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Here's an easy to make surge tank


strotter

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NO!

Don't put LN2 into the tank, the rapid expansion and chilling may dessicate the tank but the cooling (if corked decently) can suck the tank down like a beercan and will definately frost the exterior and cause moisture formation in just about any climate! Besides, it's not needed.

 

A good purge will dry it out, and then if Argon follows it will work nicely for welding without using too much gas.

 

But LN2 on the sound deadening would be KILLER!

 

 

If you have access to the gas at cost, to enhance the dessication of the tank you can make a 'preheater coil' of stainless steel (I guess you could use copper as well)---loop a 1/4" line several times around a small diameter object and run a flame in the center of it from a MAPP or Propane torch. The 'dryness' of the N2 from the bottle will be inanced by the increase in the temperature, allowing it to suck up more moisture and carry it out of the tank. We are talking a fairly low flow rate if you only use a couple of coils---a more densely cpacked coil will of course allow the gas to be heated more efficiently. Hot Gas Purging is a better idea than cool gas purging. Usually this is to make sure no gasoline residues remain, but in this case we're pulling water out.

 

Chances are you will do all your modifications, flush it with acid, dry it out, and then slosh it with the tank coating befroe reinstallation.

 

Purging before welding was the primary focus of my original post, dessication before sloshing may not be required if they use an alcohol-based slushing compound (some aircraft types)---if this is the case, make sure it is compatible with current fuel stocks. I know Aircraft Spruce had an issue with their original compounds when they started oxygenating with Alcohols, and the tank slushing compounds ( some times in place for 15-20+ years!) started coming up due to the alcohol present in the new gasoline formulations. They came out with a new formulation that is not alcohol soluable.

 

Which brings us to dessication for po' folks: If you have 99% Alcohol, splash some in the tank, and drain it out...let it sit in the sun. As a dessication process before slushing (NOT before welding!) that is fairly efficient as the alcohol will suck up the water, and will evaporate without leaving a residue with application of minimal heat.

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=/ guess my tank ain't upto standards.

I think your tank will do just fine. It's a nice piece, you should be commended for your good work. All this talk about 42" tall surge tanks is great, but what you've got there is going to be functional, if less blingy, than some of the alternatives mentioned. If the surge tank is FULL because the low pressure pump keeps it FULL (read HIGH volume pump), then it CAN'T slosh away from the outlet at the bottom. I would use it on my car if I had a fuel injected engine without any hesitation.

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i posted a while back on my surge tank and i had it out today and i took some pics for you guys... not fancy and not pretty but it works and im happy with it... well here are some pics

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its attatched to where my horn used to be

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LOL Tony, I had to think about it for a minute to see what you were saying, or cautioning against.... I was not intending to seal the tank with Ni or NiL in it, rather, just flush with Ni until the tank was judged to be clear of fumes. With a little more thought I realized I could probably just use Co2 to purge AND weld. Not optimal, but it is only the back side of the weld, and the front will still be shielded with argon. As far as heating the gas, wouldn't it be as efficient to heat the tank? (my interest being of course that it would be easy,lol) I was thinking about filling it with Co2 and while it was flushing using a small torch to heat the sides. On a side note, I was discussing this at work, and someone's Uncle is apparently a Fuel Tank Welder... meaning that he suits up, enters a large tank of fuel (gas, diesel, etc) and stick-welds with an application specific filler. I understand the technical safety of the process... still not something I would feel comfortable with, lol.

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Yeah, CO2 will work to dessicate it as well, it's -110, pretty dry!

 

The key is hot gas has more capability to hold water, than cold gas. The cold gas will be 100% Relative Humidity of -110F (for CO2-which is not much water carrying capability at all---it's dry enough to be used in alcohol to dessicate A/C systems in the old days, but that's another discussion) but then heat that same gas to 100Degrees, and it has a R/H of like 1%---meaning it will be able to actually carry out much more water vapor in the purge stream. Basically air can do the same thing---heat your air to 350F, and the air you had in the oven that started at 75 degree 100% RH will be maybe 1% R/H at 350 degrees. That hot air has a great carrying capability to carry the moisture out of the tank, out the purge holes to elsewhere where it will dissipate or condense. Same thing as condensation in an exhaust pipe. As the exhaust cools, it's capability to hold water decreases, and the liquids condense out. Running the engine speed up gets that hot hot hot gas to the tailpipe where it is still less than say 10% R/H, but upon dissipating in the atmosphere and cooling you condense out side the tailpipe. Hot goes out carrying water. If you heat the tank it's similar, but having a warmed cryogenically produced gas to carry out the moisture will be more effective than simply heating it.

 

Back to the Surge Tank Design Discussion, I mentioned the 42" tall tanks as an extreme example. They weren't more than 4" in diameter, so that's about a 10:1Ratio. A 2" diameter pipe would have similar separation at only 20" tall. The big thing to bring away is the taller is it, the better it can separate any air that eventually manages to get into it---and the key to keeping it flooded is to make that return line pass through the surge tank on the way back to the main tank.

 

Someone used a Fish Aquarium Filter Housing---I thought it was brilliant! Matter of fact I helped install one, and damned if it didn't look like it was MADE to house a fuel pump! Anything that is 'drill a few holes and use it' is eminently efficient, simply from a work output standpoint. I'm all for ease of construction, absolutely!

