Quote:
Originally posted by clubhead
I'm hearing from a few that a 996 lump will not fit in easily into our cars. Something about it being mounted 'the other way round' in the 996 so some amount of work needs to be done to get it into the Boxster. Not to mention different electrical wiring 
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Yes the 996 is mounted in a reversed direction compared to the Boxster. This is not a major problem. Turning around the intake manifold basically requires unbolting, rotating and reattaching the intake manifold. Electrical wiring is not a problem AS LONG AS YOU GET A COMPATIBLE MODEL/YEAR and keep the 996 ECU. What I hear is there are a couple of sensors, like oil pressure, that the Boxster doesn't use that need to be blocked off/taped off
The issues I am aware of are:
Air intake - An aftermarket intake/custom ducting is needed to mate the air vent on the drivers side with the intake manifold. The tricky part here is avoiding an air leak and not fouling the MAF - standard stuff.
Fuel rail - with the 996 intake manifold turned around there needs to be some bending. If the 996 fuel rail is not available the 986 fuel rail needs new ends.
Engine position - The 996 engine sits lower in the Boxster so a couple of mounting bolts need to be shimmed with a custom plate or something similar.
Brakes - If you have an S you are fine. If you stay off the track you are fine. If you have a base Boxster, you need better brakes to handle the track.
Exhaust - The 996 needs a custom exhaust. This gets tricky because the ECU expects pre-cat sensors and post-cat sensors. Lots of folks try to leave of the pre-cat catalytic converter and this cause problems in a base Boxster - let alone a converted Boxster. If I were to try this, I would try to keep the 996 exhaust as 'stock' as possible - including all the normal catalytic converters and exhaust sensors in about the stock positions. Maybe after a few months of running well, I would try to go for a free-flowing custom exhaust. There are enough new variables in this conversion, that mucking with the exhaust should be saved for later. It goes against the grain to leave horsepower on the table - but then again, it gives one a chance to gain some relatively cheap horsepower after the 996 powered Boxster starts feeling underpowered.
ECU and engine year - Get this wrong and you have months of problems. The best way to get this right is talk to someone with a successful conversion on your same model year and get all the exact same parts. By successful, I don't mean :It runs and smokes the tires and pulls like a train but I still have CE lights every week." Unless you want your wallet to stay open to the dyno & ECU experts, dealership and the parts stores, I suggest you follow the lead of someone who has a car like yours that has actually run for 4-6 months with 0 issues.
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If this seems like too much work, you can probably just hand RUF $25,000 - $30,000 for a car almost as good. If you proceed carefully, you can come out with one of the world's quickest Boxsters for about 1/2 half price. If you rush in, you may end up with a 'parts car' bargain for someone else to buy and enjoy.
IMO the risk of never getting a fully sorted car is probably worse with boring out the engine, trying unproven pistons, Shrick Cams, etc. than with the 996 conversion. Several folks have done 996 conversions, I don't know of anyone who has independantly done internal Boxster engine modifications.