My fuel tank is HOT; Fuel cooling?

[ChrisAudi80]

Some might have seen my fuel tank set up. It is a SS tank in the spare tire well. See picture. Not optimal I know, but it was the only viable option here. B4Q fuel tanks do not exist in Thailand.

The weather gets real hot here and the tank does not get cooled while driving. It is hot to the touch as in body panel in the sun hot.
I running E20 now, but will switch to E85 after the VEMS switch.

I am worried that the ethanol is evaporating fast and having a hot fuel tank.

Would having a small cooler with fan in the return line be a good idea? I would mount it under the car in the space where the old tank was.
Having a hot fuel tank in the trunk is not a comfortable thought.

[elaw]

Cooler sounds like a good idea (it probably would not have to be very large), putting it in the return (vs. the supply) line sounds like a really good idea, putting it under the car... not so much. Airflow won't be great, the air that reaches it will likely be warm/hot, and there's the possibility of it getting damaged (with really nasty consequences) by a stone thrown up by a tire or something like that.

Is there any chance you could find room in the front of the car behind the grille?

As a side note, make sure your tank is properly vented! You probably know this but in fuel-land, with heat comes pressure...

[ChrisAudi80]

Cooler sounds like a good idea (it probably would not have to be very large), putting it in the return (vs. the supply) line sounds like a really good idea, putting it under the car... not so much. Airflow won't be great, the air that reaches it will likely be warm/hot, and there's the possibility of it getting damaged (with really nasty consequences) by a stone thrown up by a tire or something like that.

Is there any chance you could find room in the front of the car behind the grille?

As a side note, make sure your tank is properly vented! You probably know this but in fuel-land, with heat comes pressure...

Good point about the positioning. I would add a small fan to the cooler if positioned in the back. There is not much room at the front behind the bumper. It is the Euro 4cylinder bumper. Not even room for a FMIC without a lot of cutting.

I should add an EVAP vent. True

[loxxrider]

I don't see how a cooler could be a bad idea. Return line would be ideal since it is easier to remove heat when you have a bigger delta in temperature. You're sure it is hot because of the fuel alone, or is it more because of the hot climate?

[SEStone]

Fuel pumps are pretty effective at heating fuel.

[loxxrider]

Yes, especially if there isn't enough of a reservoir for the fuel to go back into and/or if the pump is causing too much fuel to be bypassed at idle.

[UrSobsessed]

Get a vent in that tank! You can run it to the N80, just like it was run from the stock tank(if your 80 has that system). When you get VEMS, it can control it also.

Also, even if you had room, I wouldn't run a fuel cooler to the front of the car. Get in a bad enough collision and, uh, boom.

[ChrisAudi80]

I don't see how a cooler could be a bad idea. Return line would be ideal since it is easier to remove heat when you have a bigger delta in temperature. You're sure it is hot because of the fuel alone, or is it more because of the hot climate?

I am sure the climate is a large contributing factor.

A vent will be installed. I need to tee into the hose you see at the top of the tank. Since the stock tank is gone, I think a small cooler with fan somewhere in that space might work, small stones notwithstanding. It would be exposed to more junk at the front. Collision danger is a good point.

I looked around to see if there was any other benefit to cooling the fuel down to ambient, but it seems there is none.
Not running a 4000hp motor

[ChrisAudi80]

I have changed to E85, but using my piggyback.

The MAPECU3 piggyback has some new features, among them a new feature where it can adjust fuel/timing using a flex fuel sensor.
http://www.mapecu.com/2015/01/mapcal3-v3-5-flex-fuel/

Some of these flex fuel sensors or ECAs also measure the temperature of the fuel.
What is the purpose of this?

I have been searching, but cannot find any information of the the effect of fuel temperatures on fuel and timing settings, E85 specifically.
If guessing, I would say, ethanol evaporates faster in a hot environment.

Any of you smart guys know?

[loxxrider]

Characteristics of fuel injectors change with temperature. It may have some effect on preignition as well, but I don't think that is the senior's primary purpose becuase adaptive knock control is so good on modern engine management systems that I believe the effect would be minimal.

[SEStone]

Paul Yaw of Injector Dynamics did some testing a while back on fuel temperature. I don't believe it affected timing much, but it has an effect on fuel mass delivered due to the density change. He also found that once it reaches a certain temperature, the stoich point of the fuel can change quite a bit as you'll boil off the volatile compounds. I'll see if I can dig up his post about it.

Edit: See the chart about fuel pumps on the second post down: https://www.facebook.com/search/str/pau ... ywords_top

Sam

[ChrisAudi80]

Paul Yaw of Injector Dynamics did some testing a while back on fuel temperature. I don't believe it affected timing much, but it has an effect on fuel mass delivered due to the density change. He also found that once it reaches a certain temperature, the stoich point of the fuel can change quite a bit as you'll boil off the volatile compounds. I'll see if I can dig up his post about it.

Edit: See the chart about fuel pumps on the second post down: https://www.facebook.com/search/str/pau ... ywords_top

Sam

Second post down is by our dear friend Richard Cranium talking about techno music.

Other than that, point taken about density change and volatile compounds.

