learn me surge tanks

so im adding EFI to two different muscle cars. one is going mpfi, the other tbi. 70 duster is going mpfi, 64 el camino going tbi.

anyway, both have factory tanks. single pickup, no baffles. origonally mechanical pumps. both cars are setup to handle well, and both get autocrossed/run around CMP. so starvation will be an issue at some point.

i know the best way to do this is with an intank pump and fuel tank baffles/sump. second best way is the aeromotive drop in baffle/pump assembly, and tanks inc has a version that would come third.

ive been hearing about surge tanks, and doing some looking around. seems like this would be the way to go.

few questions: 1. can i gravity feed a surge tank, with fuel return supplementing the gravity? 2. how well does the fuel return from the surge tank when the fuel tank is above? 3. how big (volume wize) does the surge tank need to be to be effective? 4. any constraints to design of a surge tank? 5. any suggestions for best way to plumb it other than out to pump on the bottom, a return from pump and to tank on top, and feed on top? 6. do i really even need to worry about having surge tanks, or is this an excercise in overkill?

thanks guys Michael

Not the cheapest, but these are available:

http://www.gastanks.com/1964-67-Chevelle-Malibu-w_-Fuel-Injection-Conversion/productinfo/GM-37BFI/

With all that built in.

Additionally, I can't find it now, but there was a fuel injection conversion kit that I saw with a foam cylinder that got stuffed into the pickup hole giving you the surge tank internally. It was pretty slick. I'll keep looking for the link.

Dusterbd13 wrote: few questions: 1. can i gravity feed a surge tank, with fuel return supplementing the gravity?

No. At least, you won't be able to do it unless the surge tank is DIRECTLY below the tank, and the fuel feed comes out the bottom of the tank instead of up through the tom.

2. how well does the fuel return from the surge tank when the fuel tank is above?

No problems at all. How much effort does it take to push fuel through a line at zero PSI?

3. how big (volume wize) does the surge tank need to be to be effective?

The realistic answer is "how long do you expect to pick up air / how much fuel can the engine use?" In reality, half a liter is plenty. My setup is about 700cc. VW units ('86-91 Golf/Jetta) were about one liter.

5. any suggestions for best way to plumb it other than out to pump on the bottom, a return from pump and to tank on top, and feed on top?

I did mine with the feed and return from engine on the side, with the return from the engine at the lowest point. The theory is, I don't want the fuel to get aerated when the surge tank starts running down. It's the difference between fulling a bucket with the hose above the bucket or on the bottom.

6. do i really even need to worry about having surge tanks, or is this an excercise in overkill?

I went for years without one. Then I got tired of the left turn hiccups, which as I got faster, would happen with as much as a half tank in the car. Also I think my ability to eat fuel pumps was down to the pumps cavitating after they sucked air. So I came up with this:

The rattlebox pulls it from the tank and dumps it to the feed 2/3rds of the way up. The bottom line goes to the high pressure pump, the return from the engine goes to the feed 1/3rd of the way up, and the top dumps back to the tank. A VW box wouldn't fit under the car so I invented this rig.

Of course, Edelbrock just came out with a device just for what you're doing. Mounts under the hood, mechanical pump on the engine feeds it, and it has a high pressure/flow pump built in. It's about $550-600 but depending on your shop hourly rate, this may be the cheaper option.

Got it

http://www.carcraft.com/techarticles/1310_aeromotive_phantom_fuel_delivery_system/

This is what I would do in your position.

Aaaaaand, the whole thing is cheaper than the tank AND includes the pump.

http://www.summitracing.com/parts/aei-18689/overview/

A really cheap way for you to do it would be to buy/build a bare tank like this:

http://www.amazon.com/Fuel-Surge-Tank-inch-Round/dp/B00FE6DSBS/

Then run your existing fuel line into it and use an inline pump to feed the engine from the bottom fitting. If it has a return line, run that through the surge tank. It would be full to the brim until your original pump (now the lift pump) starves.

Edited because I forgot you're going to EFI

Post above edited for the 21st century!

