In a message dated 11/6/2009 9:02:47 P.M. Eastern Standard Time, bhughes@qnsi.net writes:
Thanks Lynn. What's your opinion with the 56-60 psi range I see in flight? Seems low compared to others.
Bobby
All of the pressure relief valves from Mazda open at 71.1 PSI. Through 92. This valve is screwed into the rear iron at the bottom, and has a jamb nut on it. The twin turbo engines 93-95 have that relief set at 110-115 PSI.
I have no data on the Renesis at all.
In any case the relief only determines the peak pressure. Or "cracking" pressure for safety valve fans.
At lower RPM the totals of all of the oil leak rates can outrun pump volume out, and the pressure will be some number below the cracking pressure. However once the RPM comes up along with pump volume, then you should see the oil pressure stop rising at that cracking pressure, and stay there even when more RPM are added. So that valve has only to do with peak oil pressure and nothing else.
If this is the case, say the pressure peaks at 70 pounds when at startup, then fades to 55 at operating temperature, it is usually oil foaming that is the cause. The effect of foaming is to leave the suction side of the pump pulling in some air and oil mixture. The air compresses and uses up pump volume, in effect making the pump smaller. So pressure goes down as pump volume out goes down.
This a page from the RX-8 club. The second bit has data on relief pressures for two models (ididn't know that).......... And after you read that, it looks like your oil pressure is OK for a series one engine, but they had wear problems, so in the series two engines they went nuts on oil pressure. Probably gets them pump wear problems.
Renesis OIL PRESSURE Discussion with Dealer Tech
Just got back from a face to face talk with my Mazda Dealers Service Head Tech, I sent him the pics of the Internal UK RENESIS Engine Damage/Wear for comment yesterday.
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Simply put there are two reasons why the back bearing is wearing the way it is and that is "Oil Pressure" and to a lesser extent oil viscosity.
The RENESIS 1 has the same Oil Pressure... Oil Pump Rotors, Oil By Pass Valve and Eccentric Bearings as Mazda's last NA Rotary, the 13B FC RX-7 .
Back when this model was around the recommendation for engine oil was 15W40 (here).
Because of this higher Viscosity Oil, Oil Pressure and Bearing Wear was not an issue like we see at the moment in some S1 RX-8's.
When the RENESIS RX-8 came out the recommendation (because of Fuel MPG and Emission targets) was a 5W20 or 30.
While there is nothing wrong with these oils, what was occurring over oil use/age was a lower engine oil pressure value
therefore not enough oil getting to the Rear Stationary Gear Bearing for lubrication....particularly at start ups.
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In the Series II (09~) Oil Pressure was almost doubled, but the same oil grade recommended??
I asked why the large increase in Oil Pressure Values.
60% is there to supply the two new EMOP's Lubrication System for the Apex Seals, with the other 40% for engine oil supply,
particularly all the Rotor and Stationary Gear Bearings and improved oil flow through oil coolers.
He believes the 5W20-30 weight oils for the S2's are fine because of the engines higher oil pressure.
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So, my next question was what can RENNY 1 owners do about the oil pressure, (unofficially official)
.....to use a higher viscosity grade of engine oil which will help increase the engines oil pressure at the "critical" locations.
In other words a higher oil viscosity will equate to Oil Pressure values like the NA 13B RX-7 which has the same oil pump and related parts and values as the S1 RX-8.
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I also asked him about the use of Magnets on Oil filers and or sump drain plugs...his word was DO IT....it is all good.
Then what to do about middle Apex Seal wear, and we know the "unofficial" answer to that one, and it goes in your gas tank...
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So, there you have it, I know it is not all Groundbreaking or Revolutionary news, I thought it deserved it's own thread.
What was interesting to hear is the lower oil pressure because of the lighter (thinner) weight oils, which is what some members discussed.
RG also mentioned the Bearing Wear was due to a lack of engine oil getting there.
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The second part:
do you have oil pressure data at 3,000RPM?Reference value PSI....50.8 @3000 RPM Series 1 RX-8, 72.5 @ 3000 RPM Series II RX-8..at 100c If the NA RX-7 has the same Oil Pump, chain, rotors and Oil Pressure By Pass Valve then the values have to be the same, give or take a few PSI....
The RX-8's Opening Pressure regulator for the Oil Pumps.. S1..64-71 PSI S2..156.6 PSI RX-8's Oil Filter By Pass Open.. S1..11.4-17.1 PSI S2..20.3-26.1 PSI
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Some of this problem may be due to the extra bearing clearance of the Renesis, and the tapered rear main on the shaft. This allows for shaft flex when screaming the engines,
So the 64-71 PSI is not all that far off of your pressure. Any early relief may be disassembled and a few washers dropped in under the spring to bring the cracking pressure up. You can check that with the shop air supply regulator. Or you can buy one from Racing beat as the street high performance regulator (80-85 PSI cracking pressure) as part number 11810. Now you have to call them and ask if this will work on the model of Renesis you have. The series 2 engines have the relief valve in the pump and don't use this style of relief.
It is also possible to improve pressure by changing viscosity and you can minimize foaming by using a racing oil. They have more anti foaming agents and more anti scuffing compounds (Zink). If cold weather starting is not a problem, try a straight weight oil in 30 or 40 weight. Under fill the sump by 1/2 quart.
You can install a baffle plate between the engine and pan to allow bubbles to burst before the oil falls into the pan.
Racing Beat has all of the catalogs on line for free download. Worth the paper.
Lynn E. Hanover
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