DOHC B6 Information

[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.

[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

[bhearts]

And depressurized

[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]

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

Such as? Bigger vaf?

[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]

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]

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.

[zoom zoom]

The oil pressure sending unit need swapped with b6d swaps?

[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.

[bhearts]

What's the order of operation for keeping these engines reliable at 20+ psi? Are OS valves worth it? More than just a mild head port? Are pistons and rods even with it at 220hp levels?

[bhearts]

"Doing it right"the first time can get really expensive quick. Because I couldn't stop any mods from getting done. Race port job, sure. Super balancing of assembly, definitely

[Advancedynamix]

What's the order of operation for keeping these engines reliable at 20+ psi? Are OS valves worth it? More than just a mild head port? Are pistons and rods even with it at 220hp levels?

That's like asking if a beagle is a good dog for a single mom. There are so many ways to make and use 20psi. Same goes for 220hp. I can tell you that the b6t is easy to destroy with more than 15psi on a rhb5 vj turbine. 190hp is the most I would run on that setup. But, a stock b6d bottom end will take 220+ ft.lbs of tq with no issues if the system is designed right. The miata community has had good luck with the 16g and the gt28r. Even a good old super 60 with an external gate will get you 220.

[bhearts]

I was looking at those 16g turbos today. And the 20g

[Advancedynamix]

The oversize valves are being tested shortly. I do believe they are worth the effort. These engines have very small valves. Larger bore will also help with flow because the valve area of the chamber can be relieved more.
They will support 220 stock though. It's been done hundreds of times for over a decade. Visit turbomiata.com for lots of builds. Disregard all the "just go BP" banter. The same guys who push that also think Mazda makes bad oil pumps that explode from engine TQ. As if that makes any sense at all.