FSM says front oil pressure control valve bypasses at 156 PSI.
 

If this is the case why do people always talk about modding the front oil pressure regulator?


The question is Can i just replace the rear one and be fine? I mean why put washers in there when it will never bypass. Is this something shops came up with to make money or what?

are you talking about the oil thermostat for the eshaft?

THE FSM calls it the oil pressure control valve. The other one is the oil pressure regulator valve, which is the rear one i believe.

Looking at the FSM it looks like it facing vertically under the front cover.

Im not sure about that one either.

some said its bypass at 156 and call pineapple racing bs. but some other shop said it always bypass around the same as the rear regulator and if you mod the rear you should always mod the front by either use a different spring or add shims.

I am more on the latter tho. as I already bought the FD regulator and the spring/plunge from FD.

On the FD regulator subject. According to FC3s.org, I believe, The FD regulator bypasses at 100 and supposedly the s4/s5 engine cant handle that. True or not?

I just need the 85 psi one.

the front reg is to save the hoses or oil cooler rupture if there is blockage in the cooler

its higher rated than the rear reg casue there is significant pressure drop through the oil cooler and its lines and therfore the pressure seen here pre cooler may well be higher than that at the rear reg ( post pressure drop )

if FC,, its fine to just mod the rear reg to lift the system pressure,,, and they cope just the same with 100 psi regs

in FD,, with its 100-110 psi front reg ,,,you have 2 serial oil coolers
and if you lift the rear reg rating,, add to that the pressure drop of two coolers in series ,
then you can expect that the front reg is pretty much close to the 156 psi lift rating
if it lifts,, you can expect that inside the motor,, post the oil cooler, to drop in pressure and flow

in that situation,, you would be foolish NOT to also lift the rate of the front reg to prevent this sort of bypass

I thought that with liquids pressure doesnt drop in pressurized systems. NO matter how long the routing.

OK then,, how is it the 8th sprinkler on the end of a serial hose has the smallest pattern
yet the 8th sprinkler on a ring main system is the same as the others ?

pressure drop in a serial system is cumulative,, and plant engineers have quick sums for number of standard pipe lengths and for the bends

they count the number of pipes,,count the number and type of the bends and can quickly, roughly calculate the sum of the pressure drop and so recommend a pump with sufficient head pressure

-- so the quick answer to your post is a resounding WRONG

Our oil doesnt get sprayed(releasing pressure). Your analogy is flawed.

WHat im saying is that from the oil pump to the rear regulator the psi should be at the oil pumps max unrestricted.(Of course not over 156psi)

Because they don't understand how the oiling system works.

SO its all BS and the front can be ignored when upgrading the oil pressure, right?

I got this from Pineapple racing, Great people :

I guess my post #5 confuses some people, after re-reading it - it confuses me too.

Why no edit button ... :(

Anyway, if you change the rear regulator you should do the same to the front ?

You don't understand basic fluid mechanics very well.

Oil inside an engine gets released through the bearings. The oil is constantly being pushed through the bearing, which is why it needs a constant supply. A higher pressure allows more flow of oil through the same orifice, preventing the bearings from being eaten alive in high RPM situation by offering a stronger "cushion" of oil for to ride on.


Pumps create FLOW, not PRESSURE. A restriction creates PRESSURE, but limits FLOW. Even a completely straight pipe will cause a restriction.

i was recommened by numerous people to leave the front and run an fd reg in the rear for an FC.
I was gonna shim the front as per pineapple but hailers and scathcart convinced me otherwise

how much of a pressure drop is there from the pump through the oil coolers?

#13 was an email I got from guys at Pineapple racing just this morning.

Depends on so many different build factors (bearing clearance, pump clearance, oil line fittings, feed line size, oil viscosity, oil temp, pump type, etc.) that its too hard to say. I've never measured a completely stock engine, but before and after (oiling system mods), with the engine up to operating temp and the oil thermostat open, I've seen 30-60 psi over a wide varierty of set-ups.

This seems like a lot, but keep in mind the stock oil cooler is a dual pass. While dual pass may cool mildly better, it also has 4 times the pressure drop of a single pass coooler.

The above post from pineapple is flawed:

-Anyone with an air compressor can tell you or a fact that the front pressure relief doesn't set off at 240psi, its around 160 psi, like the FSM states. Going above this usually just results in a blown front cover o-ring, and zero increase to total system oil efficiency and pressure.

-Blockage to the oiling system and the engine is fucked, plain and simple. Doesn't matter what the front oil relief bypasses at; if your oil cooler is so clogged as to limit total system pressure, shimming regulators isn't going to make a lick of difference: you'll be peeling your rotors off your e-shaft with a crowbar.

-You can't have a cooler that's both efficient and massively restrictive: that's a total misnomer.

While pineapple tends to provide great customer servuce, their advice on this subject is based on a lack of first-hand research.


The front oil pressure relief is there to prevent blowing the front cover off the engine during cold starts, when the engine is cold. Despite the oil bypassing the oil cooler, cold oil will still develop massive oil pressures through the lines at modarate RPMS`s. Shimming the front cover will have zero effect on the engine once it is up to operatng temp.

If you can keep off the throttle until your engine is warm, you can completely delete the front oil pressure relief valve. If you want higher engine oil pressure during normal driving, repalce the rear iron regulator.

Yes. Think about how the system works.

Series rated system, pressurized source.

Oil begins at a set pressure, dropping to atmospheric by the time it reaches the oil pan. The oil lines, cooler, filter, passages, and bearings all work in series, each providing a pressure drop. There is a measurable difference in oil pressure before-and-after the oil cooler, as well as between the front and rear iron oil passages (the front bearing has an extra 270 degrees of directional change change compared to the rear).
Source oil pressure will always be higher than regulator source due to pressure drops created across the front cover, cooler lines, oil passages, and oil cooler.

Wrong.

Rear OPR sets the oil pressure that the bearings and jets see. If we increase this value, we increase the load bearing capacity of the bearings, and the total load capacity of the engine.

If we increase the front OPR, all we do is increase the release pressure of the front cover passages and cooler-lineset. This only has an effect during cold starts.

How was your engine performing after not shimming the front valve? Did the pressures stay steady? What sort of climate do you live in? Thanks

welcome to the board. :)

his profile shows that he hasn't logged in since January 2020.

maybe you can get an answer from his build thread: https://www.rx7club.com/build-thread...#&gid=1&pid=26

I am happy this thread got bumped from twelve years ago so we could get another opportunity to laugh at this statement.

FWIW, I have never shimmed a front regulator because I figure that Mazda bothered with the expense of a front regulator to prevent the lines and cooler from blowing out, and speced the pressure relief accordingly. I'd rather risk losing a little oil pressure in the engine than blow an oil cooler or line apart, which has worse outcomes.