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V8 4.2L Boxster Swap

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thought i log on to let yall know about my V8 Swap in my so far.

I've seen people attempt it , but have not succeed. Things are going smooth so far.

Using boxster Transmission mated to an Audi A8 Engine(Drive By Wire)

Using Both Boxster Transmission mount, Both A8 Engine mount and using the

boxster front engine mount, totaling 5 mounts.

this saturday i will be messing with the wires.




Video of the car running

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Edited by quan717
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That's pretty amazing and it looks like the engine fits neatly in the engine compartment. I love to see people doing these mods and am curious what prompted you to take on (what seems to me) a huge project. Please post updates as you progress!! clapping.gif

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Really nice mod. Be interested in hearing about HP/whp #s and what sort of accessibility issues you have as the mechanic, and of course…cost, bang for buck. Seems like a great alternative to trying to shoehorn a GT motor in or straining the 'ef out of a modded hand-grenade of a 3.2-3.8 six..

Good Job, we're all jealous ....for now (grin),


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I Chose this Project because of several reasons.

1. I melted my piston on my engine, and pitted the cylinder wall, therefore i need a new engine.

2. Porsche engine are too expensive, so i bought this audi A8 engine for $900 shipped, with subframe, ECU, Complete uncut harness. (bang for the buck)

3. I chose Tiptronic because , that was what my car originally was. Also there was somebody who tried the same swap with a manual and couldn't figure how to

get this swap done so he sold his project. also i've talked to the lead engineer at precision industries who build torque converter, the boxster converter can safely

and easily handle the engines power to the vehicle's weight.

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1. I melted my piston on my engine' date=' and pitted the cylinder wall, therefore i need a new engine.[/quote']

Out of curiosity, was that from forced induction? Or just a random failure?

Also there was somebody who tried the same swap with a manual and couldn't figure how toget this swap done so he sold his project.

That's interesting, I wonder what issues he encountered specific to the manual transmission.

Last, does the 717 in your user name mean 717 area code? If so, I'd love to check this out :) I'm in central PA.

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And I thought I was NUTS ( actually I know that for a fact) for trying to put a 400+ hp DFI Carrera S into my 04 986 - got all the mechanical issues out of the way (I hope) now dealing with the tons of electronic issues. GOOD LUCK guy hope to see you at the track someday.

When do you anticipate being done with this project? We should start a club or something. WOW I like it.

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  • 3 weeks later...
  • 1 month later...
  • 3 weeks later...

Also there was somebody who tried the same swap with a manual and couldn't figure how toget this swap done so he sold his project.

That's interesting, I wonder what issues he encountered specific to the manual transmission.

If you're talking about me, I sold the project because I bought a Cayman S. The manual transmission from the 5-speed or the tip Boxster both bolt right up to the A8 engines (or pretty much any other Audi engine for that matter). The 6-speed is a bit different because it does not have the snout for the starter on the V8. However, my Cayman S 6-speed DOES have that snout, so an option would be to grab a 6-speed from a 987 (however, they aren't cheap).

Before I bought the 987, I also had talked myself up to converting the A8 V8 to a single-plane crank using rods from the 3.7, custom crank from King, and cams from two of the 20-valve Audis. That was to preserve the essence of the Porsche sound, which is quite different than the cross-plane Audi. However, as cross-planes go, the Audi has the best sound ever.

I love that someone is finally doing this swap! It's almost a perfect fit and it's going to sound awesome.

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  • 4 weeks later...

Its a 99 A8 4.2 V8 engine run by AEM fuel injection. The tune still needs a little work, I haven't had a chance to put it on a dyno yet, hopefully in the next couple weeks. Everything custom made. Motor mounts, transmission mounts, wiring harness, cooling system, flywheel and clutch, etc. If you're ever in MS stop by and I'd be glad to show it to you.

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  • 3 weeks later...
  • 1 month later...

ok, sorry it took me long, to come back on this forum.

i was working on my J-swap Integrea DBW, with A/C cause i live in the south.

Plus i plan on using the Integra as my daily driver, which it is at the moment.

ok back to the porsche, the beast started up, and i will post a video of it idling.

it doesn't have any exhaust at this moment, just straight headers. i'm thinking of

using the down pipe off the A8 running to the back, then i have to mount the acceleration

pedal sensor somehow so it can work with the porsche cable, by using the porsche throttle cable

to pull the A8 acceleration pedal sensor in the engine bay that way i don't have to stretch the wires

to the dash. I'll just mount it somewhere in the engine compartment and route the porsche cable

to pull it when i apply gas. once that is done i have to work on radiator hose, i have a custom hose shop

around the corner so i have to make some bends with a hanger and measure my diameter and bring it to

them.Once that is done , and have them also build my power steering line from A8 pump to porsche fitting,

then i can tow it to the custom muffler shop. once done, than its the test drive, and up for sale.

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This is my daily car that i got done building.


This was the other toy i had to fix, it had a rear main seal leak,



This was my study guide and reference guide as i pin by pin to know where to pin

each wire so that the A8 harness from the engine is intergrated to the porsche harness

and if i was to disconnect it would be easy.


I use the A8 ECU, Boxster transmission ECU, A8 cluster for immobiliser, A8 ignition lock

cylinder with the sensor on there, A8 central locking module( which i don't think i really needed to

make the car start)


This is the A8 that i raped


Here is the pix of the tranny with the new Torque converter by " precision"

They didn't know how to build it for me, so i gave them my idea, and it worked.

the idea was to use a Porsche Torque converter, with the A8 back cover so i can

bolt the converter to the A8 Flexplate. They had to cut the converter from the A8 that i

gave them in half at the weld, and cut the new boxster converter and mate them up.


But once they was done they balanced it, and i got back and install it and mate up the

tranny and engine, but there is a problem. somehow the center plate was small, i have

no idea what happen, so i have no choice but to bring the plate to the machine shop to

have them machine the hole a little bit bigger, the middle is the porsche with the bigger

opening but the bolt pattern doesn't match to the crank, the lower is the A8 but the hole

is to small the converter center shaft doesn't fit. the upper is the A8 with the center hole

bored out at the machine shop.


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  • 2 weeks later...
  • 1 month later...

you can view the video of the car idling without exhaust just the downpipe. getting it to the muffler shop so i can get some exhaust worked on. i drove it around, feels good so far.will post up pix of me driving it. I have to reiterate, the cluster was not done completely yet, the coolant gauge, the fuel gauge and the speedometer was the only ones working in the video, the rpm didn't becuase i forgot to tap the signal wire into the crank sensor. The second shifter was to test my diodes and gnd trigger wire to each shift solenoid to make sure that each gate i put that shifter in did not send gnd back into another solenoid by soldering in diodes. once i have that sorted out, I can use a computer shift box and tap it into my steering shift button to control my up and down shift accordingly. "at this moment road surge only has 3 speed" waiting for the 4 speed set up.

Edited by quan717
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  • 7 months later...

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