Project Cool Fuel Take: 1

[Milford Cubicle II]

This is a project I've been pondering for quite a while now and I finally overcame the hardest part of it... actually building the prototype. I was bored and got sick of just thinking about it and started digging in. My goal was to not only solve the infamous heat soak/rough idle issue in the 00'/01' xj's but to actually cool my fuel enough to see a slight to moderate performance gain. My thoughts being that not only is cooler fuel more dense therefore easier to meter (which should make a smoother running motor), but that the fuel might actually cool my intake air temps as the chilled fuel atomizes in the incoming intake air. Here was the plan, to run a heat exchanger system consisting of 1/4" OD copper tubing out of my coolant reservoir, coil it around my a/c air dryer (that canister that gets near or below freezing on the outside) acting as the actual heat exchanger, then being routed to my fuel rail where it will coil around it acting as another heat exchanger where hopefully the heat from the fuel rail will be transfered through the copper tubing and into the coolant where it will be deposited back into my coolant reservoir where it will make the trip again.

Pics.

The line where I cut the top off to install the in-tank pump.

Reservoir with the top off.

Two possible positions for the pump outlet. I chose the one on the right.

The 360gph bilge pump I picked up from West Marine for $20 in position. Waaaay overkill for the flow I need, which is why I had to build a flow valve w/a return that works exactly like a returnless fuel system like most newer cars utilize (including xj's). Think of it like an adjustable fuel pressure regulator.

This is what the system will look like inside the reservoir. I know it's probably way over-engineered but I need to be able to regulate the flow to find peak effeciency then I will just size the pump accordingly and/or use a simple fixed pressure regulator consisting of a pvc endcap with a certain sized hole drilled into it. Again, think returnless fuel pump set up, this is exactly the same.

Sorry the pic's blurry but this is the assembly installed in the reservoir.

Side shot. And the other side of the valve that's not attached to anything is actually gunna be plumbed back into the reservoir and that's gunna be my return from the "regulator". After I took these pics I changed the placement to simplify things but I haven't taken those pics yet and I'm tired and should've left work about 15 minutes ago so they'll have to wait

Coincedentally those pvc grommets used are actually pcv grommets for an XJ

The first heat exchanger, the copper tubing wrapped around the dryer.

Then insulated.

More pics and info to come if anybody cares but like I said, I've been at work all night and i'm dead tired, goodnight folks! :spin1:

 

[Talyn]

Interesting idea, but unless you run the pump with the engine off I don't think it will help much with the heat soak issue.

 

[Milford Cubicle II]

Wrapping and insulating the fuel rail alone will solve the heat soak issue, I'll get the pics up soon hopefully but the fuel rail is wrapped with 3/4" split tube pipe insulation then a layer of reflective header tape.

 

[wolfpackjeeper]

no offense but I think you overthought the shit out of this. Good engineering but make it simple.

I helped a buddy do something similar, his was only meant for the track so the time frame was short. Find a nice metal box of a size you can use. Small ammo tins work great. drill a hole midway up the long side of each end. Build yourself a coil that runs right through the middle, connected to a bulkhead fitting on each end. seal it up and connect the box in the engine bay just before the fuel rail. Finding space is the hardest part. After it is connected, dump a bag of ice and salt in there and top off with water. If you are really high speed you can put dry ice or liquid Nitrogen in there, you just need to vent the case if you do, since they will both sublime to a higher pressure state and burst the box. For super extra coolness, find a nice box that is the size of a small fan style cooler and stick the cooler in there instead, it would give you the room to slide dry ice in each side. Then top it off with the salt water to help with heat transfer.


Keep in mind that on his car and in my Jeep that I plan on doing this in we both have an upgraded fuel pump that spits out more than enough pressure.

 

[CanMan]

Nice to see someone building something, but why not just use one of these? Fill it with ice or dry ice.

 

[Boostwerks.com]

Sounds like a lot of work for nothing. Colder fuel will not solve your idle problem either.

To each their own I guess.

 

[wolfpackjeeper]

Nice to see someone building something, but why not just use one of these? Fill it with ice or dry ice.

got a link for that, price depending it would be worth it.

 

[Milford Cubicle II]

Sounds like a lot of work for nothing. Colder fuel will not solve your idle problem either.

To each their own I guess.

