Greg's K24 Miata

[greg1647545532]

Figured I'd contribute some actual automotive content to this ghost town. I bought this Miata 4 years ago because I wanted something less ratty and more reliable than my Integra for a dual use track/street car. When I bought it had a relatively fresh (30k miles) Mazda crate motor, which I lost at the track due to an overheating issue (I think the head cracked but I sold the long block without taking it apart). I tried to keep it as close to stock power as possible for reliability but since 99/00 motors are the motor to have for SM they're not cheap, and I installed an 01+ VVT motor instead and threw some additional mods at it. I got 2 years of track duty out of that motor until it let go at VIR last October, I think due to oil starvation. Still not sure of the exact cause. Here it is at that event before it spun a bearing:

 

 

I hemmed and hawed about what to do, not too keen on putting in yet another BP motor that made dick for power and wasn't proving to be exactly reliable, so I bought this:

 

 

It's a JDM K24A from a 2005 Honda Odyssey Absolute, 205hp in stock trim with an 8000rpm redline. The installation kit is from a company based in Michigan called KMiata, it's not terribly cheap but it's pretty thorough. It uses the stock Miata transmission for ease of installation and cost, and comes with an adapter plate, flywheel, new subframe, oil pan/pump mods, modified K24 ECU and wiring, plus a host of odds and ends. Here's the subframe ready to go in, it's outsourced to V8 roadsters and is essentially the LSx swap subframe:

 

 

The necessary internal mod is to remove the balance shafts and modify the oil pump and pickup using kit components to make clearance for the steering rack, which is going to run right through the oil pan here in the middle of the picture:

 

 

The kit also comes with a new timing chain/tensioner, OEM 50 degree VTC cam gear for a bit more power, a baffled oil pan to fit around the subframe and steering rack, and some coolant re-route bits. Now here's a random picture of the blank slate under the dash to make room for the new (OEM Honda Element) engine loom:

 

 

This setup is going to change, the kit comes with a custom pulley and belt to simplify the accessory belt situation but there's no tensioner, it's kind of a bitch to slip that pulley into some random bolt hole in the front of the block and then get the tension right with washers under the alternator. KMiata sells an A/C kit, which I have in my possession but haven't installed, which will eliminate the top pulley here and use the A/C compressor as a tensioner.

 

 

I took this picture of the AN line I made for fuel, I opted to use the stock fuel rail and just connect it to the Miata returnless feed rather than run new lines. It's straightforward but the downside is that the fuel line is now on the hot side of the engine because everything's backwards from the BP. A walbro 255lph pump is necessary to keep the fuel pressure up at high RPMs because the stock FPR is kinda shitty.

 

 

I went ahead and ordered the Skunk2 intake manifold, B-series throttle buddy (because cable driven and not DBW), and associated adapter bits from KMiata. Not seen here but tucked off to the side is an OEM IACV mounted on a custom block to keep the idle happy. Honda engine management is delightfully straight forward, all the wiring tucks up nicely. The throttle cable does need to make a full loop as you can see but I didn't see any reason to find a shorter one.

 

 

Here it is all done and driven under its own power to cars and coffee a few weeks ago. At this point I was still having some issues with cooling and wiring it that wouldn't reveal themselves fully until a couple of days ago, but I was in a time crunch due to previously scheduled track days.

 

 

Unfortunately all I got out of my first track weekend was this one picture of it not moving in the garage. A missing ground wire stymied me and a lost a whole weekend before finding it and fixing the frustrating misfire I was getting.

 

 

After I fixed the misfire it was running awesome, and I turned my attention to the terrible NVH caused by the polyurethane engine mounts included in the kit. Clay helped me figure out a solution using some Hyundai suspension bushings I'd found. Unfortunately, these bushings are hard as shit and the NVH is still pretty bad. Something to sort out in the future.

 

 

Here it is ready to go for my second attempt at Mid-Ohio, I actually washed it, clayed it, and waxed it for the first time in 4 years. Sadly, the entire day was rain and I only did a few pathetically slow laps on whatever street tires I happened to have on my style wheels.

 

 

Full disclosure, I have a vinyl cutter and the heart of a ricer, and so I do stuff like this.

 

 

I'll update this thread when I go back to Mid-Ohio in a few weeks. The KMiata sales material advertises 215-220whp with the tune I was delivered, that's up substantially from the 131whp I made on the VVT motor. Previous PB at Mid-Ohio was a 1:49.9, that's my frame of reference. I'm honestly not sure what an extra 85-90 horsepower will do, but I can't wait to find out.

