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How to do an EZ30R conversion


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Doing an EZ30R conversion

The biggest annoyance about this conversion is if you are trying to fit it into an old chassis, you will find the nose of the new cars are bigger and have more room for the radiator, which isn’t a major issue if your creative, but other wise it’s a very straight forward swap!


Exhaust: You either make up your own exhaust manifold to go around the front cross member, which will be time consuming if you want them to be a tuned length.

Easiest is to go under the cross member but then the lowest part of your car becomes the exhaust manifold which is a pain as I have bent mine up a bit because of it :S

Other option is to do between the block and the cross member which is a very tight fit and will require much beer to achieve

The way I did it though is to put the standard EZ30R extractors on the motor and scallop out the front cross member, which is the easiest and performance wise the best as it has tuned length extractors from factory. You wont have any issues with getting a LVV cert with chopping out your cross member but you need to made sure you do it smooth, and not leave shape corners in the cross member post cutting as it is a prime region for a crack to occur. The one big down side is that your headers become the lowest thing to the ground under your car and will get wrecked it you like been stupidly low.


Easiest Option: Get an EZ30D radiator out of a BH legacy as they will fit in most standard radiator areas quite easy. This is what I have done. If you are keeping it NA then this will easily do the job, you just need to make sure you have decent fans!!!

The factory ez30R radiators are LOADS bigger and most cases you wont fit them in there so its not worth the effort, you are better off doing the below.

Best Option: Alloy radiator, which will have to be custom, or a modified ver 8 sti one, as no one makes one for the ez30r off the shelf that I have found so far.

Fans - You need to use slim fans, which will take some hunting around. For my main fan i managed to score from a parts bin a thin air conditioning radiator fan with a steel shroud on it. I used this as my main fan because it was 2 speed and worked really well with the shroud on it 

Throttle Body:

Unless you want to go fly by wire, you need to scrap the standard one. Cheapest option is to get a falcon throttle body (im pretty sure mine was either that or a commodore one but I cant remember because it was so long ago) from a wreckers and a custom bracket to hold your throttle cable. Then you will also need to buy a bosch throttle position sensor to go with this also.

If you use a commodore or a falcon TB, there is lots of veins in it which need to be welded up and then have the face that attaches to your plenum milled down.

Air Con:

You can choose to hook this up, but you will need to get some custom lines made up etc. Plus you MAY have issues with the AC pump on the ez30r needing an external thermostat because of the differences in the systems between the BC/BF legacy systems and the BL/BH systems

Power Steering: Just use the EZ30R steering pump, you just need to braise some lines together, which isn’t much


ECU options are still kind of limited, the best option here is a link g3 plus (if you can find one 2nd hand, but there aren’t many around) or buying a g4 extreme. For the value for money aspect, i would buy anything else because you will end up wasting serious coin in that department. If you are considering using a standard ECU, STOP!! They are a whore of a thing, im just going to leave it at that. And if you are keen enough you still have to pay Subaru NZ to de-immobilize it, which isn’t cheap!!!

Recommended extras:

GET A BIG CLUTCH!! Because you have torque instantly, it is very easy to destroy a factory clutch by miss timing releasing the clutch and putting your foot right up it.

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im curious on the relocation of the repostioning of the throttle cable, i got the falcon throttle body today and we measured it up against the manifold and shouldnt be a huge issue but just would like more info. Also with the gearbox crossmember instead of modifying the turbo one, could a non-turbo one just be used and then no modification needed

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To mount the throttle cable you will have to fab up a small bracket out of flatbar or what ever you have around, mine mounts off the one of the starter motor bolts and a shorter one. You will have to weld up some of the galleries on the throttle body also and get it machined flat once welded up.

It wasnt the gearbox cross member that was scalloped out, it was the front cross member. You can kind off see it in the last photo with the heat wraped exhaust how it is scalloped to go around the middle pipe. Im unsure about swapping the crossmembers over as i have no idea what an NA one looks like.

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Guest boostin

Correction. Technically they're both EZ30R's.

The BE/BH version has a single exhaust port per head, alloy intake manifold, cable throttle, no AVCS/VVL etc.

The BL/BP version has triple exhaust ports per head, plastic intake manifold, electronic throttle, AVCS and VVL on the intake only.

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  • 1 year later...
  • 1 year later...

Couple of questions;

* Are you using o2 and A/F sensors? I assume so, but can\'t see any in the pics, but might be on the top side of the exhaust.

Standard ones or aftermarket? And how many (i.e 2 x o2 and 2 x A/F like stock)?

* How did you wire up the compressor and any issues with the RPM sensor in it?

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 funkytown said:

If they are tuning aftermarket i can delete air flow meters entirely. Or run 1 or two just depends on the number of intake ports.

Same with 02.. just depends where its positioned. And while u tune with it there is no reason to have it for daily running if aftermarket ecu tuned.

My ecu was tuned with closed loop narrow and by going to wideband it was roughly 25% better on gas over a 350kmish auck trip. Wideband for daily is winning.

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  • 4 months later...

Hi im going to do this conversion in my 96 sti just wondering would a g4 atom be up for the job. And did you consider just making a adapter for the ej20 throttlebody or is it too small? Could you also post up a pick of your fuel return setup plz plz ;D

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 Trent said:

Hi im going to do this conversion in my 96 sti just wondering would a g4 atom be up for the job. And did you consider just making a adapter for the ej20 throttlebody or is it too small? Could you also post up a pick of your fuel return setup plz plz ;D

ej20 tb are way to small as well to work, and the fuel return is pretty easy

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  • 1 month later...

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