T.M.808

Anyone know the difference on a 87 octane tune compaired to a 92 octane tune on a stock motor?Is the stock 87 tune just limiting timing,or is the whole tune changed.
I can't get my hands on a scanner for a week or so to check it out.

Sonic Boom NH

The difference, basically, is timing and fuel tables, or more specifically A/F ratios. Usually from the factory, for safety and warranty reasons, stock tunes are a bit on the rich side. Generally a tuner will alter the A/F ratios, fuel tables, and lean them up as well as increase timing. Both those will add horsepower mainly because the motor is running more efficient.

The reason for increased octane, such as 91, is because of the timing and leaning the motor a bit. 91 octane fuel will burn a little cooler and control the flame front much better thus reducing chance of pre-ignition (engine knock).

T.M.808

Thanks for the reply.My last car (OBD-2),required 91 or higher octane,if you put in 87 octane ,the PCM would retard the timing via the knock sensors.I seen it as low as 16*,and the power just got sucked away.I was assuming the new stangs were like that also,i am suprised to learn it has a set tune for 87 octane.So there is about 10 or so horse power to be had just by a more aggressive tune (91 octane etc) on a stock motor?I have to get my scanner back and start logging some stuff.
I think i'm going to have to start hanging out in the engine managment section more.Thanks bro.