olddragger

iTrader: (3)

hahahahaha--now that is going to pop some heads! And you are right!
OD

dannobre

iTrader: (3)

I was talking about a specific system...the engine in this car with a bypass regulator....Higher bypass pressure will result in more flow below the cracking pressure of the regulator

Still think I'm wrong?

Or do you want to go to a fluid dynamics argument? This is getting stupid

ayrton012

Maybe I'm close to the whole idea, over the regulators mod, a single cooler mod with oil temp, and pressure gauges...and much more.

Peace

ASH8

Todd, If this is the case then why are there different Oil Pressure numbers at 3000RPM for the Series 1 RX-8 (5W20) and the FC RX-7 (20W50), when Both use the exact same Oil Pump, the exact same Rear By Pass Valve.

The FC has One small oil cooler (under radiator), the Rx-8 has two separate oil coolers further from oil pump.

Oil Pressure Numbers taken by factory oil pressure tool 49-0187-230 at same location (oil filter neck)..

Can someone please explain?

rotaryPilot

So you are saying that the pump will always pump the same volume of two fluids no matter their viscosity.

As a result, whether you pump honey or water the same volume of this fluid over fixed time interval is pumped? Are you sure that this correct?

Flashwing

Yes, absolutely.

Hard to say why there would be two different pressure values. You're talking about two different oil systems. The issue being discussed was the rate of flow, not the pressure. If one oil system provides more resistance to flow than another then you will see pressure differentials between the two systems.

rotaryPilot

Ok So in case that Positive Displacement Pump always pumps the same volume independent from oil viscosity how do you comment on the following statement/diagrams that clearly shows how a positive displacement pump is affected concerning flow and efficiency by altering the viscosity ? I am referring to PD pumps

PhillipM

I went through this on the other thread...it's from the seepage past the seals, however, if you can find a graph with pump rpms vs output in differing viscosities, that might upset a few people too....

Spin9k

Same here, except a no-mess job from above. Using my evacuator, suck, jack the passenger side up, suck, lift from the front, suck. That drains the oil coolers and pan quite well. I normally get ~6qts of the 6.7qts in there.

olddragger

iTrader: (3)

what oil has a cst of 500?
Thats more like chassis grease?
OD

DarkBrew

I think a lot of us are looking at this on a first-approximation level whereas you want to calculate it down to 10 decimal places. No problem. Peace.
The simple math says that this mod gives the engine internals more pressure and flow above the opening of the stock pressure relief valve. Below it makes no difference.

I wanted to ensure that my engine maintains good flow under all circumstances of weather and driving style. Given the low oil pressure of the series 1 engine this seems like an excellent reliability mod.

HiFlite999

iTrader: (2)

Your chart proves the point. Over any reasonable viscosity range the volumetric output of a displacement pump is constant per pump revolution. Pump *efficiency* falls off because a high viscosity resists being moved more than a lighter one, so it takes more power to turn the pump shaft. (Part of the reasons for manufacturers going to lighter oils is exactly that, reduced pumping losses give better gas mileage.)

HiFlite999

iTrader: (2)

In a word, yes. I'll try yet again.

Say you look at pressure and flow at 3000 rpm. The value for 5W20 I had was about 50 psi. When I switched to 15W-40, that value under about the same conditions otherwise was 60 psi. Since the bypass valve is closed, the oil system from the oil pump to the point oil leaks through the bearings into the engine is hydralically locked. This means the flow is exactly the same for the light oil vs. the heavy, even though the pressure in the latter case is different.

For a displacement pump, the pressure of the fluid being pumped does not at all affect the volume being pumped (within reason).

(Using round numbers here), increase the rpm to 4000, and you get 60 psi for the light and 70 psi for the heavy oil; still both cases are flowing the same oil volume.

A slight increase in rpm from there, causes the bypass to open for the heavy oil, resulting in no increase in flow for the heavy case, but more flow in the light-oil case because since it's running 10 psi less, the valve hasn't yet opened. That flow difference will increase as the rpm increases until the bypass valve opens for the 5-20W oil too. From that point on, the light-oil case will be flowing a greater volume than the heavy-oil case.

For our systems, a higher bypass valve opening pressure allows an increase in flow above the pressure range allowed by the original valve. Below that range, there is no difference at all.

Academic exercise?

What I'm trying in multiple ways to get across is that the equation: more pressure = more flow is only true sometimes and is false more often than not. Even everyday experience with a garden hose nozzle will show that it's not true.

DarkBrew

Hey, HiFlite999, want to come join the other oil pressure thread?

https://www.rx8club.com/series-i-aftermarket-performance-modifications-23/increased-oil-pressure-really-needed-205900/

There seems to be a misconception that the Re Oil Pressure mod somehow achieves higher pressure through higher restriction through the engine passages...
Having done this mod I can assure everyone that this mod only affects the point at which the bypass back to the pan opens. There is no oil system restriction and the flow will be the same (at lower pressure) or higher (above the original valve opening pressure) than stock under all circumstances for any given viscosity.

nycgps

iTrader: (1)

maybe I should really get an oil extractor.

