Likely the first FA2/4 hybrid incoming

[D K]

Oddly enough, that very question led me here and ended up wanting to do the K swap.

[NoHaveMSG]

Originally Posted by Bach415

Bumping this. Not sure if anyone else saw this but it was on FB group. Shop in Thailand was able to do a fa20 heads w/ fa24 shortblock. ~260 whp w/ ecutek on racerom on e75
https://www.facebook.com/permalink.p...97121510449973

Ugh, I hate posts like that. Why can't they tell us what they did, even if it is vague. Someone asked what they did to make the heads work and the response was "the bolt pattern is the same." So no CC machining required I doubt that.

[RedReplicant]

Dyno either reads really high or there is a pretty decent bump in compression from would have to be the FA20 head combustion chambers being smaller than the FA24? Has anyone compared the two heads volume wise yet? The power rolls over at similar RPM as the full FA24.

[Evil Rocky]

Anyone know if the BRZ FA24 US is different from JDM FA24?

[RedReplicant]

They posted their stock / stock w/ tune dyno in there, for a bit more context. This appears to be plotting whp but the corrections look different.

[NoHaveMSG]

Originally Posted by RedReplicant

Dyno either reads really high or there is a pretty decent bump in compression from would have to be the FA20 head combustion chambers being smaller than the FA24? Has anyone compared the two heads volume wise yet? The power rolls over at similar RPM as the full FA24.

Not that I am aware of. Should be able to estimate it pretty closely being we know engine capacity and compression ratio. Being both engines are 12.5:1 they would have to be larger chambers on the FA24.

[Tatsu333]

Not putting much stock in the dyno numbers, and I sure wish there were a bit more detail on what was involved in adapting the FA24 short block to everything else, but good to know that someone has made it work!

This is still my preferred long-term route forward, I think. Now to wait until there are some short blocks available for non-stratospheric prices...LOL.

[NoHaveMSG]

Originally Posted by Tatsu333

Not putting much stock in the dyno numbers, and I sure wish there were a bit more detail on what was involved in adapting the FA24 short block to everything else, but good to know that someone has made it work!

This is still my preferred long-term route forward, I think. Now to wait until there are some short blocks available for non-stratospheric prices...LOL.

Yeah, I agree. That dyno reminds me of the OTL header dyno. Just take the stock curve and bump it up a bit, nobody will notice

[new2subaru]

Pardon my ignorance, but If you're going to the trouble of doing this why not just drop in a FA24 long block and all the other bits and bobs out of a wrecked 2nd Gen?

[soundman98]

Originally Posted by new2subaru

Pardon my ignorance, but If you're going to the trouble of doing this why not just drop in a FA24 long block and all the other bits and bobs out of a wrecked 2nd Gen?

one of the main issues is going to be sensor compatibility.

as an example; 2013-2015 used one version of cam sensor wheel. 2016+ used an updated version that senses the opposite way. '13-15 was a 'tit' on a wheel the computer saw as momentarily 'on', and was otherwise 'off'. the '16+ cam sensor wheel was a divot-- the computer read 'on' all the time and read 'off' in specific points. meaning that even a 2016+ cam is not compatible with a 2014 computer.

going straight fa24 is the same as doing a honda k-motor swap in terms of wiring/programming.

many of the major sensors are in the cams/heads. by maintaining the fa20 heads and sensor suite, the motor becomes more plug-n-play with the oem ecu. it just takes a tune to adjust to get the full power out of it.

[NoHaveMSG]

Originally Posted by new2subaru

Pardon my ignorance, but If you're going to the trouble of doing this why not just drop in a FA24 long block and all the other bits and bobs out of a wrecked 2nd Gen?

Price. You can buy a new shortblock for like 2200 if they will sell it to you. Wreaked 2nd gens are still pretty expensive, I think the last full FA24 out of a wrecked car I saw was like 6500. So if you can slap some sensors, heads, come up with a different reluctor wheel(pre facelift car) it has the potential to be cheaper then buying a complete engine for the DIY'r.

We just don't know yet though what it will cost since every one of these assholes that has done it won't tell you what they did to make it work

[new2subaru]

Originally Posted by soundman98

one of the main issues is going to be sensor compatibility.

as an example; 2013-2015 used one version of cam sensor wheel. 2016+ used an updated version that senses the opposite way. '13-15 was a 'tit' on a wheel the computer saw as momentarily 'on', and was otherwise 'off'. the '16+ cam sensor wheel was a divot-- the computer read 'on' all the time and read 'off' in specific points. meaning that even a 2016+ cam is not compatible with a 2014 computer.

going straight fa24 is the same as doing a honda k-motor swap in terms of wiring/programming.

many of the major sensors are in the cams/heads. by maintaining the fa20 heads and sensor suite, the motor becomes more plug-n-play with the oem ecu. it just takes a tune to adjust to get the full power out of it.

Thank for the reply. Isn't there going to be issues with tuning with FA24 short block with FA20 heads? Will the stock ECU be compatible?

[soundman98]

there would always be issues, but it's less of a concern because the ecu is already cracked and can be tweaked to however the new design needs it to operate.

[new2subaru]

Originally Posted by soundman98

there would always be issues, but it's less of a concern because the ecu is already cracked and can be tweaked to however the new design needs it to operate.

Thanks again. Good to know.