A lot of work for nothing? If fuel cooling doesn't work then cool cans are a scam and a lot of drag car guys are wasting their money on them. Besides, the 4.0 fuel rail is notoriously hot and is an excellent candidate to benefit from a fuel cooler.

So basically, and I should've mentioned this earlier, but I just wanted to replace a "cool can" with something permanent. The dryer's doesn't have to be recharged, refilled or replaced. Plus, filling a can with ice several times a day, to me, though fine for track purposes seems pretty ghetto fab for a daily driver. Also, in the future I plan on replacing the first heat exchanger (the one around the air dryer) with an actual coaxial liquid to liquid heat exchanger using a seperate refrigerant system or possibly a thermo-electric system.

Oh yea, and it did solve my idle issues

 

[CanMan]

got a link for that, price depending it would be worth it.

http://www.jegs.com/i/Mr-Gasket/720/1350/10002/-1

 

[ZomBrady]

Wow.

Think about the HP loss from running your AC and you have your answer that this is futile.

 

[Talyn]

I think I missed the part of having to run the AC to actually make this functional. But yeah, if that is the intended idea then this will create quite a performance drop.

Maybe just make a smaller completely separate cooling system for the fuel rail... like something similar in size to what is used on water cooled computers. That way it won't be using the already engine temp coolant.

 

[Milford Cubicle II]

Wow.

Think about the HP loss from running your AC and you have your answer that this is futile.

Ya know what really restricts HP? Not being at WOT. And at WOT the compressor clutch disengages anyways so there's no HP loss from running your a/c during WOT. So I think what you might've meant to say was torque. And just from the butt dyno so far, I can tell you that i've actually seen quite an improvement. Whether or not it's enough of an improvement to overcome the drag from the compressor I can't tell yet, but I figure if my a/c is gunna be on anyways, I might as well enjoy more power. Another option I have is simply turning the a/c off and still reaping the rewards of the cooler because the dryer stays colder for a very long time, especially now that it's nicely insulated.

Maybe just make a smaller completely separate cooling system for the fuel rail... like something similar in size to what is used on water cooled computers. That way it won't be using the already engine temp coolant.

Bingo:

Also, in the future I plan on replacing the first heat exchanger (the one around the air dryer) with an actual coaxial liquid to liquid heat exchanger using a seperate refrigerant system or possibly a thermo-electric system.

 

[bigdaddyjlove]

This really seems like alot of work for something that could be cured with some exhaust wrap.

Am I missing something here?

 

[wolfpackjeeper]

heat soak through the manifold from the block can still be a problem.


and exhaust wrap will rot out the manifold in a hurry.

 

[Talyn]

I was thinking wrapping the injector manifold and injectors with some form of heat insulation, like exhaust wrap. Not sure if that is what he meant though. After all, that is what the TSB for the hot heat soak issues on 00-01s does to the #3 injector.

 

[Milford Cubicle II]

This really seems like alot of work for something that could be cured with some exhaust wrap.

Am I missing something here?

This is an active fuel cooling system, not just insulation (though that's part of the system).

There's a lot of power to be gained by cooling your fuel, that's the point and that's the main reason I did this. I'll have to borrow my buddy's tuning software so I can data log and see just how effective it is but like I said before, I can definately feel a seat of the pants improvement but there's really no point in throwing out butt-dyno numbers.

 

[Talyn]

What do you expect to see in data logging?

 

[Mesh]

It’s a strange project. Do you have a picture of everything installed and how much has the fuel temperature been lowered?

 

[Milford Cubicle II]

What do you expect to see in data logging?

Torque and HP curves? I was thinking IAT's too but the IAT sensor is upstream from the injectors anyways so that won't do me much good.

It’s a strange project. Do you have a picture of everything installed and how much has the fuel temperature been lowered?

I'll get more pics up soon but now I'm in the process of replacing the pump with an actual fuel pump. Bilge pumps aren't continuous duty I shoulda seen that coming. Of course I did accidentally leave it on all night :doh: I'm just lucky my jeep wasn't on fire cause I hadn't even fused it yet :banghead:

I'll get an idea of how much I'm cooling the fuel by measuring the coolant temperature difference across the fuel rail. I'll adjust the flow rate to maximize the ΔT then measure it in GPH.

 

[Talyn]

OBDII won't display HP and torque curves.