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Old 05-30-2012, 01:52 AM   #11 (permalink)
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My brother has the same truck, the gas tank does not vent out the gas cap, the fuel vapor is stored in the charcoal canister, like every other vehicle sold in the USA in the last 25+ years, there is also a good chance that if your gas cap didn't seal and was venting fuel vapor that your check engine light would come on and tell you that there is a leak and that fuel vapors are not being collected and burned, it's pretty standard on OBDII vehicles.

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Old 05-30-2012, 03:14 AM   #12 (permalink)
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Originally Posted by Ryland View Post
My brother has the same truck, the gas tank does not vent out the gas cap, the fuel vapor is stored in the charcoal canister, like every other vehicle sold in the USA in the last 25+ years, there is also a good chance that if your gas cap didn't seal and was venting fuel vapor that your check engine light would come on and tell you that there is a leak and that fuel vapors are not being collected and burned, it's pretty standard on OBDII vehicles.
cool there great! trucks you cant fined them b/c no one whats to sale them! lol and ohhhhhhhh well it can vent out of the gas cap right? in the right conditions

is your bro a ecomodder? do u have any mod ideas for my nissan?
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Old 05-30-2012, 09:48 AM   #13 (permalink)
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The gas cap is going to offer a lot of resistance before it vents that rout, what you are most likely seeing is the check valve that lets air in to the gas cap, the Evap system on the truck is going to provide a very easy way for the fuel tank to vent but while it's venting it's capturing the fuel too, unless you walk by your vehicle on a hot day and smell fuel vapor leaking out of the gas cap and if that was the case you would notice, it would stink like someone dumped some gasoline on the ground.
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Old 05-30-2012, 10:33 AM   #14 (permalink)
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Quote:
Originally Posted by brent777 View Post
do u have any mod ideas for my nissan?
Here are a few:

65+ Vehicle modifications for better fuel economy - EcoModder.com
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Old 05-30-2012, 10:39 AM   #15 (permalink)
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Only time I ever smelled fuel vapors in my garage was when I pulled in my 2005 Kawasaki Vulcan 500 and shut it down. The hot engine right under the fuel tank heated the gas up and some of the vpaors vented into the garage. Not a good idea with an electric hot water heater and a house on top of the garage, with a few pounds of gunpowder and some loaded ammo to really enhance the explosion.

Now I park the bike just outside the door and put a fan in front of it to cool it off before pushing it in the garage a little while later.

regards
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Old 05-30-2012, 11:09 AM   #16 (permalink)
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Originally Posted by Ryland View Post
The gas cap is going to offer a lot of resistance before it vents that rout, what you are most likely seeing is the check valve that lets air in to the gas cap, the Evap system on the truck is going to provide a very easy way for the fuel tank to vent but while it's venting it's capturing the fuel too, unless you walk by your vehicle on a hot day and smell fuel vapor leaking out of the gas cap and if that was the case you would notice, it would stink like someone dumped some gasoline on the ground.
oh okay i see well i know now thanks to you do you have any mpg mod ideas?
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Old 05-30-2012, 11:10 AM   #17 (permalink)
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okay cool i will check it out!
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Old 05-31-2012, 12:40 AM   #18 (permalink)
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yes but ....

yes but
the newer systems are designed to be returnless , either by have the fuel pressure regulator with return line contained inside the fuel tank
or
with feedback controls to regulate fuel pressure to be where Mr ECM wants it to be at the time

these systems were designed to reduce
Evaporation emissions - they were designed that way for a reason at no small increase in expense because the EPA demanded
reduced Evaporation emissions of HC

yet the same PUDDINGHEADS at the EPA have no problem with huge amounts of propane being vented to atmosphere when those BBQ propane tanks are refilled at the local hardware store ? is propane not HC ? nod your head yes .


so
the OP's thoughts have some merit , i do not know how much FE would be gained , i suspect the value would be small ,
but it would not be a huge undertaking to reposition a fuel pressure regulator
(with a vacuum line routed from intake vacuum )
in the fuel tank if someone had a want to do it
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Old 05-31-2012, 03:31 AM   #19 (permalink)
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I think there is a hint of a real eco-mod in brent777's fuel cooling idea.

Reason I say this is because I know that returnless fuel systems act differently than return-style fuel systems. For instance, the returnless system on my truck goes to a horseshoe shaped fuel rail assembly. The fuel inlet is on the left bank, between the injectors for cylinders 3 and 5. The left fuel rail is connected to the right fuel rail via a hard line. So, at one end of the fuel rail assembly, fuel only has to travel about 8 inches or so to reach the fuel injector at the one end of the assembly, to reach cylinder 7. However, fuel has to travel something like 30 inches to travel to the other end of the assembly, at cylinder 8.

