Buyer Guide: 2004-2005 Mazdaspeed MX-5 Miata

By Robert Bowen
May 22, 2022 | Mazda, Miata, NB, Mazdaspeed, Buyer's Guide | Posted in Buyer's Guides | From the Feb. 2014 issue | Never miss an article

Photography Courtesy Mazda

[Editor's Note: This article originally appeared in the February 2014 issue of Grassroots Motorsports.]

The original Mazda Miata is one of the most perfect driving tools ever created. Sure, other cars have more power, more style or more luxury, but few can tame a twisty back road and put a smile on the driver’s face more efficiently than the early Miata. Despite its slightly higher weight and size, Mazda’s follow-up model was just as loved.

However, even after a 2001 facelift, by 2003 sales were more or less flat. Some of the novelty had worn off, and buyers had more choices–including Honda’s stellar, 240-horsepower S2000.

Since the next Miata–with its all-new, more powerful MZR engine–was a few years away, Mazda chose the time-honored path of employing turbocharging to squeeze a bit more power from the current car. They added a small IHI turbo, lowered the compression ratio and fitted a small, front-mounted intercooler. The result was the 2004-’05 Mazdaspeed Miata, a limited-production, high-output version of Mazda’s roadster.

A Natural Fit

Adding a hair dryer to the Miata wasn’t as much of a stretch as it sounds. The car’s iron-block four-cylinder hails from the brand’s B-series engine family, and factory-turbocharged versions had already been used in the Mazda 323 GTX and Mercury Capri XR2. And, of course, thousands of enthusiasts had already shown that the Miata could reliably handle boost. 

At first glance, the Mazdaspeed Miata’s engine bay looks as if it were designed to accommodate a turbocharger from the get-go. The ducting, for example, fits perfectly. 

Parts were chosen with an eye to compact size and good street performance. A smallish IHI turbo with a ball-bearing center section provides the necessary 8.5 psi of boost–enough to raise horsepower from 142 to 178.

Unique 17-inch Racing Hart wheels are the easiest way to identify a Mazdaspeed MX-5, but the special badges and little intercooler in the grille will also tip you off.

The turbo Miata was dubbed the Mazdaspeed after the company’s in-house tuning arm. It wasn’t the first car to be so named, though, as the 2003 Mazdaspeed Protegé held that honor in the U.S. market. Subtle Mazdaspeed badges hinted that the car was something special next to ordinary Miatas.

The Mazdaspeed Miata featured a number of other improvements over the non-turbo Miata LS, including Bilstein dampers, shorter and stiffer springs sourced from the previously optional Sport suspension, and 17-inch Racing Hart wheels. It came standard with the LS’s optional six-speed manual transmission and a limited-slip differential.

Down in Flames

The Mazdaspeed Miata bowed to positive reviews. It could do zero to 60 in less than 7 seconds–about a second faster than an ordinary NB Miata. And the best part? The boosted Mazda didn’t lose any of the midrange flexibility and throttle response that made the car so appealing in the first place. It was like a Miata, only more so.

The biggest downside to the new car was availability: Mazda announced plans to produce only 4000 of the cars per year, although this turned out to be optimistic. Despite the bargain-basement price of less than $26,000, few left dealer lots. While all the 2004 models eventually sold, a fire in the production factory late in 2004 sealed the fate of the Mazdaspeed after just more than 1400 units were shipped for the 2005 model year. That means only about 5400 cars were shipped our way. 

The car doesn’t lose any of its character when fitted with a turbo. Inside, you’ll find all the interior goodness of an LS-trim car. 

It’s difficult to see why the Mazdaspeed Miata didn’t fare better. The minimal increase in cost (only around $700 more than a Miata LS) was far less than an aftermarket turbo kit, and the car came with a full factory warranty and dealer support. Even if the buyer planned to upgrade the engine later, it was a great place to start.

Nearly 10 years on, the Mazdaspeed Miata is more than a historical curiosity–it’s one of the finest examples of the original Miata platform and an astonishing driver’s car with enough power to be entertaining. Thanks to the turbo powerplant, a little tuning goes a long way, too, making the Mazdaspeed Miata an attractive alternative to far newer cars.

Things to Know

The hardest part about buying a Mazdaspeed Miata is simply finding one. With only 5428 cars built across two model years, they aren’t exactly growing on trees. Assuming you find an example in a color you can live with–there are only four options, so don’t get too choosy–current book values are between $6000 and $10,000. In our experience, there aren’t many cars in the lower end of the range. Asking prices are generally near $10,000 and higher. 

Engine and Drivetrain

The Mazdapeed Miata hasn’t been plagued by many problems, but the most common one is the dreaded “bog” caused by a faulty three-way MAP solenoid. When the solenoid fails–usually after a long freeway drive–the car will buck and refuse to accelerate smoothly. Normally a check engine light will accompany the problem. 

