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I was looking for a RWD weekend/track/project car for some time last year, and in late autumn finally found this Turbo NB in New England. Far from perfect, but rust-free with some important mods already done. I've been adding to it over the winter with the goal of being somewhat competitive in autocross, but street-able in the summer. Hopefully a track day or two by the end of this year. I have always DIY'd maintenance for my daily cars, but this is my first dedicated "fun" car, so I'm using it to really learn mods and tuning. Already has one autox in the books this year, and performed far better than my expectations save for awful hot-start idle and stalling issues.
Specs:
2003 Miata LS 1.8 VVT w/134k
Turbo swap from MSM NB
Megasquirt MS3 Pro ECU
700cc injectors
Torsen diff swap
Koyorad radiator
Intercooler
FM downpipe and exhaust
Performance clutch and flywheel (unknown brand, not very comfortable for street driving tbh)
MiataRoadster Long Angled short shifter
Tein Street Flex-Z coilovers
FM sway bars front and rear
FM adjustable end-links
Hard Dog M2 Sport roll bar
15x8 Konig Hexaforms w/ 205/50/15 Bridgestone Potenzas RE-71RS
What it needs:
Tuning help - runs great cold and pulls strong through boost, but poor warm starts and idling. Intermittent lean condition under low-load
New soft top - as I write this it is pouring outside... I'm sure the floor is getting a bit wet
Performance alignment
Brake upgrade
I appreciate anyone's advice as to where to start for the tune (should I make a separate post in the Megasquirt sub-forum)? I pulled the tune onto TunerStudio and even with my cursory knowledge some things seem out-of wack. And any suggestions for a soft-top installer in CT/RI/MA?
Welcome to the rabbit hole that is a turbo miata track car. Nowdays it's a pretty reliable formula (compared to the dark ages), and there's no reason you shouldn't be able to dial that setup in to turn safe laps. But I would recommend you look into a coolant re-route and make sure your undertray is on and ducting is on-point. It's a weak point on these cars for sure, especially if you have A/C. Probably not needed for street and auto-x though, just talking about road course duty.
Definitely get some tuning help. Local that knows MS/miata's and has a dyno is ideal, but if not there are some guys on this forum that can help you out remotely and get you a safe tune. In fact my buddy at caffinated cat @redursidae just tuned a local MSM on a MS3 and could probably help you with that tune remotely at a reasonable rate. Also you can post your .msq and a datalog here and probably get some free constructive feedback right here if you are more of a DIY guy. I bet VVT + MSM setup would be pretty fun!
That IAT sensor location you have is hot garbage and is gonna heatsoak. I'd recommend you move it to your coldside intake for much more reliable hot starting/running. It's fine for now and you can tune around it, but again, I'd recommend it.
Your PCV system should probably be looked at, at the very least run that open breather to a can with a VTA filter as a start (and make sure your PCV valve is working ). If you end up with issues and/or want to get more track focused there's a lot of upgrades that can be done to that system.
Looks like a good clean car otherwise that could use some basic sorting to get it track ready. Nice buy!
Hey Fireindc, appreciate the suggestions! I know there's a ton of potential, just needing to sort through somewhat questionable mechanic work that I know exists - but without knowing exactly what I'm looking for. A/C and undertray were both long gone before I got the car. Heatsoaking IAT makes sense and noted on the PCV system.
Attached is the tune if anyone cares to check it out. Like I said, I know there are some weird things going on with it. I just downloaded TunerStudio this week and already feel like the previous tuner might not have known much more than me? Or at least took some shortcuts haha. Haven't made any adjustments yet myself. If anyone knows a tuner in southern New England, please let me know. Also totally down to work remote with an experienced tuner here!
A note about the datalogs - it took me a little bit to get the AFR recording and it still needs to be properly calibrated and shows a more lean reading than the actual gauge displays. For example, when it shows 18 AFR, it's actually more like 17 AFR (same approx ratio through the scale) - still much too lean for comfort! I will try to get this sorted and make some more accurate passes once it dries up here.
My No1 piece of advice is to watch out for the rods - (don't) ask me how I know this. Basically, they are the first weak point in running these engines hard, especially boosted (even with that pissy little IHI turbo). Plan on replacing them sooner rather than later, and have a contingency plan for when/if they fail before you are ready.
Common locations for the IAT sensor are the cold side of the intercooler or somewhere in the piping between there and the throttle body. Just know that if it is immediately behind the radiator, it might not pick up as accurately because of heat soak.
The difference between the AFR reading on the gauge and in Tuner Studio may be a result of a voltage offset difference. Run a ground wire between the ground of the gauge and the ground of the ECU to help normalize the readings. The gauge draws fair amount of power. I sourced power for my gauge from the power window circuit as it passes through the center console. Power windows draw a lot so that circuit is made to handle some load.
Welcome. At quick glance, Ignition table is pretty retarded, afr target is pretty rich, no idea if you're actually hitting target (didn't look at the log yet), timing correction curve isn't aggressive enough, EGO isn't enabled, your MAT density table is going to cause you headaches, and ASE probably isn't helping hot restarts. I would concur that the previous tuner probably wasn't an expert, but appears to at least be conservative.
In addition to Curly's comment, the VE table is certainly not right, and I think it has to do with the Required Fuel being set at 11.6 instead of 3.1 that it should be for 1000cc injectors, if that's what the car is really running. The injector data is also certainly incorrect, with no corrections between 12 and 17V.
Hi guys - I appreciate the feedback for sure! The required fuel calculation was one thing that cued me off with this tune. Car has 700cc injectors. Even with the conservative AFR targets, I am over lean on low load. Will enabling EGO help compensate? Thinking I should try starting from scratch on a new tune? Or can someone point me in the right direction to a baseline or someone to work with?
And unless I'm misunderstanding something with the IAT, it is on the cool side of the intercooler, right before the throttle body. Seems like a fairly standard location when comparing against other engine bays? The car does not get hot but it would make sense that the sensor is heatsoaking because my issues happen once the car sits for a bit.
Happy to be a member and thanks again for helping sort through these questions!
EGO correction might help, but you really ought to tune it properly, and you also got to make sure the AFRs in TunerStudio match the gauge. I would say starting from scratch is not a bad idea given all the things I'm seeing on your MSQ. For starters, since the REQ_Fuel is wrong, then you could start by correcting that (with the built in calculator, around 4.4 for 700cc injectors) and multiplying the whole VE table by 2.6 . That would at least give you a more realistic VE table but I'm still suspicious of the overall shape in the lower load areas. If you want to try tuning on your own, get a TunerStudio license, MegalogViewer HD, and have a read through this forum, the Megasquirt manual, and there are many youtube videos about megasquirt tuning. Most questions you may have are likely answered in one of those spots and we can help with Miata specific things.
Hi! NB Autocross & Track Build
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