What does that mean? Well, at low speeds, the fuel absorbs heat from the engine as it travels through the fuel rail assembly. There is little air cooling to be had, since the fuel rail is somewhat buried under other engine components. As the fuel travels down toward cylinder 8, it absorbs more and more heat. And... as fuel absorbs heat, and its temperature increases, its density decreases. That makes it nearly impossible for the engine computer to deliver the same amount of fuel to each cylinder. You end up with some cylinders leaning out, and other cylinders going rich. This is not efficient.

Now, some later cars might have bandaged over the problem by putting a Y-fitting that feeds two rails from the center of the fuel rail assembly, or by using a pre-cat O2 sensor on each bank of a V- engine (as opposed to using just one pre-cat O2 sensor, period), but the problem's still there.

This leads to an early eco-mod of mine, before I even knew of this board. This other truck board has my write-up here, and I saw a very noticeable increase in fuel economy immediately after installing the mod. Basically, I replaced the horseshoe with a branched setup. There's a Y that splits fuel equally to both sides' fuel rails at the center. This equalized temperatures across the fuel injectors tremendously.

It's not even my idea. Somebody who goes by the handle of duner first came up with the idea almost a decade ago, for the exact same engine I have. However, he equalized his fuel rail temperatures by using chilled liquid water instead of Y-branching. He did a dyno run of before-and-after. Here's his chart.



As can plainly be seen, duner was able to gain about 20 ft-lbf of torque throughout his torque curve.

I was able to go from about 14 MPG in mostly city driving to around 17 MPG, using my implementation.



One final thought - the idea isn't so much to cool off the fuel, but to ensure that all of the fuel injectors receive fuel at the same temperature, as much as possible. Temperature differentials between injectors are something to be avoided.
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Old 05-31-2012, 09:29 AM   #20 (permalink)
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Quote:
Originally Posted by t vago View Post
I think there is a hint of a real eco-mod in brent777's fuel cooling idea.

Reason I say this is because I know that returnless fuel systems act differently than return-style fuel systems. For instance, the returnless system on my truck goes to a horseshoe shaped fuel rail assembly. The fuel inlet is on the left bank, between the injectors for cylinders 3 and 5. The left fuel rail is connected to the right fuel rail via a hard line. So, at one end of the fuel rail assembly, fuel only has to travel about 8 inches or so to reach the fuel injector at the one end of the assembly, to reach cylinder 7. However, fuel has to travel something like 30 inches to travel to the other end of the assembly, at cylinder 8.

What does that mean? Well, at low speeds, the fuel absorbs heat from the engine as it travels through the fuel rail assembly. There is little air cooling to be had, since the fuel rail is somewhat buried under other engine components. As the fuel travels down toward cylinder 8, it absorbs more and more heat. And... as fuel absorbs heat, and its temperature increases, its density decreases. That makes it nearly impossible for the engine computer to deliver the same amount of fuel to each cylinder. You end up with some cylinders leaning out, and other cylinders going rich. This is not efficient.

Now, some later cars might have bandaged over the problem by putting a Y-fitting that feeds two rails from the center of the fuel rail assembly, or by using a pre-cat O2 sensor on each bank of a V- engine (as opposed to using just one pre-cat O2 sensor, period), but the problem's still there.

This leads to an early eco-mod of mine, before I even knew of this board. This other truck board has my write-up here, and I saw a very noticeable increase in fuel economy immediately after installing the mod. Basically, I replaced the horseshoe with a branched setup. There's a Y that splits fuel equally to both sides' fuel rails at the center. This equalized temperatures across the fuel injectors tremendously.

It's not even my idea. Somebody who goes by the handle of duner first came up with the idea almost a decade ago, for the exact same engine I have. However, he equalized his fuel rail temperatures by using chilled liquid water instead of Y-branching. He did a dyno run of before-and-after. Here's his chart.



As can plainly be seen, duner was able to gain about 20 ft-lbf of torque throughout his torque curve.

I was able to go from about 14 MPG in mostly city driving to around 17 MPG, using my implementation.



One final thought - the idea isn't so much to cool off the fuel, but to ensure that all of the fuel injectors receive fuel at the same temperature, as much as possible. Temperature differentials between injectors are something to be avoided.
thats so cool when did you do the mod? and this gives me a thought okay i have a 4 cylinder. i want to put a thermometer on the fuel rail by each cylinder and see if the temps are the same i bet the last cylinder is going to be hotter if it is i am going to put exhaust wrap between cylinders #3 to #4 to cool the gas )))

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