I didn't see it discussed earlier but you can just make your own FA24 by either using darton sleeves or using an FB25 block with FA20 heads and crank and con rods. I mean aure on the FB25 block you gotta clearence out for the starter. But other than that its not much trouble.with the fb25 you have to use fb25 pistons or just order custom pistons. The factory fb25 is 10.5:1 so great for boost, but higher comp NA pistons arent hard to obtain

I don't think the FB25 platform is compatible for many reasons besides the starter. The FB25 has a longer stroke and likely has a difference in block dimensions, so heads and intake manifold are likely not going to line up. The FB25B also has 10.0:1 compression, and it doesn't have direct injection. The FB25D has direct injection on a 12.0:1 compression, but still, it would be better to do a FA24F block swap or FA24D engine swap than attempt the FB25.

The fb25 and fa20 blocks are exactly the same in outside dimensions. Its just a matter of swapping cranks and con rods. Fb25 94mm pistons with 86mm stroke equates to 2.4 litre.

FA20 heads on an FB25 block will raise the compression a little bit. Thats why i said 10.5:1

Well.... its WAY better for boost compared the 13.5:1 or now the 14:1 on the real fa24 engine

FB25B doesn't have direct injection and has 10.5:1 compression. FB25D has direct injection and 12.0:1 compression. It sounds like you are talking about using the FA25B, so are you suggesting ditching the direct injection system? Have you seen the differences between the FA20F and FA20D blocks? They look different in many ways. I doubt even the FA24D will be identical, but it has the best chance.

https://dsportmag.com/wp-content/upl...k-1024x768.jpg
https://dsportmag.com/wp-content/upl...k-1024x768.jpg

https://dsportmag.com/the-tech/educa...s-of-the-fa20/

It there a 3rd FA24 iteration now? Haven't heard of a new one. The new twins still have 12.5:1 like the first gen.

I don't know where I read, but I did read elsewhere that it was supposed to have 13.5 or 14:1 compression ratio. Or what I have read was wrong. It may have been a prior to the anouncement

Direct injection system is built into the heads not the blocks. If you swap the FA20 heads on the FB25 block it will be capable.

THE only issue with using a FB25 block in the RWD configuration is the starter clearance. You either need to mill/machine/grind out a clearance for the starter gear.

I know someone who already did this build using WRX heads on his Impreza

The FB25 has a worse rod to stroke ratio(the FA20's is already not great), thinner rods, and thinner rod bearings then an FA20. Pass.

The new gens for sure have the bump in compression, like you mentioned 13:5.1 :)

This is on Toyota’s website:

Ok never mind? For months they advertised 13:5.1?

I really want to know now lol.

I believe this was a mistake when the BRZ launched or a simple mistake made by someone that ended up widespread all over. Toyota claims it to be 12.5:1 and I believe there was a collaboration of both not too long ago also mentioning 12.5:1 - which I would think is the correct CR. It would also make more sense for them to stick to 12.5:1 rather than complicating things more with the engine.