High Altitude / high density altitude performance

[MichaelFarley56]

I always try to be super conservative on fuel burns as I never want to land with truly minimum levels. I figure if I land with less than 4 gallons, I messed up! So, to be conservative, I figure on a total of 15 gallons if full, so at high power I'll figure high and calculate fuel burn at 7.0 gph. That gives me just over 2 hours until I run out, so I normally plan on no more than 90 minute legs. If I throttle back and only run 6.0 GPH, then I can run just under 2 hour legs and still land with comfortable reserves. I wouldn't mind having an extra 5 gallons but that's okay; I'm ready for a stretch after that long anyway!

[samiam]

This is why I think the 20 gallon tank is one of the best upgrades for the B model. Although it is only 25% more, it increases endurance by almost 50% for those of us who like to keep very comfortable reserves.

[Wyo-flyer]

That sounds about right for what I was thinking. I really wish that you could stretch a little more flight time out of them with the bigger horsepower engines but that's just the way it is. The b model tank is going to be pretty sweet. I think with a little creativity you could add an addition 5 gallon tank somewhere.

I take it that you guys running the jab 3300 are using the aero injector instead of the Bing carb, there's no leaning ability with the Bing.

Thanks for all your info, now I just need to catch a ride in a Sonex to see how they "feel".

[WaiexN143NM]

Hi all,
I believe hacman thru green skyadventures sells an aftermarket mixture control for the bing. Anybody out there using one? We are running a rotec mark 1 on our jab 3300. Love it.

WaiexN143NM
Michael Radtke

[DCASonex]

I have had the HACman mixture control on my 3300 Sonex since day one, that includes booth the original Jabiru and the new CAMit engines. Once you get the needle and jets correct in the Bing for just a tad rich with that control closed, it provides good range of adjustment for cruise at various altitudes and RPMs.

David A. CAMit 3300 in Sonex TD

[david.2.wilcox]

I have a Hacman on a Jabiru 2200. Normally the Hacman uses manifold pressure to partially evacuate the Bing float bowl, so any tweeking of the throttle affects the mixture. Closing the throttle results in a vacuum spike and shuts down the engine if you forget to go full rich before doing so.

To avoid these two issues I installed a small venturi for the vacuum source.

[7acdriver]

Hi Wyo-flyer, I'm curious about all the same questions you have. I'm near your neck of the woods in Lander so I have the same altitude performance concerns.

I hope someone here will correct me on the following if I'm wrong....

From watching the Sonex turbo video https://www.youtube.com/watch?v=AG3AmNn5CtY&feature=youtu.be I've gathered that their demonstrator shows 43.4" at 2400' WOT. Assuming the fixed waste gate turbo fades the same as a normally aspirated engine of 1"/1000' the turbovee should produce ~45" at sea level for 15-16" of boost over atmospheric pressure. So at 10k' I'd expect to still be able to produce 35". Seems like that'd be just about perfect - you could fly in the low teens still maintaining sea level power. I'd hope to see in the neighborhood of 5gal/hr at those altitudes and maybe 160 knots true with a cruise prop?

[Wyo-flyer]

Hey there fellow Wyoming flyer! Man I'd love to cruise around the wind river range in a Sonex. I used to ride with a guy in his RV-7 from star valley but I was always a passenger. I bet Lander has some cool flying areas.

I am still curious if we can run more boost at our altitude. If 45" is max at sea level then can we run 45" at 10,000 feet? That's more like 21 lbs of boost. An 80 hp engine at 10,000 feet only makes around 56 hp so we need more boost to bring it up to sea level performance.

I'd really like to see a comparison between a 3300 jabiru and a turbo vee at 10,000 feet for both cruise and climb. My guess is they would be similar but I wonder at what altitude the NA engine looses out to the boosted engine. Or does the additional 20 horsepower of the jab give it enough of an advantage that the turbo can't ever really catch up.

[kevin814]

I think an issue with a highly boosted engine at higher altitudes would be head/cylinder cooling. The more power generated, the more heat the engine has to dissipate. At higher altitudes, the air is thinner, and cooling performance goes down. I guess a lot of it would depend on the effectiveness of your cooling setup.

[NWade]

Uhhh, just remember that Class A airspace above 17,999! :?

--Noel