Numbers, mpg related, PT.1: - Team Camaro Tech
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post #1 of 7 (permalink) Old Feb 20th, 13, 03:42 PM Thread Starter
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Numbers, mpg related, PT.1:

i was doing some cleaning (surprised how much dust accumulates.....) and uncovered a spreadsheet i did concerning gas mileage and engine conversions and how much money it would take to operate each drivetrain combo:

Now, this was originally done for a pickup, but this could apply to any rear drive gm (particularly chevy) car originally available with a small block v-8. Gas was around $3.25 and diesel was around $3.75 when i did the paper i think last winter, so not too far off.

A truck with a typical stock small block is going to get around 16mpg. If you swap to diesel (the 6.2/6.5 engine) you'll go up to 24. (you might even be able to go 27 or higher, but let's go with 24 for now just to be conservative). Any rear drive car with a small block can be converted to run the 6.2 diesel engine as it bolts in the the stock mounts and has the same bellhousing pattern as a small block. If you're turned off by diesel you can substitute an LS engine in for purposes of this discussion.

In fuel costs, it will cost .20 cents per mile if sticking with gas and gas is $3.25 per gallon.

If you run diesel @ $3.75 per gallon , then the cost per mile is .15 cents.

SO after 1,000 miles, it cost $203 on gas and $156 on diesel. On one hand not too heavy because, i think, it would take, on average a few weeks to go 1000 miles on an average commute. On the other hand, somewhat significant because with weekend trips factored in, 1,000 miles can come quickly.

At 10,000 miles, it costs $2031 on gas and $ 1562 on diesel. Again, not too heavy in my opinion---it takes me about 11mos/ year to achieve 10,000 miles. Again, here it depends on how much overall driving you do; Weekend trips, shuttling the kids to soccer, do you go shopping alot etc.?

At 45,000 miles, it costs $9140 in gas and $7031 in diesel. My point here is it may take quite a while---i think it was 250,000 miles before you break even when you consider the costs in converting to diesel----a new 6.5 engine is $8000 from gm, i've seen remans for $3000 though.

If you have your money parked at 3% (shouldn't be too hard to do) OR if you had put it in municipal bonds, you'd get at least 5%. Putting money in these investments vs. buying a new engine it's likely you may never break even. i missed out on the municipal bonds among other things because i'm not a smart man. (picture Suze Orman scolding you with finger outstretched).

This is why i've decided to stick with gas.
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post #2 of 7 (permalink) Old Feb 20th, 13, 04:27 PM
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Re: Numbers, mpg related, PT.1:

what year is your truck and what is a "typical" small block?

i've gotten as high as 30mpg with a magical 350 backed with a TH350 and 2.56 gears that i built for my 76 Monte Carlo an eternity ago- 1993- and had a 305 backed by a 700r4 and 2.56 gears in an 86 Caprice that would average 28mpg.. but i've also currently got a 307 out of a 71 Nova in my 87 GMC 3/4 ton 4X4 truck with 4.10 gears that has never gotten above 10mpg..
the vortec headed L69 305 backed with a 700r4 and 3.42 gears in my 86 Camaro that has the same cam as my magical Monte motor from a lifetime ago averaged 24mpg on my 3900 mile round trip from MN to Texas last June, but didn't seem to want to average over 22mpg for the other 9000 miles i put on it after that trip was over until i parked it at the end of October.. i had a 92 Caprice 9C1 with the TBI 350 backed by a 700r4 and 3.42 gears that never got below 25mpg and hit 29 on a couple of occasions..

so, which one of these engines is a "typical" small block?

the reason you don't see people lining up to swap and old Chev/GMC truck diesel into a car is because they are awful, awful engines and most people don't want to put up with the noise and smells that come with them..

you don't plan sincerity.
you have to make it up on the spot.

wanna hear about 20 years ago when i was too smart to know any better?
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post #3 of 7 (permalink) Old Feb 20th, 13, 05:29 PM Thread Starter
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Re: Numbers, mpg related, PT.1:

