| Re: [GMCnet] Jim Bounds interesting recent posts [message #325924 is a reply to message #325921] |
Fri, 10 November 2017 12:40   |
Sammy Williams
Messages: 522
Registered: August 2010
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Senior Member |
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I'd imagine both of the "Jims" have well engineered EFI systems that will
work for us in a GMC. (Yes I know I don't have one yet. Shhhh. lol) :)
Holley also has a bolt on EFI as does others. The OP makes a lot of sense.
Carburetors and today's "gas" are NOT meant for each other. Make sure your
engine
bay has a way to stay cool, make sure you have the proper thermostat in
your engine to help with cooling. Use a "water-wetter" it will help with
keeping the engine cooler.
A hot engine is never good. A proper EFI with todays fuel and a proper
operating cooling system will help engines to stay alive longer.
Sammy
GMCless (shhh! lol) :D
On Fri, Nov 10, 2017 at 11:50 AM, Matt Colie wrote:
> I did read JimB's blog, and there is a little I disagree with but there is
> also very little hard information there.
>
> As an auto-lab rat from the early 70's (on and off), I can tell you for a
> fact that at lot of both Jim's and your premise is correct, but some is not.
>
>
> Since the early 70's (at Chrysler Proving Grounds) is has been a stated
> fact that the carburetors we all know are not a vaporizing or gasifying
> device. In actual fact, the industry has referred to them as "solid fuel"
> carburetors for years. While the droplet size does matter for emissions
> (back when a carburetor could even meet those standards), there was a
> running game (with a large number of really strange plays) between large and
> small. Small droplets cold burn faster and the larger more slowly. Not
> too different than gun powder grain size. Which you wanted depended on just
> what you were trying to accomplish at that moment. The capability to
> maintain a stoichiometric over a wide band did not arrive until the EGO
> sensors
> got reliable. Even then, the "closed loop" carburetors were not that good
> at much of anything.
>
> Other running issue is: What is gasoline?
> Even before "reformulating" this was an open question. When we were
> getting non-indolene test fuels, we always got a report with the
> carbon/hydrogen
> ratio. even if this number was in target, we still could only use
> indolene (a specific chemical hydrocarbon that can be used as motor fuel)
> because
> it was the only thing stable enough to give stable emissions values.
>
> So, the fact that reformulated motorfuel may have a stoich number that is
> other than 14.68 is just not an issue. From an SI engine's point of view,
> there is little change over a significantly wide range. Again, this is
> just one of the problems that new engine controls manage. Just about all of
> the engines that have a EGO per bank and a modern ECU, are actually doing
> a cylinder by cylinder mixture control. This has to happen for current
> standards. It was not desired in the mid-70s cat cars, because they
> counted on the rich/lean pulses to keep the cat lit and still provide
> enough O2
> for the desired reactions to complete.
>
> Then there is the issue that not all the cylinders see the same mixture
> (the end cylinders often get lean) with any central fuel feed system. The
> initial charge pressure (present in the cylinder when the intake valve
> closes) has a lot to do with what is going to happen when the fire gets
> started. No, all the cylinders of an engine are never the same and less
> than a wide open manifold only exacerbates that issue by steering the charge
> mixture in different directions.
>
> We live east of the Mississippi and rarely encounter altitudes above
> 6KMSL, but the coach rolled over the Big Horn on the way to Yellowstone and
> the
> coach did not complain. We even had to go around a couple of little
> four-wheels that could not keep speed up at 9200MSL (according to my GPS).
> They
> were all too new to be open loop. And, we still did our regular 9.2 for
> that journey.
>
> So, before you get all fired up to change to a tack-on "fuel injection",
> decide if it is something you really want to do.
>
> As Dick Paterson has been known to say, most carburetor problems start
> with the ignition. I am not fond of HEI, but it can be serviceable, you
> just
> have to be sure you have the spares along. But, you should carry ignition
> spares in any case.
>
> Matt - I'll get down off the milk crate now, I have some passcar work to
> do today still.
>
>
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
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