I just got my trans apart and figured it would be time to ask since its a lot easier when i am in the middle of replacing a main drive bearing and a few synchros. My new subaru motor is now a TURBO 300 horse 2.0 JDM Subaru with 23 lbs boost. I have stock Gearing now, looking for a nicer highway 75 mph cruising gear with a nice transmission through all the gears with that higher 5th gear.

My main crusing speeds are 45-50 mph in town and 65-75 on the freeway. (trying to get RPM down on freeway) I have 205/60/15's on rear.

thanks for your help...

Chris,

I'm no help with the gearing, but glad to see you have another subi up and running - and a Turbo at that! Too cool - err - I mean Tooo Hot!

Enjoy!

I'll be looking at what kind of answers you will get. I have two 914 sideshifter trannys I would like to combine (if possible) for same type tranny you're asking about since I have a 283 Chevy Small Block in mine. I just took mine around the block and down for a new tank of fresh 91 oktane for the first time since probably 2003 or 4. I had one heck of a time shifting precisely, 2 to 3 no prop, 3 to 2 often ended up on 4th, and 2 to 3 even some times ended up in 5 he he. Need a little adjustment I guess and would like harder springs for r and 1 lock out. I'm running 265/50/15 in the rear.

Yeah the N/A ej25 was great, the 23 lbs of boost in this one i bet will be more fun. Pics to follow once i got the transmission gearing all figured out and put back together.

http://www.914world.com/specs/regearing_901.php

There's a handy excel spreadsheet at the other end of that link.

Leave it stock ...
Andy

For 1st and 2nd you're pretty much stuck with stock. 1st is fragile enough that you don't want to use it hard anyway, and 2nd is a part of the mainshaft. Unless you wanna buy the $$$$ 904 mainshaft, that is.

For higher gears, take a look at the ratios (including final drive!!) used in the car that your motor came out of. The factory already did some engineering to figure out what sorts of ratios they thought were appropriate for a car with that engine. They're at least worth thinking about.

--DD

I have pretty much the same setup and I am happy with my stock gears. Mine pulls away smooth in first, launches well in second, and pulls very hard well past 130 mph in fifth. Oh yeah third and fourth are right where the should be too (at least in my opinion).

It all depends on how you intend to use the car, and of course the characteristics of the engine. I'm not familiar with Subi engines. Where is the meat of the powerband? Real peaky, high RPM power, or more midrange torque?

I have the same engine as Andy, a 3.6L six with power near what you are talking about. I run AA-GA-N-X-flipped H gear ratios. 1 through 4 are nice, though sometimes I wish I had a shorter 2nd when autocrossing because I refuse to downshift to 1st, lest I kill it. It's a pretty sizeable gap between 4th and 5th, though. Something a little shorter than an H would be nice, but it has gotten 32 mpg on long trips and keeping the revs down in 5th sounds like what you are looking for.

Get a spreadsheet, or make your own and play around with the possibilities. I can e-mail you mine if you want. Play around with available gears (some exist, but are too expensive) to get something you like. That's what I did. I would consider looking at the gear ratios in a WRX (although I guess they are 6 speeds) and see what they look like.

You can spends a lot of time on this. And money - some of those gears aren't cheap.

I think only the sti is 6 speed the wrx's I am familiar with are 5 spd. Some of the suby axle ratios are 3:70, 3:90, 4:44, and I think 4:11 To know for sure there is a good suby info thread on the subbug forum by Meladjusted. This may be the thread already listed above. http://www.914world.com/specs/regearing_901.php

thanks guys, i am definately doing my research while i have it apart.

Based on your comments that it's a 300hp JDM Ej20, I am going to assume that it's an v3/v4 Ej20K or a v5/v6 Ej207 engine. Either of those engines would have run a 4.44 FD with either a 0.825 or 0.738 5th gear, depending on the spec and year. Those JDM trannies are super short since they are limited to 120mph in their cars and do very little highway driving.

So, comparing to what Subaru did won't get you very far since your 914 transmission is already a 4.43 FD with a 0.71 5th gear. The simplest solution to your problem would be to get an "H" 3rd gear and flip it for 5th. That would give you a 0.59. The problem with that would be that if you really wanted to nail it on the acceleration from 4th to 5th and keep going your rpm drops a bit too much and you fall off boost a bit. An "HB" 3rd flipped will be a bit better but it's still a compromise on acceleration. However, if highway cruising is the goal, either of these will put you somewhere around 3000-3300 rpms at 75mph.

If you do want that 4-5 shift to let you keep accelerating then you'll want to consider putting something like an "X" gear into 4th. You'll lose a little 3-4 punch, but in return you'll gain some on the 4-5 shift. I have limited my suggestions to the "cheap" gears that are readily available used gears from the various 901 gearboxes. For optimum gearing I could suggest some other options, but it gets pretty expensive pretty quickly, as you likely know.

Someone asked about the powerband of this engine. It's basically going to have full spool by 4000rpm, but peak torque is in the mid to high 5's. Peak horsepower will be just shy of 7000rpm with redline several hundred horsepower above that, though you can safely shift upwards of 8000rpm if you need to.

wow seriously??? My top rpm with delta cams 2000 grind in my last N/a ej25 motor was 6800 rpm. The turbo JDM motor gets up towards 7500-8000 ?? I didnt know it was that high. Then why not stay with the stock gearing for now. 3600 at 75 mph isnt too bad. I am going to post a new thread to see if anyone has a nice slider to sell. I just replaced the main driveline bearing in the intermediate plate and all 5 synchros and i already up to $650 bucks. Anyone have a nice 2nd to 3rd slider?? Mine for some reason is a little MUshroomed!

