Increasing compression ratio (newbie question)

[Babalouie]

A compression increase is a pretty expensive way to get more power Even if you ran say 11.5:1 (which would be pushing it even on 100RON) you might get say, 3~4kw?

Increases in compression aren't a good standalone mod. If you're rebuilding the engine anyway, fair enough but increased comp is more to get a good synergy for your other mods (esp bigger cams).

Blueprinting is kinda a thing of the past too. Engines nowadays are so well made that the gains would not justify the huge cost.

The traditional route, would be intake, followed by exhaust. Those are the mods that give the most bang for the buck. You could say, fit some cams for an \"invisible\" mod, but they won't show much gain (if at all) with the stock computer, intake, headers and zorst.

Sorry, but I think you'll have to mod your car like the rest of us

[Babalouie]

Hmmm.....that's a lofty goal

Well the difference with the S2000 is that the VTEC allows it to run huge cams. If you could build the MX5 engine to withstand 9000rpm without blowing up, and then you also ran full-race cams, and ported out the head to increase the flow dramatically, you'd basically pretty much get that sort of output.

AFAIK an S2000 gets about 120kw at the rear wheels. The best racing MX5s would get that much or a little more, but those are $13000 handbuilt racing engines. It isn't just the compression that's the key, but the whole package. Really big cams require revs to work, and hence the high-revving formula is a common one for non-turbo hi-output engines.

[Brad]

Yes the S2000 engine makes great power, but purely through a good package allowing great flow at high revs. If you look at the torque figure it's still good at 208nm but at 7500rpm meaning the engine is built to flow efficiently at high rpms. It's very hard, if not impossible to get both low end torque and high end power.

[Matty]

There's more to running a high compression ratio than simply shaving the head and/or block. IF not done carefully you'll probably detonate the hell out of the engine (though you mention octane so you're obviously aware of the issues).

Head airflow and the combustion chamber shape are vitally important in being able to run high CR effectively. Otherwise, you have to retard the ignition timing, which will kill oof more power than you theoretically gain from the CR increase.

If you want \"invisible\" mods, look at ways to lighten the car and change internals that can't be seen without a teardown.

lightweight flywheel
2mm overbore
lightened crank
short ratio diff
cams (maybe, but hard without intake and exhaust to support it)
ECU


However, tearing into the engine will probably cost more than getting other mods engineered and complied.