Written by Ed Higginbotham
From the April 2015 issue
Posted in Features
Many Miata owners reach a point in their lives when they want more out of their car. Call it a mid-ownership crisis. Some dream of a V8 swap or maybe a fully developed turbo, but for those with fewer pennies to spend, there could be a new alternative.
At the 2014 Speedfest at the Classic Motorsports Mitty, a car caught our eye in the Miata corral. It wasn’t just any Miata. This one had a Honda V6 under the hood–the same engine used in countless sedans and minivans. We ran a teaser in the magazine, and our message board community erupted: Tell us more.
To our delight, we discovered that Norm and the staff at Mini Tec had been working overtime to perfect their swap kit for the first- and second-generation Miata. Now they can supply just about everything you’ll need to create your own Honda V6-powered franken-roadster.
We stopped by the Mini Tec headquarters, which is located northeast of Atlanta in a town called Royston. Once we arrived, Norm ushered us through a doorway to a garage bay where we spied three happy Miatas. The example we were most concerned with was closest to the door. There sat a V6, cozily nestled in the nose of a first-generation Miata. “Does it drive?” you ask. Oh yes, we can tell you it does indeed drive.
Norm invited us on a ride through the Georgian back roads surrounding the shop. After a flying lap of Northern Georgia’s hilly streets, we stepped out of the car with hearts pounding. This car with this engine is a match made in heaven.
The V6’s explosive torque is what the Miata has deserved since its inception. Squeeze the right pedal and you’re pushed by a wave of power that you just aren’t expecting in a Miata. The car is still able to hang in the corners, but it finally has the capability to jump on the exit, too. And that noise–oh, that noise. It’s like the engine is thanking you for finally placing it in the correct body.
Throttle response is good. And while first gear can be useless in a full V8 swap, it’s actually useful in this application–though some smoky fun can be had upon request.
The V6 Miata still feels light and agile. The extra power isn’t overwhelming enough to cause too many exciting moments without abrupt input, either. Norm’s car was set up well and fitted with some quality rubber, but even so, the driving experience was impressively similar to that of a Miata with a smaller engine.
Now, back down to earth. There are a few caveats with this swap. The first is the gearing. The 1990-’93 and 1999-2005 five-speed Miatas came with a 4.3:1 final drive, meaning the V6 engine has to turn about 4000 rpm to manage 80 mph. That’s loud.
Solution: Either swap in the 3.909:1 ratio used on the 1999-2003 six-speed cars or simply start with a car so equipped from the factory.
The second caveat is the added weight. You’re replacing a four-cylinder engine with a V6, so the front end will have to carry a heavier load. Norm estimates a 40-pound gain in the nose over the stock weights.
How to Train Your Dragon
So what goes into creating this beast? The $3500 kit includes everything you need for the swap except the Miata itself, the donor engine and a tunable ECU. You can run a stock ECU from the transplanted engine, but it will result in less power past 4000 rpm.
Thanks to Mini Tec’s supplied adapter plate and a custom front subframe, the V6 will bolt right into your engine bay. The only cutting necessary is a slot on the transmission housing to fit the starter. Also, the Honda intake manifold needs to be modified to move the throttle body. That allows everything to fit under the stock Miata hood–no need to subject it to the Sawzall.
The alternative is something like Flyin’ Miata’s fully sorted and developed V8 swap kit for the Miata. The resulting performance is simply amazing, but there’s a price to pay for being king. Their transmission kit alone retails for $4100. Then there are the parts to make the fuel system work. And the custom exhaust headers. And the stronger differential. Oh, and the engine and transmission.
So that’s it to complete the V6 installation? Just an engine?
Yep, that’s the beauty of this swap. You keep your stock transmission, stock driveshaft and stock differential, all of which have proven robust enough to handle the extra power in Norm’s prototype. To make sure the equipment was up to the task, he fitted his first example with the drivetrain from a 1990 Miata, widely regarded as the weakest of the evolutionary line. He’s used the car for street duty and a few track events, and so far he hasn’t reported any trouble. He even retained the stock Miata radiator, and it’s been sufficient for keeping the J-series engine cool.
Want climate control and power steering? No problem, says Mini Tec. The Honda power steering pump and air conditioning compressor can be adapted to the rest of the Miata’s a/c and power steering systems.
Better Than a V8?
So which engines will work? Mini Tec designed the conversion to work with a Honda J-series engine, specifically the 3.2-liter V6 found in the 2003 Acura CL Type-S and TL Type-S (J32A2), or the 3.5-liter version found in the 2002-’04 Honda Odyssey (J35A4), which shares the Type-S head.
The CL Type-S with a manual transmission is the ideal donor because it can retain its ECU. However, the Odyssey powerplant has a price advantage and also makes more torque thanks to its greater displacement.
Both engines make around 240 horsepower in stock form. They can make almost 300 ponies with a tune and an opened intake and exhaust–and that’s before you consider forced induction, which these engines take well. Even in stock form, the swap doubles a stock Miata’s horsepower while only tacking on 40 pounds.
The price is right, too. You should be able to find a good, usable J35A4 for about $300 or so. In fact, one of our online board members reported finding one at his local pick-and-pull for $170. Other versions of Honda’s J-series V6 engines may work, but so far Mini Tec only confirms the J32A2 and J35A4.
Sure, the V8 may still be king of the hill when it comes to Miata swaps, but the Honda V6 presents an interesting alternative for those seeking a solid bang-for-thebuck power increase.
Bout time we got some nougat to go with the chocolate.
and here I was thinking this was going to be about the 24 at the ring
Time to cut holes in a lot of Miata hoods... Just like dem Honda boyz
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