Remove steering wheel and take it into the house. It won't stop a guy with a tow truck but it will keep it from being hotwired and driven off.

Until he cases your car, buys a wheel with the same QR, and drives it off anyway.

I am a big fan of hidden kill switches.

Make a removable rack for the megasquirt?
Use an oddball non NRG quickrelease?
Just run a switch to the ignition coils, interrupt ground?
Use your brake switch as a relay trigger for the horns?
Turkey Call on the blow off valve?
Bike inner tube on the muffler tip?

At least it would draw more attention than the traditional alarm

Blue strobes in the park/tail lamps that activate when car is tampered with. That's sure to get law enforcement attention

Yup, cheap and will deter the people looking for easy targets since Miatas are easy to steal. Having more than one is good too. Toss in a well hidden gps tracker in case they tow it or push it with another car.Sometimes they will leave the car for a day or two in a secluded area to make sure there's no GPS/Lojack before tearing it apart. Nice simple solution without going too crazy. Doubt the thieves stealing Miatas use tow trucks, there's much more lucrative vehicles that can be stolen with a tow truck.

Alarms can be effective but not the basic $150 installed one from a car audio shop which can be easily disabled by most thieves.

As mentioned before, nothing you do will stop the guy with a tow rig from taking your car. But if you have a locator device of some sort (e.g. Lojack) you still have a chance if you can get popo on the case in time. Even in a car as small as a Miata there are still places to hide such a device. But make sure you rig up a backup battery for it!

We can talk all day about kill switches and removable steering wheels and whatnot - professional thieves don't care though.

I leave my Subaru in gear in addition to the parking brake. Then theyd just use a flat bed.

And if you remove all four wheels and put it up on cinder blocks a thief will bring four appropriately sized wheels, a jack, and lug nuts and steal your car. And if you remove the battery, they'll just bring one of their own and steal your car. And if you remove the engine, they'll bring one of their own along with a hoist and two gallons of coolant and steal your car. And if you have a kill switch they will bring a trailer or dolly with a cheap boat winch, a floor jack, and maybe two plastic trays from McDonalds and steal your car.

I thought we were talking about opportunistic thievery and not well equipped professionals. Well equipped professionals wouldn't waste time with cars as inexpensive as Miatas. I bet most pros are stealing Vettes, M3s and P-cars at a minimum and going up from there. The punks that stole the Miata were joyriders. It was a 1.6 car for cryin' out loud. Nobody serious steals a 1.6 car!

Most pros steal things like late model Accords, Camrys and F-series trucks. These are stripped for their parts and find a ready market.

These 10 cars, trucks were the most stolen last year

Honestly, we're already doing a lot of theft prevention by driving cheap, old cars with manual transmissions. Buy insurance and move on.

Those tow trucks are really aimed at drivers doing repo work. People who are behind on their car payments try to be creative to prevent them from getting towed, and being able to swoop in and grab it quickly is a big safety win as far as the driver is concerned.

--Ian

A '96 Accord isn't exactly "late model".

Modern cars have the anti-theft systems built into the ECU. If it doesn't get a proper cryptographic challenge/response from the key, it doesn't run the fuel injectors. They basically can't be stolen without either having the key or tow truck, there's nothing to "hot wire" because all of the anti-theft logic is built right into the ECU. With proper cryptographic security design (something which VW apparently managed to screw up), eavesdropping on the communication between the key and the car won't tell you anything useful either.

AIUI, these kinds of features have drastically reduced the theft rates for cars made in the last decade. It's apparently at the point that if someone reports his car stolen but still has the keys, then they take a long hard look to see if he's engaging in insurance fraud.

Theoretically you could add this kind of security to a Megasquirt. Attach a bluetooth module, write a small protocol stack, keep a shared key on it and your smartphone, have the MS send a challenge request when it's starting, write an app for the phone to generate the response, and if it doesn't get the right response then no fuel. Of course you'd need a way to stop someone from simply reflashing it... :)

--Ian

I've thought about that using a microcontroller of some sort, arduino or raspberry pi. Raspberry Pi would be double-cool because it can run tunerstudio (just keep the tuning computer in the car?) but the boot time is not good enough for using it to start, and I'm not sure if the power draw is low enough to keep it always-on.

It's good to have at least a small cheap layer of security to prevent the basic joyrider or thief. It's very easy to steal a Miata, so nothing wrong with throwing some small change at it and less than hour of your time, especially if you have aftermarket parts and plenty of time put into it. Sure insurance may cover it, but it's going to take time out of your day, receipts and they may not cover all the aftermarket parts. And time spent working on the car is all gone.

You know, that would be a cool system... I wonder how difficult it would be to make a device that checks bluetooth for a registered MAC address before allowing the car to start? You would need to find a way to quickly register a phone... might need a way to program a custom PIN to really lock it down.

DUH, I knew I read this idea somewhere... Turns out it was like two posts above this one:

Good thing you can't spoof a MAC.

Don't see this being an issue with anyone trying to steal a Miata

If you want it to actually be secure, you use a cryptographic shared secret. The MAC address is a slightly more nerdy version of the hidden kill switch that you have to know to flip to turn on the fuel pump. That's not to say it's useless, it depends on your threat model.

--Ian

Then there's always the RFID key option, either home-rolled or a kit. I think that's what OEMs have been using for the last few years.