Can this be an efficient engine design? 2

[jethead]

Can a direct injection petrol engine of compression ratio 13:1, or around that much, be designed to run on fuel of low octane number, say about 87, without knocking? I think it is possible if the fuel is injected just at the end of the compression stroke like in a diesel engine.

 

[Drumingeek]

Wouldn't you just have a engine running on the diesel cycle that uses petrol? ie: it would be a diesel engine that ran on petrol. It would be possible I think, but what would be the benifits gained by using petrol in a diesil cycle other than the higher specific energy?

 

[tr1ntx]

A potential pitfall is that the flame speed will be so fast the fuel will ignite back up into the injector. Even if that could be prevented, the combustion might take place at such a rapid rate as to cause debilitating damage.

 

[GregLocock]

All sorts of things are possible, i think lotus have demonstrated an engine that more or less runs as you suggest.

Cheers

Greg Locock


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[KENAT]

I've got a feeling some high performance aircraft engines from late WWII era may have done something like this. I'm thinking Daimler Benz or Junkers but I'm not 100% sure.

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[dgallup]

I know someone (Continental?) is working on a special turbo & head design that takes the impulse energy from just one early opening exhaust valve (4 valve head) and then lets most of the exhaust bypass the turbo from the second (later opening) exhaust valve. One of the chief advantages claimed is compression ratio can be increased about one point. I was searching for the article but can't find it at the moment but i think they were claiming up to 13:1. Not sure what octane they were using. Direct injection for sure.

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