Gas Saver Question.

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($1.16 a ltr) I was thinking of looking into these things. I'm not writing this to be flamed in any way but rather to get constructive inputs.

so is 0%

"SnoMan" wrote in message news: snipped-for-privacy@4ax.com...

you realize the dodge 360/318 doesnt have a knock sensor and does not retard timing to eliminate/reduce detonation? They have

hmmm then its a conspiracy between dialmer crysler and shell oil (for example) to recomend in the owners manual that you use only recomended octane rating for your vehicle (most are 87) so that the oil company makes more money?? seems a bit of a stretch to me.

and you also realize that you stated this in another post.

" THe main reason that diesel get good MPG is because the fuel has a higher energy content (about 140,000 BTU/gal) and with the very high CR or 16 to 20 to 1 you get much higher thermodynamic efficency (convert more heat energy to work). "

and now

" To improve MPG a lot you need to reduce power needed to roll down the road, use a fuel with a higher energy content or run a much higher compression ratio (with proper fuel) that will increase overall engine efficeny and allow to extract more work for a gallon of fuel. "

now i realize that the other post im referanceing is clipped there so ill post it again completely. and note that in your fuel examples the diesel fuel had the highest btu per gallon.

here's what you posted in the "Exchange my V-10 for a diesel cost effective?" thread

I have read about several of them and I have a 79 Jeep J20 that I want to restore someday and I am seriously considering making it a propane only vehical. The problem with some conversions is that they put propane in a stock engine (and it will burn fine with extremely low emissions too) but propane has about 25% les energy per gallon than gas so you need more of it in a stock engine but since propane has a LOT higher octane, you can raise CR to 12 to 1 no sweat and increase power and efficency and get MPG simular to gas on stock compression but with a lot cheap fuel. It also burn a bit slower so more spark advance is needed to which most dual fuel (gas/propane) engine do not properly do. The draw back is you have to install a somewhat heavy tank for fuel stored under pressure but since propane weighs 4 lbs a gallon vs 6.5lbs/gal for gas, the lighter fuel ofsets most or all of this weight. Pound for pound, propane has more energy than gas. By weight, 6.5 lbs of gas (one gallon) contain about 120,000BTU (plus or minus depending on blend) and 6.5 lbs of propane has approx 145,000 BTU's (this heat energy is what drives the engine) while the same amout of E85 has only about 60.000 BTU (and a gallon of E85 weighs almost 8 lbs too). THe main reason that diesel get good MPG is because the fuel has a higher energy content (about 140,000 BTU/gal) and with the very high CR or 16 to 20 to 1 you get much higher thermodynamic efficency (convert more heat energy to work). But, if you use a fuel like propane (or even high octane fuel) it is possible to raise CR ratio a good bit and improve efficency. Some mention running cars on natural gas or hydrogen but the problem there is it take a lot of pressue and technology to store them in a ligud state to get a lot of range where propane is a LOT easier to store and handle.

----------------- The SnoMan

a ltr) I was thinking of looking into these things. I'm not writing this to be flamed in any way but rather to get constructive inputs.

And, I believe going off a cliff with a 100 mph tail wind is required to get upto the 35%

the tailgate episode tested 2 identical ford trucks of the new vintage. I would like to see if the results hold true on Older body styles.

on a side note I was reading some where that tire pressure had a big influence on MPG on late model trucks.. it seems that most dealers under inflate the tries)low side of recommended range) so as to improve the ride, where as most modern tires actually can run very high pressures

I can tell you from first hand experience that tail-gate down on an 81 Chevy C10 deluxe longbed (20 gal tank) get's better mpg with it down vs. up. I used to drive to Penn State alot and my total round trip was

400.1 miles (door-to-door) - tail-gate up, i'd need to refuel at the KoP rest stop on the turnpike, tail gate down took me all the way home with enough gas to get to work the next day. This was originally a 6cyl. truck that I swapped a V8 350 motor into (out of an 89 IROC - roller cam motor, switched over to carbureted with an edelbrock intake and a 74 quadrobog off a big block). So it had the 6cyl. gearing but I had 31" tires on it (it pulled high 14's/low 15's in the 1/4 mile). Now why is it this thing would get better then 20mpg highway, when my modern fuel injected 02 dakota R/T is lucky to see 15-16 mpg highway (and with a 4 speed auto vs. a three speed auto to boot). I just don't get it. Hell my 1971 VW Fastback 1.6L with dual carbs got 30mpg, same as just about every new fuel injected car out there. Just goes to show that modern fuel injection is only there for emissions reasons and made no improvement on mpg.

i hate to admit it. BUT!

GM (and the jap/korean imports) seem to have a better handle on fuel management than ford or chrysler does. my step dad had a 88 c1500 (yes a c truck not k) with the 350 and got 22 highway. ive never owned a dodge (until now with the 05) that could reach those numbers. even still i like the dodges MUCH better than GM's crap.

I doubt that. Every single wind tunnel test ever done on consumer pickups has shown an increase in drag when the tail gate is lowered. No reputable test has ever shown a lower drag coefficient which would be required to improve your mpg. Some other reason accounted for your gains but it was not the tail gate.

Well, I'll have to dissagree. On a longbed pickup, tailgate down or off DOES make a measurable difference. So does a tonneau cover. On some shortboxes the difference is less pronounced, but on my old Fargo (short box) it made almost 4mpg difference at highway speeds. I generally drove it with the tonneau on.

*** Posted via a free Usenet account from ***

And I'll have to disagree with ya! It's been done over and over with regards to wind tunnel testing. There is more drag with the tail gate down. It's been well proven time and again. Read up on the physics of why that is.

Got any wind tunnel tests proving otherwise?

A tonneau cover can help mpg.

Ding...Ding...Ding...give that man a seegar...:-)

Add later Subarus. I see about 2 MPG better and a whole lot smoother running on 89 or topping up with 92 at about 2/3's tank. Must be something about that 10.0/1 CR ;}.

My old B II never seems to care about 87 or higher as lomg as it was decent gas.

This whole argument is meaningless and depending on given situations, either case can be true.

Not usually. In almost all cases dropping the tailgate will increase drag. However, most tests done indicate the difference is not enough to see a change in mpg.

Miles has been on the money about this imo. I've not heard of any wind tunnel test that suggest a lessening of drag with the tail gate down or removed.

Roy

The thing Roy is that most people don't drive in wind tunnels and from what I see, seldom in completely stock trucks either. I agree that in base stock form, it is unusual for the truck to do better with the tailgate down as this was done by design. But if you change the angle of the truck, put something in the bed, add a bug deflector or perhaps an external sun visor, now you are changing the aerodynamics of the vehicle and the airflow into the bed can be significantly changed.

Wind tunnel tests do not always give the complete picture. Unless these tests are done with all of the modifications people tend to do to their trucks such as adding bug deflectors, bed mounted spare tires, leveling kits, roll bars, ect, all these wind tunnel test can show is what a basic stock truck can will do in perfect conditions. I am sure that by design and in stock form, empty, and under somewhat perfect conditions the truck will always do better with the tailgate up but that is not real world.

I guess Hendrick will be calling you at any time for you expertise in air flow.

Roy

Such modifications may reduce drag over all but the tail gate down will still increase drag rather than decrease it.

LOL, and your proof of this is where???