ASH8

The only difference in the Oil System are the Coolers and Lines, everything else is Identical to the FC of 25 years ago.

And yes, Sorry, my question was about OP, you were talking Flow.

Phillip, you are talking Oil Pump?, there are no real "Seals" as such, it is metal to metal...you know that...but yeah, there is 'some' seepage from any Oil Pump...

It is interesting...talking viscosity/pressure....and as I have said many times before, the rear By Pass Valve in OEM S1 RX-8's was First used in 1976, 3648-14-250 (RX-5) 13B that is 34 years ago, back then 5W20 never existed....the S1's Oil Pump is from 1985, (FC RX-7), also back then 5W20 did not exist...

Clearly, IMO Mazda should have used the FD Oil Pump and BPV set up in the Series 1 RX-8, rather than any 'alleged restrictions' in Oil Coolers or Lines or Cooler Thermostat to bump up Oil Pressure as it did not work, particularly NA market with 5W20...History .

9krpmrx8

iTrader: (46)

I was looking at an FC recently at a meet and the oil cooler setup is pretty close to what I have with my Fluidyne.

PhillipM

Still a seal

Viscosity makes a big difference in bleed paths like that, 's why your dampers feel a lot stiffer when it's cold outside.
As I've said before, higher viscosity = earlier opening of the bypass valves = less flow = thinner oil film + more heat at high revs...that's without even considering the cavitiation on an oil pump with such a wide operating rpm range.
Obviously there's a balancing point, but I'll stay with my 0w-30...

nycgps

iTrader: (1)

with so many parts (not just oil pump, I have an FC so I know which parts are the same) being the same and FC use 20w50 with much less hp. hmm. I will stick with 20w50 (or maybe 15w50 for winter)

olddragger

iTrader: (3)

guys all this flow/pressure is only related to lubrication IF the lubricate has the film strength to do the job. Pressure/flow is totally irrelevant if your oil lacks the required film strength.
Do not forget that point?
Point being you can flow all you want of a 5w/20 etc and your engine will still not get proper lubrication.In many minds including what is left of mine minimal viscosity generally speaking should be nothing lighter than a 10w/40.. And it should be an oil that will hold its viscosity.
OD

Flashwing

I wonder how long it's going to take people to realize the RX8 is not an RX7. I'm amazed at how many people continue to deny this fact.

nycgps

iTrader: (1)

im also amazed they shared so many parts, including parts that will see the love of oil. difference is that the same part is having much more work to do now (pushing more power)

FC is known to have oil pressure issue (too low), so a lot of owners increase the oil pressure to around 100 psi

- either by using a press to "squeeze" the stock oil pressure regulator, use FD regulator, or use MFR's adjustable regulator (expensive ****)

Mazda is just stupid enough to leave S1's Rx-8 the way it is (oil pressure). Its using most of the parts as FC but it's pushing like 50% more power.

At least I think they got the S2 right, somewhat.

SARRAS

So how hard / possible is it to fit an FD Pump? BTW what manufacture years is FD?

ASH8

Just to set the record straight...Mazda's like most Oil Pumps have No Seals Internally, None.

Dampers or Struts or Shock-absorbers have a Seal at the top of casing that shock chromed piston moves inside through a rubber (usually) round Seal.

There are Far more Parts that are from the FC RX-7 than are exclusive only to an RX-8 short engine wise including Oil Pump, Oil Pump Rotors, Drive Chain, Sprockets, Rear By Pass Valve, Oil Pump Relief Piston, Rotor Oil Rings, Springs, Bearings, Oil Filter, Rotor Housing Seals, etc,etc, etc, ALL from 1985 FC RX-7....a Part Number is a Part Number...and these are ALL Identical.

The Series 1 RX-8 engine core is directly from the FC, of course the main differences are side exhaust ports through iron housings and intake system which is exclusively RENESIS...no one has ever said the RX-8 is and RX-7...only Many many engine parts.

No internal Seals in any Mazda Rotary Oil Pumps from 1970-2008

ASH8

FD RX-7 Oil Pumps are virtually identical in all areas except the Oil Pump Rotor set and the separation middle plate between the rotors.
FD Rotors are 5mm wider than FC or FE (RX-8) Rotors, middle plate is thinner.

Oil Pump Sprocket is identical and so is the Drive Chain.

So yes, an FD Oil Pump should fit without installation issues.

How to do it, you need to remove the front Alloy Timing Cover to expose the Oil Pump assembly, pretty easy if engine is out, a lot, lot more work if engine is still mounted in engine bay.

FD RX-7's were made in 4 Series while sold in the Australian market,
From Jan 1992, August 1993, July 1994, Jan 1996, I think there was one more minor update for JDM only in 1998-9 until it ceased in Japan market only in 2002...then the Series 1 RX-8 was made from April 2003, and Series 2 in April 2008...these are all production Start dates.