Home » Public Forums » GMCnet » [GMCnet] Injection versus Carbs
Re: [GMCnet] Injection versus Carbs [message #74194 is a reply to message #74184] |
Wed, 17 February 2010 19:31 |
mlincoln
Messages: 107 Registered: August 2006 Location: Salt Lake City
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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
On Feb 17, 2010, at 6:57 PM, Ken Henderson wrote:
> Mike,
>
> Larry W. must be off line while travelling or he'd have chimed in: He got
> all excited about an altitude compensated Quadrajet he came across. He
> spent a lot of time and his expertise on getting it working -- for a while.
> From what I recall of what he told me, it worked great as long as he kept
> working on it. As if the QJ's not complicated enough, imagine what those
> extra bellows, jets, needles, etc., would add. I don't remember whether
> he's running it right now -- I don't think so -- but I do know he's planning
> on port injecting his Cad 500 ASAP.
>
> Ken H.
> Americus, GA
> '76 X-Birchaven
> www.gmcwipersetc.com
>
>
> On Wed, Feb 17, 2010 at 6:34 PM, Matt Colie <mcolie@chartermi.net> wrote:
>
>>
>>
>> mlincoln wrote on Mon, 15 February 2010 16:31
>>> Does anyone have actual experience with "splitting the difference" in the
>> Quadrajet enrichment to suit a MSL of 4500 to 5000 feet? I was once told
>> that some old Detroit iron came with a "high altitude option" (possibly a
>> re-metered carb?). A shop in ...
>>
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Mike
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[GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Ron on Mon, 08 February 2010 11:08
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: k2gkk on Mon, 08 February 2010 12:35
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Larry on Mon, 08 February 2010 22:00
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Ron on Mon, 08 February 2010 14:31
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: tgeiger on Tue, 09 February 2010 09:51
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: USAussie on Mon, 08 February 2010 16:23
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Re: [GMCnet] Injection versus Carbs
By: Larry C on Thu, 18 February 2010 09:06
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Chr$ on Mon, 08 February 2010 16:48
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Re: [GMCnet] Injection versus Carbs
By: Chr$ on Mon, 08 February 2010 16:49
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Re: [GMCnet] Injection versus Carbs
By: k2gkk on Mon, 08 February 2010 18:12
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: tgeiger on Wed, 10 February 2010 14:37
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Re: [GMCnet] Injection versus Carbs
By: ljdavick on Wed, 10 February 2010 14:45
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Ron on Sat, 13 February 2010 16:14
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Re: [GMCnet] Injection versus Carbs
By: Surbo on Sat, 13 February 2010 17:45
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Re: [GMCnet] Injection versus Carbs
By: Ron on Sat, 13 February 2010 17:57
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Larry on Mon, 15 February 2010 14:40
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Re: [GMCnet] Injection versus Carbs
By: mlincoln on Mon, 15 February 2010 15:31
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: mlincoln on Wed, 17 February 2010 19:31
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Kosier on Wed, 17 February 2010 21:46
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Re: [GMCnet] Injection versus Carbs
By: mlincoln on Wed, 17 February 2010 22:01
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Re: [GMCnet] Injection versus Carbs
By: Kosier on Wed, 17 February 2010 22:34
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: mlincoln on Thu, 18 February 2010 08:38
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Re: [GMCnet] Injection versus Carbs
By: Kosier on Wed, 17 February 2010 20:57
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Re: [GMCnet] Injection versus Carbs
By: Surbo on Mon, 15 February 2010 14:09
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: jimk on Wed, 10 February 2010 22:18
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: psakw on Sat, 13 February 2010 21:58
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: g.winger on Thu, 18 February 2010 14:11
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Re: [GMCnet] Injection versus Carbs
By: Larry on Thu, 18 February 2010 15:08
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Re: [GMCnet] Injection versus Carbs
By: wally on Thu, 18 February 2010 15:33
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Re: [GMCnet] Injection versus Carbs
By: Larry on Fri, 19 February 2010 13:44
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Re: [GMCnet] Injection versus Carbs
By: wally on Fri, 19 February 2010 14:44
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Re: [GMCnet] Injection versus Carbs
By: Larry on Fri, 19 February 2010 19:05
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Re: [GMCnet] Injection versus Carbs
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Re: [GMCnet] Injection versus Carbs
By: Keith V on Sat, 20 February 2010 10:12
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Re: [GMCnet] Injection versus Carbs
By: GMC_LES on Sat, 20 February 2010 16:45
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Re: [GMCnet] Injection versus Carbs
By: WD0AFQ on Sat, 20 February 2010 17:35
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