow is increasing so drastically above 5000 rpm or so. After all, restriction is a function of flow. So when a fixed orifice seems to suddenly become very restrictive, it must be that that there's either the flow rate has drastically increased or the viscosity has drastically increased. We know there's no viscosity increase with temperature or RPM, so to me this points to a pretty large opening of bearing clearances due to inertial forces. That places a huge premium on hot viscosity to maintain oil pressure.
If you are going to run those temps and those RPM, and engine like this probably needs a 10w60 kind of oil like you'd run in a Ferrari or Lamborghini or such. It necessary to overcome the large opening of bearing clearances under high rpm deflections when the oil is hot.
F1 engines have a rule-spec min KV100 of 2.8cSt, from what I can find online. But F1 engines are famously "tight" and as stiff and light as they can make the internals. The have no problem maintaining oil pressure all the way to insane RPM levels with an oil that's effectively thinner than most 0w rated oils.
So that's sort of why I'm thinking the FA20 has a crank deflection issue causing it leak oil like crazy at higher RPM.
I'm trying to make sense of this.
I'll throw something out there that might surprise you. You might be witnessing the effect of crank deflection. This may explain why the engines struggle to keep oil pressure at higher RPM with lower viscosity and why they fail rod bearings.
The FA20 crank has very little journal overlap, which is a huge contributor to crank stiffness. It also seems to have the journal centerlines pretty close together, there's very little space (and beef) between journals.
As a data point, contrast that crank with the Honda K20c1 (civic Type R), noting the massive thick web area between journals as well as how much more material there is around the crank journals themselves:
As mentioned above, if there was oil pressure data taken at both points 15 and 12 over the whole RPM range then you could tell if the pump is the cause, or if it's something going on at the crankshaft. The 0W-20 @ 185F is probably pretty close to the viscosity of the 10W-40 at 265F. The pressure vs RPM tracks close between those two oils up until 4000 RPM. So if the oil pressure above 4000 RPM was effected by crank flex it would seem than the pressure vs RPM above 4000 RPM for those two oils would track about the same to 7000 RPM. If the pressure vs RPM at point 15 was also on the graph, it would add some valuable information to understand what's going on.
I don't think what we see in the pressure vs RPM graph is caused by crank flex. Besides, crank flex doesn't really change the clearance in the bearings (the crank journal and rod bore aren't changing size), but it can put higher loads on the bearings. If the bearing clearance doesn't change, then the pressure they cause at a steady oil viscosity and RPM shouldn't change. Higher loads could cause the MOFT to go to zero if it's already running with low MOFT due to hot thin oil.
Another aspect to consider is the bearing side leakage as the viscosity changes. As the RPM goes up and the oil becomes thinner, the bearing side leakage increases. If there a significant increase in side leakage, that could reduced the pressure seen at point 12. If the pressure was also measured at point 15, then a phenomena like that could be seen.
The oil pressure increases above 4000 RPM with the thicker cold oils because the oil flow is also increasing. The spring loaded pressure relief valve in the pump can not perfectly control the output pressure and flow, so there is still flow and resulting pressure creep even when the pump is in relief. Re: bold sentence. If the bearing clearance actually physically increased, the oil flow through them would increase, and the pressure feeding them (at point 12) would decrease. If the oil gets thin enough, the side leakage will increase which will have the same effect as increasing the bearing clearnce. Think of the journal bearings as mini scavenger pumps on the oil supply feeding them.
For the bearing clearance to change due to crank flex, the crank journal and the rod big end diameters would have to physically change size. If that was going on, I think the pressure vs RPM curves would be effected with all the oils shown. and you'd see more pressure roll-over for the top 3 curves than you see in that graph.
F1 engines also have a high volume oil pump and lots of oil coolers. The W rating of the oil doesn't really matter once the oil is hot, it's actually the HTHS viscosity of the oil inside the running bearings that has the most effect on the oil pressure.
The FA20 cranks have more overlap than the old EJ engines, and are said to be quite a bit stiffer. The engine block is stiffer as well.
Boxer-4 engines are inherently better balanced than inline 4's, so less mass is required for counterbalancing, and they probably don't need to be as stiff.
Back to remote filtration....
I'm thinking that the only way to do more filtration capacity and still have acceptable oil pressure delay would be electric prelube.
This would turn the ports-in-series function of the sandwich adapter into a net positive. Put a check valve on the inlet of the sandwich adapter and push oil through it with an electric oil circulation pump.
Earlier I proposed using a sandwich adapter (for an oil cooler feed) to send oil to a remote head and keep the stock spin-on. I also proposed a "bypass" that would attempt to prevent oil pressure delay by cutting out the remote filter head under some conditions.
What I realize now is that it's not a bypass that's need, it's prelube with an electric pump. Here's what that plumbing would look like.
