DOHC B6 Information

[Advancedynamix]

The oil pressure sending unit need swapped with b6d swaps?

Yes, all the stock b3 sensors need to be installed on the b6d. Depending on where you get your engine, some sensors will transfer to the Festiva harness.
Also, you'll want to use the Festiva coolant pipe on the water pump. It's a direct bolt on to the b6d. You can use a Festiva or aspire t-stat housing. The aspire one seems to fit better because the hole is moved back on the DOHC head and the aspire housing isangled forward.

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The oil pressure sending unit need swapped with b6d swaps?

[Advancedynamix]

You can adjust the VAF to work with larger injectors or more fuel pressure or both.
Also, something worth noting, the VAF on a b6t is pegged open long before full boost. I think mine was wide open at like 3psi and 2800rpm. It must be used for low throttle operation only on that setup. I'm not sure how it behaves in the b3 or b6d system. I'll know shortly though.

[bhearts]

I'm thinking about just using this for my supercharger setup. I have b6d injectors running my b3 right now. So I'd have to make a throttle body adaptor, which could rally choke that charger out, which might not be a bad idea. I'm curious though, what happens to the injector signal when the vaf gets flapped open all the way before ecu expects it. I bet I could piggy back that tps off the m90 throttle body if I found a way.

[Advancedynamix]

Such as? Bigger vaf?

No, in fact, the miata 1.6 VAF and Festiva VAF are almost identical. They have a different code, but are interchangeable. They are the same size, and Dragonhealer actually made a little more power with a Festiva VAF on a miata. This was verified on the dyno. We both figure it was just a minor calibration difference, and probably wouldn't be a consistent result if tried under different circumstances.
The modifications necessary to run a b6d on a b3 F.I. system go as follows.
1. The idle stabilizer valve plug wiring needs to be extended because the b6d valve is on the other side of the intake manifold.
2. The throttle body from the Festiva should be used on the b6d manifold. They are the same size, but the b6d tps is different and they aren't easily swapped. The festy TB is a direct fit.
3. The Festiva distributor must be used. It fits the 16v head, but the locking bolt holes don't line up. There are 2 remedies for this. You can shave a couple thousandths off the retaining cap and use it to lock the disty, or you can make a sheet metal adapter plate that bolts the head and the disty together.
4. The intake plumbing will need some custom hose work. This can be done a number of ways, but basically, the idle valve hose routing is different on the b6d and the crank vent hose is in a different place. The engine will run without the idle valve hooked up if you plug all the ports and adjust the idle with the screw and throttle stop. Cold starting and warm up will suffer and it may tend to die if you have the a/c on. If you live in a warm climate and don't have a/c then the idle valve isn't really needed.

Believe it or not, the festy injectors can be used. I would try a set of 1.6 miata injectors, but I can't verify that this works better. They plug right into the festy harness without any mods. Dragonhealer has a b6d festy running on festy injectors and it runs fine (despite the fact that the b6d is a scrap engine that he tossed in to get the car back on the road).

[bhearts]

The B3 management system will run a DOHC B6 engine with some very simple modifications.

Such as? Bigger vaf?

[Advancedynamix]

The purpose of the PCV system is to burn off the hydrocarbon emissions produced in the crankcase from blow by and vaporized oil. These systems rarely bring the crankcase into a vacuum like the pumps used by hot rodders do.
I prefer to run a separator that is vented into the intake tubing (pre throttle valve or turbocharger) because this seems to work the best and it reduces the oily smell that you get from venting to atmosphere. It also keeps the engine bay cleaner, which makes servicing the car less of a hassle.

A properly vented engine is less likely to leak oil from seals and gaskets, it will have less carbon buildup from burning the oil film that comes from the PCV setup, it will have better ring sealing and it will be less prone to detonation.

[bhearts]

And depressurized

[bhearts]

So this really isn't any different than just draining the block vent and valve cover vent strait to the asphalt, except that it drains back into the oil pan? I thought the vacuum from the intake was essential for keeping the crankcase clean of oil fume stuff

[Advancedynamix]

No. There are no check valves in this system. I wanted to vent it back into the turbo inlet pipe, but never got around to making the hard line around the back of the engine. The new owner puts the stock PCV on for emissions. The new engine runs fine with the stock PCV in place, but this system is better for ring sealing and overall performance.

[fastivaca]

Is there a check valve in the vent line?

[Advancedynamix]

Yes, that is all correct. The 4th hose is at the very bottom. The there is a chamber inside the can that baffles the air and separates it from the oil. I don't have any pictures of the factory one, but European and Japanese market cars came with one of these from Mazda.

[fastivaca]

Here you can see it mounted on the firewall. It vents the valve cover and the block to atmosphere. That engine had really bad blow by and I made that separator so I could get to madness6. Without this separator the engine burned lots of oil through the pcv. I eventually broke 2 pistons on the race track on that engine and it didn't lose any oil.

Is this correct?- hose out the top vent to atmosphere, hose off the side to block vent and hose pointing forward to valve cover. Is there a fourth hose going back to the oil pan?

Ian

[fastivaca]

The block vent is below the oil filter and towards the front of the block ( front meaning timing pulley side).
The return is in the oil pan on the b6t only. Both these ports are plugged with rubber caps from the factory. I don't have any really detailed pictures of the separator I made for tweak, but I'll look to see if I've got any of where it's mounted.

I've often wondered what those two plugged pipes were for. Does the air/oil separator replace the PCV system or augment it?

Ian

[Advancedynamix]

Here you can see it mounted on the firewall. It vents the valve cover and the block to atmosphere. That engine had really bad blow by and I made that separator so I could get to madness6. Without this separator the engine burned lots of oil through the pcv. I eventually broke 2 pistons on the race track on that engine and it didn't lose any oil.