Fuel surge tank design
02-09-2007, 10:51 AM
#1
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Fuel surge tank design
I am currently designing a custom fuel surge tank to use with my new setup and a bosch 044 fuel pump. My only real question is about proper surge tank capacity and design.
Based on looking at the one sold with the AAM stage II kit, it looks like it is 3" diameter tubing and is about 12" long. If it were .065 wall tubing that would have a capacity of approximately 1.27 liters. I've seen alot of other setups around that are 2.0 and 2.5 liter tanks. In my mind, the 1.27 liters should be more than enough, because the walbro 255 alone should always keep it full (not to mention the combined return fuel from the fuel rail that will be supplied to the surge tank). Anyone else have any ideas/comments on the capacity requirements?
The other thing I was thinking (it probably seems like i'm bashing the AAM system or something) is laying that cylinder on its side rather than it standing up on its end, like 99% of the other surge tanks I have seen. It seems like the fuel could slosh to one side of the surge tank much easier with the cylinder on its side (if it just so happened that the tank wasn't full), than it could if it were standing up and had less area to move around, side to side. Just an idea.
I really like AAM's design because it is mounted under the car, rather than inside it like many setups, which is probably a good reason why it is mounted on its side (packaging and whatnot). The only thing I don't like is the price tag...and I know I can build one for much cheaper.
Based on looking at the one sold with the AAM stage II kit, it looks like it is 3" diameter tubing and is about 12" long. If it were .065 wall tubing that would have a capacity of approximately 1.27 liters. I've seen alot of other setups around that are 2.0 and 2.5 liter tanks. In my mind, the 1.27 liters should be more than enough, because the walbro 255 alone should always keep it full (not to mention the combined return fuel from the fuel rail that will be supplied to the surge tank). Anyone else have any ideas/comments on the capacity requirements?
The other thing I was thinking (it probably seems like i'm bashing the AAM system or something) is laying that cylinder on its side rather than it standing up on its end, like 99% of the other surge tanks I have seen. It seems like the fuel could slosh to one side of the surge tank much easier with the cylinder on its side (if it just so happened that the tank wasn't full), than it could if it were standing up and had less area to move around, side to side. Just an idea.
I really like AAM's design because it is mounted under the car, rather than inside it like many setups, which is probably a good reason why it is mounted on its side (packaging and whatnot). The only thing I don't like is the price tag...and I know I can build one for much cheaper.
02-09-2007, 11:47 AM
#2
My internal surge tank in my fuel cell is 3 liters but its a twin internal pump setup and the return dumps into it and overflow just goes back into the rest of the cell. Im sure 1.27 is plenty big but i would feel safer with at least a 2 liter unit.
Last edited by meatbag; 02-09-2007 at 11:54 AM.
02-09-2007, 11:52 AM
#3
The external surge tank is the end-all solution for a race car. I have seen external surge tanks with capacties up to 6L on extreme HP track cars.
The AAM surge tank has plenty of displacement for a street or track car of a certain league, but if you were building an all-out track car on slicks with 600+ HP, than your concerns are extremely valid. You may want to consider a vertically mounted surge can of greater displacement. You could also get into custom shaped surge cans.
Here is how you look at a setup like that.
You have a single walbro filling this can. Since its not fighting any pressure, that single walbro can probably move about 700hp of fuel. Any time your engine is not using enough fuel to max out the walbro filling the surge can, your surge can should remain full at all times. Know what I mean?
This is also very important in the 350z, because you need to be able to send some fuel thru the return siphon in the stock OEM assembly just to keep gas on the passenger side of the tank. So while its typical to have a surgecan overflow going back to the stock pump assembly, its absolutely required in this circumstance and AAM knew that and thus did it.
So also under the same conditions, as long as your engine is not consuming more fuel than the pump filling the can is able to flow, there is going to be surge can overflow returning to the stock assembly to power the siphon that transfers fuel to the pump side of the tank.
Not a bad setup if you ask me - assuming its plumbed and installed how a system like that should be.
The surgecan displacement is your reserve for when you are running your engine harder then your canister fill pump can flow. At this point, the surgecans level will start to fall, and then you have to worry about fuel control. The horizontal tube obviously has its downfall in fuel control over a vertical can - but this design was obviously an understandable compromise for packaging purposes.
Shoot me a PM and let me know what your building when you have a chance, I just had a very interesting idea.
