Forum » EFI Tuning Fundamentals » Compression Ratio & Heat

Compression Ratio & Heat

EFI Tuning Fundamentals

Forum Posts



Tech Articles

Discussion and questions related to the course EFI Tuning Fundamentals

= Resolved threads

Page 1

I'm a bit confused on this topic, as I've always been told that higher compression engines run hotter eg. diesels.

The "pressure volume cycle" tutorial states a higher compression ratio emits cooler exhaust gases. That's fine as the gases have more time to cool due to the pressure drop but wouldn't the higher peak pressure in a higher compression engine generate more heat in the cylinder?

Is it as simple as saying higher compression ratio engines run hotter but just with cooler exhaust gases?


Nice topic and looking for a solid answer.

Recently I build some high compression small displacement engines with aftermarket camshaft and don't have any problem with EGT and coolant temperature even with OE cooling system parts.

I'm guessing the aftermarket camshaft in yours could help with exhaust gases cooling through different exhaust duration, inlet duration and overlap specs (or could even make it hotter). You could also say the same would apply to match extractors to an engine to help with exhaust scavenging. OEM cooling can be up to a task if its not too much of an increase in heat.

If you have 2 engines with same parts, same exhaust, same cam but different compression ratio im sure the higher compression ratio would run hotter. But I'm trying to understand if this is true or not with the video tutorial mentioning exhaust temps are lower with high comp engines.