Porsche Boxster 986 - engine swap project

Porsche Boxster 986 - engine swap project

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Escy

Original Poster:

3,907 posts

148 months

Wednesday 3rd February 2016
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Thought i'd start a build thread for my Boxster. I bought a 986 Boxster S with an engine swap in mind in Autumn last year. I like engine swaps, I enjoy the building of them and love the results. I've built a few MR2 Roadsters with 2ZZ engine swaps and they are great and have turned me onto the mid engine platform. I initially was looking into doing a VX220 with a Saab B204 engine swap but by the time i'd sold my AE86 (also engine swapped) i'd missed the boat a bit and the prices on the VX220 have started going up.

I turned my attention towards the Porsche Boxster. It's common for MR2's, Elise's and VX220's to be modified/engine swapped but it's strangely rare for the Boxster. I learned that the Boxster shares a common bell housing pattern with Audi which got me thinking. I had looked at Audi V8's, there are a couple knocking around in the USA but not much info on them. My friend has an Audi S4 B5 with the 2.7 bi-turbo which i'm impressed with. A donor car can be had cheap and they are manual from the factory unlike the V8's which would make things a bit easier. Also, the power potential on the V6 is fantastic and I felt if it's worth doing the project i'd want more power than the Audi V8 offers.

My plan at the start of the project was for about 400bhp running on some K04 turbos. As I started buying parts i'm now thinking more like 550bhp give or take.

I decided to go for the Boxster S as the base for the project over a 2.5 or 2.7 as it has an extra radiator in the front, better brakes, 6 speed gearbox, larger wheel bearings and i'd just rather have an S anyway. I picked up a nice example with the BBS GT3 split rims, hardtop and clear lights. The most important thing was it wasn't silver as they all seem to be and that's boring. I ran the car as it was for a month or so and I have to say I am impressed, they handle well and I could actually have lived with the standard 250bhp, it seemed plenty quick enough. I did actually re-consider my plans as I liked it more than I thought I would. My reasoning behind the swap in the 1st place is that Porsche engines are very unreliable and they seem to be ticking time bombs, various issues, IMS bearings, cracked cylinder heads, cracked liners, bore score, etc. I'd never have total confidence in the engine not letting me down in an expensive way, it seems a total lottery. The Audi engine on the other hand can be bought for 1/4 of the value and they are over engineered, plenty of 400+bhp S4's running around with 200k on them that have never been re-built.

These were taken on my way home from buying it.



I bought my donor car on ebay, bought it before I actually had the Porsche. It didn't matter if I had an A6 or S4 as the donor so I just waited for something suitable in manual to come along. Lot's seem to be high mileage badly maintained dogs so I avoided those. I like to take a punt and this was a total gamble, it had been sat for 3 years after the owner had passed away. The advert said it'll start on jump leads but that was pretty much it. The miles were pretty reasonable at 106k (the Boxster is on 93k). I won the auction and paid a bloke to collect it for me, I didn't even go and look at it. I'd spotted it had a lovely set of Recaro seats in it so it was worth a roll of the dice. Even though it was covered in filth and full of cobwebs I could tell it's a good car. It's only had one owner since 2001. The engine runs great and is whisper quiet and that's the only thing that I really cared about. The interior being in fantastic condition was a nice bonus as were Pirelli's all round with lots of tread. A signs it had been looked after. It also came with a free old man hat. smile





It didn't take long for things to start slipping on my 400bhp plan, I was initially going to just go for larger turbos on a standard engine. After reading up about the 2.7 bi-turbo I found that a nice upgrade is to fit cylinder heads from a naturally aspirated Audi V6, they have more aggressive inlet camshafts and much larger ports. I found a low mileage 2.4 V6 for pocket money so thought why not? So I bought it. This will change the characteristics of the engine which should suit the Porsche. The 2.7 is known as a bit of a torque monster, great on a 4x4 saloon that's heavy, not ideal for a lighter rwd sports car where the transaxle might be the weak link so it'll trade torque for more peak power.


I didn't strip many parts off the Audi as I couldn't be bothered so off it went for scrap


Part of my reasoning for this engine swap was that it would bolt to the transaxle but I knew if I used a Boxster S as my base, that wasn't actually the case. I picked up a spare 986 S transaxle (as I hadn't removed the Boxster engine but wanted to start planning things) and placed the Audi V6 spacer plate on it. Only half the holes lined up and the starter motor is in the wrong position. There is also no place to mount the crank sensor either. These issues could be worked around but I wanted a bolt on solution. A 5spd 986 trans is actually an Audi unit and bolts straight to the Audi V6 and has the right sensor locations, this was the easy option but they are weaker and replacing a 6spd with a 5spd felt a downgrade. I decided to buy a 987 S 3.2 transaxle, this has the starter in the right place and all the holes are the same. I had to drill and tap a couple of holes and open out the casting for the flywheel sensor. Fitting that gearbox into a 986 hasn't been done before so there are a few hurdles i've discovered, the driveshafts are unequal lengths unlike the originals so i've had to make up a hybrid set using the 986 ends on the 987 shafts, that was easier said than done as they outer CV's aren't designed to be serviced.


