rvmills
Well Known Member
Not sure if this post is relevant anymore, but just going to park the info here for future reference.
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All that said, if Bob is indeed pulling 23+ inches at 9.5 altitude, I want me some of that!
Michael,
All still relevant, as we're still collecting data to analyze my MP results, and the possible impacts of my intake plenum and servo.
I did one flight to take delta P measurements requested by Dan and Steve, and to run a test for Dave Anders to compare our MP at 17,500' MSL.
I ran a prelim series of delta P tests, but didn't do it at WOT, so the conditions aren't really what they are looking for. This run did show an increase in pressure from the intake manifold to the MP line that goes to my JPI. It may show the Sky Dynamics plenum and intake runners are providing a benefit there. Dan and Steve want to see some WOT runs before any further analysis or conclusions. A drop was shown between the inlet to the FM-300 and the intake plenum, due to the partially closed throttle, as expected...but this skewed the rest of the tests, so I'll be doing them again. When I do, we'll post all the locations of the pressure taps and what is being compared.
After that test, I climbed up to 17.5K and tried to match speed with a recent test Dave had run on a X-C flight. He sent me a photo (pasted below) of his -4 making 142 MIAS/ 192 MTAS, at 5.7 GPH. That's 33.7 mpg, at nearly 200 mph...wow!!
Dave's power was WOT @ 16.3" MP (very good MP at 17.5K), and 2200 RPM. My previous test at 17.5K was at 2400+ RPM, and 211 KTAS, where I saw 17.1" MP. He asked me to go up and see if I could match his speed while still at WOT, by winding back RPM. His goal was to see how our MP's compared at similar speeds, to take out the effect of additional ram air (he also has a SD plenum...and lots of other cool stuff under the hood).
I was not able to match his speed at WOT unfortunately. The prop hit the low pitch stop at 2120 RPM, and I was still at 197 KTAS (226 mph true)...so I still had 34 mph of ram effect on Dave. MP was 17.1". Not sure what that impact to MP would be, but my guess is Dave and I are getting fairly similar results, in terms of MP. My FF was 9.6 gph, so about 23.5 mpg. Not bad at that speed, but Dave crushes me in efficiency!
I ran it back up to 2440 RPM, and it accelerated to 215 KTAS (247 mph), at 11.1 gph, for 22.3 mpg.
While the MP numbers appear believable, yet still subject to further tests, my IAS and TAS readout appear to be a bit high. During flight test, I was typically indicating 3 knots faster than my chase. I've done two 4-way GPS runs, and showed 9 fast on the first, and 6 fast on the second...ughhhh. On that second test day, I was chased by F1Boss Mark Frederick, and my IAS was 3 knots above his, so that's two separate chase aircraft with the same result, and the delta from Mark was the same from 140 knots to above 210 knots, where he ran out of throttle (sorry Mark ). So am I reading 6+ high, 3 high, or ??? Mark was a legit 260 mph racer at Reno, and I had opening that day. My 4-way tests showed 231 KTAS (265 mph) on the EFIS, but the spreadsheet says less. More testing needed for sure.
I've since swapped washers under the static ports, from a pair of -L washers (1/32") to 1/64" washers that Georgetown bud Brian "Showplane" Decker had.
I haven't had the chance to test the new static port or do more delta P tests, due to pop-up maintenance. You know that kind...where you change out the static ports, then, ah, what the heck, lets fix that wheel pant that is rubbing on the tire ever-so-slightly. Turns out it was a cracked wheel pant bracket...and while taking things off, the crack in the upper intersection fairing reveals itself...and why is the gear leg fairing open in the back? Oh those 3 pulled out rivets are the culprit. And yep, there's two on the other side too...dang it. So a couple quick fixes turn into 4 glass items to paint, just like that! Ah so what the heck, lets take the floor off and adjust the angle of the stick like I've been wanting to do...and while in there, fabricate some boots for the aileron sticks like Steve has been encouraging me to do. Can you say "mission creep"?
Some pics...so the excuses aren't too hollow!
Hope to be airborne this week to wrap those tests up, and get some good data to the team!
Cheers,
Bob
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