The Definitive "don't swap in a VVT motor with a stock ECU" non-Megathread - Miata Turbo Forum - Boost cars, acquire cats.

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Old 08-28-2014, 03:18 PM   #1
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Default The Definitive "don't swap in a VVT motor with a stock ECU" non-Megathread

That is a big IF because I do not. I am running on stock 94 ECU.
Car starts, but dies immediately, I presume because the ECU doesn't see a signal from the coils to confirm it is running.
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Old 08-28-2014, 03:22 PM   #2
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I believe so. And dont those coils require a different dwell than the 94 coils?
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Old 08-28-2014, 03:25 PM   #3
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I thought I remembered it was the same dwell and others had done this on stock ECU without issue. I am now half into this and need to figure out the finish so I can have a running car again.
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Old 08-28-2014, 03:28 PM   #4
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Don't run swapped cars on stock ECUs.
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Old 08-28-2014, 03:32 PM   #5
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Don't run swapped cars on stock ECUs.
Friends don't let friends run stock ECUs.
You can get an rpm output box, but it's a bandaid.
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Old 08-28-2014, 04:51 PM   #6
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That is a big IF because I do not. I am running on stock 94 ECU.
No, it's not a big if. Get a standalone.
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Old 08-28-2014, 04:54 PM   #7
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Why stand alone? This is a NA daily driver. Not FI. Budget daily driver. Been running great on stock ECU, WHY stand alone? Makes no sense to me. I guess I will go back to 94 coils until I have time to figure out the wiring.
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Old 08-28-2014, 05:25 PM   #8
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Originally Posted by Amellrotts View Post
Why stand alone? This is a NA daily driver. Not FI. Budget daily driver. Been running great on stock ECU, WHY stand alone? Makes no sense to me. I guess I will go back to 94 coils until I have time to figure out the wiring.
With a stock ecu on a 94 there is nothing you can wire to fix the issue. The VVT coils do not output the signal that a stock ecu needs.
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Old 08-28-2014, 05:41 PM   #9
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Originally Posted by Amellrotts View Post
Why stand alone? This is a NA daily driver. Not FI. Budget daily driver. Been running great on stock ECU, WHY stand alone? Makes no sense to me. I guess I will go back to 94 coils until I have time to figure out the wiring.
Why would you want a standalone?

I don't know, maybe running a box made for a 8.8:1 motor with a 10:1 motor might not be the greatest idea in the world. I mean, you have literally nothing to gain outside of torque and power and not blowing up your motor, but you seem to have it all figured out.
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Old 08-28-2014, 05:53 PM   #10
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Originally Posted by Amellrotts View Post
Why stand alone? This is a NA daily driver. Not FI. Budget daily driver. Been running great on stock ECU, WHY stand alone? Makes no sense to me. I guess I will go back to 94 coils until I have time to figure out the wiring.
Running a 10:1 motor with 200+cfm ports on an ECU designed for 8.8:1 compression and 170cfm ports is not intelligent. I assume there's no wideband so you have no idea how lean it's been running. Not smart at all.

There is no "figuring out" the wiring - your stock '94 ECU will never drive the tachometer in the absence of the coils.

If you want to continue the discussion within the scope of the stock ECU, start another thread. This thread assumes that you're using a standalone, as stated in the original post.
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Old 08-28-2014, 06:06 PM   #11
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Quote:
Originally Posted by Amellrotts View Post
That is a big IF because I do not. I am running on stock 94 ECU.
Car starts, but dies immediately, I presume because the ECU doesn't see a signal from the coils to confirm it is running.
Yup - as a test, I tried swapping the stock ECU and MAF back in to my 95R / VVT with VVT ignition coils, and had the same results. It fires up immediately, and shuts down within a second or two.

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Old 08-28-2014, 06:08 PM   #12
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In for deleting the last ten or so posts
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Old 08-28-2014, 06:19 PM   #13
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^I wouldn't be surprised that some folks have attempted to run their VVT swap, at least initially on the stock ECU, who were unaware that it flat-out won't run for more than a second. That would be good information to put in the sticky.

