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Old 05-27-2012, 03:04 PM   #1
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Default Turbo tuning w/o OBD, 1990 miata? HOW

Very simple ? here. I searched around but as I am very illiterate on a computer i figured id ask for some quick help here. Ive got a 1990 miata that is turbo'd w/ a completely fabricated setup and no tune. I am familiar with turbo tuning for OBD cars but have never dealt with, or leared about tuning without an OBD port.

Its not like they didnt have turbo cars in '90. How is it done, a link to a post or thread would be great as im sure im reposting an old topic (sry seriously). I have tried a piggyback system one time on a toyota and I will assure you i will never again by one of those units, so any info on what that leaves me with or resources would be greatly appreciated. Im sure the compression on this car is way outta wack and its already blown one motor (not im my posession). Just bought the car with 91 motor w/ 61k just installed, id like to make this one last. Thanks ahead of time for being patient w/ another miata newb!
-R
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Old 05-27-2012, 03:10 PM   #2
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Old 05-27-2012, 03:13 PM   #3
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Only this can sufficiently sum up what it is like to try to read the OP.
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Old 05-27-2012, 03:31 PM   #4
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The Miata does not have a re-tuneable ECU. If you aren't buying a piggyback system, you'll have to buy a full replacement standalone ECU.
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Old 05-27-2012, 03:49 PM   #5
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The most cost effective standalone is the MegaSquirt. It can be purchased as a kit from DIY Autotune (DIY PNP), or as a complete unit from them (called MSPNP), or assembled by an individual like Braineak or Reverent here on the forum. What is the car using now?
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Old 05-27-2012, 04:49 PM   #6
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As far as I can tell it has no EM to accomodate the mods. Ill have to check the ECU when girlie gets off work but from the looks of the rest of it I seriously doubt this has been done remotely correct. Unknown AiResearch turbo welded all the way back catless to dual "fart cans", ghetto IC piping bits and pieces, and it came with no intake so it was just open MAF sitting right behind the radiator! IWG is run back to turbo so must just be on WG pressure. Still keeping the car completely out of boost until i can figure out where to go from here.
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Old 05-29-2012, 09:56 AM   #7
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Yeah, you can just disconnect the wastegate arm from the flapper door arm and keep it out of positive pressure.

If it doesn't have engine management it may have a rising rate fuel pressure regulator to attempt to compensate for the need for extra fuel. They are crude and barely tunable but cheap and people who are afraid of standalones have tried them occasionally throughout history. They are out there. Or they may have done nothing.
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Old 05-29-2012, 11:11 AM   #8
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Old 05-30-2012, 05:33 AM   #9
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Actually, even with a wastegate wired open you'll generate a few pounds of pressure. Do not drive the car at all, it's not safe for the engine in or out of boost. If tue turbo is good l, you will be generating boost as low as 2500rpm with hardly any throttl input.
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Old 05-30-2012, 09:27 AM   #10
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Dude, we need some pictures of your setup. Take a few pictures of the engine bay.

Specifically, we need a picture of the turbo and intake setup.
Picture of the fuel injectors.
Picture of the stock ECU (it's in the passenger footwell and bolts to the firewall).
Picture of cockpit.

Take these pics, upload them to photobucket, and post them for us to see. Do this now.

And has been mentioned, you cannot tune/flash/modify the stock ECU... you will need an external computer, either piggyback or standalone to assist/replace the stock ecu.

However, it's completely possible to get a perfectly driveable tune using a few basic mechanical "bandaids"... we just need to know exactly what you've currently got so we can point you in the right direction. TAKE THOSE PICS!
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