I already lost a turbo to crap getting caught in the little oil feed line when the dipstick melted. But when the engine is cold it is common for the internal bypass in the filter to open and let garbage through anyway.

But that was lodged in the oil pump right?

I'm wondering where the hell I can get an AN-6 source now (per BW instructions for EFR's in cold climates with long oil feed lines)

I had a piece kill the turbo before I knew what was going on with the plastic. I initially misdiagnosed the problem as a feed line failure.

So does anyone know if the FSM specifies any sort of "minimum oil pressure" for the head? I guess that would be the final piece of the puzzle here.

I was not able to find it. However, I believe you will find that my head pressure, when hot, when flowing oil out of the hose with restrictor and no Turbo (more than it will in actual turbo use), was greater than the minimums for the bottom end. To me, that clenches it.

Block factory minimum is 7 psi at 1000 RPM and I got 10 at the head while flowing oil.

I have contemplated putting the tee in at the head and moving the factory idiot gauge sender to the head along with my turbo feed. Then if the head got below the factory level for the block, it would show.

Oh snap ok I missed that part the 1st time around - so in this test scenario the head never dipped below the factory minimum for the block, despite bleeding off more than normal.

Your test was flawed.

When I first read this it seemed like you added a restriction and saw a pressure drop?

But we all know that couldn't be the case, but then I reread how you did the test and I see the issue.

https://www.miataturbo.net/attachmen...1&d=1386863572

This does NOT illustrate a ~10psi pressure drop.

Notice how when you added the turbo the pressure increased again? it's because a restriction will add pressure. You needed to do the same test as the middle drawing WITHOUT the restrictor to actually do any sort of reliable test.

But even then it wasn't setup to test the pressure drop as you're only testing the effects of the restrictor/turbo on the flow at THAT particular hole.

You to put the gauge BEFORE the head (oil pressure sender) to see if there's a pressure drop to the entire flow of oil to the head, NOT just the one outlet itself. Or if you used a two gauge setup on the outlet, much like a leakdown tester.

Yeah I basically asked that in post53

Guys, sorry that I did not see these last two posts until today.

Brain. I disagree that I should test as you propose. It would be pretty unconceivable that the pressure at the sending unit would go down. That pressure is controlled by the pressure relief valve of the oil pump. I would be quite surprised to see that drop even in the typical scenario of when the turbo feed is taken there.

Note that I am not measuring pressure drop, but rather pressure change.

I am assuming that the pressure in the head is somewhat uniform after the restrictor that is between the block and the head. That restrictor is what causes: 1) The bottom end oil pressure to remain the same; 2) the pressure in the head to drop, when there is flow.

The pressure goes back up 1psi when adding the turbo because the flow out of the head decreases, meaning the flow into the head also decreases, lowering the pressure drop (now used correctly by me) across the block / head orifice to be less.

If I run a test where I open the port completely, then I hemorage at the head and for sure will get a very low pressure.

The purpose of the test is to determine if drawing oil from that back port would cause the head oil pressure to fall to unsafe (admitedly not defined, but a judgement call) level.

Agreed, that having the gauge in a secondary port would be a little bit better, but it would still need to be a head port, not a block port. That is, after the block / head restrictor.

18: See also posts 54 and 55.

I have not opened the Turbo or the valve cover, but there have been no detectable, negative effects from this oil feed. However, I am not suggesting anyone else do it as I know it is a risk.

Oddly enough, my fucked up Frankenstein car might be of help here.

Running a 94 bottom end with a VVT head, oil sourced from the OEM location, with the factory oil pressure gauge attached.

Cold start shows ~35psi, which slowly drops to about 18psi as the engine & oil warm up. It holds steady there, it'll jump over 20psi if you wind it out all the way. My initial concern was the relatively small delta between idle and redline...I expected to see at least a 10psi difference. I would assume adding a restriction downstream would bump those numbers slightly.

I honestly had no idea what the minimum requirement was to keep the head happy (consensus seems to be 7psi), but I've never had any indication that the head was starving.

This is all with 10w-30 dino oil, and it's predicated on the assumption that the OEM gauge is somewhat accurate.

Calteg could you possibly have a partially stuck-open relief bypass?

I wouldn't be concerned with starving just the head. Sixshooter suggested somewhere that the VVT engines had a larger oil pump to supply the solenoid. What you are measuring is the bottom end oil pressure and that is scary low (though it would not cause my NB1 oil pressure gauge to indicate low pressure).

Maybe others that have put VVT's on older blocks will jump in.

