FA20 vs EJ20 crankshaft

[TouchMyHonda]

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?

[mastertech86]

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?

[OrbitalEllipses]

^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.

[3MI Racing]

Originally Posted by Draco-REX

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?

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

Originally Posted by 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?

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)

Originally Posted by TouchMyHonda

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?

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.

Originally Posted by mastertech86

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?

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.

[mastertech86]

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?

[Swift]

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.

[SkullWorks]

Originally Posted by 3MI Racing

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)

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.

[3MI Racing]

Originally Posted by mastertech86

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?

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.

Originally Posted by Swift

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.

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

[Coheed]

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.

[Sleeperz]

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.

[QFry]

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}

[Coheed]

Originally Posted by QFry

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!

[QFry]

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?

[Coheed]

Originally Posted by QFry

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.