Re: LPG/CNG cheaper?

[farna@xxxxxxx]

I knew there were other benefits, especially cleaner burning. The only thing that I've read concerns about is cylinder and maybe valve wear because LPG/CNG burns so clean. I guess when you have to take yours apart we'll know! 

Building a stroker 4.6L would be perfect for LPG/CNG. Standard 4.0L pistons w/258 crank and rods turns out 9.6-9.7:1 compression. A slight block deck and/or head shave would easily net 10:1. Chevy 3.8L V-6 and 250 I-6 use about the same bore as the 4.0L (3.875"), but compression height is wrong to build a gasoline stroker. I forget exactly, but think they leave compression to high. I do recall a discussion about one piston that would put it in the 11:1 range if used, but forget what it was. Not many ready made choices in that bore size! Plust the added inches would help. A budget stroker left at 9.6-9.7:1 should net the power of a gasoline 232 easily. 

On May 9, 2005 Tom Jennings wrote:

> On Mon, 9 May 2005 farna@xxxxxxx wrote:
> 
> What you say below is true. I did my conversion back in 1988, and
> gas price wasn't the reason; it seemed technically sweet (and it
> is). Engine life is probably closer to 500K miles instead of a
> gummed-up 150. Oil stays clean yellow after 5000 miles. I haven't
> torn it down yet obviously but I expect it's immaculate inside.
> No or little ring blowby out the valve cover.
> 
> You should be able to run 12:1 or 14:1 compression. I didn't have
> the money to gamble at the time (since I didn't know then what I
> know now) on my one, expensive-to-me engine, to dedicate it to LP.
> Its about 9.5 to 1 or so, flat-top 290 pistons in the 232 and a
> bit of a mill job on the head.
> 
> On long trips I get 19 - 20 mpg gasoline equivelant (BTUs/mile)
> using th eAUtotronics feedback computer. It would probably be even
> better if I could dial in the advance a bit higher, but I am
> pretty sure I screwed up the head squish space when I built the
> engine. Probably lopping off the (estimated) .040 to eliminate it
> would also dial in compression to where it would do the most good.
> 
> All it takes is money :-)
> 
> I suppose I could build a new high-compression head and install
> that. I've got a 70 head laying around. I would like to switch to
> the aluminum intake.
> 
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> >
> > Tom, at $1.65 a gallon and a 10% poaer and fuel efficiency loss, I can't see LPG or CNG (CNG has a 2-4% greater loss) as being cheaper in the US. Gasoline has pretty much stabilized at ~$2.10 a gallon here. $1.65 + 10% = $1.81 + 10% (for the power loss) = $2.00 (rounded up). For the $600+ cost I don't think it's worth it. There is the argument that gasoline will only rise in price, but LPG should rise in direct proportion since it's a by product of producing gasoline. CNG wouldn't rise quite as much, but there is a steady demand for it for heating and industrial use, like producing electricity. As long as it's fossil derived costs will only go up over time. Now if you built the engine for higher compression to gain back that 10% of power, you should gain the 10% in economy back as well. I guess that's why you mention that single fuel is best! If an engine needs rebuilding it could be built at 10:1 compression and still have the ability to run on gasoline in an emergency !
 an!
>  d !
> > be relatively efficient with LPG/CNG (CNG only engines are typically built for 11:1 compression in Australia and New Zealand -- that would be rough on today's gasoline!). When I move back to SC maybe I'll get a copy of Mother Earth News from the 70s and look at a methane generator. Could run a vehicle around the farm on that anyway! ;>
> >
> >
> > On May 6, 2005 Tom Jennings wrote:
> >
> >> On Thu, 5 May 2005 fljab@xxxxxxxxxxx wrote:
> >>> is LPG that much
> >>> cheaper to run?  Is there anyone running it on a converted vehicle
> >>> that can answer that?
> >>
> >> Most dual-fuel setups are LP mixers that bolt on top of the carb
> >> in place of the air cleaner. With a solenoid you run the carb dry
> >> of gasoline, then switch on the LP. It's inefficient as hell.
> >> You're far better off doing single-fuel.
> >>
> >> I've run LPG on my 232 for 17 years now. No complaints. I pay
> >> $2.50 or so at the BBQ tank fillers at the local gas station, but
> >> $1.65 at Mutual Propane, a big regional dealer. They now have a
> >> card-lock system so as soon as I get my card I can buy LP 24/7.
> >>
> >> As a rule of thumb, you'll get 10% less MPG on LP vs gasoline.
> >> Reason: BTUs energy per unit volume.
> >>
> >
> >
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> >
> >
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> >
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> .


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