Or see this: VVT with thin oil pump

Possible, but doubtful. All of my oil pressure readings were nominal prior to the VVT head swap. I think it's more so a function of where the oil pressure sender sits. Since it's on the end of the VVT oil feed, a portion of the oil is getting sent to the VVT solenoid before it ever hits the sender.

@DNMakinson...yeah, I'm not thrilled with the oil pressure readings I'm seeing. Part of that is what I spoke to above, and part of that is the fact that I'm still using the 94 oil pump. I think the bottom end oil pressure is fine, my concern is whether I can properly feed the VVT solenoid AND a turbo on the setup I currently have.

Stupid question time: The typical route is to tap the oil pan to feed your turbo. The oil pump supplies pressure if you go this route too, correct?

I made a rookie mistake and started a build around a cheap part (local VVT head). Boo.

No, the normal way to feed oil to the turbo is on 90-95.5 blocks to use the oil feed port of the driver side of the block. On the 96+-05 blocks you put a tee in at the oil pressure sender and run the line around from the passenger's side.

You drill and tap the oil pan for the oil drain line only.

FTFY

Thanks, I fixed my post.

This thread inspired me to take the miata out for the first time in a few months.
My oil pressure nearly mirrored what JasonC SBB noted in the "VVT with thin oil pump" thread:

"With 82*C oil (180*F), I only get
16-17 psi at idle,
28 psi at 3000 RPM, and
38 psi at 6000 RPM."

except mine would barely crack 30psi at 6000rpm.
Can anyone confirm that the NB2 oil pump retrofits?

^Mine has about the same without the VVT head. Engine builder built it somewhat loose because he builds race engines and he knew I was taking it to the track, FML.

Just so I'm clear, you're tracking your car with a maximum of 30 psi oil pressure?

My 1.6 has:

35 psi idle
45 psi cruising constant load on freeway
75 psi WOT

This is based off a second oil pressure gauge I installed and not the factory 1.6 gauge. The factor gauge was even higher than that.

How much oil pressure is too much pressure?

edit: stock 1.6 running rotella t6 synthetic

WOT means nothing. RPM and oil temp are the variables of concern.

No. It's about 45-50 @ 6000 now that I'm using a little thicker oil.

sorry, that's peak pressure so WOT at 6500+ RPM.
I just hooked up an oil temp gauge to I can get that info now but coolant was up to temp.

Great thread, big help! Hope somebody can advise if my oil pressure is normal and OK please.
96 na8, with AVO turbo kit(GT25xx, oil and water cooled), peaks at near 8psi. While prepping for turbo we saw some very high pressures (real gauge tapped off T at normal sender point), ~80psi, then one day nothing. On removing the pan found relief valve stuck open. Removed the slug, cleaned up roughness, refitted. Saw ~60psi on cold start. After turbo , fed with oil from T at sender fitting, fully hot through we see at 1000rpm 16-18psi, 32psi at 2k, 40psi at 4k. We used to get some HLA noise at cold start until recently replacing the oil filter - now pressure comes up quicker, and there is no HLA noise, but there is a not change between start and pressure registering on gauge. Under 2k mi on the oil, 10-50 synthetic.
Sound normal? Has under 60k miles on it, tons of power.
thanks
jp

Just now noticed this thread in which my name was called out. Better three years late than never...

Around 2009, I made precisely this observation and posted the results in another thread. I can't find the exact images which I used there, but here's a recreation based upon a photo I took of the back of a '99 block:

https://www.miataturbo.net/attachmen...ine=1455335521

The red circle marked "A" is the main oil galley, which runs from the front of the block all the way to the back, and is supplied directly by the output of the oil filter. The feed up to the head (through the restrictor) taps off of this line midway, as do all of the feeds which run down to the main crankshaft bearings. The oil pressure sensor hole is also drilled transversely into this line, and in VVT engines, the oil supply to the intake cam is also sourced from the same location.


The blue lines marked "B" outline the casting feature which surrounds the drilled passage running down to the rear main crankshaft bearing.


The green lines marked "C" outline the casting feature which, in the GTX, '90-'93 Miata and MSM blocks is drilled out to supply oil to the turbo. The casting hump is present on all BP blocks, it's simply not drilled out on most of them. If you possess the ability to make a perfectly straight and level hole a few mm wide through five inches of cast iron without deviating by more than 1°, then you can convert any '94-'05 BP block into an MSM block simply by drilling inwards from the outer surface of this casting feature until you reach the diagonal passage (B) which runs from the main galley down to the rear main bearing. This is how Mazda did it in every single factory-turbo variant of the B-series engine.

