In for the long haul Ultimate NA build thread.

[Turdinator]

@celek have you seen the threads by @Element Tuning regarding the issues they have had with oil pressure and breaking rockers at high RPMs? If so what are your plans to overcome these issues?

[celek]

A long awaited update. 8 week wait for these slugs to make it to my hands.
Huge shout out to Wiseco those guys are awesome, I told them what I wanted and like magic they are done.
13:1 CR pistons, trying to keep the knock threshold down for 92-93 octane. I do not want to be bound to E85 as in my area the closest station is a 45 min drive.

Also spoke to Pauter last week about the rods and did some measurements. This baby is going to kick some serious booty.

[FRStrent]

Awesome build. About time build threads start coming out for this car.

I also own a Honda. 615whp integra. FI, though, not NA.

[Lonewolf]

I had almost forgotten about this thread...glad to see things moving again

[Koa]

Originally Posted by Grip Ronin

im needy because id expect more from a advanced engine? oh shots fired lmao you sound like a dumb ass but lets not get that started

120bhp per cylinder... N/A.. on a subi boxer... hahahahah you must be new to subarus bro

[Kostamojen]

There are a couple 300 crank hp N/A EJ motors/cars running around out there...

This motor does 230+ chp with just an exhaust, fuel and a tune, which is pretty wild for us old school N/A Subaru guys who struggled to get to 200hp with the N/A EJ25's that never had tuning options and it was all about intake/exhaust/cams and thats about it.

I've been promoting the idea of running some sort of FA25 (FB25 block with FA20 heads, or something along those lines) Frankenstein build with this engine since before the car was even released. These kinds of builds have been around for years with the low budget Subaru crowd (early 90's gen 1 Imprezas running 1.8 or 2.2 motors could swap bits around and run 2.2 heads with 2.5 blocks and such). Hell, with my '70 Subaru I put together 1.3l heads with a 1.4l block...


Anyway, I can't wait to see more of this build Curious what direction you are going with the intake manifold...

[Valentino]

Originally Posted by celek

Hi all,
I do not really post much but I will give a quick intro/rundown on me and my plans.
I have been building Honda's Subaru's and other misc cars for over 20 years. Yeah I am that old guy. I bought my 2013 BRZ in June 2012 and just rolled 22k miles.

Chris

Respect...

Old is gold

[Slowmotion]

I'm curious to see where this goes, sub'd

A note on the compression ratio. If you look at the skyactiv 4 cylinders from Mazda, those are running 13:1 CR on 87oct with just DI and the Audi RS4 V8 is running 12.5:1 CR. So, running 13:1 on 93oct on a properly built motor as long as you use the DI and properly tuned equal length headers to your advantage, should be doable. Hell, I was looking into this myself and was thinking 13.5:1 would be possible on 93 as long any you had good fuel or a secondary e85 injection system in case you get a bad batch of 93.

Even though I'm liking what I see and interested to what the outcome is, I'm really not liking your choice on the crankshaft. Besides the benefit of the extra stoke, I'm not sure why you would want to use a crankshaft that has smaller rod bearings than what came on the FA20. If Subaru went to larger rod bearings from the FB20/25 because it will see higher rpm and bearing loads, I can't imagine why you would want to go smaller and spin it even faster. Not to mention what you will need to do with the oil galleries (block and crank)/oil pump to make sure the oil can overcome the rotational inertia within the crankshaft at high engine speeds to provide sufficient lubrication to the rod bearings, if it's possible. From that, this would be my reason for going with a custom crankshaft (or if Toda make's their 90mm stoke crankshaft) just so you could keep the rod bearings the same size, or possibly slightly larger, so it can take the extra stress from spinning at 9000+ rpm while still providing proper oil film thickness, based on your surface velocity at the interface of the bearing and rod.

I'm not hating on your decisions, its just that it doesn't make sense to me if you want longevity out of this motor looking at it from an engine development engineering perspective.

[celek]

Originally Posted by Slowmotion

I'm curious to see where this goes, sub'd

A note on the compression ratio. If you look at the skyactiv 4 cylinders from Mazda, those are running 13:1 CR on 87oct with just DI and the Audi RS4 V8 is running 12.5:1 CR. So, running 13:1 on 93oct on a properly built motor as long as you use the DI and properly tuned equal length headers to your advantage, should be doable. Hell, I was looking into this myself and was thinking 13.5:1 would be possible on 93 as long any you had good fuel or a secondary e85 injection system in case you get a bad batch of 93.

Even though I'm liking what I see and interested to what the outcome is, I'm really not liking your choice on the crankshaft. Besides the benefit of the extra stoke, I'm not sure why you would want to use a crankshaft that has smaller rod bearings than what came on the FA20. If Subaru went to larger rod bearings from the FB20/25 because it will see higher rpm and bearing loads, I can't imagine why you would want to go smaller and spin it even faster. Not to mention what you will need to do with the oil galleries (block and crank)/oil pump to make sure the oil can overcome the rotational inertia within the crankshaft at high engine speeds to provide sufficient lubrication to the rod bearings, if it's possible. From that, this would be my reason for going with a custom crankshaft (or if Toda make's their 90mm stoke crankshaft) just so you could keep the rod bearings the same size, or possibly slightly larger, so it can take the extra stress from spinning at 9000+ rpm while still providing proper oil film thickness, based on your surface velocity at the interface of the bearing and rod.

