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1.8 NA8 1994 Mx-5 , SpeedyEFI Speeduino using TunerStudio

Practical Standalone Tuning

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I'm New to tuning, but not new to cars or performance. I'm a shop owner, and a tech of over 20 years.

My passion is driving, and I decided to learn EFI tuning as a supplement to my knowledgebase, and maybe something further if it comes to that and I get a dyno and acquire the knack for it.


1994 Mazda Mx-5 Miata, 1.8L NA8

Stock everything, MAF delete changed out to GM IAT. Innovative MTX-L + Wideband.

SpeedyEFI Speeduino (I know its cheap..) NA8 (1994-1995) PNP ECU with supplied NA6 PNP basemap which requires the sensors and trigger info for the NA8 WHICH I"M NOT 100% sure I've got them in there properly, although it did start and run last week on the narrowband for 10 mins, i've played iwth it so much since then i'm probably in the weeds... As well as I have the Wideband now as of yesterday.

ANYONE have experience on getting this setup properly?

I thought I had it because I had it running last week when it was warmer out for 10 mins. Then it got warm, stalled and would not restart. (This was on the narrowband). I figured it was the lack of true AFR reading, so I installed the Widbeand yesterday. Still not starting.

Datalog of cranking is attached if anyone has MegaLogviewer.

AFR's are FAT.. 7.4-8.5 But it never stays running, honestly I got lucky it ran for the 3-4 seconds it did in this log.

I bet my plugs are fouled, but there IS SOMETHING NOT RIGHT with my initial setting of the sensors, required fuel, engine constants, and possible spark or cranking data.

Really appreciate the help if anyone has any experience.

I completed all of the courses and passed all of the tests, but knowledge is only so far if you don't know the vehicle specifics and because the ECU PNP comes with 1.6 NA6 PNP file only, I have to make the proper adjustments for the 1.8 engine. Although the base map is from what i understand a good starting point for the 1.8 as well.

Thanks again in advance!


Attached Files


So after troubleshooting with the SpeedyEFI guys, I definately should have the correct Engine constants, trigger setup ect. And as even the above picture of the log shows it did start then Die.

My Base Timing is set, 10Degrees btdc So I'm ready to get this thing running and stay running.

If anyone can see the picture of the log, it shows the AFR as going as fat as 7.4-7.8. But I notice that is after it fires and then it dies. I will try some Starting fluid to see if she will run on it to confirm that it is not getting enough fuel and I need to play with WUE and ASE.

I'm thinking that maybe I shouldn't Trust the AFR at all at this point as as i'm cranking to get it to run (cranking 30 seconds or so) It is likely loading the cylinders up with fuel unburnt and for the moment it fires it reads Rich, but it does NOT stay running, so It could be still in theory running without enough fuel to keep it running. (Add to the fact that it was 45F yesterday.)

Any Advice greatly appreciated. MY FIRST tuning endeavor so sorry for being so vague and green to everything.

I guess this Forum is DEAD, and or nobody has any experience with the NA 1994-1995 1.8 L Miata engines and tuning. *Which i find that hard to believe*

I did find that my wideband needed a recalibration the innovate widebands are able to be recalibrated. And I used the engine ground / engine Harness eyelet negative at the back of the intake manifold (And I upped the Guage wire from 22 to 18). THEN my Ignition coil goes... from all of this cranking and battery charging i guess, that plus 29 years old... ANY WAY. New one ordered. I will continue to post my "SAGA" as it continues.

If anyone is reading this and would like to offer any advice, I'll take it!

Sadly im not home atm so i cant look at logs, but when it comes to speeduino, you need to calibrate the wideband for the type of fuel you are running, and if you have done that, look in the logs what is happening, does it goes super fat or super lean when dying? Do you have any idle motor etc?

Hi thanks for chiming in.

New ignition coil came and it was for a 3 wire 1996 up even though i ordered it for 1994. Well I traded with a buddy for a 4 wire set of coils.

Had it running for 10 mins. Playing with the VE table to get it to stay running. Wideband was responding after a few minutes of running. I can see the effective change of the Burn to ECU, in the Cells I were in I got the AFR's on the guage down to 15 or so from 18. Car stalls, then would not fire again. (My Ignition base mechanical issue is at hand ATM,)

I have changed the main relay checked power and ground at my CAS sensor found a split CAS ground wire casing going into the sensor right at the connector. So I ordered a new Pigtail. Installed, checked OHMs on the Ground wire, much better. Still no Spark.

I have been talking to the troubleshooting with SpeedyEfi, and they are saying if I am getting fuel spraying that the CAS is working. I am about to check that now, I might have fried another Coil b/c of bad settings, or something else..

SO The story goes on, wideband I believe is good now.. lol.

Car running... NOPE.

It was a setting, I had it set to Going High, when it is supposed to be set to Going Low with the SPeedyEfi / Speeduino ECU on Tunerstudios. I followed the Megasquirt setup which is also using the Tunerstudio software, but it is the opposite setting for some reason, and well they warn of blowing coils, I just never clicked the (?) Note box.

So I have started playing with the tune. I'm trying everything for the first time, I have no dyno for looking for MBT timing, and so I'm not touching the base Ignition Map supplied. As for AFR Target table, I wonder if the supplied Base Map is good.

Any advice for starting out is greatly appreciated.


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