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Old 08-07-2010, 10:07 PM   #1
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Boxster Subaru conversion interest? (Now with Audi V8 content)

I'm doing a Boxster/Subaru engine conversion and I was wondering if there is an interest in a build thread here. Not sure what the demographic is here or whether most are purists, but if people are interested in watching, I'd be happy to post up some information/pictures as I go along.

Last edited by kcpaz; 12-01-2013 at 09:19 PM.
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Old 08-07-2010, 10:35 PM   #2
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Boxster engine in a Subaru or Subaru engine in a Boxster?
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Old 08-08-2010, 02:36 AM   #3
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Sure, there's always SOMEONE interested. If you are talking a Subie engine in a Boxster, I'm sure there would be more interest than the other way around. Are you gonna try a WRX motor or a Legacy H6 motor? You would probably have less trouble with a 3.6R swap as you would not have to worry about intercooler placement. Either way, it sounds like it will be quite the project. Keep us informed.

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Old 08-08-2010, 04:42 AM   #4
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I'm a "purist", but I think a swap like this would appeal to a number of folks out there as an inexpensive alternative to a blown M96 engine. Plus it is a "boxer" configuration, so it's far better than some domestic transplant
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Old 08-08-2010, 05:21 AM   #5
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I'd like to see this!
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Old 08-08-2010, 06:25 AM   #6
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Quote:
Originally Posted by kcpaz
I'm doing a Boxster/Subaru engine conversion and I was wondering if there is an interest in a build thread here. Not sure what the demographic is here or whether most are purists, but if people are interested in watching, I'd be happy to post up some information/pictures as I go along.
If it's a Subaru engine in the Boxster, what engine are you using? I don't think I'd like the 2.0 turbo from my WRX in my Boxster as much as I like my 3.2. The Porsche engine has a much wider torque band and has so much more character. The Impreza engine, as fun as it is, is more like an on/off switch in comparison.

I'd also think the gearing of the Boxster would need to be altered. The WRX has short gearing and it's still easy to catch the engine off boost going around sharp corners. The Porsche has taller gearing in general.

Last edited by blue2000s; 08-08-2010 at 06:27 AM.
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Old 08-08-2010, 11:08 AM   #7
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Just to clearify, I will be putting an STI motor, into a Boxster S that I bought with a blown motor. Why anyone would go the other way around is beyond me...
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Old 08-08-2010, 03:46 PM   #8
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Interested. I look forward to seeing more.
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Old 08-08-2010, 04:17 PM   #9
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Yup. Interested!
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Old 08-08-2010, 06:26 PM   #10
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fyi, there is a thread in another forum (914 i believe) where a capable-sounding fellow was looking into putting an ls1 v8 into the boxster. while that may sound a bit silly, the ls1 is about the same weight and dimesions as the m96. most of the thread goes on about all the work required to modify/fabricate bell housings and starter locations, but one of the interesting side notes of the whole thing is that the cayanne and audi v8's are both direct bolt-ons to the boxster transmissions. the author of the thread actually admits that an audi or cayanne conversion would be much simpler, but didn't pursue it as he couldn't afford to buy the engine (an ls1 is much cheaper). apparently the audi or cayanne would be less expensive in the long run given that transmission modifications are not required.

long story short, have a look at putting an audi v8 in there - might be easier.
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Old 08-08-2010, 08:43 PM   #11
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very interested. keep us informed
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Old 08-09-2010, 12:03 PM   #12
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Originally Posted by The Radium King
fyi, there is a thread in another forum (914 i believe) where a capable-sounding fellow was looking into putting an ls1 v8 into the boxster. while that may sound a bit silly, the ls1 is about the same weight and dimesions as the m96. most of the thread goes on about all the work required to modify/fabricate bell housings and starter locations, but one of the interesting side notes of the whole thing is that the cayanne and audi v8's are both direct bolt-ons to the boxster transmissions. the author of the thread actually admits that an audi or cayanne conversion would be much simpler, but didn't pursue it as he couldn't afford to buy the engine (an ls1 is much cheaper). apparently the audi or cayanne would be less expensive in the long run given that transmission modifications are not required.

long story short, have a look at putting an audi v8 in there - might be easier.

If you are talking about Brad Roberts, I know him and I know he's working on the LS conversion into a Boxster. We have talked at length about it. Bottom line, he is going that direction, and I am going the Subaru direction. The problem with the Audi/Porsche V8 is they are HUGE with their DOHC 32 valve design, and massively top heavy. Also, engine management could get expensive. In both of these cases, the Subaru and even LS motors are better for the Boxster than the German V8. No don't even get me stated on the cost of replacement/upgrade parts...

