Originally Posted by Bigortho
RV-14A with Superior XP-400 Installation Tips
The Vans Lycoming IO-390 Exhaust System does not fit the Superior XP-400: you must buy a $1395 Vetterman Exhaust (currently a dual independent exhaust system with no crossover pipes) to fit the XP-400. The dual pipes do not enter the tunnel, but exit the cowl bottom anterior to the nose wheel hinge, so the cowl needs two cutouts adjacent to the nose wheel cutout - not a big deal.
The Vetterman Exhaust uses 2” pipes, which results in much lower back pressure than the Vans Single Exhaust pipe. Both Heat Exchange & Sound Mufflers can be added to the Vetterman Exhaust as the low profile Superior XP-400 Horizontal Cold Air Injection Manifold allows room under the lower cowl for muff/mufflers.
When you delete the Vans Exhaust from the Firewall Forward Kit, you also delete the cabin heat components: You must order 2" SCAT Tube, 10 hose clamps and the T- Splitter [VENT-00002] from Vans. A SCAT runs from the Fresh Air intake [CB-0007] located in the right cowl vent to a splitter, which shunts air to the right & left muffs. Another pair of SCATs connects the muffs to the Cabin Heat Valves.
If you want truly independent heat controls for both the pilot & copilot you must also order two FF-00084 Cabin Heat Valve Covers. Otherwise if one side is open and the other closed, most of the heat will shunt out the bottom of the closed valve.
If an RV-14 heat system is installed per plans there is a slight interaction between operation of the left and right heat controls but it is minor.
As designed the cabin heat system works very well because of the dual/series'ed heat muffs and the use of one
FF-00084 cover. You should never
install an FF-00084 cover on both heat valves on an RV-14 (or any other model).
The whole purpose of the heat valves being designed the way they are (constant flow, so that even if the heat is shut off, the valve allows air to flow through the system) is to prevent system over heating. There must be constant flow through the system to prevent over heating of the exhaust system in the areas covered by the muffs, and the muffs and hose themselves.
Regarding the potential performance differences in the two exhaust systems....?
I am still waiting for someone to provide some test data showing a performance difference between the two.
Detailed flight testing was done on the current system using a number of different collector pipe configurations. The simplest design was used since testing showed no easily measurable difference between them.
It is not data obtained with controlled testing, but at least one RV-14 which is reported to have a tweaked engine (higher than standard HP) and a Vetterman exhaust system has speeds and fuel flows that are no different from the company prototypes.