Sandwich adapter outlet--> check valve (low cracking pressure~2psi)--> run tee--> remote filter head---> Sandwich adapter inlet.
The electric pump circuit would look like:
oil pan drain plug tee-->electric oil circulation pump--> check valve--> enter remote filter loop at run tee
This is still complex, expensive, and perhaps invites reliability problems by having your engine's lifeblood oil circulating in external plumbing. But this setup would indeed achieve the goal of adding significantly more filtration capacity while completely eliminating oil pressure delay concerns.
If you could package the plumbing reliably, you could perhaps have a system that was more reliable than OEM. It would definitely be more durable, since the electric prelube eliminates dry starts entirely.
I'm thinking that the only way to do more filtration capacity and still have acceptable oil pressure delay would be electric prelube.
This would turn the ports-in-series function of the sandwich adapter into a net positive. Put a check valve on the inlet of the sandwich adapter and push oil through it with an electric oil circulation pump.
Earlier I proposed using a sandwich adapter (for an oil cooler feed) to send oil to a remote head and keep the stock spin-on. I also proposed a "bypass" that would attempt to prevent oil pressure delay by cutting out the remote filter head under some conditions.
What I realize now is that it's not a bypass that's need, it's prelube with an electric pump. Here's what that plumbing would look like.
Sandwich adapter outlet--> check valve (low cracking pressure~2psi)--> run tee--> remote filter head---> Sandwich adapter inlet.
The electric pump circuit would look like:
oil pan drain plug tee-->electric oil circulation pump--> check valve--> enter remote filter loop at run tee
This is still complex, expensive, and perhaps invites reliability problems by having your engine's lifeblood oil circulating in external plumbing. But this setup would indeed achieve the goal of adding significantly more filtration capacity while completely eliminating oil pressure delay concerns.
If you could package the plumbing reliably, you could perhaps have a system that was more reliable than OEM. It would definitely be more durable, since the electric prelube eliminates dry starts entirely.
From what I know, it's more of an issue for tracked cars, which generally use thicker oil grades and often an aftermarket oil cooler as well.
The oil pressure graph I posted came from a car with an aftermarket oil cooler. I've heard that they tend not to help at all with maintaining oil pressure, since the added restriction generally offsets the cooling benefit. I haven't seen a comparison with detailed data though.
Oil coolers have a quadratic dP-flow curve just like the other major restrictions between the pump and crankshaft, and so would also tend to drop the oil pressure a lot more in high flow/low viscosity conditions.
The 0W-20 should have a KV100 of 11.8 cST at 185F, versus 7.9 cST at 225F, and 8.0/8.75 cST for the 10W-30/10W-40 at 245/265 F.
At 4k rpm, I think the reason that the pressure for the colder 0W-20 isn't much higher is that the oil pump PRV is coming into play at ~50 psi. With the thickest oil, we see the inflection point in the curve caused by the PRV at ~65 psi. For the next thickest oil, it's ~55 psi. For the 0W-20 at 185F, a more realistic extrapolation of the curve might show an inflection at ~45-50 psi at ~2,800 rpm. The oil pump PRV is cracking open at around 80 psi in each case, but the dP between the oil pump and crankshaft is increasing as the oil gets thinner and flow rates increase.
Colder oil is also less resistant to shear thinning, and this might be responsible for some differences in the shapes of the curves. The colder 0W-20 will start thinning at lower shear rates (lower rpm), whereas the hotter oils may not be shear-thinned very much at lower rpm, but may still end up thinning down close to their base oil viscosities by 7k rpm. The three different oil grades won't all be equally resistant to shear thinning either.
Would need the specifics on each individual car to make any logical conclusions - multiple factors going on. Could be most of those cars that have bearing failures are due to the pump sucking some air (lack of lubrication) at times while on the track, and/or they are running too thin of oil for the use conditions.
They needed to record pressure at point 15 (right after the oil filter) along with point 12 over the RPM range with and without the oil cooler to see the effect. When there is limited recorded data (ie, just measuring the pressure at point 12), it's all just theories on what's causing the pressure roll-off at point 12 with thinner oils at above 4000 RPM.
This stems back to my comments about what's going on in the rotating bearings could have an effect on the pressure at point 12. If the pressure at point 15 was also on the graph, it would help show if what's going on inside the bearings (ie, bearing MOFT, real time dynamic viscosity due to shear rate and side leakage effects) is directly effecting the pressure at point 12, which is on the downside of a restriction in the flow path (point 14). If the pressure at point 15 followed the same basic curve shape as the pressure at point 12, then I'd say the pump is lacking performance as the viscosity drops, and/or the oil cooler has some larger effect as the oil thins down.
Maybe Subaru changing the pump design you mentioned was trying to solve this pressure drop-off as the oil thins down. Has anyone did similar pressure vs RPM measurements with the updated Subaru oil pump?
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