Into the weeds engine design for fuel efficiency discussion.

mgoblue9798 said

Thanks AJ, lots of good info.

Much more helpful than being told to buy a small car which is what my post about specifics was in response to.

I am curious as to thoughts on bore v/s stroke. Bore sizes for newer v8 LS and Hemi are all close to 4 inches. Is this due primarily to emissions, fuel economy, or do both go hand in hand because of a more complete burn?

Click to expand...

Small bore with long stroke probably has a slight advantage but is it enough to worry about.

Your building a truck engine so idle-3500 rpm or so is what's most important, to build NA power in that range would be mainly be from displacement, VE% and CR obviously anything to increase efficiency in that range, and VE% doesn't mean strangle your engine to death.

Realistically a well put together /6 to 440 ain't gonna be a huge difference especially with similar performance. It takes a certain amount of hp to move your car down the road, mpg comes from how efficiently the engine makes it at part throttle, there's not a huge efficiency gap in the engines were talking about unless you do something seriously wrong design wise like a huge cam etc...