ok if you where to use meth injection you obviously need to tune for that. now if you had your flash set up to run with meth would you have to use it always. or could you go with out if you couldn't get any methanol for some reason. thanks
It depends on how aggresive of a tune you have with the meth, If alot of your power is coming from the meth and you run out more then likely you would have a blown motor on your hands. That is where a failsafe comes into play, if you run out of meth the failsafe will switch to a consevative map by pulling timing and other factors. This is about as simple as I can explain it so I will leave the "refined" explanation to Warr and others.
You have to have a separate tune for sure. You can't be tuned for meth and turn off the meth, because you'd then go extremely lean and pop the motor if you boosted. You do not "run out" of meth. You just keep a supply and refill when you get low. Most kits have a low fluid warning light. Mine comes on at a 1/3 tank, so I have plenty of time.
If you want to run without the meth, then you have to upload a separate pump gas tune.