Learn me an NA Miata recipe to win the challenge in 2026?

I'm in the "What car?" stage of a 2025-2026 build for the challenge. Wife and son like NA Miatas but I don't know anything about them. 

What is the current recipe for building a NA Miata that can win the challenge? I'm better with turbos/engine work/tuning than with engine swaps. Is there an easy button for an LSD? Can the diff handle enough power on the drags? Do I have to go aftermarket ECU, or is there an easier OEM cracked version that I can use?

I'm pretty bad at fab work, but good at haggling and engine stufff.

Learn me please =)

Don't let the wheels hop and the factory Torsen rear end (found in some 1994-97 cars) is good for 400-ish HP. That's your easy button. You can also install a clutch pack diff from an RX7, which might work better for the drags. Torsens act like an open diff if you really vaporize one tire. Note: I am not a drag racer.

ECUs are not reflashable. You'll need an aftermarket ECU.

As much as I hate to say it because it's an unpleasant place, Miataturbo.net is a good source for info. You'll probably have to lean more into fab than haggling to build a turbo car for that price range unless you find someone's half-assed project that only needs a couple of things to be awesome :)

You can get more Miata for the money if you build an NB, and they're very similar cars under the skin. NAs have taken a classic car value bump.

Isn't the recipe: bmw engine swap and add all of the boost?

In reply to Keith Tanner :

Good info on the torsen. Thanks Keith!

What is required for a 300hp engine if I used a turbo? Can the crank/oiling/block system keep up? What about the rods/pistons?

The weak point will be the rods at that power level. Stock, they're good for a reliable 250 whp. Crank and block won't even notice.

Oiling system is more bothered by high rpm than high power IIRC. The pump from the VVT engines has more volume. The weakest point in the pumps is the gears, you can either change them out for billet or upgrade the damper or (at that power level on a budget) just send it.

I don't know the Challenge points system as well as I should, but balancing pure power and response will depend on whether you think the drags or the autox are more important. For the latter, I'd leave some power on the table to build a sharper tool - more compression, smaller turbo.

BP4W, BP26 manifold, VF10 coldside on the VJ20, RX8 injectors, Ecoboost mustang fuel pump, speediuno, corn syrup and send it. 

I thought I knew Mazdas, I had to google half of those.

BP26 is the GTX manifold, right? Do you know that fits? I don't remember being terribly impressed with the one on my GTX.

Another option is to buy one of the knockoffs of the (very) old FM manifolds off eBay and use a Garrettesque turbo.

BP4W is going to cost money, it's the shortest production run with the highest demand and the highest mortality rate. Given the budget constraints, I'd be tempted to use the head that comes on the engine installed in the car. Ideal compression will depend on the autox vs drag question.

See if you can talk stampie out of his. 

It would be really fast if someone would work on it for 2 weekends in a row. 

I've got an NA with a 1.8L, a 6 speed, and a Torsen that I'm getting ready to sell. It's a good challenge candidate. Near Columbus GA

In reply to SV reX :

Lol

Edit: Messaged, of course.

Having said that, "Winning the Challenge" is now a very high bar. The drags have become increasingly important, and that's not a Miata's strong point.

I placed 3rd overall in 2015 in a turbo NA (which ran a 13.1),  and I'm not sure how many Miata's have placed higher than that since. 

In 2017 my supercharged NB was second fastest (tied) on the autocross course and fourth fastest on combined times, and I only managed a 14.72 pass on the drag strip. A turbo NB would produce more power to get a number more like SVrex did. A "plain" Miata isn't going to do well in the concourse though, I dropped from fourth to eighth because of that. Some cheap suspension tweaks and decent tires helped a lot. First place overall takes a concerted effort, but I wouldn't let that stop me from going with a well done Miata.

In reply to CrustyRedXpress :

To your original question for a recipe, here's what I'd propose. NB>NA, but if a cheap NA available you use it. Good shocks, I used the Bilstein shocks from an NB. Springs on coilover sleeves off Ebay ($60-80), rates of 600/400 if you can find them. 26mm front sway bar. I modified one from a ford ranger ($15). Find some tires, SM7 SpecMiata take-off tires worked well, even though they weren't an autocross compound.Then turbo it as much as you dare. My supercharger was only putting out 6-7 psi, so that should be easy to beat. A theme or a good story about the car would help in the concourse. I did everything on the cheap. Performance could have been better with fresh tires and some effort on the concourse.

Edit: Find a Monroe shock dimension chart on line. You can use it to see similar sized shocks to Miata units. Then scour FB Marketplace for coilovers from other vehicles and see if you can make them fit. One example.....I can lightly modify Bilsteins for a 2003ish Toyota Tundra to fit the front of an NB Miata. 

