Quote:
Originally Posted by Super_Dave
I have read that:
"Propane holds approximately 86 percent of the energy of gasoline and so requires more storage volume to drive a range equivalent to gasoline,"
"cars running on propane have less range, compared to the volume of the fuel stored, than cars running on conventional gasoline. The main difference in range comes from a difference in heat energy per liter of fuel (gasoline’s is better)."
I am not a thermodynamics professor, so we got that outta the way. I am interested in alternative performance fuels that can compete with gasoline but costs a lot less. So, how do the two statements above correlate to 104 octane of LPG being inferior to gasoline?
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Your not hijacking. Its a legitimate concern.
Most of the figures people keep posting about propane being inferior are from books written in the 60's. No joke. Technology has evolved a great deal from then. Up to having fuel injection LPG and NG systems. With modern ignition systems, you have no power loss. All you need to do is advance your ignition timing quickly. Im talking 25 to 30 degrees just off idle. This alone will bring you to stock power levels if not surpassing them. Yes, the volumetric efficiency of propane is only 86% of regular petrol. And you will notice this on a bone stock engine built for 86 octane fuel. In stock trim, an engine just cant make use of the benefits of LPG.
Now, If your engine is pushing 11:1 or higher compression or like mine, running forced induction, the benefits are out the roof. No need for highrise intakes that kill throttle response as the fuel already in a gaseous state when entering the intake. A single plane standard height intake is perfect. So unlike petrol, its does not need to atomize with a venturi and a long intake runner.
Fuel metering is dependent on engine vacuum. Open the throttle plates, engine vacuum pulls a diaphragm and fuel flows. Simple. Thats it. With Impco 425 mixers (the standard automotive lpg carb) you get instantaneous throttle response as you no longer have an accelerator jet or idle circuits to worry about. You dont need vacuum secondaries or a choke. Mechanical secondaries that open with the primaries are preferred. You will never flood the engine. It never runs lean. It will run upside down. Fuel is added depending on vacuum which is metered by the mixer and the vaporizer to ambient air pressures. So it adjusts automatically with altitude changes.
If your speaking from a carbed petrol engine to a lpg carbed engine, you may see an increase in mileage.
If you just slap on a lpg system on a stock engine, yes. You will loose 1 or 2 mpg and some hp. Upgrade your ignition coil, advance your timing and your right back at stock power levels with far-far cheaper fuel. Build your engine for higher octane fuel, and you will gain some serious ponies under the hood with lpg.
lpg is stupid simple. No electronics. Minimal maintenance. As good as an efi system for a 1/4 of the cost.
You get a TAX CREDIT for converting as it makes your rig an ultra low emission vehicle. You pollute less than a Prius.
Im stunned more people dont run it. The people who say "It sucks" have never run it or are simply ignorant.
Now, natural gas is another matter. Its simply a power sucking, fuel economy killing bad idea.