[Geeto67]

neat project.

[Cordell]

It honestly surprises me the stock engines gave up that easily, always seemed fairly durable, I guess that’s not the case when tracked hard.

 

Interesting swap, not sure why I like it, but it’s cool. I even like the vinyl work, I lol’d.

[Rally Pat]

Awesome project!

 

BTW We have a whole section of this site just for projects -

http://www.columbusracing.com/forums/forumdisplay.php?f=59

[iwashmycar]

Sorry if I missed it, but is the K heavier than the BP that came out?

[greg1647545532]

Sorry if I missed it, but is the K heavier than the BP that came out?

 

It ends up being 30lbs lighter due to the aluminum block and the subframe.

[iwashmycar]

thats awesome

[greg1647545532]

It honestly surprises me the stock engines gave up that easily, always seemed fairly durable, I guess that’s not the case when tracked hard.

 

My experience has been unique in that regard. Consider it a combination of bad luck, bad decisions, and a dash of poor design.

 

BTW We have a whole section of this site just for projects -

http://www.columbusracing.com/forums/forumdisplay.php?f=59

 

D'oh!

[Fiji ST]

Very cool project. I can't say I've ever seen this one done before. Have you caught any flack for putting that engine in your Miata?

[Rally Pat]

Very cool project. I can't say I've ever seen this one done before. Have you caught any flack for putting that engine in your Miata?

 

I would say its the second most popular Miata engine swap behind an LS, theres even a whole company that makes parts for it.

 

https://kmiata.com/

[greg1647545532]

Very cool project. I can't say I've ever seen this one done before. Have you caught any flack for putting that engine in your Miata?

 

There's very little distance between Honda nerds and Mazda nerds, and the BP is generally regarded as a turd anyway, so the only flack has come from the "why would you spend that much money on a Miata" crowd. And I have no response for them other than I've never been good with money

[Forrest Gump 9]

That’s awesome, but yeah, why would you spend that much money on a Miata?

[Smokey]

Cool project. I’ve run with a LS3 Miata track car and he can never get enough brake under any wheels that fit so this upgrade of power makes much more sense. Hopefully it’s a reliable and reasonably cost effective lapper for you. Keep us posted.

[unfunnyryan]

That’s awesome, but yeah, why would you spend that much money on a Miata?

 

because racecar

[10phone2]

greg great project. That will be a blast to drive

[zeitgeist57]

Love the Miata, Greg! :thumbup:

[ec_E92]

 

 

 

Here it is ready to go for my second attempt at Mid-Ohio, I actually washed it, clayed it, and waxed it for the first time in 4 years. Sadly, the entire day was rain and I only did a few pathetically slow laps on whatever street tires I happened to have on my style wheels.

 

 

 

Were you running this past Monday? It sucked! I was in a silver E36 M3, had I known you were a fellow CR member I would’ve said hello!

-Eric

 

 

 

 

Sent from my iPhone using Tapatalk

[Toph6888]

Were you running this past Monday? It sucked! I was in a silver E36 M3, had I known you were a fellow CR member I would’ve said hello!

-Eric

 

I was there as well in the red turbo miata parked off by the entrance to the grid. It was quite wet, and somehow I managed to not park it in the grass on course unlike some of our fellow drivers lol.

 

I will be up at gingerman this weekend and mid ohio July 12th again. Feel free to stop by and chat, I'll keep a look out for both of you.

[greg1647545532]

After a pretty miserable spring with this thing I finally got a decent day at the track and did a PB 1:46.8. There's some time left in it, there's a few issues that cropped up that I'll need to deal with before I can really push it. Still, this is leaps better than my previous PB (1:49.9) so I can't complain.

 

 

One of the issues is that I'm not currently running a booster check valve, it was integrated into the manifold on the Miata and I didn't think it was strictly necessary. Ends up having a pedal fluctuate with engine vacuum is a challenge, at the end of this video I was left foot braking into thunder valley and when I started to feed in the gas the pedal pushed back against my foot, I instinctively resisted the pressure and it snapped around on me. I stopped left foot braking after this but any braking zone with a down shift was still an interesting affair. I've got one of those on order, and I also need a new alignment now because something slipped the following session and I sort of backed off of the rest of the day as the steering wheel was never quite pointing the right way down the straights.