Caught up with fellow ImpactBumpers.com forum member Alex this week, to discuss an agreed insurance valuation for his Porsche 911. Alex’s car is a 911 3.2 Carrera, but runs a 3.6-litre engine transplant: a 964 engine, rebuilt with some 993RS trickness. The car is light, so performance is “adequate”:
One issue with the 3.6 transplant cars is the exhaust: what do you do with heat and silencer under the rear of an impact-bumper car, a chassis that has less space available than the later models? Alex’s solution is the best I’ve seen yet: all titanium and all home/hand made. Alex explains:
“I liked the first version transplant exhaust on my car: a cheap, simple set up that worked well but with a few limitations that were increasingly bugging me.
“The first system used reasonably priced 1.75″ dia headers going into a 14” Magnaflow rear box. It sounded great if a little on the noisy side, particularly on a long run, so I made up some inserts, which made it quieter without costing power. This made me wonder why I didn’t just use smaller tubes in the first place.
“The lack of heat, low ground clearance and drone over long journeys sent me back to the drawing board. I decided to follow other transplanters down the 993 heat exchanger route, then build a similar system to 993 Cup cars off the 993 exchangers.
Titanium Exhaust Porsche 911: Akrapovic GT2
“My first system followed a few tuners to through-the-bumper exhaust outlets. I was undecided before doing it, and it was interesting when done, but the novelty wore off. Eventually, finding a titanium Akrapovic exhaust silencer/muffler on eBay from a 997 GT2 sent me down a route I thought would be more in keeping – albeit lots trickier.
“One question was X-pipe or not. Some silencers are x-pipe inside and don’t seem to hurt the 911’s power, but others believed more power would come from a non-X-pipe system. I had already manufactured quite a complex system using the X-pipe idea, but the muffler also had an internal X arrangement so we decided against using two crossovers.
“The first work on version two was to finish my cheapie 993 heat exchangers. With the flanges cut off and jig made, they needed rotating, welding back on and linishing flat. The other side needed patching and a new pipe cobbled together. The steel on these is very thin and although stainless, it’s not the best grade so can corrode.
“Then it was a case of making jigs, which other transplanters were a great help with. Twisting these tight-fitting pipes can be tricky, but a fellow IB’er helped with a fitment guide that worked really well. I bought some more titanium tube, including many bends and had quite a bit prepared by a local water-cutting firm, before my welder friend came around to do the final assembly on the car.
“There’s always a few bits you think I could have done better and there’s still some finishing to do – I may do double slip joints in two places and the tailpipes are just bits of tube at the moment – but it’s on and sounds good. It’s still quite loud, although much quieter than the Magnaflow, but it now has a real rasp to it and makes a racket on overrun.
“With the new exhaust I think the car is now running a bit richer but haven’t done enough miles to really get to know it. Fingers crossed the bumper doesn’t catch fire!”
Awesome work by Alex – so many hours and for sure a pricey system, but if you’re going to think outside the box, then expect some of the costs to live there too. Read more about Alex’s car and many other Porsche 911 hot rods on the Impact Bumper Porsche 911 hot rod forum.