83

i consider a "typical" small block is basically one originally installed in the car---i.e., LG3, LG4 305s, LM1 350's. Just stock, relatively low compression---8.5 to 1 engines.

i'd kind of like to disagree about the 6.2 being awful---they are durable as hell, get great mpg. The current hummer used in the army has this engine (i think?)
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post #4 of 7 (permalink) Old Feb 20th, 13, 06:29 PM
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Re: Numbers, mpg related, PT.1:

Quote:
Originally Posted by puff puff View Post
83

i consider a "typical" small block is basically one originally installed in the car---i.e., LG3, LG4 305s, LM1 350's. Just stock, relatively low compression---8.5 to 1 engines.

i'd kind of like to disagree about the 6.2 being awful---they are durable as hell, get great mpg. The current hummer used in the army has this engine (i think?)
the only one of the examples that i posted above that wasn't stock is the 305 in my Camaro- every other one was totally stock, unless you count the headers and aluminum intake on the Monte and the aluminum intake on the 307..

i could bring up the vortec headed/HOT cammed 355 with 10:1 compression that was in my 71 Nova backed by a T10 trans and 3.70 gears that generally got 17mpg in daily driving duty and as high as 19 on a couple of 80mph interstate jaunts with the engine screaming at 3500 rpm for an hour and a half at a time..

you don't plan sincerity.
you have to make it up on the spot.

wanna hear about 20 years ago when i was too smart to know any better?
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post #5 of 7 (permalink) Old Feb 20th, 13, 10:39 PM
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Re: Numbers, mpg related, PT.1:

Why deseil.. my Camaro hasnt sen a drop of petrol since '84
Dedicated LPG....not a petrol engine running lpg but cam , timing , cR etc designed for the drivetrain ratio AND Fuel type.
Co9sts about the same per mile as a modern 2L / 2.5L car to run ansd still pull high 13s...as a daily driver.

My Spelling is not incorrect...it is creative

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post #6 of 7 (permalink) Old Feb 21st, 13, 07:55 AM Thread Starter
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Re: Numbers, mpg related, PT.1:

Yes, we can discuss LPG/natural gas as well.
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post #7 of 7 (permalink) Old Feb 21st, 13, 11:43 AM
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Re: Numbers, mpg related, PT.1:

CNG.. the problem there is the BTU per volume very low.. which requires a huge tank for any reasonable distance and the weight of the tank...but the potentual power for a dedicated engine is very good.
LPG, a 85L manchester tank fits like a clove in the trunk...gives far more room than a 65L...with a range of 250 miles plus, easy.
Keep in mind comercial lpg/ propane is not propane as such, but a mixture... pure propane is difficult to source and the extra refining makes it very expensive
LPG has a octane around 105, loves sb chevies, a CR around the 10.5 to 11 (ballpark depending on cam profiles) less total advance than petrol with a fast curve, between 28 and 32 degs all in 2400 to 2800.....
unlike petrol it is very resistant to knock, allowing good compression, and advance with very lean mixtures....petrol is around 14.7:1 with a very narrow window of effuiciency, LPG is around 15.7:1 and still runs out to 19:1 AFRs....with the advantage of very lean/ advanced mixtures not running engines hot as with liquid fuels.
Ball park numbers... a sb around town, interections, traffic etc one can expect around 15/16mpg of LPG... open road 17/18 mpg.. and these are not granny footing numbers... on carbed engine.
So depending on local prices of petrol and automotive lpg you can work out comparison.
Note: do not just the price of bottled LPG , this tends to be far more expensive...3 1/2 times more expensive here.
Valve ressesion, bearing issues, need for special oils, starter issues are all myths, created by bad installs /setups and marketing propaganda BS.
Down side, in very cold /freezing temps there can be issues...normal snow / frost, not

My Spelling is not incorrect...it is creative

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