I have the older 1715 with one program. I have read several posts saying that it requires 91+. My question is: what harm is there in running 87? Is it just loss in performance or can it do some kind of harm to sensors in the system?

 

Welcome malongway,
Using lower octane gasoline than what you're pcm is set up for can cause detonation(premature combustion) which can lead to serious internal engine problems...Kevin

 

The tuner you have requires 91 octane or higher. As mentioned in the reply above, detonation will occur and cause damage to the engine. Return to stock program or pay for 91 octane and keep the tuner. Sorry.

 

I thought higher octane was mainly for eliminating knock in higher compression engines. Does anyone know what it is about the tune that changes the octane requirement?

 

Hi.

For sure, tuners bump up the timing advance, at different throttle settings and loads. This is one of the primary ways ( but not the only way) a performance tune generates increased power. You MUST run 91+ Octane, and QUALITY , High energy fuels for best results and damage avoidance, if you use the performance tune setting on your SC.

These engines are not particulary high compression... one reason the factory tune can run 87 octane...

Cheers