Me and a friend are building a small surge tank for a setup which will accomidate a couple pumps mounted internally in the tank.

Question I have is about baffling inside the surge tank for where the feed port will come into the surge tank from the main tank, and also the return port from the regulator back into the surge tank?

First of all anyone done one of these or have experience with one, did you find baffling a good idea/ nessessary? If so, any suggestions for effective baffling you have seen or used that you would not mind sharing?

Any input welcome.

 

i think the point of having a surge tank is so that you don't need baffling in it. it should be full at all times.

 

Right, most times it will be full... well other than when the level drops under heavy load when its drawn down a bit. My understanding of adding some baffling was more about the issue with fuel being pumped into it/ returned to it without baffling would put air bubbles into the fuel and churn it up.

 

if it is setup with the proper size lines and pumps it should never have air in it. just don't put all the inlets and outlets next to each other and it should be fine.

 

Ok, thats why I am asking... it will have the ports across the top of the tank side by side but spaced apart a bit.

Thanks for you help thus far, I appreciate the info as I am not all that familar with what works in practice vs my theory and understanding from what I read.

 

What if the return from the engine went to the bottom of the surge tank? Then the fuel returning would be coming in below the fuel level and there would be no chance of it being aerated. The only issue I could see here is having a bit of "head pressure" from trying to push the fuel back into the surge tank, and that's just a matter of making an adjustment on your FPR. In fact, the only one that I would put at the top of the surge tank would be the one going back to the main tank. The other 3 could be at the bottom without issues, right?

 

The surge tank should have the fittings from top to bottom like this.

Top
Return to tank
Return from fuel rail/feed from tank
Feed for fuel rail.

 

The pumps will be mounted in the tank and pickups will be low point in the tank. I was thinking a couple pieces of small diameter tube will be extending down from the top of the tank, where the fittings will be, midway into the tank for the feed from the main tank and rail return to surge tank. Overflow return to main tank I will leave at top of course.

That way I can have all my fittings still in the top for how I am limited to fit/ mount the tank (very space limited) but have them at the correct positions internally to not cause issues.

 

If it is "drawn down" and fills with air, that means your fuel cell pump is sucking mostly air. It's a good idea to have the same or larger pump for the fuel cell pump - since it doesn't deal with pressure, it always flows more.

This is how a surge tank should be designed:


The fuel cell pump and fuel rail replenish the surge tank. The extra is dumped into the main fuel cell. If the fuel cell pump cavitates or sucks air, that will be pumped into and immediately out of the surge tank since it flows more than the fuel rail pump. They are generally designed like a swirl pop to keep air at the top.

 

But in reality the only line that NEEDS to be at the top is the return from the surge tank back to the main tank.

 

Hiprofile. Thats exactly how it will be setup but just 2 pumps from the surge tank.

When I ment the fuel level in the tank will be drawn down, it should not be to the level of the pumps sucking dry. I ment more like with an air gap in the top of the tank, the refilling and returning fuel falling down from the top un baffled would push air into the fuel like when you pour water from a water bottle into a partially filled glass of water, the falling water being added pushed alot of air bubbles into the whole glass full (if that makes sense).

I think the above mentioned tubes extending down into the fuel on the fill and return ports should stop this but originally I was thinking baffling.