The AAM surge tank has plenty of displacement for a street or track car of a certain league, but if you were building an all-out track car on slicks with 600+ HP, than your concerns are extremely valid. You may want to consider a vertically mounted surge can of greater displacement. You could also get into custom shaped surge cans.
Here is how you look at a setup like that.
You have a single walbro filling this can. Since its not fighting any pressure, that single walbro can probably move about 700hp of fuel. Any time your engine is not using enough fuel to max out the walbro filling the surge can, your surge can should remain full at all times. Know what I mean?
This is also very important in the 350z, because you need to be able to send some fuel thru the return siphon in the stock OEM assembly just to keep gas on the passenger side of the tank. So while its typical to have a surgecan overflow going back to the stock pump assembly, its absolutely required in this circumstance and AAM knew that and thus did it.
So also under the same conditions, as long as your engine is not consuming more fuel than the pump filling the can is able to flow, there is going to be surge can overflow returning to the stock assembly to power the siphon that transfers fuel to the pump side of the tank.
Not a bad setup if you ask me - assuming its plumbed and installed how a system like that should be.
The surgecan displacement is your reserve for when you are running your engine harder then your canister fill pump can flow. At this point, the surgecans level will start to fall, and then you have to worry about fuel control. The horizontal tube obviously has its downfall in fuel control over a vertical can - but this design was obviously an understandable compromise for packaging purposes.
Shoot me a PM and let me know what your building when you have a chance, I just had a very interesting idea.
Last edited by phunk; 02-09-2007 at 11:56 AM.
02-09-2007, 12:19 PM
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Thanks for the further explanation Charles, and I set you a PM.
When I first started looking at systems like this, I thought it was going to be difficult (mostly because I wasn't 100% positive how it worked), but now it seems like with a little planning, it shouldn't be very hard at all.
When I first started looking at systems like this, I thought it was going to be difficult (mostly because I wasn't 100% positive how it worked), but now it seems like with a little planning, it shouldn't be very hard at all.
02-09-2007, 12:21 PM
#6
Yes you will find that its pretty simple. You can pick up the AAM S2 or if you build your own system you just need to pick up our fuel pump output fitting so you can make a nice line to feed your tank, and then send your canister overflow back into the return correction kit that you should have already installed in your pump assembly.
checking PMs now.
checking PMs now.
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03-06-2007, 01:15 PM
#9
Charles hit it on the head. We tested a modified version of AAM's system, that returns the fuel back to the surge tank first, so there are two sources keeping the surge full. It's working nicely on the dyno...with solid pressure after 5 consecutive (3 second rest between pulls) long dyno pulls in 5th gear at 15psi. The final test will be the road course, as this is where I experienced most of my fuel starvation issues.
In a perfect world, a vertical surge tank is more desirable. The challenging, is trying to package that into a street car. I have seen surge tanks mounted in the passenger compartment, but something about 1-2L of fuel inside the cabin scares the crap out of me.
There are always ways to work around it, and make a safe surge setup.
Keep us posted..sounds promising.
In a perfect world, a vertical surge tank is more desirable. The challenging, is trying to package that into a street car. I have seen surge tanks mounted in the passenger compartment, but something about 1-2L of fuel inside the cabin scares the crap out of me.
There are always ways to work around it, and make a safe surge setup.Keep us posted..sounds promising.
03-06-2007, 01:22 PM
#10
I'd feel better if there was a surge tank in some sort of safety box - like a heavy duty battery box sorta thing. Then I'd feel a little better about having it in the rear hatch area of the car.
I'd really like to see one develped. The AAM one only fits a few exhausts on the market
I'd really like to see one develped. The AAM one only fits a few exhausts on the market
03-06-2007, 01:43 PM
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Originally Posted by phunk
sentry65: we have a prototype one that we will be cutting out for a member here as soon as brandon finishes the first small run of twin pumps that are currently in production. It actually goes inside the gas tank. details later
03-07-2007, 06:17 PM
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Originally Posted by phunk
sentry65: we have a prototype one that we will be cutting out for a member here as soon as brandon finishes the first small run of twin pumps that are currently in production. It actually goes inside the gas tank. details later
I know u could do it, u are the fuel man
03-08-2007, 08:01 AM
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Originally Posted by phunk
carlitos you are on the exclusive list of guys to get one of the very first 5. i think i need to buy a whip to motivate brandon to get them done for us!
