Higher oil PSI?

[suprarx7nut]

While I agree with almost all of this, I would like to point out that the Toyota guys have made pretty obvious and major mistakes. The 7m-GTE is well known in part because of one of these mistakes.

Head Bolt Torque specification in combination with the head gasket material was a fault, yes. In their defense, however, the cars still lasted a solid 100k-150k miles before a problem occurred. Not exactly an obvious fault when it takes most cars 7-10 years for the problem to surface. Mine didn't blow its first gasket until 151k miles and 7 years into ownership. It's still a fault, agreed.

The stock Cooler circuit is the most half assed design ever put into a car....

Pressure based means it's active when the Oil is stone cold just when you don't need a cooler.... :nono:

Agreed, the biggest flaw of the factory system is that it is active when the car is cold. However, it is not installed to assist with warm-up time. The car still gets up to temp just fine. It's not as if you need to drive around for 15 minutes extra because the cooler is keeping the oil at ambient temp.

The cooler is present to keep the oil from getting too hot. The factory cooler successfully does this at and beyond factory power levels because the times when you need the cooling (high load) will usually be in situations where the oil pressure is high. Moreover, it performs this task successfully while ensuring the engine never sees pressure below a predetermined level.

Are there any other cars from the same era that have a better factory oil cooling circuit? I'm sure Toyota's isn't the very best in the mk3, but I haven't seen many others from that late 80's early 90's time period.

 

[Piratetip]

Mazda RX-7 oil cooler was designed much better than the Supra.
http://www.rx7club.com/2nd-generation-specific-1986-1992-17/oem-oil-cooler-943711/
Oil Thermostat is located within the oil cooler.
Its basically a full flow system from the factory, like most install on Supra's in the aftermarket....

 

[3p141592654]

It seems likely that Toyota did not use a thermostatic system because they could not get the reliability they needed from it. (Back in the 80s Toyota was so far ahead of their competitors on QA that they literally taught the industry how to do it.)

While it is obvious from looking at your temp gauge when the coolant thermostat fails (and they fail often) it is impossible to know if your oil cooler thermostat has failed without pulling it off and testing it. Those RX7 thermostats are not reliable as many have found out when they buy them used.

 

[Piratetip]

Coolant thermostats don't last forever either.
No parts have an indefinite lifespan.

 

[Grandavi]

I don't mess with my oil cooler simply because I am not a huge fan of altering anything that may fail and kill the engine. If I can monitor it... then we're green lights and bubblegum.

 

[3p141592654]

Coolant thermostats don't last forever either.
No parts have an indefinite lifespan.

That was my point.

 

[Piratetip]

Anyone tested an old oil relief spring rate compared to a brand new part?
Part fatigue has been thoroughly tested for the oil squirters already.

 

[Poodles]

7mgte oil pressure is so low because the M series oil pump design was never meant to deal with the extra leakage points from a DOHC head, turbocharger, oil squirters, and oil cooler relief. This results in LESS oil flow through the bearings. People that think the 7M has low pressure and high flow through the bearings don't understand how a hydrostatic bearing works.

If this was true, the GE and GTE model pumps would be the same...

 

[IJ.]

The standard cooler circuit from memory was 10mm so under dash 6 lines/hoses into quite a small matrix, barely able to keep up with the stock power levels let alone what most modern 7M's make these days...

You can argue till you're blue in the face you're never going to convince me it's worth keeping that junk on the car...

 

[rustfarmer]

I have had bearing failure and believe it was caused by low oil pressure when coming off the interstate after running 80mph on hot day and then pulling up to stop light. The pressure went down and of course the stock cooling came out of the circuit. I always begin by using a known good mechanical gauge, and with a brand new rebuilt engine hot pressure at idle was about 6 to 7 psi (low enough to make your VW gauge idiot lamp flicker). I have installed the DM modified pump, DM braided pump to engine line, remote oil filter, Earl's thermostat, and better oil cooler. Have not finished install and run engine yet, but I will post results and pics once done (maybe a month or so).

 

[MarkIII4Me]

^
Lose the braided line. They are prone to failure. It has been discussed many times that the factory crush bent line does not produce enough of a restriction to warrant replacing. However, if you must then go with Arizona Performance's larger hard line.

http://www.driftmotion.com/AZ-Performance-7M-Oil-Pump-Pipe-p/dm629.htm

 

[super51fan]

^^^^ I agree.

 

[Nick M]

No parts have an indefinite lifespan.

That damn entropy strikes again.

 

[rustfarmer]

Wish I had heard of this sooner. Engine is back in the car and only lacks running oil lines and mounting thermostat and filter housing. The braided line looked great, and wonder in what way it is prone to fail? Seems like the same type of line run on many race cars. Please advise further if possible. Thanks

 

[3p141592654]

Rubber hoses are not designed to be submerged in hot oil. For those application special lines are needed with coating on both the inside and outside (i.e. in-tank fuel lines).

http://www.supramania.com/forums/showthread.php?107011-Chunks-Build&p=1929537&viewfull=1#post1929537

 

[super51fan]

The line lasted two year. I wonder how many miles?

So what if the cooler does not have a thermostat.

Race cars don't go 100,000 miles and have unlimited budgets.

 

[c2mk3]

Hi guys this is my first post in Supra Mania.
I just got done building a supra for my brother and i am in the process of building mine. something to consider when shimming is this: does your 7mgte block has oil squirt nozzles? my brother's engine did not. all i did was Buy OEM pump from Toyota. result: 40psi+ all the way up to the limiter. the upgraded turbo is holding fine & all parts keeping well lubricated. as for me I WILL shim mine (again I bought a OEM oil pump). I figure the oil squirters can cause a drop of oil pressure. I mean they both use the same pump.. but the squirter engine is using oil outside of the oil system circulation since its just tossing it up into the pistons. Anyways thats my input what do you guys think?

 

[3p141592654]

If it doesn't have squirters its not a GTE block, it's a converted GE. The GTE comes with a larger oil pump to make up for the squirter loss.

 

[IJ.]

^
Lose the braided line. They are prone to failure. It has been discussed many times that the factory crush bent line does not produce enough of a restriction to warrant replacing. However, if you must then go with Arizona Performance's larger hard line.

http://www.driftmotion.com/AZ-Performance-7M-Oil-Pump-Pipe-p/dm629.htm

If you must fix something that isn't broken by going to a softline make sure it's braided Teflon.. cheap braided rubber will fail as noted.

If it doesn't have squirters its not a GTE block, it's a converted GE. The GTE comes with a larger oil pump to make up for the squirter loss.

Exception being the very early GTE blocks, only ever seen 1 of those though.

 

[Bmettie]

Shimming the relief valve will do nothing for idle oil pressure. Its a relief valve, meaning when you shim it your adjusting the point at which it "reliefs" oil out of the system and back into the pan. So basically your raising max oil pressure allowed in the system when you shim the valve. Now coating gears to tighten tolerances will raise idle pressure, spinning it faster also will.