A second common problem is a failing fuel pump that won’t allow the car to start. The least expensive replacement comes from Walbro: Figure around $100 compared to $400 for the factory piece. 

The factory intake and downpipe are both extremely restrictive, so replacing both with aftermarket parts adds a quick power boost and more consistent performance. (Here’s a hint: Check out the Flyin’ Miata website if you’re considering buying one of these cars. When paired with their Mazdaspeed exhaust, the company claims that the car makes an extra 23 horsepower and 26 ft.-lbs. of torque, thanks to their downpipe and catalytic converter.)

Installing a larger exhaust will pay off in faster turbo spool times–3 inches is usually the largest that can be fitted practically. 

Once you’ve upgraded the intake and exhaust, the intercooler can become a power limiter. The factory intercooler is rather small, and larger, aftermarket replacements help in some situations. (We should note, however, that they may not pay off in increased power with the stock turbo.) 

The boost can be raised slightly via a manual or electronic boost controller, although the factory ECU is not happy above 10 psi or so. The injectors will run out of steam before that point and will have to be replaced. This, of course, will require some sort of piggyback ECU to manage the higher flow rates. 

With all the tricks, the factory turbo can flow enough air to top 200 horsepower. Flyin’ Miata offers a bolt-on package that pumps up the Mazdaspeed to 225 horsepower at the wheels. The contents include an intake, throttle body inlet pipe, blow-off valve, downpipe, midpipe, exhaust, intercooler, Hydra Nemesis ECU and 700cc injectors. They offer additional Mazdaspeed Miata packages as well.

To make big power–above 250 ponies at the wheels–you’ll need to replace the factory turbo. Flyin’ Miata offers several turbo replacements that swap the factory IHI snail for a Garrett unit with much more headroom than the stock turbo. Now you can probe the limits of the engine’s bottom end–figure results of more than 300 horsepower. 

The Rest

The rest of the Mazdaspeed Miata is standard-issue Miata, meaning few problems exist. At the same time, the aftermarket is ready to deliver all sorts of suspension and brake upgrades. 

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View comments on the GRM forums
jharry3 GRM+ Memberand HalfDork
11/20/20 8:15 a.m.

If the cooling fans stop working don't trust the temperature gauge.  MSM's over heat easily for some reason, even if you aren't using boost a lot.

The engine is running to hot without the fans even if the temp gauge does not move past center and you are just cruising along. 

This slowly cooks the head gasket.  Which then leaks compression into the cooling system and blows up the radiator.       Literally.    

dherr (Forum Supporter)
dherr (Forum Supporter) GRM+ Memberand Dork
11/20/20 4:04 p.m.

Great to see the MSM covered. It is an amazing car, especially as a building block for a giant killer. My car has an FM built motor, basically the full FM catalog of go fast goodies installed and the performance is just amazing. Drives like a standard Miata but can kill Porsches on a track. Values are rising fast, so better act fast if you want in on the fun!

jhhyde New Reader
11/25/20 8:21 a.m.

I can vouch after having a fully loaded MSM that it's an amazing little car. For my needs doing some autocross and about to hop on track I'm really pleased with it. Regarding cooling issues perhaps this is only during hot track days and haven't seen the needle climb (yet) during car control clinics in summer and definitely not on highway. The solenoid is absolutely an issue, though is easily cleaned to get it back to rights. I did the FM Little Enchilada and honestly don't really feel a need to go past it. I had a buddy take a ride along so if you want to see some guy car banter as well as hear the FM kit, you can check it out here. (There are fact inaccuracies there for sure, though hey, we're not perfect.) It's a blast and I've had it for 11 years now, fighting rust every season though still loving it. If you can get your hands on one it's nice to see what the engineers can accomplish and yearn for the days when they try again.

dxman92 Dork
12/27/20 9:17 a.m.

Never knew that the block had roots from the Capri/323gtx days. Friend of mine had one of these a few years ago and really enjoyed it.

Feedyurhed UltraDork
5/18/21 6:59 a.m.

Wow, both the cars pictured are beautiful. Forgot how nice the NBs can look.

Rodan Dork
5/18/21 10:01 a.m.

Prices have appreciated significantly over the last several years on the MSMs... even before the current craziness.

They are a great platform, and can be serious performers with some minor mods.

gardnpc New Reader
2/23/22 7:29 p.m.

Had a 2004 for a short time and it was a fun little car.  I always liked the subtle updates to this car.  However, I found that I just didn't fit well inside an NB and sold it to my son.  For some reason, I felt even more cramped than in an NA.  Now I enjoy an NC but still miss the little 2004 MSM.  

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