FA20 vs EJ20 crankshaft

[Draco-REX]

Crawford Performance posted this pic to IWSTI.com. I don't remember seeing it here, so hopefully it's not a repost.



The FA20 crank is the black one at the bottom. Interesting changes. It looks a lot beefier.

[Tainen]

How does it look beefier? Sorry I've never really studied crankshafts before

[boredom.is.me]

The plates or whatever you call them look a little thicker. That could just be the picture though.

[Draco-REX]

The counterweights and webbing are thicker, the main bearings are larger in diameter, and it's tough to tell but the rod bearings look larger too. It's apparently 4lbs heavier than the older EJ crank.

[dabocx]

BRZ crankshaft weighs 4 pounds more apparently

[ahausheer]

Toyota crank shafts are usually very robust no? Perhaps this was in part a result of Toyota? Larger bearing surface means less friction right per unit area right?

[Draco-REX]

Originally Posted by ahausheer

Toyota crank shafts are usually very robust no? Perhaps this was in part a result of Toyota? Larger bearing surface means less friction right per unit area right?

Yup. But this engine only makes 150lb-ft of torque and the open deck means it isn't made for large power levels. The EJ20 crank is probably good for 7K rpm, so I don't the extra strength is for just 400rpm.

So it's really interesting. I would have thought it'd be lighter to make the engine more efficient and accelerate quicker. But they saw a need for a heavier crank in a new, smaller, lighter, higher revving, and more efficient engine. So there has to be a reason.

Perhaps 7400rpm isn't the upper limit of the FA20 block....

[Bonburner]

Originally Posted by Draco-REX

Yup. But this engine only makes 150lb-ft of torque and the open deck means it isn't made for large power levels. The EJ20 crank is probably good for 7K rpm, so I don't the extra strength is for just 400rpm.

So it's really interesting. I would have thought it'd be lighter to make the engine more efficient and accelerate quicker. But they saw a need for a heavier crank in a new, smaller, lighter, higher revving, and more efficient engine. So there has to be a reason.

Perhaps 7400rpm isn't the upper limit of the FA20 block....

sure its open deck but there're lots of open deck FA blocks out there with +60k miles.
Wasn't the actual chambers short too, less movement in the actual block anyways.
I'm not too worried, considering Suby made it, I'm sure it can take a turbo without a hitch - this is an assumption because Toyota wanted people to be modding the heck out of this baby so I'm sure they made Suby make the block beefy.
Which what it appears to be .. and yeah I'm pretty sure it can rev higher .. according to one of the articles the the engine block was just tossed in and tested and they were surprised to see it hit 7k without a hitch and they went with it.

[Tradewind]

It does appear to be MUCH stronger than an EJ crank, which even in NA for were fine for 10 - 11psi boost.

This new unit looks the goods for high compression + mild boost. Love it

[Bristecom]

Is the black some kind of coating?

[3MI Racing]

Originally Posted by ahausheer

Toyota crank shafts are usually very robust no? Perhaps this was in part a result of Toyota? Larger bearing surface means less friction right per unit area right?

Larger diameter also means a higher bearing speed and more friction and requires more oil flow. The EJ cranks are quite robust. I only know a handful of failed OEM cranks.

Originally Posted by Draco-REX

Yup. But this engine only makes 150lb-ft of torque and the open deck means it isn't made for large power levels. The EJ20 crank is probably good for 7K rpm, so I don't the extra strength is for just 400rpm.

The EJ205/7 revised oiling crank, not shown above, I actually have guys spinning well north of 9k.

The crank was beefed up because with the tighter bore spacing of the block architecture, the crank had to be shortened. With the increased stroke to make up for reduced bore (see bore spacing) the bearing overlap was reduced, hence the increased bearing diameter. The throws are then thickened to further strengthen the crank and reduce flexure that comes with the increased stroke (as stroke is a moment arm) and the flexure also increases with cylinder pressure (more so acceleration rate of the piston).

I can go on but I think you have the idea


EDIT: pending confirmation of actual values from the long block and not what another shop had told me...read with a 'spoon full of sugar'.

[Draco-REX]

Originally Posted by 3MI Racing

Larger diameter also means a higher bearing speed and more friction and requires more oil flow. The EJ cranks are quite robust. I only know a handful of failed OEM cranks.



The EJ205/7 revised oiling crank, not shown above, I actually have guys spinning well north of 9k.

The crank was beefed up because with the tighter bore spacing of the block architecture, the crank had to be shortened. With the increased stroke to make up for reduced bore (see bore spacing) the bearing overlap was reduced, hence the increased bearing diameter. The throws are then thickened to further strengthen the crank and reduce flexure that comes with the increased stroke (as stroke is a moment arm) and the flexure also increases with cylinder pressure (more so acceleration rate of the piston).

I can go on but I think you have the idea

So do you feel the FA20 crank is adequately built for its current application (86mm stroke, 151tq, 7.4Krpm), or do you feel it's overbuilt?

[Bonburner]

Originally Posted by 3MI Racing

Larger diameter also means a higher bearing speed and more friction and requires more oil flow. The EJ cranks are quite robust. I only know a handful of failed OEM cranks.



The EJ205/7 revised oiling crank, not shown above, I actually have guys spinning well north of 9k.

The crank was beefed up because with the tighter bore spacing of the block architecture, the crank had to be shortened. With the increased stroke to make up for reduced bore (see bore spacing) the bearing overlap was reduced, hence the increased bearing diameter. The throws are then thickened to further strengthen the crank and reduce flexure that comes with the increased stroke (as stroke is a moment arm) and the flexure also increases with cylinder pressure (more so acceleration rate of the piston).

I can go on but I think you have the idea

Please go on, I wanna read everything you can say about our engine blocks!

I'm hoping this block is 'overbuilt'

[SkullWorks]

alright...I'll take the bait,

what is the boreXStroke of the old EJ20?

I had been lead to believe they shortened the stroke and increased the bore form the normal Subaru 2l formula... but increased bearing diameter and less bearing overlap doesn't add up to a shorter stroke, or a tighter bore spacing.


What did I miss?