FA20 Engine Oiling, Bearings, and Starvation

[Spartarus]

Originally Posted by rice_classic

Thanks for the info. I hope the pump does the trick. One of the driving schools around here is considering buying a fleet of FRS's for their school car and were asking me about what should be done for track reliability. So the results here are interesting.

In all these quandaries regarding oiling, nobody has even attempted modifying the pressure relief valve. Can you explain why? All this talk about changing pumps and displacement when nobody has even addressed altering the point at which the relief valve bleeds system pressure. Adding a higher volume pump may increase system pressure but it would be doing so by overwhelming the pressure relief valve. That doesn't seem like a proper fix. Has any definitive testing been done that suggests that no amount of shimming (stiffening the spring changing the point at which it bleeds system pressure) of the PRV has any affect on system pressure at temp?

I just had a new engine for my race car built (previous engine had shimmed pump). This one barely made 60psi at 7k 220F.
Added a shim.
Made 65PSI at 7k 220F but at 240F+ it wouldn't make more than 60psi at any RPM.
Added a 2nd shim.
Makes 60PSI at 240F but I want another 10 PSI. I can still yet increase shim thickness but I am currently running a very thin 0w-30 which is only 10cSt @ 100C so before I go through the hassle again I'm going to try bumping to an oil with a ~14 cSt @ 100C (a thick 10w-30 or a 5w-40) should finally put me where I want to be when I eventually see 260F in the pan. If not, in goes another shim.

Most oil pumps produce enough volume that without a PRV they would greatly overwhelm the oiling system. The likelihood that the FA20 came with a pump that couldn't do this exists but that likelihood is pretty minimal and from all the reading I've done, nobody has proven it so.. yet.

Element suggested earlier in this thread that he is convinced it's the pump and admitted he didn't attempt at shimming the PRV. Considering how easy it is to shim the PRV and test vs. playing around with pumps I'm surprised nobody tried this first..

Agreed. I'm considering shimming the PRV, as it's going to be right there when I open up the cam cover - but it isn't that easy on this motor, as every time you experiment with shims you waste o-rings and need to spend hours scraping sealant. Also considering using a hand pump to see what the opening pressure of the PRV is, unless anybody already has that information. Is your race car an FRS? Also seconded, how thick are the shims?

Originally Posted by 350matt

How thick are these shims of yours? 1mm ?

Also what about a sump baffle plate? as is this engine like the EJ20 / EJ25 where the oil can easily run out of the sump and into the cylinders under hard cornering?

Regarding the baffle - The stock upper oil pan is pretty well baffled. @Element Tuning and @CSGMike are running without extra baffling and see plenty of track time and plenty of lateral G's

[350matt]

OK thanks,, so do we think a baffle isn't required at all?, As personally I'd run one if I could as its cheap insurance

[Spartarus]

Originally Posted by celek

Its not a rebadged FB25/FB20 thats for sure its a whole new forging with a different mix alloy(Secret according to HKS) As for FB20 in the Crosstrek its the same SOA part number as the FB25, they share the same crank at a smaller bore 84mm bore = 2.0ltr , 94mm bore = 2.5ltr. What scares me is people putting turbo kits on them with the weakness listed below but thats another story.

Attached you will see the specs of HKS Japan's site stating the differences. vs stock.
I had a FB25 crank and measured the rod journal space at 0.752" of an inch. You will see in the other attached pic ACL website specs for the RB/SR bearing.

There should be 1.5mm clearance left and right on the rod for oil to escape (Was told by Pauter its an industry standard).
Total width is 0.6732" of the RB bearing, + 3mm for oil to escape will give you the total HKS journal width around .7916". (Still waiting for the crank to arrive to confirm)

For the FB20/FB25 crank at 0.752", subtract 3mm for easy math on each side you are left with .6336" for bearing/rod space then subtract the crown on the edge of the bearing leaving you with a .5152" width of usable bearing surface area. on the pin or Crank Rod journal area.

I would rather have .5548 sq.in surface area width vs .5152 sq.in
Both at 48.. Pin diameter its 1.0475" vs .9727" in surface area. about a 10% increase for oiling.

On to FA20 I know the Pin diameter is larger at 50mm vs 48mm but as for width it is unknown to me. No manufacture has published that. My stock rods and crank are sitting 3 hours away so I can not measure them. Maybe @Element Tuning has a measurement of the stock bearing.

In order to have the rod clear the case halves the pin or journal was decreased to allow for a smaller Big End rod.
HKS like Cosworth like bolt in perfection with no modification and high longevity. Hence why the large capacity stroker kit from HKS is only offered in stock bore. Now boring required, bolt it in and go.

THANK YOU SO MUCH!!!!!!

I'm having a bit of trouble following some of your figures though. @ .5152" useable bearing surface width and a journal circumference of 5.9338" (48mm times pi) plus small change for bearing clearances you should have come up with more than 3.057" inches of surface area. Either way, not important - the important part is it itsn't an FB crank and the bearings are wider. On to the meat of the debate:

So, the SR20 rod big-end width is 0.896" and it has a .6732 inch wide bearing. The FA20 connecting rod big end width = 0.843in / 21.41mm, with an unknown bearing width. Curiously enough, the EJ20 rod is .840 wide. I know the FA20 mains are thinner than the ej, and it has been asserted that the rod bearings are thinner too, but nobody has both measured and documented on this or any other forum. We know the FA mains have a narrower diameter than the EJ20, revvproject pointed that out. Whatever, the bearing widths are going to be pretty close if the rods are the same width.

