So what's your take on this discussion Sav?

As clean as the head port is, I don't like it. The head is fed through a fairly small orifice, so the pressure/flow is already restricted, and pulling from that doesn't seem like a good idea (and the data that DKMakinson posted backs that up).

There's also the fact that Mazda went through the hassle of re-drilling and re-tapping those ports in the block when they did the MSM, instead of just pulling the oil from the head. We'll be sticking with a block feed for our kits.

For the VVT block that doesn't have a pre-drilled port like earlier engines, I still wanted to feed the turbo from a source as close to the oil pump as possible (so, not from the head).

I looked at teeing an adapter under the oil pressure sender but didn't like all the pipe thread ports, and the resulting extra-super-cantilevered sender looked like a disaster waiting to happen. Hokey, kludgy shit.

So my solution was to make a different banjo bolt to replace the stock one that secures the VVT oil pipe to the block. My banjo bolt is identical except it has a -4AN male port protruding from the hex.

Bingo, a clean, bullshit-free turbo oil supply solution that's close to the oilpump yet still sources oil from downstream of the oil filter.

(As an aside, or more fuel for discussion, Keegan frowned at the factory oil port location on the driver side of the block since this galley location diverts oil directly from the rearmost main bearing. So there's that...)

Mazda used that location on thousands of factory turbo vehicles. Everything from the 323GTX to the MSM used that port AFAIK. Keegan is going to have to come up with a lot more than "I don't like it" to counter that kind of empirical data.

Believe me, I hear you. Just passing along the observations of someone who spent a big chunk of his career building Champcar & Nascar engines. His take was more along of lines of: "why deprive the rearmost main when you have an alternative?"

I found that logic hard to argue with.

It's a custom manifold, I have never seen a begi or FM mani in real life.

Dann

I find that logic easy to question, particularly when the alternative is to deprive the head.


The #4 main bearing is fed by a passage only a few inches off of the main oil galley, which is extremely large in diameter- around 1cm, if I recall correctly. There is relatively little restriction in this path, and the amount of oil drawn by a turbocharger as a percentage of the capacity of that passage to supply oil is quite small.

By comparison, the entire head (10 bearings and 16 lifters) is fed through a single, restricted port which is smaller than the port feeding the #4 main bearing. The oil flow through a turbocharger as a percentage of this flow is much larger.

Claiming that a turbocharger is going to deprive the #4 main bearing of oil is like claiming that sucking water out of the Mississippi river through a drinking straw will cause its level to drop. Technically true, but so incredibly insignificant in magnitude as to be entirely dismissable in practice.

The oil supply to the VVT is in the block just off the main galley, between the #3 and #4 mains, and upstream of the restrictor.

Ok. And the relevance of this is... what?

F2T has the same location, for whatever that's worth.

Uhm, that's where I sourced the oil supply for the turbo.

I understand you already said you don't want to end up in a pissing match with me Joe, but hear me out.

I understand the restrictor thing, and we should find out if the HLA cars have the same sized one as the solid lifter cars, because this would tell you pretty quickly that it's definitely good for the solid lifter cars.

I just wanted to point out that the head is under so much little stress than the big ends it's not even funny. If you have ever oil starved a BP, and I have twice, you would know that the head doesn't even care and the very first thing you flog is the number 3 and 4 big ends. The forces in the head are completely laughable compared to your regular 200-250whp turbo miatas big end bearings. We are talking about a hardened cam on a hardened lifter which in the case of solids just needs to be a bit wet with oil on top. Not requiring any pressure at all.

Each cam has 6 bearings each as wide as the rod bearings, and the forces are so low that with the cam belt off and NO oil pressure you can easily put a 4" long spanner on the cam gear bolt and turn them with a finger or 2.

These are just points for consideration.

Dann

There is no "cam bearings" in a miata head...unless you are referring to the casting that the cams sit in (you can't remove those like a conventional bearing). Just clarifying here...

Ah, Gotacha. I thought that this was meant to be relevant to the question of the stock oil outlet on the block vis-a-vis the #4 main bearing.

Yes, I'm sure that the VVT outlet is also a find place to take the turbo oil from, functionally comparable to taking it from the oil pressure sender as is commonly done on the '95 and later Bell / FM kits.





I really can't see how this is relevant. Under normal operation, the amount of oil "consumed" by the hydraulic lifters is nearly zero. Once they're pumped up, they require a significant pressure but very little volume to remain "full."



I'm not sure why I can't quite seem to see things from your point of view, but from where I am standing, the volume of oil consumed by the turbocharger, relative to the capacity of the main oil galley and #4 main passage to supply oil, is trivially insignificant. I'm sure that, in actual practice, the rearmost galley in the head is also capable of supplying a sufficient amount of oil to satisfy the needs of a turbocharger, however the safety margin at this location is simply going to be much lower. That's all.

Insomuch as this location is the alternative that addresses any concerns (no matter how small/perceived, etc) associated with that stock oil outlet on the block, it seems pretty relevant.

BTW here's a pic of said VVT banjo tur-bolt. Stock one on top:

https://www.miataturbo.net/attachmen...ine=1387666100

JKav: Is that the block banjo bolt (PN 9YA3-51-001C) or the upper banjo bolt (PN 9YA3-41-601) that connects the 2 VVT oil feed lines together?

I'm also guessing you made that as a custom part that I can't just order from somewhere...

Thanks!

That banjo bolt is slick as shit. Will that fit the upper banjo that'll give a shorter line. I'm not 100% happy with the cleanness of where I tapped into the VVT connector.

Just curious, would a double banjo bolt setup work for the vvt oil take off?
https://www.miataturbo.net/attachmen...ine=1387669959

Interestingly the IL motorsport kit uses the head port to feed the tubro on its 1.6 NA kits.
http://www.ilmotorsport.de/shop/get_...cc20f7e350d8d6

Have there been reported failures attributed to using the head port?
It is not ideal..... but is it good enough?

That's really the key point in all of this.

It obviously works "well enough," and is hugely unlikely to cause any catastrophic failure. Any damage resulting from this setup, were it to occur, would be extremely gradual and most likely masked as ordinary wear.

The question then becomes- is it worth taking the chance just to save a few feet of hose and a tee fitting?

Block. Yeah, custom.