mx5cartalk.com

Might be a bit of a noob question, but is it worth getting a megasquirt (or any after market tunable ecu) for a stock mx5? In particular a NA 1.8.

I have read a few opinion's, but nobody really provides any hard evidence, and I am struggling to find some figures/proof of people showing stock ecu vs aftermarket ecu horsepower gains.

I would imagine with some bolt on's it may be worth while, (Intake + exhaust setup). But I am curious if there are many gains to be had on a stock car.

Like most factory cars, one would think the stock ecu for the MX5 is on the safer/richer side of things, and probably designed on older 89 octane fuel?

i think you need to define worthwhile better.

Will it increase HP? probably a couple
Is it worth the dollars if that is all you going to do? No

I can suggest a couple of advantages an aftermarket ECU can offer:
1. POWER :-)
2. Driving features like flat shifting, launch control
3. Tuning flexibility, eg for E85
4. Diagnostics, like logging or dash output for a dash/aux display
5. Bragging rights

With a stock engine in a road car, #1 to #3 offer little improvement, so you are left with #4 & #5.

Consider that there are certain requirements for an aftermarket ECU to be considered road legal.

In general the tune needs to conform to the emissions laws that were current when the vehicle was made and it also needs to be locked so no changes ccan be made.

Given that it's an NA8 there are some other options if you're good with a soldering iron and understand your electronics and coding.

The simplest one is to buy and assemble Jaycar's digital fuel adjuster and hand controller. This is around $150 plus a few hours work. It allows you to modify the input signal from the MAF sensor to the ECU to trick the ECU into thinking it has more or less flowing under particular conditions. This means you can tune fuel to much better values right across the range. I got either 7rwkw or 9rwkw (can't remember which) using this on a stock NA8 simply by hand tuning on the off-ramps, then repeated it later on a dyno.

The other one is extremely geeky. Take out the stock ROM from the ECU and solder in a ROM holder into which you insert new EEPROMs with revised fuel and ignition timing maps. The investment is only about $60 in parts and tools but a LOT of time learning your way around code software and EEPROM burning. To really get value out of it you need to get a wideband sensor so you can accurately measure fuel mix. It's probably good for around 10rwkw on its own but it's a cleaner more efficient mod than the Jaycar which is pretty rough and dirty. With sensible exhaust and intake mods plus some cleanup of heads and maybe mild cams this will get you to 90rwkw from a stock NA8's 65-68rwkw. There's a very long read at http://forum.miata.net/vb/showthread.php?t=226162

Both options limit you to a fairly stock engine config, i.e. non-turbo, retaining the MAF and all the other sensors and using pretty close to stock cams but you do get all the advantages of OEM management of cold starting, idling, A/C and P/S switching, etc combined with aftermarket like ability to redraw all your fuel and timing maps and set your own rev limits.

At the moment, I have no plans for any major engine mods, down the line would probably be a exhaust system, possibly some cams/head work but it would be at a later stage.

I would like to learn to tune my own cars, and figured maybe it would be better if i learnt on a stock motor, I like to think I have a basic understanding of how tuning works, but still have a million questions!

Hi There,

I have a Jaycar DFA with hand controller to suit, fully built and ready to plug and play. Throw me an offer if you're interested.

I intended to put it in my NA8 a number of years ago but it was written off. I've since bought an SP and have built a Megasquirt for it.

Regards,
James

manga_blue wrote:Given that it's an NA8 there are some other options if you're good with a soldering iron and understand your electronics and coding.

The simplest one is to buy and assemble Jaycar's digital fuel adjuster and hand controller. This is around $150 plus a few hours work. It allows you to modify the input signal from the MAF sensor to the ECU to trick the ECU into thinking it has more or less flowing under particular conditions. This means you can tune fuel to much better values right across the range. I got either 7rwkw or 9rwkw (can't remember which) using this on a stock NA8 simply by hand tuning on the off-ramps, then repeated it later on a dyno.

The other one is extremely geeky. Take out the stock ROM from the ECU and solder in a ROM holder into which you insert new EEPROMs with revised fuel and ignition timing maps. The investment is only about $60 in parts and tools but a LOT of time learning your way around code software and EEPROM burning. To really get value out of it you need to get a wideband sensor so you can accurately measure fuel mix. It's probably good for around 10rwkw on its own but it's a cleaner more efficient mod than the Jaycar which is pretty rough and dirty. With sensible exhaust and intake mods plus some cleanup of heads and maybe mild cams this will get you to 90rwkw from a stock NA8's 65-68rwkw. There's a very long read at http://forum.miata.net/vb/showthread.php?t=226162

Both options limit you to a fairly stock engine config, i.e. non-turbo, retaining the MAF and all the other sensors and using pretty close to stock cams but you do get all the advantages of OEM management of cold starting, idling, A/C and P/S switching, etc combined with aftermarket like ability to redraw all your fuel and timing maps and set your own rev limits.

Hello magna blue. I have a complete stock na6. Do these options apply to 1.6l as well? Also, what do i need in order to read coding and tune the car? Thx

I socketed mine 5 or 6 years ago. It's been rock solid ever since so I haven't had to keep up with developments.

At that time they had only cracked the NA8 ECU. This was the easiest one because it had separate ROM and processor chips. The ROM holds all the code and the data, including the fuel and timing maps, while the processor just processes.

I think the NA6 ECU had a single combined ROM/processor chip which was defying all attempts to decipher it at that time. I don't know how that went. If you go back to the original miata.net thread at http://forum.miata.net/vb/showthread.php?t=226162 then you'll find some chat about spinning off a second project to crack the NA6. You might track it from there.

What do you need to do it?
- ability to read through 100 pages of the NA8 tread and then through whatever's been written about socketing the NA6
- soldering iron and solder and desoldering wick
- ROM socket holder and new EEPROM chips from http://au.rs-online.com/web/
- cheap EPROM programmer like this off ebay
- old PC with parallel port (mine was an old Dell desktop from a hard waste collection)
- TunerPro software
- working knowledge of binary formats, binary editing, machine coding, etc,
- sample NA6 BIN (ROM code/data) and XDF (ROM code/data format) files from a forum
- also helps for tuning to have wideband sensor and data logger for O2 and RPM

Let me know how you're going.

Thx for ur reply. This is completely new learning curve for me. It will probably take me months to sort it out. Dont even know if i will diy now lol..