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I want to see emissions levels of this directly compared to a modern 4 stroke. Sure, it's novel, but if it can't meet or exceed 4 stroke emissions performance, it's already dead.
this post was submitted on 29 May 2025
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Engineering
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That really is the final question that determines whether this can be marketable. I assume they haven't published numbers or even attempted to measure it because that's part of the long, expensive development cycle. They have a lot of catching up just to meet the effort already put into optimizing 4-stroke emissions, and I'm sure once it has a catalytic converter, lower compression, and an intake designed to idle efficiently then the weight and power numbers will be less impressive (think what people can do NOW with race/offroad/custom gas or diesel engines that don't have to meet emissions).
Though as he said in the video, conceptually it should have all the features necessary to be clean (as much as a 4-stroke), since it doesn't burn lubricating oil or permit fuel-air mixture to be lost. D4S covers a lot of novel combustion engines with a good mix of enthusiasm and skepticism, so if he's excited then I'm definitely still excited.
I'm not a petrol-head, but I very much loved this video and awesome engine design! 220hp at 550cc seems great.
The ICE corpse is twitching