This is probably overkill for what you're doing, but there is some good info here on how surge tanks should be setup:

http://www.motoiq.com/MagazineArticles/ID/3312/Project-Rotary-FD-RX-7-Part-3--Fuel-System-Chassis-Side.aspx

Subscribed... Building a surge setup on a couple of my rides is on the to do list.

Buying one of those off Amazon for a bill is a good way to go. Add a $50 low pressure pump from the gas tank and a $75 high pressure pump to the injectors and you're done. Ideally, the incoming fuel should enter at an angle and swirl down/in, not just be dumped straight in. Billzilla used to have a good drawing on how to make one. If I recall, input on the side at the top angling along the wall so the fuel swirls. Output at the bottom to the injector pump. Output at the top for the overflow back to the gas tank.

GameboyRMH wrote: A really cheap way for you to do it would be to buy/build a bare tank like this: http://www.amazon.com/Fuel-Surge-Tank-inch-Round/dp/B00FE6DSBS/ Then run your existing fuel line into it and use an inline pump to feed the engine from the bottom fitting. If it has a return line, run that through the surge tank. It would be full to the brim until your original pump (now the lift pump) starves. Edited because I forgot you're going to EFI

exactly mu thought. i was also planning about a half gallon tank if I can fit it on both cars. figured that I shouldn't run out of fuel except in extreme situations.

and tuna: those were the top two of my three solutions listed. unfortunately, at this stage of the game, they are prohibitively expensive. so not really an option financially. the last systems to sort out prior to either conversion is the supply system. I alrady have a rail mounted tbi pump for the elky, and I think I have one for the duster.

on the elky, I know I have enough room for a 3"x 2' horizontally mounted round surge tank along the frame. pretty sure on the duster I can run a 2"x4' similarly on the duster. have to measure.

im off to read the rx7 article.

home fabbed solutions are DEFINATELY encouraged. my welding sucks, so keep that in mind. and both tanks have a few years on them.

thanks again, guys. thank you for all the input so far. please keep it coming.

I built one out of a large fuel filter and a remote filter mount. Tank pump filled the filter, fuel pump sucked off of it and returned to the tank. Worked like a champ at lemons.

Crappy pictures and it's painted flat black with dirt thrown on it. You don't want "new" stuff under the hood of a Lemons car. The rear lines are the supply and return to the tank. The front line is the supply to the engine, the return from the rail went back to the tank. This let us burn the entire tank in a Civic instead of having to pit at 3/8 of a tank.

The engine pump was mounted under the breather. Also spray bombed flat black.

It's ugly, but it works.

Can you solder copper?

A 12" piece of 2" diameter copper tube. Install a 1/2" or 3/8" outlet near the bottom to flood the FI pump inlet. 1/4" inlet and outlet for the cheapo supply pump and 1/4" or 5/16" return from regulator in the top

I like this idea, I would add that I would turn it sideways so the FI pump inlet is flooded from the clean side and tank return is up on the clean side. This will maintain fuel at the FI pump inlet and purge any air back to the tank. Might be a little small though.

bentwrench wrote: I like this idea, I would add that I would turn it sideways so the FI pump inlet is flooded from the clean side and tank return is up on the clean side. This will maintain fuel at the FI pump inlet and purge any air back to the tank. Might be a little small though.

What you don't see is the center port inside the filter is drilled and tapped for a pickup tube that goes to the bottom of the filter. Turning it on its side would do the same thing, but if the lemons judges questioned it, I wanted it to look as much like a regular filter as possible. Regular filters aren't mounted sideways.

There are Marine canister fuel filters (water separator type) with a fitting at the bottom of the canister.

Take a piece of 1/4" plate steel, cut out two 3.5" circles with a hole saw. In one of them cut another 2.5" circle with a hole saw using the same center hole. Add to that 10" of 2.5" exhaust tubing.

Weld the 2.5" circle in one end of the pipe and the 2.5" ID/ 3.5" OD ring to the other. The other circle is your cap and the hole saw holes are the first couple of holes.

If you really want to do it up right size the works so you can weld the mounting ring from a gas tank to the top. Then a whole in-tank pump assembly can be dropped in and sealed up.

I nominate that ^ for tech tip of the week.