Das Beast: My E30 track / street build

[digger]

So the purpose of removing the block mounted pressure relief is to stop it sticking in the fully open position?

[dvallis]

Yeah. I've read a lot of threads here, over at E30 Tech (before it died) and on Spec30 about oil problems. You were on some of them. The pressure relief valve failing seems to be a common theme. Getting rid of it means one less thing to break.

[moatilliatta]

Properly cut valve seats don't need lapped in, and should not be lapped in.

More cage pics though!

[dvallis]

Machinist used a fancy CNC to cut the seats, so we're fine. Lapping was more a placebo than mechanical requirement.

My cage builder is an Artiste. She won't be rushed. Kind of like the Soup Nazi. "Cage is ready when cage is ready." :devil:

[dvallis]

Turbo Time

Working on the downpipe design now. Seems to me this should be a stock item for RSI exhaust manifolds and an M20 engine. If anyone is interested in a group buy, PM me.

Here's the manifold, turbo and waste gate test fitted. Going to make some CAD drawings from this view. No laughing at my ghetto temporary turbo bolts.

Notice how the turbo exhaust is angled UP? That's unexpected. Unless the M20 engine sits at an angle in the car. Anyone know offhand?



Here's a top view. Notice how the turbo exhaust is angled towards the engine. Didn't expect that either.



Turbo outlet is a V-flange, flat, 3-5/8" lip, 3" ID. This is different from others I've seen with a secondary male or female inside lip. Good to know.



Final bit tonight ... permanent heater core delete. Here are the parts. Modified head fitting (chopped and filled with JB Weld), fabricated sheet metal backing and stock sealing gasket.



Installed on the head.

[digger]

Properly cut valve seats don't need lapped in, and should not be lapped in.

strictly speaking this is true, the lapping at most should be used to check the quality of the valve job and the position of contact on the seat after using a cutter or stone, done by a quick spin or two, its not to remove actual material to help it seal. if you rely on the lapping to get it to seal it wont seal well, lapping is the wrong process on anything but seats that are good to begin with. the valve spins on the seat anyway so they will bed in together

in the case here lapping them wont hurt anything as they were recut first, as long as all the grit was removed properly its not an issue

[jeffnhiscars]

I'm with digger on lapping. My machinist says I don't need to but I've never heard it said you shouldn't.

[sonomabimmers]

Engine at machine shop. Will have updates next week.

what machine shop are you using here in austin?

[peterman]

I did the same thing with my oil pump but I was wondering if there will be a noticeable difference because the hole that the pump sucks in from remains the same.


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Oil pumps are positive displacement pumps and oil is considered an incompressible fluid. Yes the viscosity changes with change in temp. Their volumetric flow rate is directly proportional to the speed of the pump. The oil passages in the block are a specific size so that oil pressure is maintained at the bearing surfaces. Increasing these cross sectional areas will not get you increased oil pressure or a better oil supply. The Germans were not having a "bad day" when they designed the system. You may be underestimating the number of calculations that occurred to get proper oil pressure to every bearing surface in the engine. You can increase the intake of the pump all you want, pump efficiency and the passages will define how much fluid flows through. I suspect the BMW engineers sized the pump intake for proper flow, manufacturability, and reliability.

I don't know about the pressure relief delete mod. That sounds like a bad idea. If you start this up on a cold morning you could crack a cam journal in the head with the excess pressure of the extra viscous oil. I'm not sure how much pressure will build, but I know my gauge sits at 60psi when the engine is cold. You can shut down an engine if you get low oil pressure, you can't avoid too much oil pressure until it grenades. Again, the engineers were concerned about something breaking enough to install a pressure relief valve.

[digger]

it doesn't hurt to blend transitions as these make the aperture act smaller than it really is. MM do this with their blue printed oil pumps

In theory you could make a smaller intermediate shaft gear to spin the pump slighty faster it wouldn't be hard to design one but youd be limited by the amount of adjustment in the timing belt tensioner

[dvallis]

I'm not sure how much pressure will build, but I know my gauge sits at 60psi when the engine is cold. You can shut down an engine if you get low oil pressure, you can't avoid too much oil pressure until it grenades. Again, the engineers were concerned about something breaking enough to install a pressure relief valve.

There are two pressure relief valves: one in the block, one in the pump. I'm deleting the block valve and modifying the oil pump pressure relief valve to open at ~75 psi. Same result but one less thing to break.

[peterman]

There are two pressure relief valves: one in the block, one in the pump. I'm deleting the block valve and modifying the oil pump pressure relief valve to open at ~75 psi. Same result but one less thing to break.

Good move. I just read your post on modifying the oil pump pressure relief valve. You get the right idea on calculating the spring rates, but you may want to actually double check your calcs by calculating actual pressure over the valve surface area, just to make sure what you calculated using interpolation matches up with a from scratch calculation.

[tonygrig]

WOW. This build thread is amazing, I'm working on something similar minus the GIANT turbo! :) Subscribed.

[dvallis]

Final numbers on the oil pump replacement spring:

Toyota 9008050248 ~$2
Outside diameter: 0.890" (-0.055)
Free length: 1.825" (+0.132)
Installed height: 1.350" (+0.051)
Rate: 120 lbs/in
Seat pressure: 46 lbs
Calculated oil pressure (cold): 75 psi

New spring and tester arrived today. Will check it out and post results.

[peterman]

Final numbers on the oil pump replacement spring:

Toyota 9008050248 ~$2
Outside diameter: 0.890" (-0.055)
Free length: 1.825" (+0.132)
Installed height: 1.350" (+0.051)
Rate: 120 lbs/in
Seat pressure: 46 lbs
Calculated oil pressure (cold): 75 psi

New spring and tester arrived today. Will check it out and post results.

Thats a seat pressure of 57 lbs
(1.825 - 1.35)in× 120lbs/in = 57 lbs

Unless I'm missing something...
What's the diameter of the working part of the valve?
Looks to be about 22mm-ish in which case -
Thats a surface area of .589"^2
75lbs/in^2 * .589"^2 = 44lbs of force to get the valve to open.

A more exact dimension on the valve diameter will yield more exact results, obviously.

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