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Re: [GMCnet] Injection versus Carbs [message #74201 is a reply to message #74194]

Wed, 17 February 2010 20:23

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

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Senior Member

mlincoln wrote on Wed, 17 February 2010 19:31

Has anyone tried a carb (a fixed carb, not an altitude-adjusting one) that has been specifically leaned for altitude? Does it detonate (too lean) at sea level? I'm thinking that one of the experienced tinkerers might know.

In airplane flying in the Rockies one leans to peak rpm (fixed pitch prop), then richens to make the exhaust gas temp 50-100 degrees cooler for takeoff. There's a big difference in power: running full rich (firewalled mixture control) compared to optimally leaned makes a huge difference in a high density-altitude situation. In the Utah mountains I once foolishly filled up a Cessna 152 (a little underpowered straight-tailed 152 from the 1950's) with avgas the night before, and then took off the next day. My friend and I flew the plane in ground effect for three miles to the edge of Bryce Canyon (airport was 9000 MSL), in order to throw ourselves off the edge and get some altitude beneath us. If I hadn't leaned for altitude I'm sure we would never have even gotten into ground effect. (By the time we got to the Grand Canyon 45 min later, I had thermaled to 14,500 feet, and LA Center didn't believe our type aircraft--an 89 hp 152--given our altitude-encoding transponder rea
ding, but that's what rising air will do for you).

Therefore I suspect an optimal air *mass* to fuel mixture might make a significant difference in the GMC too. But, without the manual mixture control, it may be that the altered air/fuel volumetric mixture of the "mountain carb", when running at low altitude with the air mass much greater, would result in a too lean situation, with unacceptable detonation or at least higher cylinder head/EGT and wear in the valve train.

Has anyone tried it?

Mike

I had a similar experience on my way to Alaska coming out of a hot Montana airport fully loaded with fuel, passengers, and camping gear. I could not clear the power lines 2 miles off of the end of the runway. I thought about going under them. Then it occurred to me to just turn left or right and I won't have to go over them. It took quite a while to get up to cruising altitude that day.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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[Message index]

