vykanos

Howdy --

Long time car guy, first turbo 1.6 Miata build. I'm transitioning from my history of 5.0L Fords and turbo Subarus to this 1991 Miata project, and I've ordered a Kraken GT2554R kit direct, it's probably still several weeks away according to the fellow who runs the place. I've got 25 hobbyist years of theoretical knowledge and wrenching experience on turbos and natural cars alike, but this will be my first time adding boost to a car that had none before.

While I'm waiting for my kit to arrive from Bulgaria, I've installed an MS2PNP, removed the stock airbox in lieu of an Autozone hot air intake with a GM IAT, and switched to a SpeedyEFI variable TPS, all of which I've now tuned up pretty well. I haven't yet installed my AEM wideband since my downpipe isn't here yet, so I'm a little blind on AFRs but the car runs 99% great, and I'm making good progress on the cold start/idle settings over time. It's already noticeably quicker in the upper RPM band than it was, at least until the HAI takes my intake temps up into the 140s.

Question one: I have very slight tip-in stumble when the car is hot and I blip the throttle at idle, for downshifts, et cetera. It was terrible at first, I had to move the AE map much richer/more aggressive than the megasquirt base map, and had to use the %WOT TPSdot to get it working well off-idle. Now it's 99% perfect but RPM still dips the tiniest bit on the first throttle stab after a long idle, and I get a teeny little clatter of detonation no matter how rich I tune the AE for the first hard stab off-idle. Any suggestions to help that out? I'm using TPSdot only, you can see the effect of that at the very end of the attached log, if you're so inclined. Only the first throttle stab in a series causes this, after that (presumably?) it seems like there's enough fuel from my rich-*** AE map soaking the ports to prevent this.

Question two: Is anyone running the 700cc Bosch injectors that Kraken supplies with great success? I threw a set of them on the order because the price was right, but I'm growing concerned that they might be overkill for my 8-10psi goal. My intention was to begin with the stock injectors at 6psi and not to do anything more until I had that tuned in just right, and then deal with the injector upgrade tuning, then up the pressure later on. Sound like a good idea, or would you suggest a different order of operations for my first time through? Is there any hope for a decent idle with these in batch-fire?

Grateful for any advice y'all have to offer, thanks!

Edit: I can't get the log to attach, working on it.
Edit 2: Fixed that

Dr.Sep

I, personally, wouldn't run any boost with stock injectors -- tunerstudio makes scaling for different size injectors really easy and I would absolutely rather have more fuel than not enough with boost

Joseph Conley

I agree with Dr.Sep.

Modern injector designs are much better than what originally came on the car. They are a cheap investment to get a well-running car. Worth every penny. Are you in the US? 1.6 cars typically have batch injection(non-CA). If your SpeedyEFI supports sequential injection, look into converting to that. The car will idle better, have better drivability, and make tuning easier.