[celek]

Originally Posted by Slowmotion

I'm curious to see where this goes, sub'd

A note on the compression ratio. If you look at the skyactiv 4 cylinders from Mazda, those are running 13:1 CR on 87oct with just DI and the Audi RS4 V8 is running 12.5:1 CR. So, running 13:1 on 93oct on a properly built motor as long as you use the DI and properly tuned equal length headers to your advantage, should be doable. Hell, I was looking into this myself and was thinking 13.5:1 would be possible on 93 as long any you had good fuel or a secondary e85 injection system in case you get a bad batch of 93.

Even though I'm liking what I see and interested to what the outcome is, I'm really not liking your choice on the crankshaft. Besides the benefit of the extra stoke, I'm not sure why you would want to use a crankshaft that has smaller rod bearings than what came on the FA20. If Subaru went to larger rod bearings from the FB20/25 because it will see higher rpm and bearing loads, I can't imagine why you would want to go smaller and spin it even faster. Not to mention what you will need to do with the oil galleries (block and crank)/oil pump to make sure the oil can overcome the rotational inertia within the crankshaft at high engine speeds to provide sufficient lubrication to the rod bearings, if it's possible. From that, this would be my reason for going with a custom crankshaft (or if Toda make's their 90mm stoke crankshaft) just so you could keep the rod bearings the same size, or possibly slightly larger, so it can take the extra stress from spinning at 9000+ rpm while still providing proper oil film thickness, based on your surface velocity at the interface of the bearing and rod.

I'm not hating on your decisions, its just that it doesn't make sense to me if you want longevity out of this motor looking at it from an engine development engineering perspective.

I would like to point out that the Rod bearing journal is the same Diameter as the K24 Honda, SR20 Nissan 1AZ Toyota and EJ20 Subaru. Additionally I will not be using factory bearings which are designed for non spirited driving.