NA BP-4W Build (HELP PLEASE)

Micheal · Postby **Micheal** » Thu May 28, 2015 10:47 am

Hey fellow topless drivers,

I've had my NA6 for just under half a year now and I'm getting tired of every other car on the road having more guts than mine. Now I've acquired the NB engine which unfortunately was dríven through quite a large puddle and will require a complete reconditioning, which is lucky because I don't want to mess around with weak internals. As this is my first MX5 build I was hoping someone out there would be kind enough to answer a few questions I have.

1. I've been told that once I have the adapter and mounting kit everything else (bar ECU) will be pretty much plug and play. Is this true ? (I understand that I will need an exhaust fab and I intend on doing and oil filter relocation)

2. Internals. As well as sending block and head away for a machine and acid bath, I will be building the engine while it's out of the car. As such do I go high comp or low comp. I will be strapping a turbo to the car, probably a T28 Ball at this stage. I intend to run it around 7psi for daily driving and maybe 9 -11psi for spirited driving. Where would I get the internals from ? Flyin' Miatas prices are just scary and I'm not sure if Mania do rebuild kits.

3. Handling. Ive noticed that when I notch past 110km/h my Miata gets VERY light footed. It wobbles and shakes a lot more than it should. I thought it might just be a problem with my car till I drove a mates NB and even with coilovers it had the same problem. Am I right in understanding that a full brace kit, upgraded bushes and sway bars, Yellowspeed Coilovers and improved aero will fix the problem ?

4. Once the engine is in and car is running I'm assuming she'll need to be engineered ?

5. Will the gearbox bolt up to the 1.8 engine. I have the stock NA 5 speed atm.

6. Lastly, any advice you guys have on ECU would be appreciated. I've been told Haltech, Adaptronic and some other brand I can't remember the name of.

Cheers people

Magpie · Postby **Magpie** » Thu May 28, 2015 11:12 am

Point 1 - Automotive Plus sells all the parts required to put a 1.8 engine into a 1.6

Point 2 - Nitrodann's area of expertise.

Point 3 - Get a decent alignment, make sure the wheels are balanced and have the correct tyre pressures before going any further. Have a look at Guran's NA6 http://mx5cartalk.com/forum/viewtopic.php?t=39676 and see what a stock car can do with.

Point 4 - Pass

Point 5 - Pass

Point 6 - Decide who will be tuning it and use the ECU they recomend. If self tuning then pick an ECU with a DIY customer base.

kazama · Postby **kazama** » Thu May 28, 2015 11:44 am

5. yes

Jeo · Postby **Jeo** » Thu May 28, 2015 1:49 pm

3. Alignment, then go from there.

4. Probably not; mine didn't in the ACT but check with your local state body.

5. Yes.

6. I'm pretty happy with my Autronic, but pick your tuner first then run with what they recommend. No point in having 'brand x' if the closest turner who knows anything about it is hours away.

thehillsarecalling · Postby **thehillsarecalling** » Thu May 28, 2015 2:33 pm

Note that while the NB and NA8 motors are both 1.8s, they have different electrics, and so you will either need to hack up your NA loom for injectors, coilpacks, TPS & IAC, or you will need to transplant a NB loom, computer, immobiliser and key barrel into your NA.

madjak · Postby **madjak** » Thu May 28, 2015 2:41 pm

thehillsarecalling wrote:Note that while the NB and NA8 motors are both 1.8s, they have different electrics, and so you will either need to hack up your NA loom for injectors, coilpacks, TPS & IAC, or you will need to transplant a NB loom, computer, immobiliser and key barrel into your NA.

It may be easier to run new wiring if your going an aftermarket ECU. Upgrading the loom or downgrading the sensors isn't the easiest task... it's probably just as easy to use the existing loom in the car for lights /chassis and run a new loom to the required engine sensors / injectors etc. It also means you can run a range of ECU's that aren't "plug in".
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bartmanftw · Postby **bartmanftw** » Thu May 28, 2015 2:59 pm

I've swapped a BP-4W into my na6 and am using a megasquirt ecu to control it. If you're using an aftermarket ecu you don't need any extra parts to swap the engine in except a throttle cable adapter which you can get from mx5mania and the correct engine mount cups if the engine doesn't come with them. The gearbox bolts up just fine and I also reused the 1.6 clutch. For the sensors I used all the NB ones and wired them into my existing wiring loom. The hardest part would be wiring in the NB cam and crank angle sensors since they're in a completely different location or you could just keep the CAS sensor on the rear of the head.