So, the EJ20 has a .650" (16.5mm) wide bearing. (Info from ACL) and max 0.0591 crown either side.

From this, we can approximate that the total bearing surface area of the HKS bearing is .5548 x (2.0079x3.1415) = 3.4995 sq. inches for the HKS bearing.

The FA20 bearings, using EJ width and smaller FA diameter are .5318 x (2.0866x3.1415) = 3.4859 sq. inches for the FA bearing.

The big end widths come from both CP Carrillo, Pauter, and Brian Crower. It isn't a typo. Reliable sources.

Either way, the HKS does have a small increase in surface area over the assumed size of the FA20 bearings. Either way, we're down to a difference so small it's splitting hairs, and I'd rather work on fixing the oil system.

Thoughts? Tell me if I've missed something or gotten some huge detail hugely wrong.

[EAGLE5]

I would expect that, between aero and slicks, you would need some lower oil pan baffling.

[celek]

Originally Posted by Spartarus

THANK YOU SO MUCH!!!!!!

I'm having a bit of trouble following some of your figures though. @ .5152" useable bearing surface width and a journal circumference of 5.9338" (48mm times pi) plus small change for bearing clearances you should have come up with more than 3.057" inches of surface area. Either way, not important - the important part is it itsn't an FB crank and the bearings are wider. On to the meat of the debate:

So, the SR20 rod big-end width is 0.896" and it has a .6732 inch wide bearing. The FA20 connecting rod big end width = 0.843in / 21.41mm, with an unknown bearing width. Curiously enough, the EJ20 rod is .840 wide. I know the FA20 mains are thinner than the ej, and it has been asserted that the rod bearings are thinner too, but nobody has both measured and documented on this or any other forum. We know the FA mains have a narrower diameter than the EJ20, revvproject pointed that out. Whatever, the bearing widths are going to be pretty close if the rods are the same width.

So, the EJ20 has a .650" (16.5mm) wide bearing. (Info from ACL) and max 0.0591 crown either side.

From this, we can approximate that the total bearing surface area of the HKS bearing is .5548 x (2.0079x3.1415) = 3.4995 sq. inches for the HKS bearing.

The FA20 bearings, using EJ width and smaller FA diameter are .5318 x (2.0866x3.1415) = 3.4859 sq. inches for the FA bearing.

The big end widths come from both CP Carrillo, Pauter, and Brian Crower. It isn't a typo. Reliable sources.

Either way, the HKS does have a small increase in surface area over the assumed size of the FA20 bearings. Either way, we're down to a difference so small it's splitting hairs, and I'd rather work on fixing the oil system.

Thoughts? Tell me if I've missed something or gotten some huge detail hugely wrong.

You are right I was in a hurry had to run into a meeting I took the diameter * width, DOH

[D K]

Originally Posted by celek

Excellent Thanks I want to see some feedback on this.
Also looking into some of the oil pan baffle options as well.. I am Lucky my rod bearings are from a RB26.

Are you using RB bearings?

David

[celek]

Yes because I have the HKS stroker crank, its been manufactured with SR/RB crank pins

[cdrazic93]

Much JDM, so wow. Very bearing.

[Andreas83]

The reimax pump gears are installed.
Installing the motor again soon.
Just have to figure out how to install all the new parts.
Supercharger, wasp splitter, massive skunk2 radiator with oil cooler.
Some of the parts and chassie needs small mods to fit.
I am also Installing a oil pressure gauge.

[Lee]

shimming the PRV wont help up the oil pressure at high rpm at all. Thats not how a PRV works. It only opens when there is too much pressure, its a relief valve.

At high rpm and temperature with dropping oil pressure the PRV will be closed.

[celek]

Originally Posted by Lee

shimming the PRV wont help up the oil pressure at high rpm at all. Thats not how a PRV works. It only opens when there is too much pressure, its a relief valve.

At high rpm and temperature with dropping oil pressure the PRV will be closed.

I thought it was the other way around PRV is closed at idle for max PSi, higher the revs more pressure the PRV starts to open to reduce pressure.

Shimming causes it to open later at higher pressure with more spring tension, Hence why my Honda Race motor made 90 PSi idle on stock pump with a 1/4" washer in it. all the way to 9500 RPM

[celek]

Originally Posted by Andreas83

The reimax pump gears are installed.
Installing the motor again soon.
Just have to figure out how to install all the new parts.
Supercharger, wasp splitter, massive skunk2 radiator with oil cooler.
Some of the parts and chassie needs small mods to fit.
I am also Installing a oil pressure gauge.

Please post idle and Max RPM numbers, Although the PSi should in theory remain the same. It is flowing more though.

