---------------------------------------------------------- RV4-List Digest Archive --- Total Messages Posted Sun 07/03/05: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:43 AM - Re: FAB help! (Dave Durakovich) 2. 07:35 AM - Re: FAB help! (rob ray) ________________________________ Message 1 _____________________________________ Time: 06:43:25 AM PST US From: Dave Durakovich Subject: Re: RV4-List: FAB help! --> RV4-List message posted by: Dave Durakovich Thanks Rob, That's what I suspected. I think I'll pass on adding another scoop at this point. I do like the idea of the ram air. How do you handle the issue of carb heat? Run that through the filter for ground use. If so, any significant reduction in power? Do you put in a bypass valve to force the issue? I've looked at the archives and they are a less than clear regarding filtered air! Thanks again, Dave ________________________________ Message 2 _____________________________________ Time: 07:35:43 AM PST US From: rob ray Subject: Re: RV4-List: FAB help! --> RV4-List message posted by: rob ray Hi Dave, The engineering on the Tunnel Ram was performed by my good friend Arvil Porter. The K&N filter sits directly on top of the Tunnel Ram on a 2" aluminum tube that is 4" long. This places the filter 4" below the sump. The inner flapper door closes to seal off ram air to allow air to duct through the filter from inside the cowling. In the ram air position, the flapper covers the 2" hole into the filter, and leaves the tube wide open to outside air. It's simple but effective. The fit on the flapper is close, but not airtight, but closing the flapper inflight causes a loss of 2" MP. In the past 10 years I have encountered carb ice one time flying in light rain at 12,500' across Montana in the summer of 97. I closed the valve and in 30 seconds the symptoms cleared up. It's not heated air but it is WARMER air. In dusty environments people ask if I have any problems, I have none and my carb at 1000 hours was clean inside. The secret? I coat the inside if the ram with regular doses of LPS 3, dirt sticks to it like glue. Wipe it out every oil change with a pistol cleaner and re-apply. I also riveted/epoxied a small magnet to the very back of the ram to catch stray metal that might get sucked in. To measure and fabricate the Ram and give Arvil accurate dimensions I first cut a piece of cardboard to the approximate size and stuck it to the base of the carb and fit up my lower cowl. With a sharpie and some acrobatics I was able to mark the cardboard enough times cut it very close and adjust the angle. As you know, the inlet on the RV4 cowl is offset, so the ram protrudes from the carb at a 3 degree offset to the left. Arvil built the ram 3" square made from aluminum stock, and the carb flange is welded on top. The flapper area is back riveted flush from the inside to allow freedom of movement and a close fit for the flapper. Arvil is on the list and could give better details on the actual construction. Needless to say it works, very well. I like simple.... Rob Ray Dave Durakovich wrote: --> RV4-List message posted by: Dave Durakovich Thanks Rob, That's what I suspected. I think I'll pass on adding another scoop at this point. I do like the idea of the ram air. How do you handle the issue of carb heat? Run that through the filter for ground use. If so, any significant reduction in power? Do you put in a bypass valve to force the issue? I've looked at the archives and they are a less than clear regarding filtered air! Thanks again, Dave --------------------------------- Rekindle the Rivalries. Sign up for Fantasy Football