SP (re)build from down under
 

Hi everyone,

Here is my MX-5 SP. There were only 100 of these made exclusively for the Australian market. Picked her up in 2014 from a very regretful seller and I'm her second owner.

For those unfamiliar with this model, the build consisted of a standard NB2, which had a GT2560R hung off the side pushing ~8psi. Goodies included custom Mazda cast exhaust manifold, dump pipe and a lovely carbon fibre airbox. Mine was optioned with lip, skirts, and spoiler. The dealer took it one step further and had the seats trimmed in black leather with the SP logo embroidered on the head rest.

The car is fantastic fun, however there were some weak points. For a start, the car had no internal work done on it whatsoever, and distortion in the block show that some detonation was occurring due to high comp, boost and probably fuelling. These things have been known to ping a bit from the showroom floor. The car also came with an open diff, standard brakes and suspension and stock clutch. As I said, car is great but some room for improvement.

After seeing some oil on the garage floor I took the opportunity to pull the motor and learn how to do a rebuild. The head has been serviced and the block is now with the machine shop. Getting closer, but man progress feels slow.

So far we've got:

Top end:

• Supertech valves std. diameter
• Sealed Power VS-855 valve springs
• DIY coolant reroute

Bottom end:

• Crank balanced
• Supertech 83.5mm 9.5:1 pistons
• K1 rods
• ACL Race bearings
• Boundary Engineering oil pump shimmed to 72psi
• ATI Superdamper

Misc:

• Cometic head gasket
• ARP mains, head and rod bolts
• Gates cast impeller water pump

The plan is to make a little more power than before and bulletproof the thing, but not to deviate too far from the original recipe due to the car being 1 in 100...although I look at the shopping list above and wonder if it's too late.

Damn, it's the mazdaspeed miata they should have made!

The 150KW and 289Nm is fantastic but it could really have benefited from the polish given to the MSM, like the LSD and Bilstein dampers. The MSM was more of a complete package in my eyes.

Here's a filthy shot of the unique SP kit

Welcome! Yes, the SP is special! It has its shortcomings, but then again the SE/MSM has its fair share too, in fact some would say more than its fair share!

Rods would be the priority, but good idea to do the rest while the engine is open. A Torsen is readily accessible, and that will make a big difference, add some good (not just decent) shocks and the car will be transformed (MCA get a good wrap).

Brakes are only wanting for decent pads, and you are looking at a highly proficient sports car!

I am assuming this will remain a street car, but will it be seeing any track work?

Are you plugged into the local MX5 community? mx5cartalk.com - Index page

Nice car chief.

I had no idea they made an MX5 SP, had seen the RX-7 SP before though!

Hi! I should have started my build thread from the very start. After getting the car back to Sydney I felt something wasn't right, found that the left-rear caliper pins had seized and so the pad was dragging on the rotor. After hitting the pin with enough heat to unstick it I realised I'd also melted through the rubber boots.

Cool, excuse to overhaul!! So I tore them down, painted them black, rebuilt with fresh rubber seals and boots, then refit with stainless steel lines and QFM brake pads. Things felt much more responsive after that.

Additionally, the prior owner fitted Koni adjustable dampers on King Superlows, so she already handled quite well. I quickly tired of scraping on everything so bought some stock springs.

She will remain a weekend car with double-duty on the track. Here is our first time at Wakefield. Yes, I do pop my head into the local forum occasionally.

Thanks! Many people don't, but I love telling the story.

I dunno man. It's easier to add a torsen etc than build a car stock that can handle a 2560 on the stock ecu...
The IHI turbo on the MSM and the setup that came with it was meh. The MSM billies are nice, but more so once given the DIY treatment and the torsen for it has very rare axles. So basically your car with a torsen sounds like an awesome way to go. How much boost can the stock MAP sensor slash the ECU/Injectors handle?

Like I said, some decent shocks will make a big difference ;) . Koni/Kings was all the rage when that car was new, but have now been well and truly surpassed in comfort/performance.

If you haven't done so, do some searching on the forum, there are a few threads about issues with the SP which will make life easier, but for the obvious reason I have only noted them in passing. I think there are a couple of SP build threads where people have done what you are doing, and it might be worth comparing your plans with their experience.

Yes, I have had that problem too (RR for me), I was doing my OLT at Oran Park and it cost me half a day of the two day program, plus a replacement calliper, plus the labour ... couldn't have been timed worse!

Did you buy the car from a bloke named Peter, from the Southern Highlands (airline pilot)? Small world, if so.

ETA You have started the SE transformation already - that is an SE front lip if I am not mistaken, and you have a flat top IM!

I look forward to following your progress.

No MAP. It's a stock NB ECU running the MAF and a tune. Another one of those compromises :)

The injectors were uprated, to what exactly I'm not sure.

Gentleman named Frank 15 mins outside Melbourne CBD. Props to him, he really looked after this car.

I do believe the lip is the same as the MSM however it was installed by the dealer prior to sale.



UPDATE:
Block and crank have returned from the machine shop!

• Crank balanced
• Pistons/rods balanced
• Bored for 0.5mm oversize pistons w/0.0030 piston-to-wall
• Polished journals, all the usual jazz

Shop went the extra mile and installed core plugs and painted it. Including a photo of my supervisor.



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With the last box of parts on their way from MiataRoadster, it's time for an update.

Scratched the crank and trashed a bearing doing a test fit to triple-check clearances with the ARP studs. Devastated, but I suppose it's better to find out now that my cleaning isn't up to par than find out later and break expensive components.

Going with MiataRoadster Delrin diff and engine mounts, added an ATI Superdamper. Slowly making progress.

Hey team, it's been a while.

After putting the engine together and seeing coolant/oil spewing out the tailpipe, I was discouraged and let life's issues get in the way of the project.

Since then I replaced the CHRA and after blowing smoke for 20 mins it cleared up, passed inspection and has been running clean since. Can't thank the community enough for the guidance.

Powertrain has been solid and the project rolls on. Major upgrades include a set of BC Racing coilovers, Konig Hypergrams and Hankook RS4 tyres. Swapped the Delrin engine mounts with Mazdaspeed mounts, that was a dumb idea for a streetcar. Left the Delrin diff mounts though.

Next up is to Megasquirt.

The car looks really nice on those wheels. A really cool special edition that I've never heard of, that turbo setup looks a lot better than the MSM setup.

Thanks for the updates!

Good to see! Yeah, DIY path is never as smooth as we would like :o ;)

I didn't notice first time around that the oil(?) lines for the turbo do not seem to have a direct drain into the sump - is that something you addressed in the build. Conventional wisdom here seems to be that having a good flowing short drain (10AN or better) into the sump is A Good Thing.

Upgrade to an MS a great step - ANY programmable ECU would be a good step up from those re-chipped Mazda ecus. After a few Haltechs (E8 :eek4: ) and an SM4 Autronic, I now rock a pnp Link G4X :D

Looking forward to more updates!

It's been a while :likecat:

Local tuners had no real experience with Megasquirt so the car instead got a Link G4X PNP and a set of Deatschwerks 700cc injectors.

Car is totally transformed. Thought it drove well under the stock ECU, but this tune is unbelievable. Power delivery is smooth as butter, super linear and a pleasure to drive casually.

Kudos to MX5 Mania in Sydney!
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Did you steal my dyno chart :vash:? I presume you got the same recipe as me - button clutch?

Nice work, pity about the double demerits for the next couple of weeks though ...

Yep, lightweight fly and button clutch

You ever drive at Marulan mate?

Looks BEEFY. Good work! I bet that's fun, nice tq curve!