DIYPNP - 00 to 03 VVT Tune Changes
 

Installing a new 03 VVT motor this weekend, however the car was originally tuned on a 00 motor.

I reduced spark advance by 5 degrees for the added compression safety buffer, and will obviously need to re-tune the VE tables, but I'm wondering if there are any settings I will need to change to get the car up and running. Experience so far tells me no, but I'd rather be safe (with a drivable car) vs sorry (stuck).

I have Savington's extremely helpful VVT wiring directions so I should be set with wiring.

Any input on tune changes is greatly appreciated, even if it's just to tell me I'm being overly-paranoid. TIA

New motor is in but car will not start.

Tried to put in OEM ECU, injectors, and MAF to get the car running quickly but I am not getting a CEL with key in On position, no spark, no fuel pump activation so no fuel pressure. Tried another OEM ECU with same no-start results.

Investigating possible fixes now. If anyone has any ideas, I'm all ears.

Make sure all your grounds are attached.

What'd you do for spark? Is the CAS still hooked up?

All grounds appear to be in place. I have the one on passenger side behind the #4 injector, the one in between the throttle body and the motor, and the one that attaches to the transmission plate on the driver side. Any others I am missing? Car is a 96 chasis.

Spark is OEM '03 COPS, wired with Savington's directions linked in the first post. CAS is used and motor is timed correctly.

Looking into the main relay now since ECU isn't registering, but the relay looks good on inspection after removal...

It's the main relay. I checked the wrong one until I found this:

https://www.miataturbo.net/attachmen...-mainrelay-jpg

Pulled it out and one of the male connectors is covered in goo at the base.

Confirmed that the main relay failed.

If anyone is interested here's the broken one on the left and a working one on the right.

So I got the Brain DIYPNP back in today after seeing some lean WOT AFRs using the OEM ECU, but it's running pretty rough. I think there could be an issue with my spark settings after rewiring so I can use the '03 OEM COPS. I searched, but all threads I found focused on dwell times which I adjusted, however I'm confused where to focus my efforts next.

Basic setup is a '03 VVT long block (replaced a '00 long block) in a '96 NA chassis. I am using the intake manifold/TB, cam angle sensor, along with the crank angle sensor and 4 tooth trigger wheel from the '00 motor. Ran pretty well on OEM ECU, except for WOT was too lean for my liking.

Tune changes:

FUEL
- req fuel to 11.8 (for NB2 265cc injectors)
- injector dead time to 0.60
- voltage correction 0.10

SPARK
- Cranking dwell to 5.0
- Nominal dwell to 3.5
- dropped 4800+ spark 5 degrees for safety margin with added compression

Any ideas past what I've done so far? I've been spending a lot of time searching, but nothing I've found explains why it runs so rough.

Attached basic idle log and current tune. I am more than willing to provide pictures or any other info, just let me know what's needed.

Thanks in advance. Any help greatly appreciated to get my car drivable again.