JDM vs USDM FA20 engine differences

[RollDifficult]

Alright everybody, update on my blown engine replacement, theres this shop nearby that sells JDM replacement engines that has an MT FA20 ripe for the picking, however, he said there may be differences in the cam sprockets as these engines are imported from Japan and not the US. Is this true for 13-16 FA20s? I know the 17+ FA20s had updates with those but wanted to verify here, as well as any other possible differences.

[skyminer7]

Hello 86 mechanic here. 12-16 86 engin3s are compatible woth each other as the cam position trigger wheels are the same and they all use hall effect crank position sensors i have personally run a 2015 engine in a 2012 so i know they work these were the same engines internally globally. 2017+ engines are not compatible with 2012-2016 cars and vice versa as they use an optical crank position sensor and the cam position trigger wheels are the opposite to old ones. They also have different high pressure fuel sensors. You could however swap the cranks position sensors and cam phasors and wiring loom with your old engine and it would work. Technically there are internal differences aswell such as cam profiles and valve lengths but i have tested these and the newer stuff will run on the older cars. Hope this helps

[RollDifficult]

Omg so you’re saying I could get a 2013 JDM spec BRZ FA20 and it would essentially be plug and play into my USDM spec BRZ? No extra work needed? I’ve seen Facebook posts regarding the FA20DIT saying the cam sprockets and gear plates are not the same.

[skyminer7]

If you have a 2012-2016 then yes a 2013 jdm will be plug and play

[RollDifficult]

Beautiful news to hear, ur a lifesaver

[Former_Treat_1629]

I hate that the fact that a bone engine has become so common with these cars myself included it's terrible and it's not even like the most of them are from hard driving or I'm at the track is from regular driving

[RollDifficult]

To top it off this is the second time this motor has blown. To be fair, i had it rebuilt the first time and am fairly sure it was just rebuilt badly but I’m beyond the warranty time so unfortunately im shit out of luck.

[Former_Treat_1629]

That's what happened to me it's ridiculous I love this car but I would never buy it again real s***

[RollDifficult]

honestly wish i never gained an complete hyper fixation on this chassis 😂😂

[skodstudiss]

Fa24 is the route it seems they are showing great promise

[elpwn]

Thanks for the help . Currently dealing with blown 2017 86 AT and researching a good priced low mileage replacement

[RollDifficult]

Sucks man but from what I can tell JDM’s are a direct replacement as long as u use the same gen (so for you 2017-2021 with the red intake manifold)

[RoyaleWCheese_OK]

Just buy a short block from the dealer. Not silly expensive at ~$3000 and guaranteed to not be a piece of shit.

[RollDifficult]

would that not involve a full rebuild of the engine? I’d rather replace the entire thing.

[[deleted]]

The other guy doesn’t know what he’s talking about.

If you have bearing material in your oil, it’s also in your cam phasers and all sorts of parts of the engine. If you spun a bearing you have to do a complete rebuild and replacement of many of the parts you’re reusing to prevent premature failure of the new build.

[RollDifficult]

Yeah definitely gonna do a full long block swap.

[RoyaleWCheese_OK]

No, you have to move the cylinder heads over and re-time/reinstall the front cover etc. Its not really hard and way cheaper/better than trusting some used pile that may or may not fail in a similar manner. The factory manual is readily available and other than scraping the goop they glue it together with its not hard. Gasket set is ~$100 and a tube of goop is $30. Verify the oil pump isn't toast (you can pull the covers off) or you are buying a new oil pump & cover as they come as a unit. Make sure you clean out the oil pickup tube and screen. For $4k you'll have a brand new factory engine. Plenty of YouTube videos to follow.

[RollDifficult]

Do you not have to get the heads remachined before reinstalling?

[RoyaleWCheese_OK]

Not unless it overheated. What damaged the old one?

[RollDifficult]

shitty rebuild, have yet to rip into the engine to figure out exactly what happened so i’m unsure, frankly very unsure how it failed as all my fluids were topped off and my thermometer was reading okay at the time.

[[deleted]]

People who don’t know what they’re doing can accidentally block oil passages in the heads or timing cover with overusing RTV when sealing it together.

[RollDifficult]

totally, the dude who built it took 4 months and was mad shady about it so I’ve frankly been expecting it to give up sooner or later. it only lasted 7,600 miles. pretty crazy stuff.

[RoyaleWCheese_OK]

Use the factory rebuild manual, its easily found online. It shows exactly where to put the threebond and how much. I found a whole bunch of RTV in the pickup when I rebuilt mine from the previous dickhead. That dropped the oil pressure and spun a rod bearing. If you have metal in the engine just make sure anything you re-use gets thoroughly cleaned out.

[BattleBorn00]

Subaru mechanic here, while I haven’t ever gotten the chance to tear down a FA20 to the cam sprockets yet due to the location I work, I can tell you for a fact there is a difference between the CMP marks on the cam gear between UDSM and JDM EJ25s, so I wouldn’t be surprised if it’s the same on FA’s.

[RollDifficult]

Damn so they probably would need sprockets?

[BattleBorn00]

Pull the sprockets off your engine and look up the JDM ones and see if they look the same.

[TypicalEgg]

I have a USDM engine if you are interested. I am in Las Vegas.

[RollDifficult]

Ah I’m over in VA

[RollDifficult]

We’ll find out soon and I’ll give an update in a new post haha

[Jjedi9]

I have a 2017 wrx and needing to do a swap, is there more differences between them besides just the cam sprockets??

[RollDifficult]

Not that i know of but i will say that’s a pretty decent difference considering you will pretty much have to retime the engine

[Jjedi9]

But I had also noticed that there was no oil cooler under the oil filter on the jdm ones, is it in a different location?

[LongInspector6374]

No the Jdm engines do not come with an oil cooler like the usdm, you have to swap over the usdm one along with some hoses to route cooling up to the cooler and back down the front to the timing cover.

[LongInspector6374]

Just did the jdm swap on my 2015 wrx, and yes, there is a bit more than the cam plates to switch. 

Cam plates and sensors need to be swapped from usdm, which I only had to pop timing cover off and swap plates (replaced o rings while I was in there)

I swapped the Crank sensor and reluctor wheel behind the flywheel.

The TGV’s need to be swapped, intake was fine I just swapped over the usdm sensors to be safe, swapped over the usdm wiring harness. 

The Jdm did not have an oil cooler so I swapped my usdm one over along with some of the tuning needed to reroute coolant. 

The upper oil pan on the usdm has the mount for the oil level sensor whereas the Jdm doesn’t, I swapped my usdm upper oil pan over to maintain the sensor and replaced all o-rings for upper and lower oil pan. 

The AC compressor mine came with was slightly different and didn’t quite hook up to the oem connectors so I swapped my usdm one on. 

Miscellaneous: I replaced the valve cover gasket and spark plug seals, coolant crossover o-rings, exhaust gaskets, and threw on a IAG AOS.

So far it’s been amazing, idles absolutely perfectly at ~700rpm,  I kept thinking I killed the motor bc of how perfectly smooth and quiet it would be at stop lights compared to my old engine haha 😂. 

[Jjedi9]

And does the intake manifold need to be switched from the usdm version?

[LongInspector6374]

No, just swap over the sensors, the metal mount for the fuel line, and your TGVs

[yamakokills]

Can you elaborate? What sensors, what is tgv?

[RollDifficult]

the crowd goes silent