I put a fresh MOT on the Boxster before I pulled the engine to make testing and mapping easier at the other end.


I bolted the trans to the engine and offered it up inside the engine bay. It's a surprisingly good fit. I will need to reverse the inlet manifold, like in the picture and the trans will need to sit half an inch lower and an inch further forward. The distance between the 987 trans diff output flanges and the bellhousing are shorter than on the 986 trans, that's a good thing as it will improve on the driveshaft angles which plagues the standard 986 S but as i've had to move the trans an inch forward it's making the driveshafts foul the suspension arm carriers. So these will be getting modified for clearance. So far so good, the engine and box fit with only minor modifications to bolt on parts. I'll also need to modify the throttle body angle to have enough clearance for the engine cover. I'm currently in the process of making my engine subframe.


The standard location for the turbos is no good as it will foul the boot, i've decided it makes more sense to go for a large single (which I think i'll mount on the back of the transaxle). I bought a hybrid Holset, which is a combination of the HX35 and HX40. Should be capable of 650+bhp. Here is a picture of it next to a standard KO3 turbo.


This is pretty much where the project is, i'll be updating as I go, hopefully things will move along at a reasonable pace, i'm aiming to have it done before the summer.

LukeDM

467 posts

122 months

Thursday 4th February 2016
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Fantastic! cool

dom9

8,040 posts

208 months

Thursday 4th February 2016
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Looking forward to seeing this one progress!

Good luck and keep us updated!

R6VED

1,365 posts

139 months

Thursday 4th February 2016
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Awesome, I look forward seeing this progress.

chryslerben

1,168 posts

158 months

Thursday 4th February 2016
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Sweet project, definitely keeping an eye on this thread.

Don't tell me you sent those calipers on the A6 off to the breakers as well though?

Escy

Original Poster:

3,907 posts

148 months

Thursday 4th February 2016
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I did, one of the front calipers was seized solid so I decided they weren't worth the time and effort.

chryslerben

1,168 posts

158 months

Thursday 4th February 2016
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Dammit! I was after a set.

Keep us updated with your progress though as it should be a right monster when done

lewisco

380 posts

118 months

Thursday 4th February 2016
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Bookmarked this one!

harrykul

2,770 posts

225 months

Thursday 4th February 2016
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Fantastic! Bookmarked.

Johnnytheboy

24,498 posts

185 months

Thursday 4th February 2016
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I was wondering how possible this would be as I imagined it would be quite a tight engine bay on a Boxster, but you've proved me wrong!

C70R

17,596 posts

103 months

Thursday 4th February 2016
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Mother of God, that's quite some build. Very much looking forward to seeing this completed.

pidsy

7,958 posts

156 months

Thursday 4th February 2016
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have you got a timescale in mind OP?

Altrezia

8,517 posts

210 months

Thursday 4th February 2016
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Oh my, what a great project!

Love it. Good luck smile

rallycross

12,747 posts

236 months

Thursday 4th February 2016
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wow - that is one way to create a lot of work or yourself doing this project. Hope it goes well.

5potTurbo

12,482 posts

167 months

Thursday 4th February 2016
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Bookmarked as I can't see the pics at work.


Escy

Original Poster:

3,907 posts

148 months

Thursday 4th February 2016
quotequote all
Thanks for the positive comments.

pidsy said:
have you got a timescale in mind OP?
I'd like it done by late spring so I can use it in the summer. It seems realistic to me but projects like this can sometimes eat up time.

The engine mounts will be finished this weekend, then I can concentrate on mounting the turbo and making the exhaust. Once the exhaust is sorted, that's the major fabrication out of the way and the progress should speed up.

KarlS

80 posts

173 months

Thursday 4th February 2016
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Excellent - looking forward to seeing your progress, also bookmarked smile

steveo3002

10,493 posts

173 months

Thursday 4th February 2016
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cool thread , spose the good runner pork engine can be sold for good money to help pay for the new bits?

Mark Benson

7,498 posts

268 months

Thursday 4th February 2016
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Johnnytheboy said:
I was wondering how possible this would be as I imagined it would be quite a tight engine bay on a Boxster, but you've proved me wrong!
Having recently seen a Boxster parted from it's engine, and the engine on the bench, I thought there'd be more height issues than there are.

I love engine swaps (thinking of the Mk3 MR2 swap myself as a bit of a garage project, though tempted by a 3VZ-FE or even a 2GR-FE.....).

Jabosoc

2,335 posts

230 months

Thursday 4th February 2016
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Commenting for updates, this is a great project.