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Previous Next Up Topic Engines / Subbug - Subaru Power / Converting to Subaru (88432 hits)
By Mel Adjusted Date 2008-08-07 02:05 Edited 2008-08-07 20:40
Alot of people ask about converting to Subaru, so I'm going to attempt answering what I know about this subject. I've had lots of Information on the Subaru's and because of my age and time I have I want to post as much as I can here in hopes it will help someone. I am happy to help answering questions, but I am a busy boy trying to build 3 cars before my time runs out. What I'm mostly going to be talking about is the EJ series subaru engines, however most of the principles also apply to other Subaru boxer engines.

What follows is my opinion. I say MY opinion, which is not to say it is the right or only way to do things.

As I see it, the Subaru engine is a modern VW which is on steroids.

Benefits of Subaru power:
Subaru boxer engines are 50 YEARS ahead of air-cooled VW boxers in design and technology.
They run smoother and rev quicker.
They have two more main bearings than a VW and a full flow oiling system.
Standard features EFI, electronic engine management and multiple camshafts/valves per cylinder.
They are plentiful and parts are easily available.
Extreamly reliable.
They are under stressed and so make a great engine for mild to wild performance modifications.
Aftermarket tuning parts available are readly availble.
Dollar for dollar they are cheaper and more reliable than a VW boxer engine of the same capacity/power rating.

Disadvantages of Subaru power:
Subaru boxer engines are a bit heavier due a bigger case, extra oil and water cooling.
Subaru boxers are physically bigger than VW boxer engines, but not really that much.
Parts are more expensive than VW boxers in general.
The oil sump needs modification to be safe in most conversions.

What does a 'Subaru conversion involve?
Depending on weather your doing a Subaru to VW or mid-engine will determine what needs to be addressed

Things that need to be addressed are which engine you'll be using, fuel system, exhaust system, cooling system, engine mounts, Bell housing, flywheel, clutch, ECU and wiring and other bits and pieces.

Fuel system:
Putting a Subaru engine to your VW is going to take some different thinking and needs. as far as your fuel tank goes. I use two pumps. 1 in the tank is a low pressure and high volume and a inline high pressure high volume to feed the injectors. The need to provide fuel to the pump at all times is very important, and to avoid starving them of fuel during hard cornering or acceleration. The fuel needs to be collected in a reserviour.
The tank should have return supply fittings on it and a vapour line fitting.  Two extra solid lines are needed to service the EFI system. One is a return line from the engine to the fuel tank. The second is a vapour line that draws fuel vapour off the top of the tank for the emission control system on the inlet manifold.  In reality, the best option is to fit two new solid lines for the fuel supply and return and use the old fuel line as a vapour line.. Do NOT use COPPER tube, it work hardens due to vibration and will crack allowing high-pressure fuel to spray all over the place. The tube should be rubber mounted had have grommets around it when it passes through any panel (other wise it will wear through and leak). Running the lines under the car is ok as long they have a guard of some sort over them. Through the tunnel is ok as well. Do not run the lines through the passenger compartment. Don't weld them either, it will lead to localised brittleness and cracking Also, make sure you have good clamps and high-pressure hose between the EFI pump/injectors/return-line, etc.

EFI demands well filtered fuel. I use two filters. One low pressure one near the tank outlet, and a hi pressure one after the high pressure pump and before the fuel rail.

Cooling System.
If you can use the original one great but chances are you'll be using a different one. Most of my cars use multi radiators. I usually mount one on each side in front of the rear wheels out of harms way.
As for a place to mount the radiator, the best place is in front of the car. You can put the radiator under the car with a scoop to direct air into it. In this set-up it may even be laid flat racing car style. Angling radiators forward when mounting them is also good, as it slows down the air flow and helps it to remove more heat. Have an accurate water-temperature gauge. make sure enough air gets to the radiator to keep it reasonably cool at highway speeds.
I have seen radiators mounted in about every place you can think of and the best one is the one that keeps the engine at operating temps all the time. You'll also need a big fan on the radiator to cool the engine in traffic or on hot days. The fan should NOT be operating continually. This will actually restrict airflow in certain circumstances. It is also a constant and unnecessary drain on the electrical system and only used when needed.
As for hoses and water pipes I used wire to make a pettern and then have tubing of the right size bent and couple the tubing with rubber hoses. Use as little rubber hose as possible. Also try and keep the hot pipes out of the way so no one gets burnt.
Also, don't forget to hook the heater pipes up to each other so the coolent circulates through the system properly. Just blocking them off will make the engine overheat.

Exhaust system.
OutFrount makes headers for the non-turbo and turbo'd engines. Remember, the catalytic converter should be about the same distance from the engine as the standard system is if you want to use the factory ECU. Also, you will need to make sure that the exhaust oxygen sensor is in place and working. After that make it as loud as you like.
For the turbo engine work with a turbo specialist till you get the hang of how it works. If you do go the turbo route be ready to experance the rush of your life.

