Boost spike is when your boost shoots up past the desired amount and then quickly settles back down. Your boost should come on quickly, but only to your desired amount. A spike can cause you to hit FCO, run lean, blow off intercooler hoses, basically anything that could come from boosting higher then your system is designed to do. If your spike is within the safety bounds of your system, then you should be boosting higher to get more power out of the entire curve.
You don't want the wastegate to open until the last possible moment. However with most setups that needs to be about 1-3psi before your desired maximum boost otherwise it may not open in time and you'll get a spike or an unstable boost curve.
You don't want the wastegate to open until the last possible moment. However with most setups that needs to be about 1-3psi before your desired maximum boost otherwise it may not open in time and you'll get a spike or an unstable boost curve.