Hey, everyone. Longtime lurker hitting the point with my project Miata "PJ" where I could use some advice.

First, about me: I live in Arvada, a suburb of Denver about halfway between Denver and Boulder at about 5300' elevation. I autocrossed for years, drove in a few HPDEs, and taken a couple driver training courses. I've enough driving experience to know that I have more to learn than I know today. All the car/engine work I've done the last few years tells me I know even less about tuning.

My cars: 2005 Mazdaspeed Miata, 2005 Base Miata "PJ," and a 1999 Jeep Wrangler TJ (the "Jeep").

My 2005 Mazdaspeed Miata is my baby, my garage queen. I've owned it for 15 years, bought (and modified) long before prices went crazy. It now runs FM's Garrett GT2560 turbo kit supported by E85 fueling (ID1050x, pump, sensor, rail), cooling upgrades (crossflow, reroute, FM stage 2 brushless), driven by an MS3 ProPNP. Xidas, 15x8 wheels with 200TW tires, plus a bunch of interior upgrades (seating surfaces, short shift kit, sound system w/amplifier, etc). On a Mainline dyno at 5000' it hit 250whp at 12psi. I worked with AIM Tuning on all other things driveability. It has a few minor lingering issues and currently does not have a pump gas tune, but overall drives excellently.

I ran Mobil 1 5w30 for a long time. I started see sparkles in the oil, switched to Rotella 5w40 this summer it went away. Since it'll need bearings an engine rebuild is being planned...


"PJ", the 2005 Base Miata Project Car, is why I'm here. Goal is ~300whp on gas, hoping for 400whp on e85 but I'm realistic about the build and impact of elevation.

At the recommendation and with the support of my wife, I picked up this 2005 Miata base instead of experimenting on a new engine build on my beloved MSM. Good foundation: LSD, "hard suspension," sport brakes; no rust, but needs some paint work.

NB block bored to 84mm with Manley rods, 9:1 Wiseco pistons, ACL/ARP hardware, Boundary oil pump, sump baffles. MSM head with SuperTech dual valve springs. Skunk2 intake and throttle body, FluidAmpr damper. DW1000cc, DW300 pump, FM fuel rail, e85. 3.3 gearset. Kraken EFR 6758 top-mount kit w/3" exhaust, dual-port Turbosmart actuator, driven by a MS3 ProPNP. SuperMiata crossflow and coolant reroute. Runs a stock 6-speed rebuilt by a local shop to solve for the 4th-gear circlip issue. A few minor interior updates, no suspension updates.

Gas tune is roughed in with a few issues to work out. E85 needs a lot of work, that's where I am right now. I plan to dyno tune e85 only. I have a list of issues, some I'll be posting about.


Off topic: My 1999 Jeep Wrangler TJ, bought in the height of COVID before prices exploded. Nothing exciting here: 4.0 I6, 5-speed AX-15 transmission (excellent for my hoped-for LS-swap), Dana 30 front end, Dana 35 rear end (bummer for my hoped-for LS-swap). Nothing done on the engine beyond routine maintenance. Rides on OME 2.5" lift springs, Rancho shocks, JKS adjustable front and rear trackbars, JKS swaybar disconnects, plus has BestTop soft top, ARB in-bay air pump, Badland Apex 12000 winch, low-end front and rear bumpers, LED headlights, Amazon lightbar, 1" transfer case drop, 31" wheels and tires, and a recovery kit with ropes, shackles, etc. in the back.

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I'll see you on the boards soon.

 

Damn dude, nice rides! Welcome to the forum. Not many souls are brave enough to have two turbo Miatas on their plate Stoked to follow along and see what happens with "PJ" and what power it makes once you get it on the dyno.

You said a local shop rebuilt your 6 speed to fix the dreaded circlip failure. I'm sure more than a few users on here would like to know the shop in question. Doesn't seem to be easy finding someone to do that mod currently...

 

Thank you! Twice the opportunity to break, but equally twice the likelihood at least one is running.

I'm running out of season to get PJ dyon'ed. I plan to get Open Loop boost control running then hit The Boost Creep in Longmont.

Jack's Transmissions, Colorado Springs. They do a lot of work on BR-Z/AE86 transmissions. Since the BR-Z/AE86 use a derivative of the AZ6 transmission, they also work on the NA/NB Miata 6-speed. They require the full transmission, they don't machine parts individually. Base service is $2000, with options it'll push $3200 (shot-peening, polishing, upgraded synchros), but not including replacement gears if such are needed. Shipping extra /obvious.

 

Welcome, that's a nice looking MSM! Watch those rods though, I bent mine at 140rwkw, corn may be easier on them but in your shoes I'd be doing them sooner rather than later. While the engine is out, it would be smart to do the gearbox on that one too - there is chatter about the MSM box being stronger, but I have never seen any confirmation.

That 2005 must be one of the last NBs? That should be a fun project!

 

Thank you! My MSM has over 100k miles, and absolutely doesn't look the part. My neighbor recently asked when I got it painted, and didn't believe me when I told him it was completely factory.

I'm right at the limit of the factory rods - torque is torque, whether from gasoline or ethanol. That's one of the reasons I stopped at 12psi and 250whp. I have plans to rebuild that engine with rods/pistons. I'm targeting about 300whp on corn, right at the limit of the 2560. I might put in valve springs, but the extra RPM likely won't do me any good aside from a little extra misshift protection.

So far as I know, the MSM 6spd is identical to any other Miata. That said, PJ's 6-speed is also from a (JDM) MSM. Either way, yes, I plan to have my trans rebuilt at the same time as the engine rebuild.