 

BTW, this meshes nicely as a side factoid about the Accumulator/Dryers form AC systems. When they are "Rebuilt" many times they are simply baked at 350+ for three hours. This will dry out totally the Activated Alumina or Silica Gel used in them. As long as it gets corked up well, it will not adsorb any water from the atmosphere. This is the same material that is in compressed air dryers---and those are either regenerated by heating the beds when moisture saturated and then purging them with a 'polishing airflow' from the downstream side of the dryer to bring the beds up to room temperature. Or you can simply 'purge' the saturated tower with about 15% of the output flow from the downstream side of the dryer---and that -40 or -110 degree air will suck out that moisture from the beads and take it out the vent to atmosphere.

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I think your tank will do just fine. It's a nice piece, you should be commended for your good work. All this talk about 42" tall surge tanks is great, but what you've got there is going to be functional, if less blingy, than some of the alternatives mentioned. If the surge tank is FULL because the low pressure pump keeps it FULL (read HIGH volume pump), then it CAN'T slosh away from the outlet at the bottom. I would use it on my car if I had a fuel injected engine without any hesitation.

 

you... i like you :mrgreen:

 

Now, what kind of pump am I looking at to fill this thing? I'd figure a high flow pump for a carb system is a good start? They're relatively cheap too, only thing is, I've seen Walbro EFI pumps at 255lph, and carb type pumps at 125lph, which is just about half the flow of the EFI pump, which is probably what i'll use.

 

Where do we get low pressure high vol pumps, or what's a good place to shop around? quality names?

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Where do we get low pressure high vol pumps, or what's a good place to shop around? quality names?

 

V8 Carburettor Fuel Pumps

 

I have seen mechanical fuel pumps used to flood the electrical pumps' tank...

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  • 6 months later...

Wow! Just saw this thread. I havent been here very long and have been trolling around looking at different threads. It is funny I came across this one because I just finished fabbing my surge tank about 1.5 months ago. Here is the one I made and will be using.

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The reason it has a fuel cap on top is for the days I go to the race track. I disconnect the pump that feeds the surge tank and cap it off, Drain the surge tank (which is only 1 gallon) and then I can fill my surge tank with race gas. This way, I am not introducing street gas with my race gas while I am at the track. I dont have to worry about running my main tank down to vapors just so I can get as much pure race gas to the injectors as possible. When I am done at the track, I just plug everything back up normal and I have my normal surge tank again.

 

I have a 255 walbro feeding the surge tank and a Magnafuel fuel pump pulling from the surge tank. Cant remember the part number for the Magnafuel pump, but it is good for about 1000+ WHP In turbo applications. I dont need all of that but I will need about 800WHP worth.

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  • 1 month later...

I have a really dumb question. I've read several threads on here about surge tanks, seen many pics of similar designs (except the one above), etc.

They all have 1 fitting on 1 end and 3 fittings on the other end. Can somebody PLEASE explain the positioning and where each one leads? All I can figure out is that one is going to the hi-PSI fuel pump, one to the low-PSI fuel pump, and I think one is overflowing back into the fuel tank, but that still leaves one fitting unaccounted for. Maybe I'm just having an "elder moment", but if so it's lasted a couple days now...

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the fitting on the bottom goes to the efi fuel pump. then on top you have one for the return line from the fuel rail. one for the feed like from the high flow fuel pump, and one for the over flow back to the tank

awesome, that makes perfect sense. Thank you!!

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  • 1 month later...

I currently have SUs on my L28/240z. I'm planning on turboing in the near future. Is is possible to use the mechanical fuel pump currently running the SUs as the low pressure pump?

 

I was hoping I could to save some cash and it's also brand new.

 

Thanks guys!

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That's actually a fairly cool idea. I don't see why not off the top of my head, though it might be complex to "be sure of"; you have to guarantee is that the mechanical pump can push as much fuel at "0" head as the motor demands, for all loads and speeds. The difference between the mechanical and an electric pump of course is that the output of the mechanical will vary with RPM; that output will be small at low RPM. The situation you'll need to be careful of is at high load and low RPM, when the mechanical pump is moving relatively little fuel but there's a large demand. What will happen is that the fuel level in the sump will drop as the high pressure pump moves more fuel than the low pressure pump can supply. It doesn't really have to push enough all the time; really all you need to be sure of is that there's enough capacity in there as a reservoir for a long enough time for the mechanical pump to "catch up" with the demand.

 

If you can find some information about the capacity of the mechanical pump at 0 back pressure at some known RPM (and I wouldn't even know where to look for it), you can assume the mass-flow ("m-dot") is linear (zero flow at zero RPM, twice the flow at twice the RPM, etc), and compare that flow rate to an estimate of WOT demand for your particular build at every RPM. It would suck to run out of fuel at high load, which would of course push the motor lean at the worst possible time.

 

Personally, I'd stick with a pair of electrics just for the peace of mind, but making things work is part of the fun of this hobby.

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  • 2 months later...
  • 1 year later...

Sorry to revive such an old thread. This is a great alternative to doing a complete fuel cell swap or running the foam, my only question is do you still have to run the stock evaporator tank if I run this surge tank?

 

FYI, the car I am working with is a '73 240z.

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This setup really doesn't really involve the expansion tank at all; you can keep it or lose it at your pleasure.

 

 

Sweet. Thanks.

 

Another question though, for this surge tank set up, do I just get rid of the sending unit since I am using external pumps? Do I have to modify anything else on my tank?

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