Here is the spot where you would drill from:

https://www.miataturbo.net/attachmen...ine=1455335521

Note that the commend I made on that image about "early NA block" should read "1.6 or MSM block." That was a very old image from before I'd started thinking about the MSM.



TL;DR: The block casting is identical across all 1.8L B engines, and is conceptually identical (in terms of the oil passages) to all 1.6L blocks, be they 323GTX or stock Miata. Only the machining differs, to expose the oil (and coolant) through casting features which are present regardless of whether the machining operation is performed or not.

So all you need to do is mount the engine block on a lathe and... :)

--Ian

Joe, it cant be that precise. No machine can do that at a mass production level. A true position of 5 thou on that hole is more reasonable given the length, diameter, and material. And then a careful machinist could do it in a freshly rebuilt bridgeport.

The level of precision you have specified (a few thou) is more precise than one the I specified (1° of arc over 5", which comes to an error or .0873", much more than "a few thou.")

So realistically, I could do this with a drill? Maybe.

With a really really rigid drill press, a couple thousand dollars worth of fixture (miata crank mandrel, 18" sin table, etc), a couple days worth of setup, and a few blocks you're willing to scrap till you get it setup right? Sure.

And joe, you're right. I should have done the math out.

I guess i need to look into this. Does it really require this much precision? You're just intersecting another hole. Would be nice to see what size hole the MSM used.

From what I remember of older threads theres a coolant passage you have to miss along with having a small range to do it. If the boss on the block is faced accurately at the factory then maybe you could setup off that and get away with making a smaller jig with a drill bushing based off the boss and maybe be ok. But I dont believe it is.

Actually, I should have done the math first. You're probably much closer to what's actually required; .084" is actually quite a lot of error, given the very narrow passages that we're dealing with.

Easy enough to try.

Go buy a 1" x 6" plank of hard wood. Measure the diameter of a crank main oil passage, and drill a hole that size through the plank the short way, 5" from the edge.

Now, try to perfectly intersect that hole from the perpendicular face 5" away.

Then, imagine doing the same in cast iron.

It seems like you could fixture it by welding up a couple of U-shaped brackets out of square tubing, then bolting them to the head bolt holes on one side and the main cap holes on the other. Set it on its side, put some kind of adjustment screws on it so you can level it, then clamp it down. I would want to use a mill though, not a drill press. TechShop has 'em.

If I still had my old block I'd be tempted to give it a try (I tossed it out when I moved)

--Ian

Couldn't you use a pretty small bit, like 1/4 ? Since it is only going to feed a turbo, which will then neck down to like .030" . A short bit to start the hole, then finish with something longer. I am by no means a precision machinist, but with a mill, some time spent to level things out, I'd go for it.

Is this seriously a discussion we are having?!

I laughed at first, when I noticed it was a multi year old thread.

I guess if you are really hurting for this one specific spot to pull oil from, and your block doesn't have the port...

EDM or GTFO

It is.



Coming up after the break, we'll show you how one Chantilly man fit an MSM exhaust manifold onto his 1.6 engine. And later, residents are shocked by a gruesome discovery involving a local man, his wife, their cats, and a common household item which may pose a lucking danger for all of us.

Stay tuned.

https://www.miataturbo.net/attachmen...ine=1455417857

'94-'95 blocks have this passage drilled from the factory as well. They stopped doing it midway through 1995.

next lets discuss how to convert a bp4w to 1.6
allz you gotta do is weld up the cylinders, then hone em out, and voila, supercar revs

If you get it right, you gain some perceived benefit from pulling the oil from that location vs. from the other side of the motor. More oil pressure to the crank mains, but how much oil pressure are you actually losing off a 40" -4AN line pushing against an .030" restrictor?

If you get it wrong, you scrap a fairly substantial amount of money in engine seals/gaskets, plus a set of bearings and probably a set of rod bolts, plus the cost of the block itself, plus the cost of re-doing all the bore/hone machine work. If you value your time at anything more than minimum wage, you're looking at $1k+ to replace the block if your hand drill deviates substantially.

How do you plan to clean the passage out afterwards? Run the engine with the port unplugged? Use air pressure with the oil filter unplugged and then re-prime the motor afterwards?

All this for what? Have you actually measured the benefit of not pulling from the passenger side?

Who are we even talking to? I was drinking beer, watching supercross, and posting in a three year old thread. I forgot what the question was now. Pass me the chicharrones.

