I don't know about the density of the fuel but, my car has 2 fuel temp sensors.
One is located on the fuel rail, the other is back toward the tank. I would imagine that with the temp of the gas you could get a pretty good indication of the fuel density.
Not exactly sure if this info help, but Toyota is infamous for mounting their fuel filters right on the engine block. Makes them a real PITA to change (Toyota says they are a lifetime part) . I've always thought the reason was to warn the fuel shortly before it hits the injectors. Can't think of another reason they'd do it this way.
Because of mounting it there they have to use a rather beefy filter which costs 3 or 4 times as much as others I've changed. Metal case, much larger than the little plastic one my mazda 323 had.
Filter is under pressure too so metal is a good idea. Makes me wonder where mine is - had some people have engine problems and were going to change it to see if it helped. They had start and stall problems.
I learned something new after reading through a repair manual for my car, I was reading the part about fuses and relays, and It said something about a fuel warmer relay, so maybe there is already something already on there. I wasn't to sure because the manual covered many years and 2 different engines.
I think it has to be strong enough to handle the gas line's PSI. I have a fuel heater for my hydrogen-booster system, but my mechanic didn't want to install it because of safety issues. From what I have read, the real problem is "vapor lock". I *think* the best fuel heater is one where you can somehow control the temperature :
Definition: When gasoline overheats and boils inside the carburetor bowl or fuel pump of a hot engine, it ceases to flow. This can cause stalling or hard starting. This is called vapor lock, and it usually happens during hot weather. If a hot engine won't start, all you can do is let it sit and cool off. You should check the cooling system to see if anything is causing the engine to run unusually hot (a bad thermostat or cooling fan, for example). Switching brands of gasoline may also help.
Fuel heaters are common for diesels in the northern climes :
* The Arctic Fox "Series 400" shut-off thermostat stops the coolant flow when the fuel flowing through it reaches approximately 78? F/ 25? C to 95? F/35? C.
* The "Series 440" shut-off thermostat operates at a range of approximately 104? F/40? C to 125? F/52? C.
* Helps keep the fuel within the recommended temperature limits for maximum horsepower as suggested by engine manufacturers.
* With the shut-off thermostat you can convert your existing or any coolant type warmer into a thermostatically controlled fuel warmer.
* Utilizes proven sensor module technology used in engine coolant applications.
The problem with these is that you can't program the shutoff temperature, . For GasSaver purposes, we would want to control this.
On my '75 Malibu, i had vapor lock with the factory routing of the fuel lines...
On that car, the fuel pump is mechanical off the motor, then the fuel line goes against the motor to the carb. For me, the only time it was a problem was when I went to start it on very hot days, after it was already warmed-up. When there is no air flowing in the engine bay is when it locked itself most often. It would just take a lot of pumping of the gas pedal and lots of turns of the started to get it started again. Not really a safety issue, just annoying.
On the never-ending quest for better gas mileage...
I tested a fuel heater on a carbed 1.5 L using copper coiled around the upper rad hose. Usual measured fuel heat right before the carb without the heater was 110F in summer.
With the heater it ran around 125-135F at cruise in summer. Got as high as 156F or more in summer in traffic. Once had the engine start to run like a diesel at idle in summer.
Despite using a rad block...I could get no mpg gains in winter.
Gains were around 8% in summer. Had no issues with vapor lock until around 150F when the engine might stumble some...never stopped though.
I've heard that the temp to shoot for with EFI is around 150F.
Ok, then if that's the case, then the "Series 440" shut-off thermostat (104? F/40? C to 125? F/52? C) would be a workable if not optimum fit. I think I will e-mail them and ask them. I wonder what they'll think if I ask if I can use it for non-diesel applications? Gotta do some homework.