DOHC B6 Information

[EscortSportage]

Have any B6D oil pans laying around?

[theastronaut]

A XR2 ecu is the only one that will work, or possibly a 323 GT/GTX but those would be even harder to find. Most people parting out Capris keep the engine/harness/ecu together so finding an ecu won't be easy.

[Jesse Norris]

Hi there,
I'm looking at fixing up an old capri xr2 that has been sitting for years, and I've found out the ecu is dead due to water damage. I saw your 2016 post regarding the similarities of these engines, and since I cannot find an xr2 ecu anywhere, what would be the best system to buy or modify in place of the original ecu? (as you said something such as a b3 engine management system could run a b6 with simple modifications)

Thanks,

Jesse Norris

[Dragonhealer]

We have stopped cutting heads to get compression, but yes, you can get 10:1, you will have no room for better cams, and if the valves float, they will bend.
87 octane will depend on your tune.

[Kevrone1288]

If the B3 intake manifold will bolt on, the simplest swap is to put the relevant B3 parts on the B5 long block, this retains the B3 management.
if you wish to run it as it ran in the Familia, that's harder, you will need the Familia harness (or most of it!) And ECU and probably other parts I'm not thinking of......and a lot more time!

If the B3 intake won't bolt on, there may be a carby B6 manifold that will.

Not to post in a reasonably old post, I was told shaving the b6d head on a manual n/a b6d would bump the compression up around 10:1? be safe on 87?

[Dragonhealer]

If the B3 intake manifold will bolt on, the simplest swap is to put the relevant B3 parts on the B5 long block, this retains the B3 management.
if you wish to run it as it ran in the Familia, that's harder, you will need the Familia harness (or most of it!) And ECU and probably other parts I'm not thinking of......and a lot more time!

If the B3 intake won't bolt on, there may be a carby B6 manifold that will.

[121MOXY]

Engine will run perfectly on B3 management

Thanks for the reply! Just checking on this, my car is Carby at the moment, and the new engine is Single Point, Throttle Body Injection.
What ECU will run this motor? Can I use any old Familia ECU or does it have to be specific to the engine?
Sorry I am really new to EFI.

Cheers,
Sam

[Dragonhealer]

The B5 will match up to the E series trans, use B3 flywheel and clutch.
As we did not get this exact variant in the US, I don't know which manifolds will bolt directly to the B5 head. Some fetteling/fabrication may be required.
B5 advantages:
Shorter stroke allows higher revs
Exhaust system can stay B3
Engine will run perfectly on B3 management

[121MOXY]

Does this information translate across to the B5 motor 1.5? I have found a B5 from a '93 familia/323 that I plan to drop into a DA 121. Will these engines match up with the bell housing/mounts on the original gearbox?

[Sleeper]

Awesome info guys! I was toying with swapping a BP for a while. But i just feel the B6D/T engines are better suited to our cars. ( unless 1/4 mile times are your goal ) And knowing a have several options when it come to producing the HP Goals I have in mind is great.

[Dragonhealer]

The fuel pump is fine if stall pressure is still over 85psi.
The B61P (B6D in 90-93 Miata USD) is 9.4:1CR and can run 5psi boost with a high quality rising rate regulator. More and you will be doing it over again and could have done a B6T for the effort of doing it twice!
Use 1.85 inch (2" if that is all you can get) exhaust pipe from turbo to cat (or expansion chamber) and 2.25 inch pipe and muffler post cat. The expansion chamber is important when not on boost if you are not running a cat.
91 octane minimum, don't get happy with the timing, don't cruise more than 30 seconds at boost. (Don't ask me how I know)

Keep in mind the XR2 uses boost more effectively due to the low CR, and has knock sensing....

[william]

From what I've seen the festiva and xr2 pump are the same part number and rocket man has tested to stock xr2 pump at 19 lbs of boost so I say your gunna be fine at 5 psi boost .

[Sleeper]

It won't run well with larger injectors on stock engine management. For low boost, the easy way out is a rising rate fuel pressure regulator. Like the one Gready (sp) used in their Miata 1600 turbo kit.

Thanks for the reply! Would a stock festiva fuel pump be able to keep up with a low boost B6D? And how much boost do you think a B6D running on a festiva ECU could handle with a rising rate fuel pressure regulator? obviously running B6T with its electronics and ECU is a much better option. But i love the simplicity of a B6D on festiva electronics. I would imagine that a B6D with its higher compression rate @ 5psi should produce as much power or more than a completely stock B6T running at the factory 7ish psi...

[Dragonhealer]

It won't run well with larger injectors on stock engine management. For low boost, the easy way out is a rising rate fuel pressure regulator. Like the one Gready (sp) used in their Miata 1600 turbo kit.

[Sleeper]

If you ran a B6D on the festiva engine wiring and ECU. Could you add a turbo at low boost ( 4-5psi ) if you added larger injectors?