Engine and Transmission mates

[maclonchas]

Folks,

Hello and first post to the forum (please be gentle) and reading as much as I can from the previous posts and I am in information overload and a constant state of confusion . I am trying to visualize and understand the mating of JDM and USDM engines with transmission and harnesses. The more I read, I think I have a lock and then I read another post and I become confused again.

Let's start what I am trying to do and maybe you can give me some gentle pushes in the right direction. I am looking to build an 818C for street use only! I want to have the challenge of building a car (at a resealable price) that is fun. I am an engineer by trade but not an auto-mechanic, but my step son is very comfortable with modifying and racing cars. I understand the donor program and the need for parts, but do not necessarily want all of that teardown and build in the same place. I would like to do this car in stages as the manual has laid it out and get the suspension and engine/transmission completed upfront.

I am trying to see if JDM engines need JDM trans or we can use a USDM trans. That is my first big question. Is there an upside or downside to this approach?

Thanks
Bill

[q4stix]

As far as I know, every EJ series motor (EJ205, 207, 255, 257) has the same bellhousing bolt pattern and crank pattern. This makes most Subaru engine and drivetrain components like Legos that will fit together in whatever combination. After the engine and transmission things can get a bit mixed. This can include stubs in one year transmission while the splines in a later year will be in the axles.

I think the larger concern will be if you can get the right ECU with the engine and then have a way to tune it as necessary. I'm 'old school' with my 07 daily driver and use open source which works with tons of various years and markets but I'm not as familiar with the AccessPort for JDM engines and conversions.

[maclonchas]

q4stix,

Thanks for the reply. I guess the bottom one is to stay away from the JDM motors and transmissions. I will continue to look at COPART and others for a parts car.

[Sgt.Gator]

I've swapped in JDM 5 and 6 speeds to my USDM cars. The only difference from USDM is they may have different ratios. There are charts with the ratios that specific to the model # of the transmission.
JDM engines are good too. Generally speaking a JDM engine and trans will have far fewer miles and be better maintained than any USDM of the same model year.
For tuning solutions the Cobb Access Port is the most widely used. You can use a USDM ECU on a JDM engine, the biggest issue is that you will lose the AVCS function on older JDM engines because the USDM ECU didn't have it. The AP won't work on a JDM ECU.
NASIOC can be very useful for figuring out swaps.

See the above sticky: THE Transmission Thread 2.0, Now with Pictures. There is a link in post #46 to the transmission chart from Rallispec.

[maclonchas]

Thanks. Will look at that information.
Bill

[Hojo]

Check with your State Inspection dept. My JDM EJ20 motor came with a JDM ECU. The ECU was not recognized by the Mass State Inspection computers. I had to find a used USDM ECU. It works fine now except that the USDM ECU ignores the variable valve timing that the JDM ECU manages. My JDM 5 speed popped out of 5th occasionally. My friend building a coupe had a USDM 5 speed with a less aggressive final ratio. Wee swapped trannys, clutches, slave cylinders, and axles with no problems. He tore open my JDM tranny and found that both primary and secondary 5th gears were fine, as was the 5th gear syncro. The problem was the shifter fork. Cheap repair.

[maclonchas]

Hojo,
Thanks. Glad to see someone making JDMs to work

Bill

[maclonchas]

Sgt Gator,

I am still digesting the tables and the transmission thread and I get myself confused on terms and years. Two questions if you do not mind answering. First is with the 6MT direct versus cable. My understanding the newer 6MT are all cable. If this is correct, can we do the hobby racer mod to all 6MT's (up to what year?). Is the catchup between the engine and tranny (bolt pattern different for FA and FB engines?

Thanks

Bill

[Hobby Racer]

... can we do the hobby racer mod to all 6MT's (up to what year?).

The mod I outlined will work on any 6MT that is NOT a split case design. The split case 6 speeds are an evolution of the older split case Subaru 5 speed and came in the newer WRX models (2014+). You want the 6 speeds from the STI as they are similar to the 2004 - 2007 6MT that everybody uses.

I actually want to take a newer 6MT split case apart to see if it will work for the 818 if anyone has one they want to donate for the cause