If you were doing this you'd do it on the block before rebuilding it when the block was bare. You do gain the nice benefit of not having an oil line cross the back of the engine and avoid all the oil pressure sender T breaking off issues or the leaky cheap sandwich plate issues.

oil supply
 

I have a 96 na8 block converted to turbo, using the oil sensor port for oil supply - Eng no BP22..... in a Clubbie. As a backup for a rebuild I have just bought off fleabay whats described as a JDM engine, no BP88.... and on inspection it has at the left rear of the block a bolt plugging the outlet described as an oil supply used by the 323GTX etc. Despite the engine no being higher than the 96 it looks like it might be a 94 or 95 block?

jp

If by "higher" you mean the distance from the bottom of the oil pan to the top of the valve cover, all 1.8L BP engines, including all Miata engines from 1994 - 2005, are identical in this measurement (excepting the protrusion of the oil control solenoid on the top of the VVT engines.)

They all had the same bore and stroke, the same rod length, and the same basic head-casting dimensions (although the '99 and later heads had a much superior internal port shape.)

The block casting of all 1.8L BP engines is identical. The only differences are in the machining; the early blocks (as well as the '04-'05 MSM blocks) had the holes cut for oil and coolant on the exhaust side, and the very late engines had a little extra machine work done at the bottom to accommodate the main bearing support plate.

oil thread
 

By 'higher' I meant the number of the engine . The block I am sure is 96 is stamped BP22xxxx, while the unknown one is BP88xxxx, but this one looks like a 95 because it has the turbo feed gallery drilled.
Was NOT talking of block height!

jp

Interesting.

Very little data exists (on English-speaking forums, at least) concerning JDM Miata engines, mostly because apart from the intake manifold on the NB models, they are wholly unremarkable. This isn't Hondaland, where the North American market got watered-down weaksauce while the JDM cars were fitted with monster powerplants.

I can't see any reason why Mazda would have continued machining the turbo oil passage on blocks destined for RHD cars, but I can''t find any data to prove otherwise. By the same token, there is no universal registry of engine numbers that I'm aware of...

I'll see if I can sneak a peak at a JDM NB 1.8 motor to verify some what but I doubt it has the oil passage tapped on the exhaust side.

My NB B6 doesn't have it tapped.

No clear answer? In 10 years???
 

I had just read through all of these posts and there was still no clear answer on if teeing off the back of the head on a BP4W would starve the valve train of oil other than a maybe lol. I personally wouldn’t see a problem with doing so since the valve train wouldn’t necessarily need as much pressure as the bottom end does for it to keep the clearances on the rods and crank. I know the cams have floating bearings and need the pressure, but do they need as much as the bottom end since Mazda had put in that restriction.

Also would there be any benefits on running a vvt oil pump then opening up the restrictions a tiny bit to allow more oil up top to possibly counter act the loss of pressure when teeing off the head to a turbo.

With that being said I’m just going to full send and tap off the head with no changes at all and see what happens, I’ve got a jank BP4W with Eagle rods, that had surface rust and slight pitting, and CP pistons that came with the rods from a $250 motor. I took those rods and pistons and slapped it in a running 96 1.8 block I got for $180 and put in some new bearings but no machining so I wouldn’t be losing too much for science if anything goes wrong. Although I did get the head machined and the whole point of this test is to see if the head is starved of oil…

Anyway it’s been running strong with a 52mm eBay turbo until today when the turbo gave out, so I just ordered a new slightly less cheap eBay turbo and wanted to change the oil feed location cause I hate how the line goes around the motor, so wish me luck if anyone ever comes across this dead thread

I just tried to measure oil pressure from an oil galley on the head on a recent build. The sensor only saw 10-20psi at that location. Move it to the stock OP site, and it’s seeing typical 30-80psi. Use that info however you’d like.

Appreciate curly, that seems to be a massive difference, I may stay with the tee at the OPS but what motor was this test on? Did you have hydraulic lifters or solid lifters? I wonder if they’d be any different even though the block restrictions are the same. I wish the BP4W blocks had that passage on the driver side, it would be so much easier to make it look good.

Although with less pressure in the head the turbo shouldn’t rob so so much especially with a restriction plate, would it even matter? I’m still very torn between this, I guess when I get everything installed I can do my own testing and report back.

I have 43K miles on my turboed BP4W with oil drawn from the driver's side port on the rear of the head (the subject of this thread, and I'm the OP).

Engine is stock and the head has never been off.

I moved the oil pressure switch from the block to the passenger side port on the rear of the head. This switch purportedly activates at 7psi. It goes off within a second of engine start-up and stays off as long as the engine is running.

The turbo is a TD04 (Subie) with a 1mm restricter.

Make a decision and go with it. Squirrels die from indecision.

DNM

Alright sounds good enough to me, I’ll go ahead and use the port from the head