Oil pressure drop when on boost Saph 2WD

[Andre]

Hi guys.

Haven't posted for a while now but need some help please...
I've just finished rebuilding the gearbox and turbo and installed the MSD wasted spark kit 3 weeks ago and gave it some beans this weekend but noticed some blue smoke coming out the rear and noticed that the oil pressure was coming down when on boost.
All these readings were done with the engine hot and oil at about 100ºC and I'm using 100% synthetic 10w60 oil (it's 40ºC here in Portugal):
I'm getting 45psi on boost (at 4000rpm for example) and when I let go the throttle (still geared) the oil pressure goes up to 55psi. If i give it throttle again it goes down to 45psi.
I had to put oil in the car this weekend (the dip stick was at the lowest) and I haven't done more than 350 miles since it was full.
I have a racetech capillarity gauge.

Could this be a faulty turbo (it's new)? Main bearings? oil pump? all of them?

Can someone help me on this one? I'm getting a bit desperate now... I've had the car for 17 years now but it's becoming more and more frustrating. There is always something terribly wrong with it... I'm about to give up on him...

Thanks, André

[Graham]

odd, as there isnt any relationship between boost and oil pressure

[mrmk2]

Could be sealings in turbo, exhaust goes down return oil pipe to crankhouse and "whips" oil with airbubbles. If so, you should have a lot of pressure in the crankhouse. Check if you have oil in the intercooler, if you have one.

[katana]

Speculating here - boost is loading worn bearing shells to open the clearances on unloaded side dropping oil pressure? Blue smoke on load could be ring blow-by / crankcase pressurisation - is it blowing oil out into catch can?

[Andre]

Wow, Thanks for the replies! All them make sense!

What I've done so far:
-disconnected wastegate actuator and it still does the same thing.
And it does it immediately since the engine is turned on.
-tested compression and got 125psi across all cylinders (4x4 pistons on a 2WD).

What I will do:
-Check oil breather
-Check oil return pipe
-Change oil and Filter

After that:
-Send turbo CHRA back to test pressure.
-Sell the car and forget the last 17 years...

Thanks for all the help guys!

[rallyrob]

Wow, Thanks for the replies! All them make sense!

What I've done so far:
-disconnected wastegate actuator and it still does the same thing.
And it does it immediately since the engine is turned on.
-tested compression and got 125psi across all cylinders (4x4 pistons on a 2WD).

What I will do:
-Check oil breather
-Check oil return pipe
-Change oil and Filter

After that:
-Send turbo CHRA back to test pressure.
-Sell the car and forget the last 17 years...

Thanks for all the help guys!

There's no doubt that owning any kind of Classic Car is definitely a Labour of Love.

Be a shame to get the hump with it after 17yrs though... But don't

Mine's not progressed at all since about 2008 but it's still mine and it's going nowhere.

[Andre]

I'm also going to check the plugs for oil because, with this kind of oil consumption, if it is being burnt inside the compression chamber, the plugs must have some oil.

[Andre]

There's no doubt that owning any kind of Classic Car is definitely a Labour of Love.

Be a shame to get the hump with it after 17yrs though... But don't

Mine's not progressed at all since about 2008 but it's still mine and it's going nowhere.

Don't get me wrong... I've had a love afair with this car for the best part of the time I've owned it.
But, at this moment in my life, I just can't get my head around the fact the all the money I pour into it could be better spent somewhere else that gives me more joy...
I've rebuilt the gearbox myself, installed an MSD wasted spark kit, brand new turbo, new fuel pump wiring, sorted all the electrical bugs and, when I finally get to drive it it's burning oil like there is no tomorrow and the oil pressure starts acting out... All this in the last month because I had the car on stands for 1 year waiting for the gearbox parts...

I've got no one that is an expert on cosworths here in Portugal like you guys have over there. All of you know that, worst case scenario, you can find someone to troubleshoot and solve your problems for money.
I had to do the gearbox myself because no one wanted to do it here...

Honestly, I haven't had a good night sleep since I got it back on the road 15 days ago... Just spend my time rolling in the bed trying to understand what's the problem this time around... It's a joy to drive; true! but can only do that 900km a year... the rest of the time it's broken...

I've just hit rock bottom this time around...

[Miniliteman]

Before you do anything major, try a normal oilpressure gauge first.

[Andre]

Before you do anything major, try a normal oilpressure gauge first.

will do. Makes sense!

[mrmk2]

Don't sell because you got this little hickup, I have learnt a lot of the guys on this forum, and suddenly you are the expert down there who everyone turns to.