MrJoshua said:

In reply to SV reX :

Lol

Edit: Messaged, of course.

Mumpkin 2: Electric Boogaloo

Backstory: I'm targeting 300hp because online drag calculators indicate that's what I'll need to hit 12.5 in the drags. 5 of the top 10 finishers in 2023 were sub 12.5, although interestingly 2nd and 3rd place were about a second slower. Huh.

2023 Challenge results

I did some reading last night and I think I can stay within budget and hit 300 hp with rods, pistons, ECU and some engine mods, but 300hp also seems to be beyond what the 5 speed will handle, and right on the edge of what the 6 speed will do. 

Can anybody confirm or deny that the 6 speed can reliably handle  drag and auto-x from a 300hp engine? 

Alternatively, what is the solution if it can't?

SV reX said:

Having said that, "Winning the Challenge" is now a very high bar. The drags have become increasingly important, and that's not a Miata's strong point.

I placed 3rd overall in 2015 in a turbo NA (which ran a 13.1),  and I'm not sure how many Miata's have placed higher than that since. 

I thought a miata won last year.  Didn't the bmw swapped miata win?

In reply to wvumtnbkr :

I'm not sure how well Miata's have been doing the last few years. 

In reply to CrustyRedXpress :

Reliable?  Challenge?  
 

Those 2 words don't go together! Haha!

In reply to CrustyRedXpress :

I'd be interested in knowing how many Miatas have ever beaten 12.5 second drag time at the Challenge. 
 

The problem is the launch. The independent rear suspension squats, and that challenges your 1/4 mile times. 

We had slicks on the Mumpkin, lifted the rear end for the drags to fit the slicks under, and were almost able to lift the front wheels, but didn't run that fast. 

...IIRC, our rear spring rate was about 750 lbs

I have a turbo, ic, meth kit, and other Rand m stuff that came off a Miata I would sell for challenge money. Pm if interested

In reply to CrustyRedXpress :

I think you need a bit more nuanced approach to the scoring...

Another way to look at that 2023 scoring is that only 5 of the top 10 cars were sub 51 seconds in the autocross.  If the Lotus had not been squirrely on the autocross, it may have won.  There is more than one way to skin a cat. 
 

In 2015 with the Mumpkin, my goals were to win the autocross, beat the 2nd place autoX by a full second, and beat Andrew Nelson by 4 seconds on the autocross (because that was the margin I needed to feel comfortable heading into the drags- I knew he'd be deep 10's, and we'd run 13's, so that left me 1 second margin of error)
 

I wasn't wrong.  That's what it would have taken to win the overall, and we didn't accomplish any of those goals. 
 

We only beat Andrew Nelson by 1.5 seconds on the autocross.  I knew he would win the overall before we even started drag racing. 

wvumtnbkr said:

SV reX said:

Having said that, "Winning the Challenge" is now a very high bar. The drags have become increasingly important, and that's not a Miata's strong point.

I placed 3rd overall in 2015 in a turbo NA (which ran a 13.1),  and I'm not sure how many Miata's have placed higher than that since. 

I thought a miata won last year.  Didn't the bmw swapped miata win?

You're absolutely correct-he did! It was dominant as well-  fastest at the 1/4 mile with an 11.8 and within .1 sec of the fastest autox time. 

I should have rephrased my question-I'm trying to figure out how to win the challenge without doing a complete drivetrain swap.

I'm pretty sure we had customers running in the 12s on "stock" FM II turbos back in the day. That's about 250 whp, and I don't have any further info. 

A set of adjustable upper rear arms could let you quickly adjust rear camber for drags, if that's allowed. Zero it out for maximum traction off the line, dial it in for autox. 
 

A 5 speed might handle some drag passes at 300 hp wheel, and should be strong enough at 300 hp crank. IIRC they tend to strip teeth off the gears as a failure mode but I'm blanking on which ones. We didn't shell a lot of transmissions ourselves.

I'm not sure if using shocks from another car would be a big benefit, there are some good Miata options out there. That may come down to buying the right car to start with. 

Keith Tanner said:

A set of adjustable upper rear arms could let you quickly adjust rear camber for drags, if that's allowed. Zero it out for maximum traction off the line, dial it in for autox. 

This would be beneficial, and not hard to do. I have a bunch of cheap Heim joints if you get to the point where you're modifying the upper arms.

Edit: Forget I said this. I forgot the bushings are in the uprights and not in the A-arm. Still easy to do with a bolt and some scrap steel though.

In reply to DeadSkunk (Warren) :

Alternately, cut the stock arms in half and bolt them back together with some shims.