Don’t know about 175 KTAS at 13.5k, but here’s 171 KTAS at 11.5k running LOP. Note FF is 6.3 GPH! That’s an IO360 with BA Hartzell. Sometimes you just find the sweet spot, but 170 KTAS at 7 GPH is very repeatable. Or if I’m in a hurry I can get an extra 10 KTAS (180 KTAS) at a little over 8 GPH.Until G100UL is available, which is way overdue to the market thanks to some obstruction within the FAA, and now sorted.
As for engines, the parallel valve IO360 or IO375 are a good fit. I have no idea how you get a true real and verified TAS of 175 at 13.5k' while LOP, but hey, you will do 164 +/- for sure with the BA Hartzell.
I consider the IO-360-M1B and Hartzell CS BA prop to be the perfect combination for the RV-8, both for power and weight.
The last cross country I did was 13.5K’, 175kts TAS at 7.5gph (LOP). The airplane was built for high efficiency cross country and I’m happy with the result.
One non-trivial point. The parallel valve IO-360 can burn 94UL or non-ethanol 93 octane pump gas. The IO-390 cannot.
Carl
Guys, I trying to decide what engine size for my 8.
Guys, I trying to decide what engine size for my 8.
Curious as to why IO-390 cannot burn the above? Is it purely the detonation margins?
Slightly higher CR won't allow enough detonation margin at the temperatures specified by certification standards. Given moderate CHT/oil/intake temperatures, standard ignition timing, and a cognizant meat servo on the knobs, it should do fine. Certification doesn't allow those caveats.
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_33_47-1.pdf
Thanks Dan. Check your PM's
Jim
Angle Valve Pro: More power
Angle Valve Con: More weight, more cost, future fuel availability?
Parallel Valve Pro: less cost, less weight, greater variety of options
Parallel Valve Pro: mods needed for more than 180hp, and still likely not quite as much power as a fancy -390
The "weight" Con means much more than just payload penalty. Those who have not flown a truly light RV have no idea what they are missing.
With the price increases from lyc, at least entertain an engine from Titan. I have a quote from Them for less than $32K for a 195 HP O-370. I have not pulled that trigger yet so I am still geeking out on engine choices and have lots of time to decide.
That being said my RV6 had a 320 with Catto 3 blade and was fine. But when I was renting my buddy’s 8 with O-360 and fixed pitch prop it was substantially better performance wise and with PMAGs it had way better performance up high. I would be perfectly happy with his rig. So for now I will just stay out of CS airplanes or I’ll want one..