		[GMCnet] Injection versus Carbs By: Richard Lister on Mon, 08 February 2010 10:01
		Re: [GMCnet] Injection versus Carbs By: Mr ERFisher on Mon, 08 February 2010 10:10
		Re: [GMCnet] Injection versus Carbs By: GeorgeRud on Mon, 08 February 2010 10:17
		Re: [GMCnet] Injection versus Carbs By: Ron on Mon, 08 February 2010 11:08
		Re: [GMCnet] Injection versus Carbs By: Matt Colie on Mon, 08 February 2010 11:14
		Re: [GMCnet] Injection versus Carbs By: Steven Ferguson on Mon, 08 February 2010 12:25
		Re: [GMCnet] Injection versus Carbs By: k2gkk on Mon, 08 February 2010 12:35
		Re: [GMCnet] Injection versus Carbs By: Mr ERFisher on Mon, 08 February 2010 12:46
		Re: [GMCnet] Injection versus Carbs By: Steven Ferguson on Mon, 08 February 2010 18:31
		Re: [GMCnet] Injection versus Carbs By: Larry on Mon, 08 February 2010 22:00
		Re: [GMCnet] Injection versus Carbs By: Steven Ferguson on Tue, 09 February 2010 07:19
		Re: [GMCnet] Injection versus Carbs By: bill schurman on Mon, 08 February 2010 13:11
		Re: [GMCnet] Injection versus Carbs By: Ron on Mon, 08 February 2010 14:31
		Re: [GMCnet] Injection versus Carbs By: Ken Burton on Tue, 09 February 2010 02:11
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Tue, 09 February 2010 06:40
		Re: [GMCnet] Injection versus Carbs By: tgeiger on Tue, 09 February 2010 09:51
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Wed, 10 February 2010 07:57
		Re: [GMCnet] Injection versus Carbs By: Jim Galbavy on Mon, 08 February 2010 15:30
		Re: [GMCnet] Injection versus Carbs By: USAussie on Mon, 08 February 2010 16:23
		Re: [GMCnet] Injection versus Carbs By: Larry C on Thu, 18 February 2010 09:06
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Thu, 18 February 2010 11:17
		Re: [GMCnet] Injection versus Carbs By: Gary Worobec on Thu, 18 February 2010 11:33
		Re: [GMCnet] Injection versus Carbs By: Chr$ on Mon, 08 February 2010 16:48
		Re: [GMCnet] Injection versus Carbs By: Chr$ on Mon, 08 February 2010 16:49
		Re: [GMCnet] Injection versus Carbs By: k2gkk on Mon, 08 February 2010 18:12
		Re: [GMCnet] Injection versus Carbs By: Rick Williams on Mon, 08 February 2010 18:45
		Re: [GMCnet] Injection versus Carbs By: David L Greenberg on Mon, 08 February 2010 19:55
		Re: [GMCnet] Injection versus Carbs By: George Beckman on Mon, 08 February 2010 20:14
		Re: [GMCnet] Injection versus Carbs By: Matt Colie on Tue, 09 February 2010 13:25
		Re: [GMCnet] Injection versus Carbs By: Richard Lister on Tue, 09 February 2010 14:36
		Re: [GMCnet] Injection versus Carbs By: George Beckman on Tue, 09 February 2010 20:50
		Re: [GMCnet] Injection versus Carbs By: GeorgeRud on Tue, 09 February 2010 15:04
		Re: [GMCnet] Injection versus Carbs By: Jim Galbavy on Tue, 09 February 2010 15:54
		Re: [GMCnet] Injection versus Carbs By: Jim Galbavy on Tue, 09 February 2010 17:03
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Wed, 10 February 2010 05:41
		Re: [GMCnet] Injection versus Carbs By: klassic kampers on Tue, 09 February 2010 17:34
		Re: [GMCnet] Injection versus Carbs By: Bob de Kruyff on Tue, 09 February 2010 18:35
		Re: [GMCnet] Injection versus Carbs By: Sandra Price on Wed, 10 February 2010 11:18
		Re: [GMCnet] Injection versus Carbs By: tgeiger on Wed, 10 February 2010 14:37
		Re: [GMCnet] Injection versus Carbs By: ljdavick on Wed, 10 February 2010 14:45
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Sat, 13 February 2010 08:20
		Re: [GMCnet] Injection versus Carbs By: Bill Freeman on Sat, 13 February 2010 09:01
		Re: [GMCnet] Injection versus Carbs By: emerystora on Sat, 13 February 2010 09:47
		Re: [GMCnet] Injection versus Carbs By: Bill Freeman on Sat, 13 February 2010 15:47
		Re: [GMCnet] Injection versus Carbs By: Ron on Sat, 13 February 2010 16:14
		Re: [GMCnet] Injection versus Carbs By: Surbo on Sat, 13 February 2010 17:45
		Re: [GMCnet] Injection versus Carbs By: Ron on Sat, 13 February 2010 17:57
		Re: [GMCnet] Injection versus Carbs By: Bill Freeman on Mon, 15 February 2010 13:33
		Re: [GMCnet] Injection versus Carbs By: emerystora on Mon, 15 February 2010 13:42
		Re: [GMCnet] Injection versus Carbs By: Larry on Mon, 15 February 2010 14:40
		Re: [GMCnet] Injection versus Carbs By: mlincoln on Mon, 15 February 2010 15:31
		Re: [GMCnet] Injection versus Carbs By: Bill Freeman on Tue, 16 February 2010 07:49
		Re: [GMCnet] Injection versus Carbs By: Matt Colie on Wed, 17 February 2010 17:34
		Re: [GMCnet] Injection versus Carbs By: GMCWiperMan on Wed, 17 February 2010 17:57
		Re: [GMCnet] Injection versus Carbs By: mlincoln on Wed, 17 February 2010 19:31
		Re: [GMCnet] Injection versus Carbs By: Ken Burton on Wed, 17 February 2010 20:23
		Re: [GMCnet] Injection versus Carbs By: Kosier on Wed, 17 February 2010 21:46
		Re: [GMCnet] Injection versus Carbs By: mlincoln on Wed, 17 February 2010 22:01
		Re: [GMCnet] Injection versus Carbs By: Kosier on Wed, 17 February 2010 22:34
		Re: [GMCnet] Injection versus Carbs By: klassic kampers on Thu, 18 February 2010 14:22
		Re: [GMCnet] Injection versus Carbs By: Jim Bounds on Thu, 18 February 2010 09:09
		Re: [GMCnet] Injection versus Carbs By: Matt Colie on Thu, 18 February 2010 07:49
		Re: [GMCnet] Injection versus Carbs By: mlincoln on Thu, 18 February 2010 08:38
		Re: [GMCnet] Injection versus Carbs By: Kosier on Wed, 17 February 2010 20:57
		Re: [GMCnet] Injection versus Carbs By: Surbo on Mon, 15 February 2010 14:09
		Re: [GMCnet] Injection versus Carbs By: Jim Galbavy on Mon, 15 February 2010 14:38
		Re: [GMCnet] Injection versus Carbs By: Bill Freeman on Tue, 16 February 2010 07:38
		Re: [GMCnet] Injection versus Carbs By: Carleton Douglas[1] on Wed, 10 February 2010 14:53
		Re: [GMCnet] Injection versus Carbs By: jimk on Wed, 10 February 2010 22:18
		Re: [GMCnet] Injection versus Carbs By: Richard Lister on Tue, 16 February 2010 10:55
		Re: [GMCnet] Injection versus Carbs By: bryant374 on Tue, 16 February 2010 12:21
		Re: [GMCnet] Injection versus Carbs By: Bill Massey on Tue, 16 February 2010 13:24
		Re: [GMCnet] Injection versus Carbs By: psakw on Sat, 13 February 2010 21:58
		Re: [GMCnet] Injection versus Carbs By: emerystora on Sat, 13 February 2010 22:07
		Re: [GMCnet] Injection versus Carbs By: rallymaster on Thu, 18 February 2010 11:45
		Re: [GMCnet] Injection versus Carbs By: g.winger on Thu, 18 February 2010 14:11
		Re: [GMCnet] Injection versus Carbs By: Larry on Thu, 18 February 2010 15:08
		Re: [GMCnet] Injection versus Carbs By: wally on Thu, 18 February 2010 15:33
		Re: [GMCnet] Injection versus Carbs By: Larry on Fri, 19 February 2010 13:44
		Re: [GMCnet] Injection versus Carbs By: wally on Fri, 19 February 2010 14:44
		Re: [GMCnet] Injection versus Carbs By: Larry on Fri, 19 February 2010 19:05
		Re: [GMCnet] Injection versus Carbs By: GMCWiperMan on Fri, 19 February 2010 19:23
		Re: [GMCnet] Injection versus Carbs By: Keith V on Sat, 20 February 2010 10:12
		Re: [GMCnet] Injection versus Carbs By: GMC_LES on Sat, 20 February 2010 16:45
		Re: [GMCnet] Injection versus Carbs By: WD0AFQ on Sat, 20 February 2010 17:35

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