Increasing compression ratio

[Inferno]

Using forged pistons to increase the compression ratio slightly to 11.8:1 will there be an increased risk of detonation without doing anything else to the engine or management?

 

[Fred@BTM]

yup, no point without mapping the car for it

 

[GordonD]

yup, no point without mapping the car for it

What would a remap do that the ECU wouldn't do itself when it detected knock? How is there any difference between the power of an engine that has the timing backed off a couple of degrees because its been remapped that way to prevent knock, and an engine that's had the timing backed off a couple of degrees because the ECU has detected knock and backed it off?

In fact if you remap it you won't get any more power if you put higher octane fuel in, but if you leave it to the ECU to react to knock when you put higher octane fuel in the ECU won't detect knock, it won't back off the timing, and you'll get more power. Not remapping the engine at least allows you to produce more power by using higher octane fuel.

The way I see it the ECU comes mapped for an optimum octane rating, and is able to use fuel up to so many octane points lower. Increasing the compression ratio moves the optimum octane rating and the lowest octane fuel its able to use up.

 

[stan*]

If you want to be critical, you could say increasing fuelling a tad would increase torque/power due to hotter combustion temps associated with a higher Cr, and so an increased level of disociation of tri-atomic molecules CO2 and H2O...part of the reason we find higher power output with fuelling rich of stoich.