High oil pressure?

[Spetz]

Hi everyone,

I have a 6A12 MIVEC Mitsubishi FTO engine that's had a rebuild done.

I use SHU 5W40 in it (manual calls for 5W30) and I installed an oil pressure gauge today.

On cold start up and high idle it goes to 8 bar.
When it reaches temperature and base idle is sits at 2 bar.
When the oil is warmed up (70-80C) the pressure is 1 bar.
When I rev it the pressure goes to 8 bar at around 6,000rpm when the oil is hot.
MIVEC (like VTEC) once engaged should drop the oil pressure.

Does this seem like reasonable oil pressure?
Also when cold the needle is a bit bouncy.

 

[turtlevette]

Maybe the pressure relief is blocked? Or the spring pressure on the relief is too high.

15 psi is kinda low for an engine with new bearings. The answer is to run it and not worry though.

 

[ZeeOSix]

Sounds like the pump's pressure relief valve is set to 8 bars.

Of course oil pressure will decrease as the revs go down and the oil warms up and gets thinner.

What's the service manual say the normal oil pressure should be?

 

[Lubener]

Connect an accurate gauge to really see what the pressure is. 2 bars, eight bars means little.

 

[Trav]

Bar is just another measurement of pressure like psi and totally acceptable, he installed a gauge, whats the problem?

OP 14.5 psi (1 Bar) at hot idle is acceptable but 8 Bar (116 psi) seems a little high, check it against the FSM, some Japanese bike engines run 100 psi at idle and 150 psi at full throttle so its not abnormally high for a high revving engine and may be normal.
When this engine was rebuilt did they know it was going to be raced? If so they may have used a stronger spring on the pressure relief if not it may be stuck if in fact it is out of spec.

 

[mx5miata]

Originally Posted By: Spetz
Hi everyone,

I have a 6A12 MIVEC Mitsubishi FTO engine that's had a rebuild done.

I use SHU 5W40 in it (manual calls for 5W30) and I installed an oil pressure gauge today.

On cold start up and high idle it goes to 8 bar.
When it reaches temperature and base idle is sits at 2 bar.
When the oil is warmed up (70-80C) the pressure is 1 bar.
When I rev it the pressure goes to 8 bar at around 6,000rpm when the oil is hot.
MIVEC (like VTEC) once engaged should drop the oil pressure.

Does this seem like reasonable oil pressure?
Also when cold the needle is a bit bouncy.


I always thought MIVEC VTEC CVVT-I ETC. Uses oil pressure to activate the solenoid. Why would oil pressure drop?

 

[billt460]

Originally Posted By: Spetz
.... Does this seem like reasonable oil pressure?....


Sounds perfectly normal. When I had my Diesel Volkswagen back in Illinois in the Winter, it would peg the oil pressure gauge at 100+ PSI after a cold start. After everything warmed up to operating temperature, it would drop to around 40 PSI at idle. When I told the dealer about this he told me that was perfectly normal. I ran 15w40 Kendal non synthetic oil year round.

 

[MolaKule]

Originally Posted By: Trav
Bar is just another measurement of pressure like psi and totally acceptable, he installed a gauge, whats the problem...?

...When this engine was rebuilt did they know it was going to be raced? If so they may have used a stronger spring on the pressure relief if not it may be stuck if in fact it is out of spec.


Unit converters are all over the internet. We use Pascals as the International unit of pressure.

https://www.unitconverters.net/pressure/bar-to-psi.htm

http://www.npl.co.uk/reference/faqs/pressure-units


I'm with TRAV that the engine rebuilder may have used a stronger spring on the Pressure Relief Valve.


What were the original Oil Pressure specifications?

 

[Snagglefoot]

Originally Posted By: billt460
Originally Posted By: Spetz
.... Does this seem like reasonable oil pressure?....


Sounds perfectly normal. When I had my Diesel Volkswagen back in Illinois in the Winter, it would peg the oil pressure gauge at 100+ PSI after a cold start. After everything warmed up to operating temperature, it would drop to around 40 PSI at idle. When I told the dealer about this he told me that was perfectly normal. I ran 15w40 Kendal non synthetic oil year round.


If you had a plexiglass valve cover you would have seen the oil slowly oozing like peanut butter. This is why they developed 0w40 oils.

 

[BrocLuno]

I suspect the the rebuilder installed a "high pressure pump" ... Common in the rebuilder world. Wastes power and is a bit hard on the pump drive. Dunno how hard it is to get to the pump and the relief spring on this one?

If a simple pan drop, I'd put a "normal" spring in there which is about 50 psi (~4 Bar) and call it good ...

I'd also drop back to xW-30 as the bearing clearances are nice and tight after the rebuild. No need for teh 40 at this time. 100,000 miles later, maybe