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Old 02-04-2019, 02:04 PM   #1
shiroi
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Smile 65.8mm Crank Build

Thought you guys might appreciate this.

I'll be putting a 65.8mm (EJ15) crank in EJ255 case halves in a build over the upcoming 6 months to a year. This puts it squarely in 2.0L range. Plans are:

GSC S3 Billet cams (280/280)
GSC beehive springs/Ti retainers
Dual AVCS Z20 heads (matched to cylinder, ported)
Custom connecting rods (material TBD, likely 7068 or Ti6Al4V)
Manley Tuff Extreme "9.8:1" 83mm stroker pistons (these will put me at ~8.0:1 at .040 quench, weigh less than standard compression height pistons)

Obviously many other bits and bobs, some yet TBD. Machine work is going to be done by me, so there's that particular expense taken care of.

There is no particular goal in mind yet other than "rev to the moon," just gonna see how this pans out. I have a car sitting with a blown engine and more salary than brains enough to keep me from spending it. I will update as things happen. Input wanted, especially from those who have built high RPM EJ's in the past. Let me know what your struggles were so I can learn from them.



-S.
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Old 02-04-2019, 02:09 PM   #2
Hyper
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what's moon?
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Old 02-04-2019, 02:16 PM   #3
shiroi
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Quote:
Originally Posted by Hyper View Post
what's moon?
Figure I'll start with 10k. From there, I'd like to at least match GotItRex's "Betty" at 12k. The motor in the car "blew" (head gasket) at 8k and 22psi, somewhat mild build. I figure, reduction of nearly half an inch and lots of valvetrain weight reduction should get me that 2k at least. As for head work... not sure yet. I'll be digitizing the ports and doing some flow analysis, we'll see what that says. Not sure exactly how much room for porting I've got.

-S.
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Old 02-05-2019, 03:32 AM   #4
vicious_fishes
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the SOHC heads are roller-rocker, if that makes any difference?
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Old 02-05-2019, 07:29 AM   #5
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First thing first, how did you find an EJ15/6 crank?!!

Second, I wouldn't go with 7068. I think a 2024 would serve you better for the elevated temps.

I know this build has been brought up numerous times but I don't think anyone has gone through with it. Should be fun.

You'll also want to think through your engine assembly before you do it. I find on the +4 builds that it's easier to:
1.) torque rods 2&4 to the crank.
2.) install an assemble 1&3 piston and rod
3.) torque rods 1&3 to crank
4.) install pistons 2&4 into their case half
5.) invert case half for 1&3, obviously use something to protect deck finish (has rods and pistons in it, as well as the crank, with 2&4 rods dangling.
6.) apply seals and sealant to 1&3 side of crankcase (at this point you see why I started with which side)
7.) strategically place some shims to not jack up the sealant and to keep the halves spread so that you can pass the 2&4 pins through. You can usually get away with OEM dowel pins being a bit bound up.
8.) align pin end of rod with pistons and finish assembly (can be a bit of a pain).
9.) go about removing shims, check that sealant is ok and seals are still in place, and join the case halve.
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Old 02-05-2019, 02:49 PM   #6
shiroi
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Quote:
Originally Posted by Homemade WRX View Post
First thing first, how did you find an EJ15/6 crank?!!
I bought it from the UAE of all places, it was $250 shipped (shipping being half of that.) It was a real pain to get them to measure the crank throw, they didn't understand that later EL15 engines got the 79mm crank, and I was unsure if it was a true EJ15 crank or an EL15 crank. Probably a week of back and forth to get things sorted, week of shipping, and now it's out in the shop all lubed and wrapped up pretty.

Yeah, I've seen this talked about (owning two LGT's, I lurk a lot trying to fix issues...) but I've not seen it followed through with. It seems the issue up until now has been just getting the needed parts to begin with, let alone the custom work this is going to need. For anyone else who is looking: AUS has a rather large supply of EJ15's being torn apart! Many of the sellers on eBay and elsewhere are willing and able to ship to the US. Currently I'm trying to source some 48mm connecting rods so I can get accurate big end dimensions.