Engine mounts and bellhousing.
Subaru engine have engine mounts. These need to supported from underneath to mount the engine properly. The standard four engine/gearbox bolts will not hold an EJ properly and You will need to fabricate something to support the engine using the factory mounts in some way. The mounts will need to be solid also. Subaru boxers have a lot of torque and can move around quite a bit.

For me this is the easy part. I use the Subaru transmission, clutch and bellhousing as my cars are mid engine cars and use a Bremar adaptor to convert my transmission to a mid engine setup. For everyone else there are a number of companies make good quality conversion kits. Kennedy from what I hear make a good kit. 

Once again I use the Subaru Clutch with there 5 speed transmission, but Kennedy and Outfront have anything you'll need. My understanding is the Adaptor comes with a flywheel so 1/2 the problem is done.
In keeping with a modern setup I use a hydraulic clutch. Makes installation simple.

For most cars, the standard EJ sump will need too be modified, shortened. Outfront and Kennedy sell these, or you can have a shop fabricate you a unit that will do. It's important, not to compromise the volume as this can shorten engine life.

ECU and Wiring Loom.
You have two choices when it comes to ECUs. Both have good and bad points. First using the standard ECU. The standard ECU is a highly developed and tuned computer w/self diagnosis, closed loop functions and smooth operation with no programming needed. The ECU will operate best when the engine is setup as close to standard as possible. What I'm saying is the inlet, exhaust and sensors need to stay as close to original as possible.  Also, your pretty much stuck with the factory tune. You'll also need to strip down the factory loom and wire it up properly. For those needing to meet emissions laws this is your only option.

The other option is to use an aftermarket, programmable ECU. Many of these are available as a plug-in unit for the N/A and turbo engines. The tuning possibilities available are infinite, But for the best tune, you really need dyno time and an experienced tuner for the ECU in question. John over at Outfront or Paul here on DBA can help you with your stand alone ECU's

Gearbox and drivetrain.
Which gearbox? Myself I use the Subaru 5 speed transmission in the Mid-engine setup so alot of my problems are solved. I'm also going to the Subaru automatic transmission so I can set it up even better. But for those of you that are going to use the VW transmission, your going to need something with moderate to high strength.
For people using IRS (independent rear suspension) For non turbo engines (EJ20, 22, 25) the 002 or 091 Kombi boxes are strong enough in standard form if treated with some respect. These are ideal for offroad work. For road cars the box of choice is the single side-plate Lbug (1303) box with the 3.88 diff ratio. If you want to go drag racing you will want a super-diff and maybe different ratios, but this box is a great place to start.

For turbo engines (EJ20t, EJ20tt), plan on spending some money. No standard VW box will handle 200hp for long, and all EJ turbo motors make more than 200hp stock. Using one of the gearboxes mentioned above, with all the tricks here apply. Hardened keys, welded 3rd and 4th gears, strengthened side plate and a super-diff are mandatory for longevity. This will cost thousands of dollars and that is before you go putting special ratios in. That said, once the box is built properly it should last.
Some people prefer Porsche 5 speeds but be prepare to spend big dollars.

Because of it's design, it is amazing what can be done with swing-axle. That said, using this style of gearbox with any EJ motor means a completely worked gearbox, These boxes will need hardened keys, welded 3rd and 4th gears, strengthened side plates and a super-diff for any real hardwork. If you really want go nuts power wise (with turbos), a Rhino case is probably a good start too.

Anyone interisted in the mid-engine setup I'll add it here.

The way I see it, it's the cheapest way to go to get lots of big numbers in the HP battle. It will cost a bit but that will depend on how much work you can do yourself. If you send your car out to be modified it'll cost, but if you do it yourself it will be considerable cheaper.

My expertise is more in the Mid-engine conversion that the VW gearbox conversion so any of you experts in this area jump in with your knowledge base and fill in the blanks.

CV joints 101



VW Transmissions

Eagle Performance

Here is where I got my idea for a mid-engine Subaru car
At my age.. Everything I buy comes with a lifetime guarantee..
By Terry F Date 2008-08-08 19:06
Another great post Mel!
By Oneil G 1147 Date 2008-09-02 20:44
Hi Mel,