In my case, I needed a replacement engine, and it just so happened, a VVT was available locally, for a good price. Luckily for me, I already has an MSPNP in the car. If I only had the stock ecu, and bought the engine, I'd have been out of luck.

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Old 08-28-2014, 06:28 PM   #14
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The wide band shows a perfect AFR everywhere but idle where it is a little lean. Car runs GREAT on stock ECU. I wonder if the VVTuner can give me the signal I need?

The stock 94 ECU runs the VVT engine perfectly. I am using a VVTuner to control the VVT functions.
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Old 08-28-2014, 06:31 PM   #15
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It's much more efficient to have a writeup of the proper way to do things instead of listing all the donts.
Running a VVT engine using 1.6 ECU + AFM is not a smart thing either.

Remove the coil near plugs, ziptie the 94 coils somewhere and run it that way, until you decide not to.
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Old 08-29-2014, 11:09 AM   #16
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Originally Posted by Amellrotts View Post
The wide band shows a perfect AFR everywhere but idle where it is a little lean. Car runs GREAT on stock ECU. I wonder if the VVTuner can give me the signal I need?

The stock 94 ECU runs the VVT engine perfectly. I am using a VVTuner to control the VVT functions.
This is some straight up TDR ****.

I found it guys... the Perfect AFR... It's so beautiful...

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Old 08-29-2014, 11:22 AM   #17
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Originally Posted by Amellrotts View Post
The wide band shows a perfect AFR everywhere but idle where it is a little lean. Car runs GREAT on stock ECU. I wonder if the VVTuner can give me the signal I need?

The stock 94 ECU runs the VVT engine perfectly. I am using a VVTuner to control the VVT functions.
I do not believe that the VVTuner will output a proper tach signal. I can believe that a stock 94 ecu with VVTuner could run a VVT engine in a way that would be safe and fun to drive on the street. Yes a standalone may be able to get a better tune, but if you are not tracking the car or driving it extremely hard I doubt you would have any problems with stock ecu and VVTuner.
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Old 08-29-2014, 11:30 AM   #18
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Originally Posted by Dunning Kruger Affect View Post
This is some straight up TDR ****.

I found it guys... the Perfect AFR... It's so beautiful...

Dude calls me a liar with no evidence at all that what I say is false? I guess we know who was bottom this morning! Don't be a dick

The stock ecu runs the VVT engine perfectly. And, I drive it very hard in the mountains spending many hours above 6K.

Lars, I am already putting the 94 coils back on, Thanks!

I will see if I can find the dyno run from a dyno day, not sure if they printed the AFR's or not. Either way, I don't care. The car runs great and has been seen doing so by many at several of the miata gatherings in the area.
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Old 08-29-2014, 11:34 AM   #19
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at title change.

Good read though. I had been tossing the idea around of a VVT swap. Good thing I have a MS2.
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Old 08-29-2014, 11:49 AM   #20
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Originally Posted by Amellrotts View Post
Dude calls me a liar with no evidence at all that what I say is false? I guess we know who was bottom this morning! Don't be a dick

The stock ecu runs the VVT engine perfectly. And, I drive it very hard in the mountains spending many hours above 6K.

Lars, I am already putting the 94 coils back on, Thanks!

I will see if I can find the dyno run from a dyno day, not sure if they printed the AFR's or not. Either way, I don't care. The car runs great and has been seen doing so by many at several of the miata gatherings in the area.
I didn't call you a liar, but hey, keep continuing living in your fantasy world with your singular perfect AFR and where I'm making up ****.

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Originally Posted by shuiend View Post
I do not believe that the VVTuner will output a proper tach signal. I can believe that a stock 94 ecu with VVTuner could run a VVT engine in a way that would be safe and fun to drive on the street. Yes a standalone may be able to get a better tune, but if you are not tracking the car or driving it extremely hard I doubt you would have any problems with stock ecu and VVTuner.
You forgot to mention that the safe way to run it is an AFPR.
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