Haven't been on the board for awhile b/c I've been busy tearing my built motor all back apart. Some of you may remember I lost oil pressure back in April after only about 1000 miles on my new motor. After getting it all apart I didn't really find any one main cause, but everything - pistons, oil pump asseumbly, rod bearings, cranfshaft bearings, and the crankshaft itself - are all pretty well scored, as if metal filings or shavings went through the lubrcation system and destroyed everything or, a "lack of oil" caused it all to score. I had some big time murky looking oil.

Anyway, I'm saying all this b/c the mechanic I'm working with had some interesting points to say about the oil fed we all tap off the back of the block for our turbos ... I'm wondering if any of you guys have input on some of things he's saying .... I'll paste in his email below:

"The basic setup you have is with a tap coming off that main feed in the middle of the block. I'm not an expert in fluid mechanics but I know that the bulk of the oil is going to take the path of least resistance which I think in this case would be to go to the turbo and starve the main crank bearings for oil. That may not be the case but it is something for us to look inot deeper. I really don't like where this thing picks up it's oil. I did some checking and the mitsu motor (4g63) uses the end of the lube circuit to lube the turbo. I'm not so sure if you can maintain oil pressure in the bottom end of the motor the way it is hooked up now. I'm not sure but I just don't like it. It also makes me wonder since the main bearings were so badly worn but the rods only had debris running through. Maybe the stroke of the cranks is long enough to dunk the rod bearings in the pan oil (??) I looked at the fitting were you turbo hooks up and saw it was restricted but I just don't like stealing oil from the crank to lube that turbo. There is roller bearing in the turbo the hardly needs any oil at all. If it were hooked up at the end of the line in the head somewere I would feel a lot better. The way it is now you are running to different loops. I think that is asking a lot of that pump. I will send you some more pics so you can see what I mean."

So, any feedback would be appreciated. The two questions I would have from all this would be, (1)has anyone on 2GNT fed oil to their turbo differently than off the back of block, and (2)does feeding the turbo this way in fact starve the crankcase for oil?

Sorry this was long guys. :)

As long as oil pressure is still around 55psi that would mean the engine is still getting the same amount. If you were taking too much oil you'd see a big pressure drop.

his theory is correct to some degree, but the fact of the matter is that there are oil passages in the motor to allow for distribution. If oil pressure is built up within the crank case, then it will still filter through the block regardless of where it goes first. Was the return line ever checked?


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know me as santiago
boosted 420a and ej2o..(my 2liter v8 eaters)

Yeah, my return line is fine, no problems there. And I did have sufficent OP when the car was running well, as breif as that was. I believe the reason I lost OP was b/c my oil pump began to score internally and most likely not function as it should, I'm just not certain as to where all these filings came from that caused all the scoring.

and in regsrds to fluid dynamics, he is right in the fact that fluid (oil) will take the path of least resistance. but you have to stop and remember that your running a 4AN sized oil feed line to the turbo so:
A) thats not a great amount of oil to "starve" anything else of and no more or less "restrictive" than anything else in the block, and
B) its a reltively short distanse back to the pan for said oil to get back into circulation, and
C) if the oil tap location was THAT big of a problem, you'd have seen/heard about it long before now and there wouldn't be nearly as many turboed 420a's runnin around.
whatever your issue was that caused your woes, it isn't a result of the oil tap location.

That was my first thought as well, so many guys have done this before it would have been a problem a long time ago. I'm still curious though, is there any other places we could tap to feed the turbo, b/c I may give it a shot when I put this all back together.

It's not the feed line. I bet your oil pickup is borked and sucking up air.

All 5 main bearing oil feed passages are larger than the ID of a -4 line, and all the mains are half grooved. Path of least resistance indeed.

In theory, it shouldn't matter where you get oil for the turbo, as the system is hydraulic (using an incompressable liquid, oil). It is like a fuel rail in the sense that the same pressure is present anyplace in the rail (or anywhere in the fuel system, for that matter). In theory, anyways. Fighting gravity (as well as other resistance) can affect this, somewhat, though.

Some 4G63s pull oil at the oil pump (first in the oiling system), and others pull oil at the head (at the end of the oiling system). Most people with 4G63s, however, wind up pulling oil at the oil pump to ensure good flow to the turbo.

Where would I pull oil? For a conventional turbo, as close to the oil pump as possible, after the oil filter. For a BB turbo, I would entertain the idea of pulling from the head.

I think that the turbo oil feed placement in the oiling system is more likely to affect (and maybe kill) your turbo than is it to affect your motor.

Originally posted by Ducking_Fumbass I think that the turbo oil feed placement in the oiling system is more likely to affect (and maybe kill) your turbo than is it to affect your motor.

absolutely, a guy on the board here was blowing turbos left and right. I went and took a look at his car, took his oil feed out of the head and into the block and he hasn't blown one since. as soon as i saw where the feed line was coming from, i knew that probably had something to do with it.

Well, if that's the case then I'll just feed my turbo the way I've been, I'm already on my 2nd turbo. I guess overall I'm just pissed that my car is all apart again. This is 2 summers in a row now ... I think it's been like over 2 years since I've been a 2GNT meet with my car ... sits all winter, and sits all summer ... why do I even have it?

cause u love us!

Originally posted by techboy
why do I even have it?

You know i ask myself that sometimes too, but it seems im too attached to my car, even tho i hate so much about it.

I guess i just see hope in the future and imagine it running smooth and not leaking anything anywhere, like thats gonna happen....