As far as I have understood, there isn't a plug-n-play Megasquirt version for 01-05 MX-5s. Is it really so? What exactly do you mean by DIY - it comes as bits and pieces which need to be assembled? I do not have any experience with electronics, if I buy an MS I suppose I shall need an expert to set up the hardware and then another expert to tune the software!
Which exactly type of MS should I be looking for ('02 1.8 VVT)?

Maybe I'll proceed with EMU, it isn't such a bad idea after all...

Your first premise, that you can get the EMU and harnesses for less than the cost of an EMB is the kicker.

I have been running EMB with my own version of "Autotune" because that is where I started years ago.

I wish that the EMU had been available when I first got into it for the versatility that it offers that others have pointed out(Most especially getting rid of the AFM on early NA's and reducing injection directly)

All things being equal, I think you would be best served with an EMU modified with an O2 clamp to keep the ECU from fighting it.

I went for the Emu from Bipes/Powercard/Aquamist at 200flywheel bhp because the a/f's were leaning out at the top end.

Certainly out of my comfort zone but I wanted to try 'proper' tuning. As has been said above you will need a clamp - though I am told some cars don't - and a wideband. I've recieved a lot of help, encouragement and advice from fellow enthusiasts on the forums. I would really recommend a boomslang harness as it eliminated the worry of iffy leccy connections. There are still hook-ups to be made and I am getting quite good at it now. Also some form of knock detection, I have the pigging great knocklite (Eunos1800 will tell you all about them) Really looking forward to fitting a set of 450 blue tops and an smaller pulley. This will be after I've been to the dyno to see if better fueling has given more power without spinning the blower even faster.

In short I am happy with an Emu though I did think long and hard about getting either an Adaptronic or Megasquirt. It's all a lot to get the old head round and I've made some classic mistakes but - ahem - ultimately worth it.

I'll finally proceed with EMU, it's now in my trunk and soon to be wired! Let me ask you guys something else: I've read that EMU can cope with idle droop (I have a TDR-like A/A I/C in front), could someone briefly explain to me how is this done?

Do not forget the custom solutions with piggybacks like mine.

The 8 injector set up with EMB. https://www.miataturbo.net/forum/t4097/


1)VERY EASY to tune
2)perfect driveability-almost like stock
3)low price-value for money

and 4) I handle over 400whp with this setup, I use it 3 years with no problems and 2 bar (30 psi) boost pressures.

Think it again sometimes.;)

I installed yesterday the E-manage Ultimate combined with an O2 clamp from Olderguy (thanks Bruce!).

Everything seems to work fine and AFRs I saw on the dyno are pretty good, except from the fact that my (narrowband) AFR gauge doesn’t move at all (!!!) while off-boost (looks as though the ECU isn’t cycling the injectors at all, is that possible???) but works fine while on-boost. Moreover, I have now a CEL after I drove for 50-60kms. Do you have any idea what’s going on ?? Just for your reference, the clamp was installed with the voltage provided by Olderguy (I think 0,32Volts)

I connected to OBDII reader yesterday and saw a Fault Code P0153 - O2 Sensor Circuit Slow Response (Sensor 1).

For your reference, I have connected the clamp to ECU pin 4W (Front O2 sensor) and to pin 4AF (+12Volts switched). My Miata is MK2.5 (2002).
The question (apart from the CEL) is why doesn't the AFR gauge have any indication while off-boost? Is the O2 sensor dead?

Do you see something wrong regarding the connections?

Answered your email question. The narrowband wire must be attached to the wrong wire if it was working before. It should be attached to the wire coming FROM the O2 sensor which is going to the Normally Closed switch connection.

If the gauge is not connected correctly since the beggining, how did it work in the first place? And something else...The AFR gauge DID work for some time after I connected the clamp/EMU and during the tuning on dyno, it just stopped working off-boost after 1-2 hours. Something happened in the meantime...But surely we didn't change anything with regards to connections, wires, etc. The only thing we did was placing the ECU cover back on.

If the gauge worked for a little while, then there is something amiss with the O2 sensor; Or; there is a possibility that the pressure switch is defective and is remaining activated all of the time.

Hook a continuity tester to the switch and blow into it to see if it is operating correctly.

Refer, please to my second email which asks why you have the white wire connected to a wire other than the switch.

I think you should decide which communication route you want to pursue and stick to it.

We can do it here for others to learn, or we can do it by email. But; both will cause confusion.

The wiring diagram for the O2 circuit is here:

https://www.miataturbo.net/forum/t2572/


The internal part of the diagram has been changed in the product itself, but externally, that is where the wires go to the power supply and switch.

The "problem" was solved: The wire carrying the front O2 signal towards the ECU had been caught by one of the 4 screws that hold the ECU cap on the co-driver's floor (remember, mine is Euro spec), thus acting as ground and sending out zero signal:bang:. So nothing was wrong with either the O2 clamp or the wiring layout (Olderguy, sorry for the trouble...). Now the signal towards the ECU is correct and the AFR gauge is alive again-with one exception: For the first 1-2 minutes after cold start it's dead, then it starts working again. Any ideas???

Let me add that it's not an AFR gauge issue (it works 100% fine), it seems like the front O2 sensor is "dead" for this short period of time after cold start, is this possible?