NB vvt vs non-vvt compatibility
 

So turns out that my motor did in fact have a bottom end issue and it ended up spitting a rod through the side of the block. I have someone selling a 99 non-vvt motor and I'm planning on buying it and building it to put into my 01.

Are there any weird compatibility issues between the fuel system or sensors or anything between the two or is it a direct swap? Sorry if this is a noob question but I couldn't find anything else from a Google search.

:party:


Thanks,
James Gasek

You could put your VVT head on the new block and not change anything. Otherwise, there will be differences. I'm not the expert though.

I'm fine with differences as long as I won't have any crazy issues with wiring or anything. My only concerns really is the fuel rail fitment and sensor plugs and locations. Everything I've read so far says there shouldn't be any issues sonim not too concerned, still doing research though.

Thanks,
James Gasek

Pretty sure the fuel rail and injectors are interchangeable, although NB is return-style vs NB2 being return-less. Long story short, you can use everything that is already on the car with the new engine, but you will have to extend the cam sensor wiring (NB is in the front of the intake cam). I would consider swapping the VVT head in though, along with the VVT MBSP/pan, after giving them a proper cleanup to avoid any residual debris in your oil.

NB1 and NB2 are both return-less fueling in USA Miatas.

Use NB1 head gasket, regardless of which head you use; and do CLT reroute while engine is out of car.

DNM

Great idea with the coolant reroute didn't think of that. Funny enough cylinder 4 was the one that threw the rod. Don't know if it was heat related

Why do you say to use the vvt head? I don't plan on using vvt at all because it only adds like a few horsepower and I could sell it for a good amount if its fine, unless the vvt head flows that much better. Does the vvt pan have a different shape or something that makes it fit better with the nb2s?

Now that you mention oil pan. I remember reading that the oil pump has thicker gears on VVT engines.

https://www.miataturbo.net/engine-pe...il-pump-55188/

The VVT head casting is identical to the non-VVT one AFAIK. The VVT intake cam has shorter duration though. The VVT pan is slightly different to accommodate the main bearing support plate (MBSP).

And indeed, the VVT oil pumps have thicker gears.

What ecu are you using? Stock 01 will not play nice with a BP4W.

It's a megasquirt 3 mini off bofi racing.

I would still use the VVT head; you already have it, it is supported by your ECU, you will have slightly better midrange, has the same flow capacity as a BP4W. I also think that the non-VVT head would fetch similar money. The only reason against I can think of is intake cams availability and cost.

If you want to use a VVT head you will either need to swap in an 01-05 wiring harness and use an 01-05 MS3 Mini ECU, or modify your MS3 Mini to use the VVT and run additional wiring and pigtails. The ECU needs control of the VVT solenoid, plus the 01-05 ignition setup is different (but you should probably be running LS coils anyways).

There is a flow difference between 99-00 and 01-05 heads. They are not cast the same and IIRC the 99-00 heads flow better. The only thing interchangeable between the two is the exhaust cam, and the VVT cam has shorter duration. If you want longer duration or more lift, aftermarket VVT cams (like the ones from Tomei) are almost double the price of a regular cam.

If you already have a 99-00 Miata, stick with the BP4W head. Like you said you only gain a few HP but that alone is not worth the work it requires to adapt it for your wiring harness and ECU in my opinion.

My bad I read your question wrong. In your case just leave the VVT solenoid unplugged, everything else will bolt up the same just use a 99-00 head gasket (or Cometic MLS if your engine will be overbored) and coolant reroute like others have mentioned. The intake and exhaust manifolds will bolt up the same, as will the fuel system, the only other difference is the ignition but I'm sure you can come up with a solution for that.

It's really up to you if you want to use VVT or not, using a BP4W head with the MS3 Mini won't be much extra work at all in an 01-05 chassis, you're just leaving stuff out and have to tune it differently. If you have both heads, I would just sell the BP4W head and leave the VVT head in, the block from 99-05 are all the same. A head rebuild is going to be the same price regardless of which one you go for so might as well use the VVT.

Yeah I think that's what I'm going to do, and I'll probably get some arp head studs while I'm at it. On my vvt head and block there's an oil line on the back of the motor that goes to the vvt mechanism, am I going to have to remove that from my vvt motor and somehow attach it to the not vvt? Or is the line already there?

The only other thing on that line is the oil pressure sender, you will have to adapt the banjo fitting off the block to BSPT to still use the OE pressure sender or to NPT for an aftermarket oil pressure sender. Either way you will be removing the entire oil line if using the BP4W head; you can come up with a way to block it off, adapt it for an oil pressure sender, use it as an oil feed for the turbo, etc.

I do not recall the thread size but someone else might know. I suppose that oil feed and the MBSP/pan baffle are the only differences between 99-00 and 01-05 blocks, nothing else comes to mind.

Sorry I don't think I was clear with my question. There is an oil line on the vvt valve cover that isn't on the non vvt valve cover. So my question is how do I feed that oil line if I use the vvt head on the non vvt motor

The hardline bolts into the same port on the block from 94-05.

I removed the hardline and tapped it for an AN fitting.. I used a braided -4 or -6 AN line...I forgot which...But can't you just jack the hard line from the VVT and use it? I believe the threads are all BSPT

Ah, yeah I'm 80% sure the thread is different on the 99-00 blocks where the oil pressure sender is. On 01-05 they changed it a banjo bolt instead of BSPT and then ran the sender off of the VVT line. I'm not at home atm so I can't check what size it is. If it is the same size then it's just a matter of installing the VVT line in the sender's place but if not then you will have to tap it to the correct size for the banjo to thread in.

Isn't the thread size/style different on 01-05 blocks because it uses a banjo bolt?

Found the answer to my confusion in this thread:

https://www.miataturbo.net/diy-turbo...k-81526/page2/

OP just bolt the hardline in place of the pressure sender.