ayrton012

Sorry I can't sleep well for days because of this pressure riddle, so my mind gets slow now.

olddragger

iTrader: (3)

we will soon see what the regulator mod(shims also) will do. Maybe by this w/e/
OD

madcows

What I find interesting is the fact that while the FC turbo supposedly has a larger displacement oil pump than the non-turbo (and the 12A presumeably? Sorry, I can't remember everything said 800 posts later), yet they are rated as having similar OP @3k. So, the oil circuit is in question, though I don't know if there are any differences (between T and N/A 13Bs) except for the turbo plumbing.

This discrepancy also occurs between the S1 renny, and the N/A FC 13b which supposedly have the same oil pump. If the 13b-msp is only at ~50psi @ 3k (15-20psi less than front valve opening pressure) while the FC is already at 70psi though they have the same pump means there much be a pretty noticable difference in the oiling system (and I don't think it's the coolers). Difference as in the msp has less restriction to oil flow in the system. I'll be damned if front shims raise the OP @3k.

I would love to try it out on mine, but I already got a car in the garage that needs to get finished. Looks like it's up to you for now, od and ayrton. I can't wait to know!

olddragger

iTrader: (3)

soon
at 3k and 170f oil temp with 15w/40 my pressure before any mods is approx 63psi
OD

ASH8

Yes mate you have it correct...

The Front pressure Spring, Plunger/Piston and Oil Bleeding NUT (# 0839-14-)
is originally from and used in the 1971-72 12A Mazda RX-2 and is carried over EXACTLY to the 1985 13B FC RX-7 with or without TURBO (same Front Relief Valve parts), but, the Turbo's FC and FD have the larger Displacement Rotors (because of the Turbo Oil Feed line), as there are NO other differences from the Front Oil Circuit area apart from a different Spring by Part Number, also the FD Turbo (only) does have a different REAR By Pass Valve Assembly though).

In regard to the S1 RX-8's Front Valve, all the parts are identical to the FC (NA and Turbo), all except for the Front Spring by Part Number.

It would be great if OD and Aryton replace the spring to the FC one # 0839-14-273A, instead of shimming, because how many shims do you really need?

secret8gent

Shimming should be enough to get the pressure through the stock OC's. A rear upgrade would help to increase OP levels above what stock 'should' be. Right?

Though I guess the real question is, while you have the pan dropped, why not do what you can?

madcows

Well, there is a point where if you try going over a certain psi (~90?), you will need both front and rear bypasses modified.

madcows

I forget - is your extra cooler for oil or coolant?

Hmm, if you see 63psi at the sandwich plate, it might not be unreasonable that the pressure in front of the cooler is high enough to start opening the front bypass. If that's the case, then shims (or FC spring - though it might allow more pressure than the coolers can handle(?)) would obviously increase your OP @3k. But that's also using 15w-40, so lower weight oils would have a different result. As it was discussed before, I think anyone using heavier oils should really be doing this bypass mod!

9krpmrx8

iTrader: (46)

When I went to the single oil cooler I also upped my oil to 0W-40.

ayrton012

So I was testing the front regulator this weekend, but I begin the story with the front regulator's "piston", which is opening and closing the oil bypass hole in the front regulator "cylinder"



Here are the closer pictures about the piston. It shows wearing signs (like polished) and longitudial scratches. This engine ran only 13000 miles. This kind of wearing tells me, that the piston is moving up and down frequently in the S1. Am I wrong? What is your opinion?



....


...

...

ayrton012

I took out the oil pump's pick up pipe (I dont know its english name), and plugged in the pump's "oil in" hole to avoid air leaking while I will testing with high air pressure.



I made a T adapter to connect my high pressure compressor to the oil pump's "oil out to the coolers" hole, and an oil pressure gauge. (We are calibrating our gauges every half of a year.)



...

ayrton012

About the result of the test:

Well, I did not experienced exactly that what I was waiting for. Strange, but the front regulator valve was bypassing a lot of air even at very low pressure from my compressor. The air was coming out like a tornado from the little hole of the regulator's end screw, when I saw only 20 PSI ( from 20 PSI) on the gauge.
------------------------------------------

My service compressor is able to store 174 PSI in its tank. When the pressure reached the 174 PSI in the compressor's tank, I switched off the comp. power. After that I stucked my eyes on the compressor pressure gauge, and the other pressure gauge, that was connected the T adapter of the oil pump's "oil out" hole. Don't forget, my compressor was directly connected to the "front regulator-oil out hole" section.

The data was the nexts while the pressure goes down continuously:

Compressor's pressure: 174 PSI Front regulator section pressure: 108,7 PSI
Compressor's pressure: 166,7 PSI Front regulator section pressure: 121,8 PSI
Compressor's pressure: 143,5 PSI Front regulator section pressure: 101,5 PSI
Compressor's pressure: 127,6 PSI Front regulator section pressure: 87,02 PSI
Compressor's pressure: 104,4 PSI Front regulator section pressure: 72,5 PSI

I think it shows that the front regulator is able to bypassing a lot of oil (pressure-flow) quickly which is coming from the oil pump.

