FA20 vs EJ20 crankshaft

[dabocx]

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

[Element Tuning]

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.

[Element Tuning]

Originally Posted by Coheed

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!

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.

[Coheed]

Originally Posted by Element Tuning

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.

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.

[SkullWorks]

Originally Posted by Coheed

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.

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)

[Element Tuning]

Originally Posted by Coheed

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.

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.

[Crawford]

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

Interesting opinions here...

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

[Crawford]

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

[Crawford]

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

[3MI Racing]

Originally Posted by Crawford Performance

Interesting opinions here...

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

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

[Crawford]

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.

[3MI Racing]

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

[Crawford]

If you wanted to be creative, you could put a 86mm FA crank into an EJ motor... now see if you can sleep tonight! Lol...

[serialk11r]

Whoa what is the EJ257 rod length? The FA20 rods look to be not that much shorter!