Question about tuning
 

My Miata will be going in to get tuned in the next few months (early March) and I've never had a car tuned before. The shop that's doing it is usually squeezing every last bit of power out of the motor and I'm not sure if that would be safe for my build transmission and/or diff. Do I tell the tuner to stop at a certain horsepower/torque or how does it work? Currently have a 10AE 6-speed with a euro 3.636 rear end equipped with a torsen and the engine is a built bottom end, rebuilt BPZE head, and a Garrett GT2860 turbo.

Just from years of creeping this site and as my build ended up about identical (minus VVT's) to some YouTuber with a red Miata the motor might be capable of making 400whp on full e85 and if that's true I have serious concerns about blowing my transmission and/or diff while it's on the dyno before I even have a chance to drive it. Would you tell the tuner to stay under a certain limit or is that not how tuning works? Do they just tune you on a low boost setting and then everything adjusts if you turn the booth up and then I just need to keep it turned down? I might be worrying for nothing too and over estimating my potential numbers. I really am only looking for 300whp on the high side to use at my two somewhat local tracks (MPH and RPM in Nebraska).

What ECU are you running?

If you want 300whp tell them to tune fo 300whp. Should take between 15-18psi to get you there on a disco potato.

You shouldn't blow up a trans or diff doing power pulls on the dyno. So, make sure it's tuned for higher boost but with safe timing, don't worry so much about numbers when doing this. Then tell him that you look to run the car at around 300hp and have him finish it at and set it at whatever boost level that may be.

This way when you are bored at 300hp you just turn up the controller.

Running an MS3 with an AEM flex fuel sensor. Also, why do people refer to the GT2860 as a "disco potato"?

Tuning is generally started at wastegate, then slowly build your EBC map for optimal spool, then increase the duty cycle gradually, ensuring fuel and spark are happy. Eventually you'll add a few PSI and only gain a few HP, at which point there isn't any point, beyond blowing motors up, on going any further.

If you set a desired HP and/or TQ limit, they will stop when the reach it, a good shop will call you from the dyno with any issues, or to verify you're ok stopping. For instance, if you ask for 250/250, and they make 220/250, do you want them to stop at the TQ limit or continue to the HP limit?

I agree with the above however, dyno pulls don't generally grenade drive train components. Ask them to tune within the efficiency of the turbo, but finish with your HP/TQ limits.