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Old 09-17-2019, 02:36 PM   #1 (permalink)
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Low power fuel tank heater for better winter mileage?

I already know the benefits of an oil pan heater. What about a fuel tank heater? Could probably get away with 12v 120w. I'd imagine 60 degree gasoline burns better than 32 degree gasoline and would help with cold starts, complete combustion, etc.
Any thoughts on this?

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Old 09-17-2019, 03:34 PM   #2 (permalink)
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IMO with modern fuel injection this is not a big issue. High idle is more about getting the CAT up to temp than it is about idling nice.

If you are running a carburetor it is more of an issue.
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Old 09-17-2019, 03:36 PM   #3 (permalink)
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Best to heat the fuel line after the fuel has been pressurized. Otherwise you may lose too much fuel vapor.

Also heatin all of the fuel seems counter intuitive as you may not use all of it.

Be wary of vapor lock, where the fuel vaporizes in the lines, and the injector pushes out a gas instead of a liquid, this produces almost no power. Also the injectors use the fuel to keep themselves cool. Vapor does not absorb much heat. In the long run it may damage the injectors.
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Old 09-17-2019, 11:34 PM   #4 (permalink)
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Quote:
Originally Posted by Daox View Post
IMO with modern fuel injection this is not a big issue. High idle is more about getting the CAT up to temp than it is about idling nice.

If you are running a carburetor it is more of an issue.
Most cars also retard ignition timing for a while to get the catalyst up to temperate. All this does is start the burn late, so that it's still burning when the exhaust valves open. Some of the combustion that would have pushed on the pistons goes out the exhaust and heats the catalyst.

Disabling cold ignition retard help cold start fuel economy but gets rid of acceleration of cat heat up.
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Old 09-18-2019, 02:55 AM   #5 (permalink)
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Warm fuel is also less dense, so: fewer btu per method of measurement. Does that affect anything? Maybe, maybe not.

The pumps in NV have a variable delivery sensor after a successful lawsuit complaining someone was being shortchanged buying fuel on 110 degree days.
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Old 09-18-2019, 08:58 PM   #6 (permalink)
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Quote:
Originally Posted by Ecky View Post
Most cars also retard ignition timing for a while to get the catalyst up to temperate. All this does is start the burn late, so that it's still burning when the exhaust valves open. Some of the combustion that would have pushed on the pistons goes out the exhaust and heats the catalyst.

Disabling cold ignition retard help cold start fuel economy but gets rid of acceleration of cat heat up.
Any way for the layperson to do this without a tuner? I own an NA Subaru Impreza, perhaps the least mod-able car currently out there.
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Old 09-18-2019, 09:56 PM   #7 (permalink)
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Quote:
Originally Posted by quagss View Post
Any way for the layperson to do this without a tuner? I own an NA Subaru Impreza, perhaps the least mod-able car currently out there.
Maybe? A coolant temperature spoof might do the trick. You may also be able to disable it with whatever OBD/flash based tuning is available for your car.
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Old 09-18-2019, 10:29 PM   #8 (permalink)
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Does the timing retard to heat the Cat only work during Open loop?, my Cobalt XFE most days is in open loop for only 2-3 blocks, if that's all the longer it takes for most cars it doesn't seem like the effort to spoof it.

O2 sensor doesn't care about fuel temp, only looking for free oxygen so it will adjust fuel trims regardless of fuel density.
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Old 09-19-2019, 07:27 AM   #9 (permalink)
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You're trying to heat the wrong component in the combustion process.
The combustion process should run about a stoichiometric air-fuel ratio of 14.7 - 1 (mass related) so by heating the fuel you are just heating 7% of the mass involved, which will have very little effect.
If you heat the air instead you heat the other 93% involved - and it is way less risky.

I experimented a bit with heating intake air. It does have an effect: it makes the engine idle lower earlier and (anti intuitively) the engine heats up less fast, probably because the combustion process itself is running more efficiently. I may well have another try at the eWAI coming winter.
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Old 09-19-2019, 07:52 AM   #10 (permalink)
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Quote:
Originally Posted by roosterk0031 View Post
Does the timing retard to heat the Cat only work during Open loop?, my Cobalt XFE most days is in open loop for only 2-3 blocks, if that's all the longer it takes for most cars it doesn't seem like the effort to spoof it.

O2 sensor doesn't care about fuel temp, only looking for free oxygen so it will adjust fuel trims regardless of fuel density.
I'll have to turn it on and see, but I believe the answer is "no". I'm not sure what determines when it shuts off.

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