I hope it was clear that I was writing and you are understanding the method of my test.., because of my "far from perfect" english.

ayrton012

Good idea! I checked it quickly, but the European Mazda has not got this spring in stock now. If they won't has it in short time, I will stay at the shims. I will make a paper seal for the oil pan, so I won't have to fight with the silicon glue while I will testing the right thickness of the shim, shims.
After I found the suitable shims I will use the silicon glue again for sealing the oil pan.

madcows

Thanks for your contribution, ayrton! (and good idea on blocking the oil pickup location)

To be honest, I was not expecting those results. As Phillip mentioned (I believe it was him), air under pressure should always flow between the regulator's cylinder wall and piston as there is no sealing system in place, but apparently the tolerances are fine enough to make this (edit: not) a real issue - especially when it's oil that's flowing.

As for the scratches on the piston, it would be interesting to compare it to a new one. If a new one is polished without scratches like this one, then it might be fair to conclude that this piston is in fact moving around under normal conditions, and not when there is "severe blockage".

Back to your results.. Besides for your reading at 174psi compressor pressure, and to some extent, your 104psi compressor pressure reading, the regulator is dropping ~40psi (the lower the compressor pressure, the slightly lower the drop through the bypass). This shows the interesting dynamic of these units - they can't simply regulate the OP regardless of flow to ~70psi. The more flow you have, the higher the pressure that you will see. This also has me thinking that the increase in pressure you get when using high viscosity oils isn't as dangerous as some have suggested. Since the thicker oil wont flow through the bypass as easily as lower visc oil, the volume being bypassed might not be that substantial even though pressure is at the beginning of the bypass threshold.


Also, that spring looks a lot more substantial than I originally thought for some reason. It's around 6.5cm fully extended? It looks like at full compression it would be around 5cm.. I think shims is a satisfactory way to up the regulated pressure threshold. Ayrton, if you're going to play with it some more, do you think you can take some close-up shots of inside the bypass cylinder?

ASH8

Interesting...

Piston looks almost normal to me...I almost guarantee if you bought a new Plunger/Piston (0839-14-115) (Mazda Europe should have this one), you would see similar markings.

These front Relief Valve parts are not a "seller" so it does not surprise me Mazda Europe does not stock the earlier model Spring as it was last used almost 20 years ago.
Japan, would have it.

I think I have said before, I have never sold any of the front piston or spring.
The rear regulator piston, YES, because it is also used in Mazda's Banger 'oil pump'.
0221-14-115 and 0221-14-116.

Ayrton, you could try the RX-7 FD Spring (Mazda Europe "may" have it) to compare with the RX-8's, the 7 uses the same piston and nut. (N3A1-14-273A Spring)

olddragger

iTrader: (3)

good data --thanks.
so the front regulator is bleeding off a good bit of flow?
There fore it would be the front that is really controlling the pressure at this point? not forgetting that other things in the total system have their own affect on pressure/flow?
Is this safe to say?
OD

madcows

To me, it sounds like the front regulator is what's ultimately controlling the pressure with the stock cooling system. With a high-flow system, it might be a little bit of both.

ASH8

Off Topic...but I just noticed the 09's (S2's) have an "O" Ring for the 'new" Water Pump instead of the typical Gasket!...gee, I don't know how this one will go along with the 'plastic" impeller after many years of use???

I can't ever recall Mazda having an O Ring for a water pump fixing.....No I can't, they were always a paper type gasket....

I wonder why they did this?

9krpmrx8

iTrader: (46)

Just my thoughts but my Honda's were always "o" ring gaskets on the water pumps and it was never an issue.

ASH8

Oh..OK..9K, being a Mazda Parts man and a Mazda ONLY sort of Guy...I have not seen Mazda use an O ring before..

So, in your Honda's the O ring is pretty reliable?

9krpmrx8

iTrader: (46)

Yeah I have built many D and B series Honda motors over the past 15 years and I can't think of a water pump gasket ever failing and in all my years on www.honda-acura.net I don't remember it ever being an issue. The "O" ring did sit in a groove though if that means anything.

ASH8

Yeah, I think this would be the same for the S2 Water Pump..in a GROOVE that is..

Seen plenty of other uses for O rings in Mazda engines..like Oil Control Ring O rings, Oil Galleries, Rotor Housings, Oil Pumps, etc..

Thanks mate...

ayrton012

I'm glad if I could help something to solve this mistery. Yes, the air can flow easier then oil, but the pressure (no matter it is oil or air) definitely makes the piston moving down in the cylinder, even at the very low pressure. Actually the piston close airtight at the end position in the cylinder. The question is, that the little hole on the end screw only gets oil or air from between the walls (piston-cylinder), there is no oil channel to it, and the real bypass hole of the cylinder (upper on its wall) is about 0,3 inch (8mm) far from the oil channel. Is the oil leaking between the walls like air but smaller amount, or the better sealing (higher pressure) can push down the piston 7-8 mm down to open the big bypass hole?


I was trying to make a useable shots about the cylinder, but I couldn't do one. But I did not spend much time with it, so I will play again.

ayrton012

Thanks the infos Ash! If I would be able to get an FD spring, that would be a big step forward.
Edit: Now I checked it too, they do not have it.

Anyway a take here my worse shots about the piston-plunger:

ayrton012

I agree with this.