Could you please post details about the mid-engine conversion.  I learned a lot from your prior post. Thanks!
By Mel Adjusted Date 2008-09-03 03:42
My personal opinion is to use the Subaru Converted 5 seed manual transmission or the FWD Automatic Subaru transmission. What are you looking for?
At my age.. Everything I buy comes with a lifetime guarantee..
By Mel Adjusted Date 2008-09-03 03:56
Depending on which transmission you use will determine how you setup your transmission needs. For shifting I use heavy duty inboard/outboard cables. There somewhat cheap and work really great and postive shifting. For the 5 speed you'll need a Hydralic master cylinder for the clutch.
In the past I've used the VW bearing carriers, stub axles and brakes but the new car I'm building will be using all Subaru parts to make repairs easier in the event of breakage or a warn out part
At my age.. Everything I buy comes with a lifetime guarantee..
By Mel Adjusted Date 2008-09-03 04:01
try to stick with small diameter wide tires to keep the final gear ratio low and keep the strain down on the drive train. With the stock gearing on the Subaru you'll be able to go over 170+ MPH and trust me you dont need that kinda of speed so stay with smaller diameter tires will also lower your top speed plus what I've stated above.
At my age.. Everything I buy comes with a lifetime guarantee..
By Herman J 1340 Date 2008-12-31 23:46
Hello Mel.  I hope this post reaches you well, in good health, and hopefully a Happy New Years.  I am new to this site but am very glad I found you.  I am extremely interested in the Subie mid-engined setup with an automatic.  I've seen the Bremar conversion for the 5-Speed but what is done to enable the automatic setup?
By Mel Adjusted Date 2009-01-01 17:07
Subaru makes a great FWD automatic transmission thet would be great for a mid-engine setup.... With a little tweeking it could be made into a paddle shift setup...ala F1 and Indy car style.
At my age.. Everything I buy comes with a lifetime guarantee..
By Herman J 1340 Date 2009-01-01 21:49
Now that would be awesome but truly out of my scope of capabilities.  I am wondering if the 'auto' option is a matter of simply rerouting of cabling for the shifter or is it going to require modifying the tranny in anyway?
By Mel Adjusted Date 2009-01-07 05:36
You don't have to touch the transmission.... The car you'll be putting it in will be considerly lighter and less stress on the transmission... It should last as long as you.... As for the cable, I use a extra heave duty marine outdrive cable and have never had a problem with shifting.
At my age.. Everything I buy comes with a lifetime guarantee..
By C L 1333 Date 2009-01-13 16:23
maybe i've overlooked it on here if i have somebody point me to the right forum topic.. but im doing a subaru conversion and using a 091 aka 6 rib tranny. i need to know what super differ and what ratio gears i need to change out to adapt to a subaru turbo ej20 engine. i started my searching and trying find this info out so i can adapt my tranny to handle the motor.. i'll be using street tires and prob light drag racing, nothing hard. i also heard i should go with harden keys while im at it.. but i have no clue which gears i need to buy n that sort. would appreciate the tips n help.
Need a kustom paint job thats high quality, reasonable priced, with no overhead.
By Mel Adjusted Date 2009-01-14 03:02
You haven't overlooked anything... Your question is like asking what cam is best or which engine oil is best... I've used 091 6 rib, 002 5 rib and Mendeola's on the Subaru. I've had good luck with them all yet my 1st choice is the Subaru 5 speed transmission, but then I run mid-engine cars.
A lot depends on what you intend on using the car for and how much you plan on building the engine.. These engines can and will develop a lot of power and handeled wrong make scrape metal out of anything put behind it. That being said I suggest you go to the following site and see if it will answer any of your questions.

Myself when I was using a 5 or 6 rib transmission these boys did my work....
At my age.. Everything I buy comes with a lifetime guarantee..
By dewayne b 1137 Date 2009-02-08 07:37
i have the 091 in my car. i started with stock gear ratio's and a super diff. all was good except 4th gear was tacking to high for freeway cruising, so i changed 4th to a 0.77 ratio. that change put me just 50 rpm higher in 4th gear than a subaru in 5th gear at 70 mph. if i'm not mistaken the 091 gears and shafts are all splined so there are no hardened key issuses. just be very carefull on who you pick to do the trans build. i've been burned twice and a friend of mine was also just ripped off.
By charliew Date 2009-03-16 16:30
Also to add to Mels great info. Porscharu on the 914 site, I can't remember which one, too many paint fumes, narp, 914 world or 914 club, gets some nice tranny flange adapters made to use vw bus 100mm cvs and axles in the 914 with the suby 5spd. They are not cheap but are well made by a driveline shop and come heattreated and nitrided. Also a member (spunone)does neat aluminum dust covers that go over the tranny seals on the flanges. The adapters are the correct length to use the bus axles when the motor is mounted straight inline with the 914 control arm carriers. If you go to the 911 flanges and stubs you will get the 5 bolt porsche hubs also.
By Rick M 333 Date 2009-03-16 17:41
Mel, great info as always. I am curious as to your automatic Scooby transaxle. I haven't seen any that were strictly FWD; does Bremer handle the adapter plate for autos as well?
By charliew Date 2009-03-17 16:04
I'm not trying to take Mel's place but the bremar blocks off the rear drive shaft output and locks the mainshaft to the tranny gears to make a fwd tranny.
By Rick M 333 Date 2009-03-17 17:49
That's what I'm trying to figure out, if the auto tranny locks in the same way as the stick shift tranny :-)
By charliew Date 2009-03-17 20:51
There are fwd only suby trannys but I'm not sure how strong they are but Mel thinks they are strong enough as he has already posted.
Previous Next Up Topic Engines / Subbug - Subaru Power / Converting to Subaru (88432 hits)

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