So let's say that in a hot climate with the sun beating down and the fuel being heated by the pump and the returned fuel from a hot engine, the temperature would reach 60-70C. Is that an issue with E85?

[123quattro]

What is your fuel pump setup? If you are running a big pump all the time that will really heat the fuel up. If that is the case putting a PWM controller on the pump can help under low load, or running a small pump with a big secondary one that comes on under boost.

If you are running a normal pump disregard.

On my 928 it has the fuel system tied into the HVAC system. There is a block where both the compressor outlet and return fuel pass. It's up on the firewall behind the engine. It cools the fuel anytime the AC is on. Of course my AC doens't work so I took all that stuff out because racecar.

[ChrisAudi80]

What is your fuel pump setup? If you are running a big pump all the time that will really heat the fuel up. If that is the case putting a PWM controller on the pump can help under low load, or running a small pump with a big secondary one that comes on under boost.

If you are running a normal pump disregard.

On my 928 it has the fuel system tied into the HVAC system. There is a block where both the compressor outlet and return fuel pass. It's up on the firewall behind the engine. It cools the fuel anytime the AC is on. Of course my AC doens't work so I took all that stuff out because racecar.

I am running an AEM 320lph E85 pump with a stock K03 AEB. Not much to get excited about. However, because my fuel tank is SS sitting in the spare tire well in the 80 and my trunk lid is black with the Thai sun beating down on it, it gets quite hot.

I am still thinking about running the return line through a small oil cooler like rad with a fan. Is there a big difference between 35C fuel and 60C fuel?
I do have a good spot for the cooler.

[ChrisAudi80]

YAY! Found the article explaining fuel temp relevance.

http://injectordynamics.com/articles/in ... -feb-2013/

"Gasoline, ethanol, methanol, toluene, etc all have a similar CTE value of approximately .001 per degree Celsius. This means that for every change in temperature of 1 degree C, our volume will change by a factor of .001, which you math geeks will recognize as 1/10 of one percent per degree Celsius.

Let’s apply this to a sample 1000 cc/min injector, and calculate the mass flow rate at a few different temperatures.

We start by looking up the density of ethanol, and we find that the density of .789 is stated at a temperature of 20 degrees C.

Multiplying our 1000cc/min by ethanol’s specific gravity of .789, we get a mass flow rate of 789 grams per minute at a fuel temperature of 20 degrees C. Now let’s consider what happens after a half hour of driving in stop and go traffic when the fuel temperature climbs to 70C, using the following formula:

(((Reference Temp – New Temp) * CTE) + 1) * Reference Density = New Density

Using the values from our example:

(((20 – 70) * .0011) + 1) * 0.789 = 0.746

As a result of the density changing from 0.789, to 0.746, our injector mass flow rate has now gone from 789 g/min (13.2 g/sec, or 104.4 lbs/hr) to 746 g/min (12.4 g/sec, or 98.7 lbs/hr)

Putting that to numbers that we can more easily relate to, our air fuel ratio of 11.5 to 1 has just become 12.2 to 1 and would need a trim of approximately 6% to bring it back in line. Not the end of the world as long as our tune is conservative, but potentially ugly if we are cutting it close."

[ringbearer]

good maths, lol

Sounds like a fuel cooler will be helpful as well as a good fuel temp to enrichment map.

[ChrisAudi80]

good maths, lol

Sounds like a fuel cooler will be helpful as well as a good fuel temp to enrichment map.

Yep. Quite applicable to my situation, I believe.

If there is a 6% difference between 20c fuel and 70c fuel, that will have impact on my tune. It would not surprise me if my fuel hits 70c+.
Getting the correct sensor would be a good idea, but 180 bucks plus shipping and tax makes it pricy.

[ringbearer]

$200 is better than a melted motor

[ChrisAudi80]

$200 is better than a melted motor

More like 250, but true.

[ChrisAudi80]

Got this fuel cooler from a buddy of mine today. Don't know what its from, but it is meant for fuel cooling.

Will instal it soon in the cavity where the old fuel tank was, close to the access cover and see what happens.

[Fundahl]

Good info here! I will be running a flex fuel/temp sensor as well on my s6.

[loxxrider]

Nice score!

[ChrisAudi80]

Nice score!

Thanks, I thought so too. It kinda looks like of of those PC heat sinks. I might attach one of those small PC fans to it (or 2), if I can find a 12v version.
Patch it into the fuel pump power lines.

I would like to get one of those IR thermometers. you know, they look like a plastic pistol. What are they called?

With regards to fuel trim adjustments, would the ethanol content and temperature adjustments not be superfluous by just using EGO correction?

[loxxrider]

I don't know the "official" name of those thermometers, but I think everyone knows what you're talking about when you say IR thermometers. Best $20 gadget ever!

Yeah, EGO correction should indeed take care of it, although having the ability to adjust timing based on the fuel temp could also be nice. However, I'd think you already have MAT compensation on and that probably dials it back plenty enough to compensate for both things when its hot out.

How hot does it get there? I can't imagine it being too much worse than FL in the summer. 95 F with 100% humidity...

[DE80q]

Most PC fans are 12v. At least here in the states. I used to test car stereos with an old PC power supply.