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I'm looking for a little bit of help, advice, and potentially photos regarding how Andial and Ruf (others, too) dealt with the heater crossover pipe when combined with a twin plug distributor.
I have a 993 C4S that was "converted" to a Turbo using genuine Porsche parts in the 90s by EVOMS and the Porsche North Scottsdale. It was dealer serviced its entire life, and it's a clean machine—my first 993 at 32. I'm a sucker for a project.
Since I've bought it, I've been diving into what parts it needs to finish the "conversion" as there were a few things leftover from the Carrena motor that I wanted to change, like the correct fan and shroud and a few others things.
At the moment the engine is out for a reseal and refreshed turbos, along with a bunch of other modifications (p-trap lines, check vales, that sort of stuff) and one of the areas I'd like to refine is the Carrera heater crossover pipe that EVOMS adapted (in the 90s) to work with the turbo exhaust system.
Being foolish and a little bit hopeful, I bought the OEM Turbo crossover, thinking it would work, and it did not as it hits the 993NA twin distributor. There's not really anything wrong with how EVOMS fabricated the crossover pipe that is on there, but the system is a little bit sloppy, and it has be wondering how RUF and Andial took care of this on their conversions to twin plug.
I've scoured BAT listings and car advertisements trying to get a closer look at how they did it, but the crossover is in a somewhat obscure area and something that's not normally photographed.
Any assistance in the form of photos or advice from the Rennlist crowd would be greatly appreciated.
I don't believe that Ruf twin plugged their 993TT cars but Andial did. That part is really buried when the engine is in the car, otherwise I would take a photo for you. Mine was done by Schneider Autohaus in Santa Barbara. You can check with Henry at Schneider's as they rebuilt many Andial 993TT 3.8 twin plug engines and have experience with that part.
I don't believe that Ruf twin plugged their 993TT cars but Andial did. That part is really buried when the engine is in the car, otherwise I would take a photo for you. Mine was done by Schneider Autohaus in Santa Barbara. You can check with Henry at Schneider's as they rebuilt many Andial 993TT 3.8 twin plug engines and have experience with that part.
I used in my 993tt a 3.6 normal aspirated rear thin with an 993 RS heather plastic tube with the nipple that feeds air for the distributor belt. Plenty of clearance for the twin distributor.
Everything is factory, bolt on and no mods and you can revert to single plug turbo.
After a lot of searching I found a photo of an Andial twin plug turbo with the modified heater crossover pipe installed. In this instance they have headers without heat exchangers so you’re able to clearly see it.
Trying to provide this as a resource for future 993TT twin plug or Carrera conversions retaining the twin plug.
The necessity for altering the heater crossover pipe lies in the differences between the twin plug and single plug distributor and how it effects the position of the heater duct which leads to the heater blower. The larger twin plug distributor necessitates that the heater duct is moved further from the center of the engine due to space constraints. This is best visualized in the differences between the Turbo and Carrera rear engine tins. It appears that Andial moves the intake of the crossover pipe further away from center, approximately 2-3 inches to line up with the Carrera rear engine tin, and henceforth the heater duct which allows the heating system to work.
it would seem easier to modify the turbo crossover pipe, than to modify the Carrera crossover pipe.
With my particular situation I’ve discovered that they modified a Carrera crossover pipe, in conjunction with a custom exhaust, which is causing poor figment and alignment issues where the crossover pipe connects to the exhaust system.
It appears that the best course of action in my case is to have a fabricator modify the turbo crossover pipe in the style of the Andial modified unit.
Hopefully this helps someone.
Last edited by Matthew Scott; 01-08-2023 at 01:32 AM.
01-03-2023, 07:53 PM
993TT Twin Plug Heater Crossover Pipe
