FA20 vs EJ20 crankshaft
 

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

http://sphotos-a.xx.fbcdn.net/hphoto...19489161_n.jpg

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

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

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

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.

BRZ crankshaft weighs 4 pounds more apparently

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....

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. :iono:

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

Is the black some kind of coating?

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 :thumbsup:


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'.

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?

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

I'm hoping this block is 'overbuilt'

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?

Excuse my sorta ignorance. It doesn't seem that the crank is "beefier". It looks to be heavier which would cause more rotational effort needed to spin it. Kinda like a heavy vs a light flywheel.

Also the barring Journals look skinnier, not sure if that is considered more beefy or not. Anyone wanna challenge my thoughts?

interesting to note comparing the two cranks, the width of the main journals does looks skinnier on the OEM crank but the actual diameter of the mains is definitely bigger when compared against the crawford crank, at least according to the picture comparison...so that would leave me to assume less rotational speed on the mains so distribution for oil lubrication at higher engine speeds would be better...thats my two cents. time to research =)

and also the surface area on the counter weights are a lot "smoother" than the crawford crank which would mean better oil drainage and smoother operation due to less resistance against the oil although very slight, could possibly make a big difference at higher RPM...anyone else got any insights?

^Those are both OEM cranks, bro. The top one from the older 2L engine (EJ20) and the bottom one from the new FA20 found in the twins.

Won't give an input just yet. Still need to do my full study on it.

I think you have things backwards. The FA20 got a smaller bore and longer stroke.
FA20 is 86x86
EJ20 was 75 (stroke) x 92 (bored)

Weight is part of the picture. Keep in mind that a longer moment arm and a shorter rod ratio aids in low RPM acceleration of the crankshaft. I don't have exacts measurements on the bearings but a larger diameter and narrower bearings can be held to the same frictional losses as a smaller diameter but wider bearing. It all depends on exacts, clearances, oil weight, temp, pump size, etc...it all plays into the power demand of the oiling system.


Um, they are both OEM cranks...one EJ20 and one FA20 (black nitrided one). The black color is also indicating it's a salt bath and not gas impingement :(

I also think you are meaning windage when you're saying drainage.

My biggest concerns do come in the crank. I already know limitations found in the EZ36 cranks and then also the changes and limitations with Subaru's change in metallurgy when switching to nitrided cranks. Testing will tell the full story.

oops, i read crawford but didnt see it was just a picture they posted =) and windage would be the word im looking for but 3MI Racing, you said they would have the same frictional lose, but what do you think about what i said about the oiling for larger diameter mains? true?

3MI Racing,

Nice to have a guy around that not only knows cars but knows subies well and willing to educate. Hard to find on forums nowadays.

took some digging but I figured it out, the reference about destroking to Square was from a FB20 which is under square, interesting that all the EJ motors were over square.

No, I said 'can be' and that all depends on exact dimensions and several other factors that I listed.
Assuming the oiling passages are the same through the crank, then it is true that in terms of ration, the oil port will spend less time perfectly aligned with the oil port meaning a larger pumping/pressure loss to the oil to the rods but those are items that are taken into concern from initial design. When you get to aftermarket use, then it may become something of concern but will a full groove main bearing...I think we have no concern ;)

I also noted the difference in timing of the journals. Looks like the FA went to a 'straight shot' style of rod journal oil delivery.

Can't wait to get the FA20 apart and start the real work.

Glad that it's appreciated. I have LOTS more shared on the EJ platform on NASIOC (3MI Racing and Homemade WRX) where you'll see I started my in-depth engineering work years ago.

I doubt much, other than principles, will carry over to the new FA platform. Time will tell :)

The larger journals will likely increase bearing surface area. Which is good for oil retention, and was my primary concern with the new crank vs the old one. The larger bearings can retain more oil and help distribute more load.

The thinner bearings look very toyota-ish. Narrow isn't great for big power applications, and the EJ wasn't the best for bearing surface area to start. It would take some measurements to really see how well the bearing can distribute the load. I'm used to seeing 17-19mm rod bearing thickness, but many Toyota engines utilize a weak 14mm bearing that is prone to failure under light detonation or boost. Most OEMs reduce bearing width to reduce frictional losses from oil drag. Not the best thing for wear rates, but again, there are other things to consider. How many oiling holes in the crank bearings, and their degrees of crankshaft rotation with full-flow can impact how well the engine will support big hp.

It definitely looks like it is built to rev though. Though it is heavier, it does look like the surfaces of the counterweights is smoother. Hard to tell if this is a camera byproduct? But this smoother surface will help with windage losses.

Does it look better to me? Not initially. I would have to measure the total bearing size and do other calculations. But it definitely looks like the 0w20 recommended oil is just there for the MPG rating. Seems to be too thin of an oil to run on that small of a journal.

I'm sure it will handle 400whp without issue. Just gotta make sure rod bolts don't ever stretch or skew the tolerances because it will cause premature bearing failure.

FA20 makes more HP but about the same torque. With the longer stroke I would have thought it would make more torque.



FA20 : 86x86 - 200 HP 151 ft-lbs

EJ20 : 75 (stroke) x 92 (bored) 145 HP 148 ft-lbs torque


The old 2.5L 170 hp/170 lb-ft. I hope they bring out a 2.5L version of the FA20.

