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-   -   CNG alternative? Dual-fueled Husky to be at AirVenture (https://vansairforce.net/community/showthread.php?t=102546)

Mike S 07-31-2013 11:42 AM

Quote:

Originally Posted by tmbg (Post 793312)
Correct, but higher octane fuels have higher detonation margins can be run leaner and with more advanced timing, which directly leads to more power.

"Can be" is the gotcha here, the quote from the link only says the higher octane gives more power. Nothing was mentioned about changing (in flight no less) the parameters of the engine such as compression ratio, ignition timing etc when changing the fuel.

With a higher octane fuel you can do a few things to boost power that a lower octane fuel will not support without detonation. But changing the fuel alone will not make a difference if the engine is tuned for the lower octane fuel.

It is all about inter cylinger pressure. Supercharging, higher compression ratio, advancing timing, intake runner tuning, exhaust tuning------all can lead to higher ICP, and that is what will give more oomph------and will likely require higher octane to keep the engine from self disassemble. But the octane is not the cause of the power increase in any significant percentage.

Read what the quote from the link says, not what you extrapolate from the statement.

Quote:

Originally Posted by Mike S (Post 793147)
" We have noted several performance advantages using CNG over aviation gasoline. One is increased power output given that octane rating of natural gas is typically 138 vs. aviation gasoline’s 100."

As I said before, I have trouble with their statement.

John Clark 07-31-2013 12:39 PM

This exercise is more a PR stunt than a realistic alternative to avgas. I can see limited applications, but the availability/infrastructure problem will make it impractical for a long time. All of the buses and trash trucks in my town are CNG powered, but that is easy, they all return to the same spot every evening. Because of that, they do not require dual-fuel ability and can be built to get the maximum performance on CNG by running very high compression, they are converted diesels, to take advantage of the octane available.

John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA

walkman 07-31-2013 11:00 PM

Quote:

Originally Posted by Mike S (Post 793179)
At 40 or so pounds full, not an issue.

Also, the BBQ runs on propane, not CNG.

Having shopped numerous times for a cruising sailboat (but never pulled the trigger.....yet) I can tell you that CNG is significantly less available than LPG. That is true in the US and much more true out of the US. Doesn't seem like a good choice of fuel to me.

Now, when they fly a Husky on used fryer oil from Maccas....


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