[Spartarus]

Originally Posted by Lee

shimming the PRV wont help up the oil pressure at high rpm at all. Thats not how a PRV works. It only opens when there is too much pressure, its a relief valve.

At high rpm and temperature with dropping oil pressure the PRV will be closed.

Not quite correct.

Originally Posted by celek

I thought it was the other way around PRV is closed at idle for max PSi, higher the revs more pressure the PRV starts to open to reduce pressure.

Shimming causes it to open later at higher pressure with more spring tension, Hence why my Honda Race motor made 90 PSi idle on stock pump with a 1/4" washer in it. all the way to 9500 RPM

Closer, let me expand on this.

Lee, the valve is not an on / off switch. There are 2 channels for oil being discharged from the pump. The gallery that leads to the filter, and the PRV. The PRV routes oil back into the pump inlet to regulate pump discharge pressure.

A partially open valve will rob oil pressure from the engine. The initial pressure at which the valve cracks open and starts diverting oil can be very low. This is determined by the valve preload (the amount of pressure exerted by the PRV valve spring when the valve is closed.)

The preload can be increased by adding a shim, thus reducing bypass oil flow, and increasing engine oil pressure at a given pump flow and oil temperature. Think of it like a turbo waste gate, or a thermostat, and not an on / off switch. Mechanically, those things have almost nothing in common, but use it as a metaphor. Understand it.

***The fact that nobody has documented the preload on the forums means we don't know if shimming the valve will help in this specific engine yet. The concept, however, remains sound. I will be testing the pressure at which initial bypass starts with a hand pump as soon as I have my motor apart. Until you have numbers, it's all just speculation. Or pissing in the wind. Or arguing theories over mechanical concepts you don't fully understand yet... But that's what the forum is for! Learning!! I've learned a ton so far.

[rice_classic]

Originally Posted by 350matt

How thick are these shims of yours? 1mm ?

~2mm thick each.

Originally Posted by Spartarus

but it isn't that easy on this motor, as every time you experiment with shims you waste o-rings and need to spend hours scraping sealant... Also seconded, how thick are the shims?

Yup, working on cars is... work. I'll give you that. I'd rather just be in the car on track than under it in the garage.

Like I said above ~2mm but then I had to add a second one. However my engine is a D16a6. Simple 4 banger design but I've shimmed D and B motors alike and have seen other engines shimmed as well. Common practice in race engine building. The hottest I've seen so far is 240 in pan (and I have a cooler) but I'm headed down to PIR (portland) this weekend and the weather is predicting a 93F day on race day. I emptied the very thin amsoil 0w-30 and put in a 5w-40. The 100C cSt rating is going from 10 to 14 and the 5w-40 + the 2 shims should put me at 65-70psi at 7krpm at 260F temps.

The PRV in the FA20 is a dual spring setup so a shim may be needed to act upon one or both springs. I'm not sure. If I were to do it on this engine I would add a ~4mm shim to enact upon the larger spring. Any remaining gap in desired pressure can most likely then be achieved by jumping up in viscosity a tad. (like from a 0w-20 to a 5w-30 or 5w-40)

Originally Posted by Lee

shimming the PRV wont help up the oil pressure at high rpm at all. Thats not how a PRV works. It only opens when there is too much pressure, its a relief valve.

It's a relief valve... not a relief "switch". It's a plunger with a spring so it's an infinitely variable orifice depending on pressures enacted against it. Not an on/off switch. Do not forget Pascals law.

The PRV's system-pressure-relief-point is proportional to the viscosity of the fluid acting upon it assuming all other system parameters remain static. Since the pump is driven by the crankshaft and increases flow with increased RPM let's say our max RPM is 7k and for point of reference the oil pressure peaks at 6k and stays steady to 7k (no increase in pressure for final 1k rpms).

If my oil is at 15 cSt at 100C (212F) and I see a max oil pressure of 80psi from 6k-7k then I know that the fluid enacts on the plunger enough to escape and limit system pressure at that viscosity to 80psi.

If my oil is at 7 cSt at 130C (266F) and I see a max oil pressure of 60psi from 6k-7k then I know that at 7cSt is so thin that it will enact upon the plunger and escape at a lower "window opening" limiting system pressure to 60psi.

The thicker oil needs more pressure behind it to move past the window opening created by the PRV. The thinner oil escapes much easier so it can flow past the PRV with a much smaller window (think of the size of the window being proportional to system pressure).

So I can add a thicker oil, but thicker oil can be at the sacrifice of flow.. So how do I get more pressure without sacrificing flow? So how do I get 70psi in this engine with 7cSt viscous oil? I need to create more spring pressure on the back side of the plunger of the PRV so it forces the 7cSt fluid through a much narrower opening, holding more of it "in the system" which creates more "system pressure".

Originally Posted by Lee

At high rpm and temperature with dropping oil pressure the PRV will be closed.

It would be the other way around. The PRV would be, for all intents and purposes, closed at lower RPMs and high heat but would then be "enacted upon" as the RPMs climbed and the greater system pressure would allow a very viscous fluid to move past the plunger with greater ease.

I addressed more of it here.
http://www.ft86club.com/forums/showp...&postcount=142