It sounds like there is some interest in atleast watching the project here so I will post up some pictures as I go.

Last edited by kcpaz; 09-04-2010 at 01:37 PM.
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Old 08-09-2010, 12:22 PM   #13
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A Cayenne engine in a Boxster sounds interesting. A V8 Audi engine sounded interesting until I spoke to my Porsche Indy who could not have more bad things to say about their engines after I mentioned an interest in buying an R8 once the prices had come down.
Subi Boxer engine would be pretty bad ass. A guy in one of the many autocross clubs around here made some exhaust mods to his and it sounded like a .50 caliber cannon.
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Old 08-09-2010, 12:37 PM   #14
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A Cayenne engine in a Boxster sounds interesting. A V8 Audi engine sounded interesting until I spoke to my Porsche Indy who could not have more bad things to say about their engines after I mentioned an interest in buying an R8 once the prices had come down.
Subi Boxer engine would be pretty bad ass. A guy in one of the many autocross clubs around here made some exhaust mods to his and it sounded like a .50 caliber cannon.
Cayenne V8 = Audi V8. It's the same thing.
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Old 08-09-2010, 12:57 PM   #15
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I wanna see this
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Old 08-09-2010, 04:46 PM   #16
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very interested in a build up with pix!
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Old 08-10-2010, 08:11 AM   #17
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Very interested as well. I own a 2008 Subaru Legacy GT, which has the exact same engine as the STi except with a different turbo (and obviously engine management).

The 2.5 liter Subaru engine is capable of safely putting down 350awhp without modification to any internals and with a mildly upgraded turbo , as long as it's got plenty of fuel and is running a solid tune. The only real soft-spots internally-speaking are the pistons & piston rings, which seem not to like detonation as much as perhaps some forged pistons would

In stock format, with an opened up exhaust and conservative tune, 280-300whp is easily accomplished with no other modifications.

At the same time, expect peak torque (of about 300+ lb/ft) to be delivered by 3000rpms and power to stay on until 5500-6000 rpms.

I think Porsche purists would miss the buttery smoothness of the flat six engine and how it never gets out of sorts, even at very low rpms in higher gears, but otherwise the engine is a great replacement if someone can make it work.

I'm not worried about the intercooler...plenty of ways to make that work....but I'm curious about the transmission adapter, starter mounting, and electronics.

Also, I think the boxster 5-speed's gearing is actually ideal for this engine. The taller gearing means the turbo will get a higher load, which means earlier spool while giving some nice long-pulling times. Combine that with the drop of ~300-400 pounds + 2 less wheels to drive, and I think the engine will drive like a dream.

Good luck to you. This is one swap that's been waiting to happen.
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Old 08-11-2010, 08:48 PM   #18
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Interesting discussion going on here. I have an 08 STI with a TBE and a stage 2 tune. It is putting down 340 HP to the wheels and 390tq. This is my second STI, started with an 06. I also just got a 2011 Spyder. The 2 cars are totally different, my STI is my DD and the Spyder spends most of the time in the garage covered. The STI is an in your face kinda car, it's ruff around the edges and just want to be driven hard all the time. It is the funniest cars I have ever driven, that is until the Spyder came along or along came the Spyder . The STI handles very well and I love to drive it when the roads are wet, it slides through corners with total control.. IMO the high roof line makes it a little top heavy and at limit driving does under steel some. The Spyder on the other hand is the cut above the STI in every category , the most neutral, balanced, smooth car I have ever driven and that includes a GT3/RS. The handling is almost like the car reads your mind, it's like you move your eyes and it's there. Putting and STI motor in a boxster would be cool, you might have some fit issues with the motor and as you mentioned the trans, but I think the idea is a good one. That would be one bada$$ car. Good luck with it if you decide to do it.

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Last edited by pcw; 08-11-2010 at 08:58 PM.
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Old 08-11-2010, 09:53 PM   #19
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It's not a question of whether or not I'm going to do it. It's already started. I have a donor car already (a 2000 "S" with a blown motor) and I already have the first adapter plate finished. Here are the initial pictures of the project...

Last edited by Brucelee; 08-13-2010 at 03:58 AM.
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Old 08-12-2010, 02:58 AM   #20
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Nice work! I didn't realize you were the guy that did the Subaru engine in a 911. I saw your site a few months ago and saw your videos on your exhaust also. Nice work on those as well. With a race prep shop at your disposal this conversion should move right along. Looking forward to see the progress.
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