Exhaust manifold options

[tweety2300]

My manifold is cracked from what seems to be the normal place around the o2 sensor.

My options are

Buy one of 4 left that Mazda has for $370

Have a flange made, buy a cheap ram horn with a t25 flange for a Honda cut and weld them to work

Make one from scratch

Which would be cheaper/ better? Or is there one from another car that will bolt up that's available.

Also I'm pretty sure the ihi turbo uses a t25 flange am I correct or are they different?

Sorry for my newb questions but parts and info are as scarce as the car I just want to get it back on its feet

[bogaut]

What manifold do you have now ? The o2 bung for the bpt is in the downpipe elbow

[tweety2300]

After doing some research on the miata forums I read that the head on the b6t and bp ze are the same so an exhaust manifold will work from an early 90s miata. Or at least it should but I still need to know what flange the vj11 turbo uses

[bogaut]

Yeah I just assumed you were bpt for some reason. You could put up a wtb for a b6t mani, I'm sure there are plenty of people here who have spares.

[Rocketman]

What manifold do you have now ? The o2 bung for the bpt is in the downpipe elbow

It's in the manifold on the B6T

After doing some research on the miata forums I read that the head on the b6t and bp ze are the same so an exhaust manifold will work from an early 90s miata. Or at least it should but I still need to know what flange the vj11 turbo uses

The BP is *not* the same manifold. The BP is a longer engine/head and manifolds are longer to match. You can use one from an early miata with modification (have to move the flange) but it's got to be for a early 1.6L Miata

The IHI VJ11 uses a proprietary flange, noone makes them you'll need to get it made somewhere

[tweety2300]

Sorry the b6 ze in the miatas and according to them the exhaust is exactly the same because it's the same dual cam head, of course I can only go by what I read though. Also the vj11 uses rhb5 flange found on egay for $15 cut off t25 flange and weld on the rhb5

Btw I do have an unhooked o2 sensor in my dp does that mean anything?

[Rocketman]

Yes the head flange is the same as the 1.6L Miata.

It's not quite as simple as chop & replace the flange, the cheap Miata log manifolds ("OBX" brand" are intended for top-mount turbos so the flange has to be relocated to the bottom)

Regarding the "egay" flanges - this is the first time I've ever seen them listed there, someone's making them now. It's not a perfect match to the CAD drawing I made here but looks like it should work

What style connector is on the o2 in the dp? someone might have had wideband installed in it

[tweety2300]

The ones I'm seeing look close to what I have on the car now, tubes come down with the flange for the turbo facing down.

As for the o2 sensor it looks like a little single wire but there is no wires coming out of it, looks like they used it as a plug but there is a narrowband gauge that came with the car but it's in a box with other stuff. I'll be ordering a wide band tomarow though.

There's a machine stop in my area that's pretty good at what they do so if they can't replace the flange I'll be getting a t25 turbo. And if I have to change the hot/ cold pipe I'll deal with it when it comes. Is there an fmic kit for our cars or would that be a custom job too?

I was hoping this car wouldn't be as much of a headache as its turning out to be

[Perfect Balance]

Btw I do have an unhooked o2 sensor in my dp does that mean anything?

When using the VJ11 turbo you use the probe downpipe as well. IIRC the sensor on the dp is for the Probe and isn't used on the 323.

[tweety2300]

It's your old car so you would know lol

[Perfect Balance]

Yeah but I didn't put those parts on it, I was told by the previou owner that was for the probe o2.

[Rocketman]

Yes the stock Vj14 downpipe won't fit the VJ11, the VJ11's O2 sensor is indeed in the downpipe right after the turbo. You can use that location if you like, I used it for my wideband for a while.

How bad is the manifold cracked? There are many, many that are cracked but don't actively leak

[tweety2300]

From th top down to the o2 sensor. I'm not sure if it's actually leaking there yet because the major leak is where the turbo bolts to the manifold. But the bolt closest to the motor on the passenger side we can't get to, we'd have to pull the manifold to get to it or at least with the tools we have.

Btw I'm not sure who installed the turbo but they missed a nut lol

[Perfect Balance]

Btw I'm not sure who installed the turbo but they missed a nut lol

If you're talking about the bolts holding the intake side on, then it's because the bracket for the wastegate has to be bent to clear the engine block with the larger turbo, and with the bracket bent the bolt no longer fits, but as far as I know it didn't have any leaking issues from there, unless something worked itself loose. All other bolts were installed, so if they're missing then I've no clue where they went lol.

[tweety2300]

All 3 were loose enough for me to turn them by hand. I've re tightened them twice now but it's hard to do it right with such little space. I need to pull the entire manifold off to get to them and tighten them properly. But I don't want it to crack more. It had loosened up on you which is the weird noise you were hearing from the turbo and why it was only hitting 14 psi. When they're tightened down enough it makes no noise and hits 16 psi. When I get the new manifold I'll have to lock tight them or something