Project Miata Update

 

Finally got a chance to do some street tuning of the Miata with my dad behind the wheel and me in the passenger seat focused on the laptop computer. We started off slow just in the neighborhood and as we gained more confidence we ventured further away. Filled up with fresh 93 octane fuel. Did some auto tuning and tried to hit as many throttle position / rpm bins as we could, riding the brake to simulate loads when necessary.

 

 

Coolant temps were stable around 200F the whole time, with brief spikes to 215F immediately after a hot restart (when we filled up gas) and during a few wide open throttle runs, which seems reasonable. But my intake air temps (MAT) were much higher than desired, especially given it was a cool day (50F). I think this is due to the coolant return hard pipe that is routed right underneath my velocity stacks. I’ll need to insulate this bare aluminum pipe with some fire sleeve and possibly fabricate a splash shield to go between the pipe and the air filter and insulate it with some of that gold foil stuff. I’ve got some ideas….

I’d say the tune is about 25% of the way there. I have some pesky sync loss errors that need to be addressed before I feel confident enough to spend the $ to book the dyno time to really get this thing dialed in. Not really sure where to begin fixing those, but I might just start by throwing new cam and crank angle sensors at it. I’m think I’m also going to revert to MS3 1.4.1 firmware as the developers of 1.5.0 paid no mind to Alpha-N users when they added the new “engine states” feature that uses different logic than before to determine when the engine is in overrun. Because I have no MAP sensor connected to my engine I have disabled the Overrun Fuel Cut feature for now.

We definitely need some acceleration enrichment to address the poor drivability immediately off idle. With ITBs, at very small throttle openings, very small changes in throttle position results in very large changes in the amount of air entering the motor. This can only be overcome with acceleration enrichment. The manual recommends tuning AE only once the main VE table is dialed in, but in this case I don’t think I have much choice. I’ll have to add some AE to address that one area and then retune. It’s all iterative. Same thing with my after start enrichment (ASE) % and taper and warm up enrichment (WUE) settings. To get started I did what I had to do to keep the car running until it was up to operating temperature. But now that we’ve changed so many parameters on the VE1 table I need to go back and spend more time dialing in those settings.

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