My initial idea behind the 7068 choice was actually strength. FEA shows failure using 7075 and dimensions similar to a BME top fuel rod. 7068 shows marginal survival at a safety factor of 2 and at fatigue strength. This is quite obviously overkill for a rod I know is going to be short-lived anyway. I will be exploring other options soon. As for Ti6Al4V... we'll see. It's obviously a difficult material, both in sourcing and machining.

Seeing as this is actually a -13 build... I'm foreseeing issues going the other way. I may need to assemble the rods/pistons in the bores in each case half, then lower the crank in, assemble and torque one bank of rods, line up the second case half, assemble torque the other bank (between the webs, how am I going to do that?) and then finish case half assembly. Time will tell. If I'm lucky it will simply go together as a normal build would.

-S.
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Old 02-05-2019, 03:07 PM   #7
shiroi
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Sorry, double posting instead of edit.

Quote:
Originally Posted by vicious_fishes View Post
the SOHC heads are roller-rocker, if that makes any difference?
Seems to me the valvetrain weight of the SOHC heads is actually higher. There is simply more metal to be moved to actuate a valve. With the DOHC heads, your only mass is the spring, retainers, keepers and bucket. With the SOHC heads you're removing the bucket and adding a roller-rocker with probably 5x the volume of material, if not more. The ideal would be finger followers, but a retrofit like that doesn't seem to be possible short of casting/machining an entirely new head design. Seems to me the absolute best route while keeping the current heads would be using only a lash cap. This has its issues; there oiling holes for the buckets that need plugged, the valve now experiences side loading that would otherwise have been taken up by the bucket, etc. Both may be possible, but they're also most likely impractical.

EDIT: Anyone know anything about adding piston oilers from a 22T to 25 case halves? Simple as drill and thread a hole, screw them in?

Last edited by shiroi; 02-05-2019 at 04:54 PM.
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Old 02-06-2019, 12:17 AM   #8
Homemade WRX
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Quote:
Originally Posted by shiroi View Post
AUS has a rather large supply of EJ15's being torn apart!
Actually had a favorite Russian of mine reach out with an offer to ship me EJ15 cranks as well. Apparently they're a thing there.

Quote:
Originally Posted by shiroi View Post
My initial idea behind the 7068 choice was actually strength. FEA shows failure using 7075 and dimensions similar to a BME top fuel rod. 7068 shows marginal survival at a safety factor of 2 and at fatigue strength. This is quite obviously overkill for a rod I know is going to be short-lived anyway. I will be exploring other options soon. As for Ti6Al4V... we'll see. It's obviously a difficult material, both in sourcing and machining.
I'd be curious to know more about your model and how you're estimating the loading for the rods. Also curious what software you're running.
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Old 02-06-2019, 02:13 AM   #9
shiroi
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Quote:
Originally Posted by Homemade WRX View Post
I'd be curious to know more about your model and how you're estimating the loading for the rods. Also curious what software you're running.
Think BME aluminum rod dimensions scaled mostly linearly to match needed dims. The current model is a one-piece rod for sanity, failure is happening at the bottom of the small end bearing. Rough estimates of loading were arrived at using published data on the pistons, some math to figure the reciprocating mass of the rod, and an (absolutely overkill) 200 bar assumed peak cylinder pressure, roughly what a light knock event would look like. As I've got more data, things will be adjusted to suit.

I've been using Fusion 360 for quick FEA but have access to ANSYS through work, it will be worth it to sit down put in some hours on it once I've got more than a rough idea of my needs.

As for work accomplished today...
These are in EJ20X heads (dual AVCS Z20 castings, from a JDM Legacy)




Sensor with P/N ending in 0713 is a no-go.




Sensor with P/N ending in 0707 is a perfect fit.

Figured I'd share, since somebody else is going to be in this position someday.

-S.
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Old 02-10-2019, 04:24 AM   #10
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Old 02-10-2019, 04:24 AM   #11
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Old 02-10-2019, 10:18 PM   #12
bp05obxt
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Id be most concerned about oil supply and pressure in this build. One thing unfortunate about ej cranks for the most part is how the oil is distributed unevenly across the journals.

I also saw mention of oil squirters being implemented. I have seen a company in the States use them but again not sure how oiling may have been affected or changed by/for their use.
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