I'm not hating on your decisions, its just that it doesn't make sense to me if you want longevity out of this motor looking at it from an engine development engineering perspective.

I would like to point out that the Rod bearing journal is the same Diameter as the K24 Honda, SR20 Nissan 1AZ Toyota and EJ20 Subaru. Additionally I will not be using factory bearings which are designed for non spirited driving.

[Grip Ronin]

Originally Posted by Koa

120bhp per cylinder... N/A.. on a subi boxer... hahahahah you must be new to subarus bro

I am new to subarus, i came from honda and nissan. Im still learning fa20s as people make advancements.

[Koa]

Originally Posted by Grip Ronin

I am new to subarus, i came from honda and nissan. Im still learning fa20s as people make advancements.

Subaru boxers in general aren't well known for making and sustaining power like that without significant overhaul.. some say they're weak platforms entirely (EJ series motors typically spun bearings and starved cylinders due to weak oil passages- especially their open deck variants.. ringland failures on other series...). Mods to oil system were few and far in-between (KillerB oil pan, anyone? ).. just pretty common for these engines, even the fabled EJ257, to pop at that power level and that's turbo'd and supposedly "forged" internals.

Given the FA series (DIT, ours) are new and seem to address some of the glaring problems of their past performance motors.. time and energy, resources spent will tell the story as more people push the limits

[Grip Ronin]

Originally Posted by Koa

Subaru boxers in general aren't well known for making and sustaining power like that without significant overhaul.. some say they're weak platforms entirely (EJ series motors typically spun bearings and starved cylinders due to weak oil passages- especially their open deck variants.. ringland failures on other series...). Mods to oil system were few and far in-between (KillerB oil pan, anyone? ).. just pretty common for these engines, even the fabled EJ257, to pop at that power level and that's turbo'd and supposedly "forged" internals.

Given the FA series (DIT, ours) are new and seem to address some of the glaring problems of their past performance motors.. time and energy, resources spent will tell the story as more people push the limits

Hm interesting, ya only thing i heard was ej25 always blowing that 1 rear cylinder. The fa does have its weaknesses definitely being oil pressure first. Ive been following elements thread on that. the high compression is the biggest handicap against safe low boost on this engine i think.

[Slowmotion]

Originally Posted by celek

I would like to point out that the Rod bearing journal is the same Diameter as the K24 Honda, SR20 Nissan 1AZ Toyota and EJ20 Subaru. Additionally I will not be using factory bearings which are designed for non spirited driving.

Good point, but the only one that you directly compare to is the EJ20. The crankshaft loading on the rod pins in an I4 are very different and would not be directly applicable to a boxer. Even then, it would be difficult to use the EJ20 as comparison as it only made ~150hp and spun up to 7200rpm (aftermarket tune), so the rod pin never saw the same level of stress the FA20 does that has higher combustion pressures. Not to mention the EJ20 is oversquare so it can spin faster without spinning a large amount of mass (92mm bore, 75mm stroke), as long as there is sufficient oil flow rate from the oil pump.

/tangent (pressure isn't as important as flow rate since your pressure will change depending on your cross sectional area of the oil passage. I've performed an actual engine flow analysis before and your bearings don't care about pressure, they live off of oil flow. The only reason why we use pressure is because no one, OEM's or race groups, can realistically install a flow meter in the main oil gallery before the bearings) /tangent

Also, aftermarket or racing bearings are only useful when you do not have a film thickness to float the bearing. If the system is designed properly, where you want the engine to live, the crank, rod, cam bearing or any other bearing using oil are completely floated by oil.

Either way, even if what I have said may seem harsh, I'm hoping what you put together works for you. I just want to give you some information that might help you create a badass NA FA20 that won't try and fling itself apart at 9000+rpm due to all the inertia you will have with a 94mm stroke crankshaft, because I would love to see this succeed.

[celek]

Originally Posted by Slowmotion

Good point, but the only one that you directly compare to is the EJ20. The crankshaft loading on the rod pins in an I4 are very different and would not be directly applicable to a boxer. Even then, it would be difficult to use the EJ20 as comparison as it only made ~150hp and spun up to 7200rpm (aftermarket tune), so the rod pin never saw the same level of stress the FA20 does that has higher combustion pressures. Not to mention the EJ20 is oversquare so it can spin faster without spinning a large amount of mass (92mm bore, 75mm stroke), as long as there is sufficient oil flow rate from the oil pump.

/tangent (pressure isn't as important as flow rate since your pressure will change depending on your cross sectional area of the oil passage. I've performed an actual engine flow analysis before and your bearings don't care about pressure, they live off of oil flow. The only reason why we use pressure is because no one, OEM's or race groups, can realistically install a flow meter in the main oil gallery before the bearings) /tangent

Also, aftermarket or racing bearings are only useful when you do not have a film thickness to float the bearing. If the system is designed properly, where you want the engine to live, the crank, rod, cam bearing or any other bearing using oil are completely floated by oil.

Either way, even if what I have said may seem harsh, I'm hoping what you put together works for you. I just want to give you some information that might help you create a badass NA FA20 that won't try and fling itself apart at 9000+rpm due to all the inertia you will have with a 94mm stroke crankshaft, because I would love to see this succeed.

It is a 90mm Stroke and 89.5mm bore as for the pins and other parts we can not compare OE cast parts to forged aftermarket parts designed for 3X the factory power ratings.

I guess there is only one way to find out though.