Wouldnt the real limiting factor in the rev ceiling be the Valve train first? With an increase of max engine RPM to 8861 you reach the practical limit 5000FPM piston speed (according to most engine builders ive talked to and books ive read say). This is from trying to build an SR20 to rev higher with a safety margin (same 86 bore and 86 stroke) which also happens to be the same FPM range of the S2000.
{...hmmmm when i started typing this i am sure i had a point i was going to make but i will post it anyways because i already typed it}

The valve springs are likely only good for a temporary 8000rpm, they will probably float the valves around that point.

5000fpm is the practical limit for a factory rod/piston combo. A built engine can see speeds over 6000fpm.

My SR20 revs to 9000rpm. VE baby woot!

Coheed VE is a whole different animal (in a B15 or b13?) from the DE but that is a topic all on its own (i am jealous by the way...) and we were talking about stock components and there limits arent we? ;)

True. The VVL and DE are different animals. http://s923.photobucket.com/albums/a...-22-25_268.mp4

10psi on a GT30r. It's now got a precision 6262 making 520whp on 20psi. Search Super Sentra on youtube.

I think 8000rpm is just fine. I hope the factory head can support that engine speed. Otherwise, smaller turbos would be best suited. I like to rev and use slightly bigger turbos than what is "conventional". Built it to be NA, then throw a turbo on it. There's more to it than that, but that's basically what I'd be looking at doing.

I cant wait till we see headwork and cams on this car, i really want to see what the upper limits of N/A for a street application will be.

Or even more crazy things like Knife edge cranks O_o

What I'm looking at doesn't look ideal for high power at all compared to the EJ20 crank which is very good.

As noted the newer material with nitride coating has proven inferior regardless of what the keyboard experts say. Is it a deal breaker? No.

The narrow bearing journals could be a deal breaker for really high power. In general the rod bearings on the EJ20x and EJ25x need very high and consistent oil pressure to survive because the narrower the bearing surface the greater the psi. Lets face it the FA20 is about efficiency, not handling high power. You can forget about that 0w-20 oil with high power since these bearings will be even smaller.

Now much of the engines geometry is better and should put less stress on the bearings but still I'm going to be monitoring oil pressure very closely as we build up this engine's power.

Subaru builds pretty stout valvetrains and you would be suprised at how good the oem stuff can be. I've already beaten this motor up good and she's a gem. I was running 8k RPM with my Hydra EMS powered FRS and man thats what the engine needs to stay in the sweet spot.

That may very much change with boost. We shall see.

Well said, and it's good to see someone shares my point of view on the narrow bearing journals. Maybe they use crank bearings that feed oil through the crank through several degrees to help maintain oil pressure as long as possible.

I guess we can hope for the best right? Most older cranks were shot-peened instead of nitriding. I'm sure nitriding is more cost-effective and is likely just as good. But I've never tested the strength differences. One changes the metallurgy and the other changes the grain structure.

Good call on the oil pressure too. I'm hoping they supply a stout oil pump in this engine as well to handle high rpm and maintain high oil pressure with the light oils being used. I'm still thinking 0w40, 5w40 etc is going to be better for a turbo build.

You find anything out about internals, let me know. I'm very interested.

you're doing it wrong lol,

When I built my RWD/VE i went for 10.5:1 compression stock P11 cams and E-85 then threw 22lbs at it out of a GT2868 (FP billet compressor on GT28R CHRA)

Makes all the torque, now I'm worried im gonna snap the crank at low RPM lol

Gotta love VVL though

(just poking fun, to each their own)

Oil pressure is going to be key and we learned on the EJ motors what you could and couldn't get away with at various power levels. I plan on skipping the lets see how low e can go oil pressure wise. LOL Those bearing journals are tiny so high oil pressure will be mandatory as power increases. I suspect current oil pressure is low since higher oil pressure does drop efficiency. Its definitely fine for the oem setup as i have raced this car hard on slick tires using a synthetic (probably only available) 0w-20. Honestly i would have run thicker but i wanted dyno numbers to be under similar baseline conditions.

Interesting opinions here...

The bore spacing is the same as is the length of the crank.

There are many differences in the FA block over the EJ, but there are many similarity's as well..

Sorry for the giant photos! This is the new rod on top of an EJ257 rod.

So you're saying the bore spacing is the same as the EJ? If so that is great news. I'd suspected and had a shop (that I don't know well) confirm that it is the same as the EZ.
Please confirm and I'll change my quote. Quirt, please tell me what you think is wrong with my 'opinion' on the logical reasoning of an engine design. I'm happy to change the quote with confirmed numbers :)

My FA20 still isn't here yet :mad0260:

The problem Mica is that you are presetting your opinions as facts... this is very misleading to the community. It would be better if you stated that your intuition tells you that X is like this and Y is like that. Rant over :)

Yes, the bore spacing is identical as is the placement of the journals on the crank. They even used the same spacing on the head bolts. The crank does not use a strait shot oiling system, they just rotated the holes on the mains 70/80deg.

Yeah, I reread it and see that I stated and engine design 101 as fact...put an edit in it already.
So rotated them, I'd be curious to see how the oil drilling aligns with the mains and peak cylinder pressure angle.

So anxious to get hands on already...and I'm done listening to others on 'facts'. It always backfires on me. So the bore spacing is still 4.4xx" or whatever it was (don't recall off-hand) :)

-Micah