Generator comparison question

So wrote:

robert@honda wrote:
In addition to starting/choke issues, propane and natural gas burn hotter than gasoline. This can cause the exhaust valve and exhaust value guide to overheat and possibly fail sooner.

With all due respect, propane actually runs cooler than gasoline when properly set up and adjusted. Why?... because it contains lower BTU's. The reason valves burn on dry fuels is because of the lack of lubrication & cushioning on the valve's face & seat. The constant metal-to-metal contact of the valve face & seat, disrupts the seal and eventually causes exhaust leakage. The continued exhaust leakage eventually burns the valve, not because of direct overheating. This isn't an issue when Stellite valves & seats are used.

-kenny-

Sorry, wrong...

Having spent a few thousand hours around LPG, Imco carburetion with more test instruments than Lawrence Livermore Lab, I can tell you for A FACT that the finest "tuned" conversion, even those using an LPG only carburetor run WAY the hell and gone hotter than a gasoline comparing exactly the same horsepower developed. I got SUCKED into the LPG gig by having to be around generators and then waiting and waiting for so-called LPG engine techs to waste enough of my time waiting that I had to shoo them away and get things to the point where I could go to work on the electricals.

Here is how I prepared a GASOLINE motor fuel pickup truck engine to NOT OVERHEAT while using propane. The vehicle used an IMCO 425 carburetor...

Fuel Injection cylinder heads, with the largest valves that wouldn't touch. Big ports. LPG robs room that air normally takes up. An Edelbrock Tarantula intake manifold with huge runners. Venolia 12.5 to 1 pistons - that is A LOT of compression ratio. Bruce Crower cut a roller camshaft for me with near .600" lift and short duration. Then hardened valve seats, exhaust AND intake. Titanium valves to take the heat. Wanna know HOW HOT things get? With a dead stock engine, towing the cast iron exhaust manifolds glowed BRIGHT RED; enough to burn rubber a foot and a half distant.

Why all the uproar over LPG? At the time Mexico had almost-gasoline that would screw up an engine in no-time-at-all (or even sooner). Then, BUTANE was inexpensive and clean.

With all that expense (the engine was 100% blueprinted) it ended up having very near THE SAME horsepower as a stock Chevrolet V-8 with quadrajet carburetor. Before, unloaded the truck got 15 mpg, after the LPG conversion 11.5 mpg.

But it did NOT heat up. Yeah, I even let "The Over The Hill Gang" with Carroll Shelby and Ak Miller, have a stab at it. The improvement may have been marginal if anything. These guys were the best in the LPG engine business.

ONAN after ONAN (4cyl water cooled 12.5KW) I had to tell the owners to back off their KW expectations or suffer a melted engine. One LPG only VOGUE motorhome I troubleshot ****** me off, with overheating. So I ordered up a radiator 16" taller than the original, increased the fin count per inch from 12 to 17, tripled the tube count (it was a SIX ROW radiator), and I managed to keep the temperature under control. You'd better know what you are doing with LPG or you are going to be in for A LOT of surprises. LPG powered engines leak lube oil a lot more than gasoline powered engine. Work around them enough and you also learn this point.