I've got a 2/3 op sleeve for you. PM me and we can sort out the details.

Do you know what ECU you have for your JDM engine? I can give you more exact information on redline, boost, etc for it if you get me the 10 digit Subaru alpha-numeric parts number and the 2 digit code off it like 6S, Z4, or SC. Though it's not putting out that boost number you posted stock. That's got to be with a boost controller and depending on ECU maybe even a FCD.

Do you know what turbo is on the engine? It should be a VF series turbo from IHI.

the numbers on the turbo are 377-14000 and it looks like a mitsubishi symbol in front of those numbers. Its the bigger turbo for the stick shift cars, guess the automatics had a smaller one due to they needed a lower torque curve for the auto trans.

engine numbers 093660092371 on back of engine EJ20 on front alone with JAPAN words and below the numbers are 7142 it looks like

stamped on engine is maybe build number? 956271

more numbers DOCH and 3J on turbo also.

sucks but sticker on timing belt cover is gone, thats prob where the numbers were. Sticker is solid white, no more numbers

thanks,
Chris

Oh i am also using a $1700 Link STORM G4 ECU so everything is fully programmable, and i am getting a programmable boost controller to go with it. Running no cats, only a glasspak after turbo and an HUGE water to air intercooler with a nice size 2008 mustang cobra intercooler heat exchanger in front of radiator.

pics of engine

another

That's an Ej20G from a 1994-1996 WRX. It's rated at 260hp and the turbo is a Td05-16g. I wouldn't go much past 16psi on it withouth upgrading the injectors. Those injectors are only 440cc and it will start to run lean beyond 1.1 bar. That will have you at 280chp+/-

That also won't rev as high as the other engines I was talking about. It has hydraulic lash adjusters under the lifters for valve lash. They tend to float above 7200rpm or so. Plus the cams are more conservative than the later engines, so power really falls off quite a bit past 6800rpm. They also have issues with the coilpack cracking at the tips, which leads to the spark breaking up at higher rpms. If you get coil problems it may be worth your while to switch over to USDM coil packs with integral ignitors. They are far more reliable and give better spark at higher rpms.

That said, it's still a very reliable engine and one of my favorites of the JDM swaps. That's what I had in my 1991 Legacy and it was a bunch of fun. If I can ever get my 914 swap finished, it's the engine I am using.

Cool thankyou for the advice. I'll watch the boost. I will have gauges on everything and a wideband not just the narrowband so keeping an eye and making adjustments so i dont blow it up will definately be my priority. I know delta cams makes a set of cams for this engine too. I was EXTREMELY happy with their grind for the n/a Ej25 motor. Cool i'll look into the USDM coil paks too, sounds like a good setup. ( my setup i am running individual ignitors for each side)
260 hp is good!

thankyou

Always glad to help. Also, let me know if you are still looking for that slider. Porsche gears and trannies are all I do these days and have a pile of those sliders as good used parts. Most of the builds we do get new ones, so we've got lots of extras that are perfectly good but aren't worth much to us. I'd sell it to you for not much more than shipping cost.

Matt what ecu will you use on the jdm ej20g? I have a 96 ej20h and was going to try to use wrx stuff on it as I have some extra 02 wrx ecus, intake parts and so on if I can. It came with the tt stuff and I have all those parts but it would be a nightmare to keep all the control stuff working. I might also try the tranny that came with it in the 914. It is the outback version.

just tore down the turbo from the block.....it is a TD04. I read that is the stocker subaru turbo and that it actually spools up the quickest. But is my horsepower actually lower now with the TD04 than with the 16g?

I am using factory 1995 WRX STi-RA ECU. Basically the one that came with the engine. There's about 6 options for the 1993-1996 ECU's and some of them are readily available. Others, like mine, are very limited in production.

You can also use a USDM EJ22T legacy turbo ECU. Even though they are only rated at 160hp with a boost controller and a fuel pressure regulator they will run an Ej20 just fine. I used that one on my 1991 swapped Legacy and it put down numbers on the dyno that suggested it was making 240 at the crank.

Whichever way you do the single turbo conversion, you'll want a new wiring harness because the Ej20H TT harness is the next generation and uses a 3 plug configuration that's different from the earlier 4 plug set ups.

Chris,
If that's got a TD04 on it, it's rated at 220chp. However, you are right that they spool a bit better than the td05. It's trimmed different than the USDM Td04 and can hold boost a bit higher in the rpm-band. It's the turbo I used on my Legacy because it was my daily driver. Plus, a Td05 can bring $400-500 on the open market and I needed the money for clutch and flywheel at the time.

However, all is not lost. The longblock itself is IDENTICAL to the ones with the bigger turbo. You've got the 440cc injectors, so you can really maximize the td04, run it around 16psi and not have it be outside of it's efficiency range.

I guess there's no way I can use the tt ecu because of all the extra controls it came with. It sure would save a lot of swapping if I could use it and just use a wrx single turbo. I do have the tt turbos but they seem pretty small. I have some extra tdo4's that I bought for this motor. I know it has higher compression so that will be another hurtle to deal with. I have some good usdm motors but I wanted to use this motor for something as I kinda like the hyd lifters and the big ports.

On second thought, go dig around on the Liberty forum downunder:
http://www.rslibertyclub.org/forums/
Those guys frequently convert over to single turbos on their cars. Because the twins are largely vacuum actuated, I suspect that you may be able to run that engine on the TT ecu as a single. It's a very very common conversion for those guys because of the VOD (valley of death) between the spool of the two turbos just shy of 5000rpms. Post back with what you find out.

I've tried to get registered on two different aussie forums and it's like they don't want to bother with me. They never send the email sign on reply back to get started searching.