Gary Ray wrote: > For comparison this may help: > I have run Water Manometer testing on my 601XL with a baffled system. The > pressure differential would range between 3 inches of water to 4.2 inches > depending on angle of attack and airspeed. Your airspeed being higher > should produce better. This was with standard 4.75" WW inlets and a front > starter. I have since increased the openings to 5.25 " however I have yet > to re-run the manometer testing.
Here's the message I sent Joe and Oscar the other day after my initial plenum testing: I installed the low pressure "transducer" under the engine, tie wrapped on top of the engine mount below the cylinders. The high pressure is just stuck in from the back of the plenum, left laying around on the outside of the head near the intake manifold, centered on number 4 cylinder. I wouldn't call my plenums "well sealed" around the front end by any stretch. The transducers are some thin wall 3/16" OD tubing with about 8 holes drilled across them, stuck into the end of the urethane tubing. The ends are plugged up, ala static port. At startup, the gauge barely moved, maybe registering .1-.2". Statically, it takes 1930 rpm to get a 1" difference, 2720 rpm to get a 2" difference. That would explain poor cooling at idle! On climbout at 100mph and about a 15 degree angle, 5.4", which reduces 4.9" at 6000', which I guess makes sense since the air is thinner to the difference would be smaller, although another explanation would be rudder may be the difference, since I can swing the needle from 6.8" to 10" with HARD left rudder and then right rudder, but most of these tests were ball centered (feet on the floor in a KR with differential ailerons). Readings below are in inches of water and were at whatever rpm was required to stabilize altitude at 7500' and constant IAS: 2.3" 80 mph 2010 rpm (this becomes 4" just by opening the throttle wide open while maintaining 80 quickly, so the prop helps) 2.9" 90 mph 2180 rpm 3.6" 100 mph (forgot to get that one) 5.3" 120 mph 2560 rpm 6.5" 130 mph 2820 rpm 7.5" 140 mph 3010 rpm 8.8" 150 mph 3200 rpm 10.0 166 mph (forgot this one too) but this was at 2500', since I can't do much higher than 155 IAS at 7500 with the current prop. 10+ (pegged needle) was easy to do at lower altitude, but I deliberately didn't run it wide open so as not to hurt the delicate thing! I could effect a 20% change in the reading just by using half of the left or right rudder pedal. It's not surprising that there's a difference, but the magnitude of the change is surprising to me. Next flight will be moving the lower probe to the right plenum to see the difference in those two to see how that figures into the higher temps that I've alway seen on the right side compared to the left. Others are welcome to "take the test" and post results... Mark Langford N56ML "at" hiwaay.net website at http://www.N56ML.com --------------------------------------------------------
