Detonation, engine design, compression ratio and fuel octane

[E4ODnut]

In the "Determining best power ratio without a dyno" thread it was mentioned that often optimum timing will be before detonation, depending on the engine.

Matt mentioned the Miata running 93 octane. Do you know what the compression ratio was and do you have you any other examples?

Nigep cited his VW 2.0 16 v. If you are in on this, what what is your compression ratio and what grade fuel were you using ?

Peter, Do you have examples of the engines that you've had this experience with?

[morrische]

the highest poweroutput you will have is when the highest combustionpressure is around 10°atdc....... I thought is bacause of the thing with pythagoras............. and now the art is to get this pressure at this point with the different rpm's and the different burning speed of lean an rich mixture.............. by the way if you can scope this pressure you can see it very very easy....... when you have a normal combustion you will see something like a smooth wave........ if you have detonation you can see small spikes in this wave.............. (http://www.gapo4.com/pressure_sensors.php) (a 2 channel scope 1 pressure mesuring sparkplug and a self made trigger at 10° atdc).............

[bubba2533]

Pressure sensing spark plugs are big $$$ (at least for your average DIY tuner)

Take a look at ion sensing. There has been a few posts about it too.

[morrische]

But how many OEM-Ignitionsystems with Ion Sensing are out there (exept the one from Saab) working?
And why you can buy this measure sparkplugs for a few bugs (for a Dyno-Company or Engine resarch is it a few (900 -1200$) how much is a used Igniton module of Saab in Ebay) but almost no Ion Sensing device (if it has the same benefits speed precision......) . think there is still a lot to develop for a propper Ion Sensin device wich is fail safe.......... And if you want it cheap............ you know this right?? http://www.msextra.com/forums/viewtopic ... 25&t=43766 this is the DIY-Way..... support the amazing developers the MS "product Line"