Turbo Miata Guys - Standalone EMS Questions

A few months ago I bought a turboed '94 Miata project. The turbo setup is an older version of the FMII system, running the Link piggyback engine management.

Overall, I'm happy with the bits-n-pieces on the car, but unfortunately all the goodies were installed in a pretty crappy manner. After filling a notebook with all the issues that I want and/or need to address, I've decided to just dismantle the whole damn thing and start from scratch.

The car recently developed a strange electrical glitch, causing a loss of spark, loss of tach and a re-boot of the Link keypad. Injectors continue to fire, however.

Since the previous owner decided that a good location for the factory ECU case was on the passenger floor, with the harness carefully strewn-about, and since the Link is beyond its sell-by-date, I've decided to go the standalone route.

Basically I'm deciding between the Hydra-Nemesis, or the Megasquirt PNP Miata system. Since I've never really messed around with engine management much, which would be the least painless to install and come up with a base map for?

This will be going on a fresh engine, so I would like the fewest headaches as far as getting a base tune for engine break-in, before it goes on the dyno.

Thanx for any input!!!

Both have excellent support communities. The Megasquirt saves you enough money to buy wider wheels and tires, which you will need with a well-tuned FMII system

I'm using the MSPnP. It works really well once you get the learning curve down. That learning curve, for me, was steep. The benefits are that support is an email away. Those guys at DIYAutoTune respond FAST! Also, I was able to start tuning my car the day I installed the MSPnP. I just didn't know what all the adjustments meant.

My car runs well so I can't complain. I installed larger injectors and had them up and running in a day. All in all I'd buy the MSPnP again. Just get a wideband to go with it. I can't imagine tuning without one. Hats off to Hess for tuning via narrowband on his projects.

Only time I’ve lost spark and tach randomly with Megasquirt was due to a bad cam angle sensor. It might be something to look into before swapping out engine management.

In reply to Pseudosport:

+1, miatas are about as easy as it gets with modern fuel injection. I had a similar issue with my stock 90' that ended up being a loose negative battery terminal.

Also, the factory ecu is supposed to be on the passenger floor, but with a substantial metal cover over it.

On a 94, the stock ECU location is behind the passenger's seat.

Obviously, I'm biased. But from what I've seen of a coworker trying to get a MS working on his car, the Hydra is quite a different beast in terms of ease of installation and setup. It simply doesn't get any easier than the Hydra, and I think the support is pretty good Plus it comes with a wideband, knock sensor and a number of other items that are optional on the MS or have to be sourced from different suppliers. I believe the Hydra offers more margin for safety of your engine as well, and it's a modern ECU instead of being based off an old processor.

But keep in mind that swapping to a different ECU might not solve your problem unless the Link is the problem. If you have bad CAS wiring, a bad ground to the ECU or some other problem in the car, you're still going to be chasing - but you won't know if you screwed up the ECU install or if you're dealing with the same problem.

Since you're losing the tach and the keypad, I'd be looking at power supply to the ECU. A CAS problem wouldn't affect the keypad display. How are you determining the injectors continue to fire during these momentary outages?

The keypads can also develop problems with the electrical connections that are easily repaired in 5 minutes with a soldering iron, and sometimes (rarely) these can cause problems with how the car runs. If you unplug the keypad, does the problem go away?

I wonder if you're losing your ground on that link. If the guy did a half-assed job installing it I'll bet the ground wire is either lose or has a broken connection.

If the link is installed in the stock location (behind the passenger seat) AND the cover is on the ecu, check to see if the delicate ribbon cable to the keypad is pinched by the ecu cover. On my link, the cover managed to nick the cable and cause all kinds of intermittent resets and shorts. Worth a quick check. When I replaced the cable, I reworked the cover, and wrapped the cable with additional material to keep it from happening again.

Keith wrote: On a 94, the stock ECU location is behind the passenger's seat. Obviously, I'm biased. But from what I've seen of a coworker trying to get a MS working on his car, the Hydra is quite a different beast in terms of ease of installation and setup. It simply doesn't get any easier than the Hydra, and I think the support is pretty good Plus it comes with a wideband, knock sensor and a number of other items that are optional on the MS or have to be sourced from different suppliers. I believe the Hydra offers more margin for safety of your engine as well, and it's a modern ECU instead of being based off an old processor. But keep in mind that swapping to a different ECU might not solve your problem unless the Link is the problem. If you have bad CAS wiring, a bad ground to the ECU or some other problem in the car, you're still going to be chasing - but you won't know if you screwed up the ECU install or if you're dealing with the same problem. Since you're losing the tach and the keypad, I'd be looking at power supply to the ECU. A CAS problem wouldn't affect the keypad display. How are you determining the injectors continue to fire during these momentary outages? The keypads can also develop problems with the electrical connections that are easily repaired in 5 minutes with a soldering iron, and sometimes (rarely) these can cause problems with how the car runs. If you unplug the keypad, does the problem go away?

I'll try unplugging the keypad tomorrow. For the time being, I've decided to hold off on switching engine-management. You're absolutely correct about chasing. The engine is coming out this weekend anyway, so that will give us a good chance to go through the wiring.

Right now, I'm leaning towards a bad ground somewhere. Drove the car around for a bit before work today, and the glitch hit twice. The first time, I was making a left turn, lost all guages, stereo, and turn signal. Rolled to a stop, dead. Turned the key off and waited a few seconds, then the car started on the first try.

A mile down the road, same thing, except I only lost the tach and keypad, but the car maintained a normal idle. Wouldn't rev past 800 rpm or so, but still had fire. After kicking the throttle a few times, everything returned to normal.

Hence the scratching of my head... I can't find any discernable pattern to when it happens, or even what happens when it, ummm... Happens.

Anywho, I appreciate all the input guys!!!

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If you're losing other things like the stereo, it's definitely not related to the computer. If you keep track of what goes down, you might be able to isolate where the bad ground or power wire is by seeing what all the problem circuits have in common. Losing the tach and keypad but retaining a running engine is a weird one, I can't think of how to make that happen.

The way this car was put together, I think I may be facing multiple bad grounds or kinked wires. As I said, the ECU is on the floor instead of behind the seat, and therefore there's about 6' of harness just kinda thrown in on top of it.

These things happen when you rely on pictures on the 'net when buying a car. The guy used quality parts on it, but very poor judgement in the build. For example, it's got the full 3" FM exhaust, but he failed to install a couple mainfold studs. Then he tacked a HUGE fart-can muffler on the back of it. That's gotta go!!!

Oh well, the engine is hopefully coming out on Sunday, so I can start the process of spaghetti-sorting.