Jump to content

Surge tank only with returnless system


turbogrill
 Share

Recommended Posts

Hi,

 

Car is a 2006 NC Miata.

 

We need some more fuel but moving to a fuel cell is too much for us right now, and stock fuel system works very well and is safe. We have very little slosh or starvation, no puking fuel, no fuel smell, etc.

A few times we have ran out of fuel and limped back. It sucks because any chance of doing well is gone (took me well over 10min at COTA to finish the lap....)

 

This is the plan, our MC MIata has return less with the OEM pump and regulator in the tank:

- Use a Radium FST-R (integrated pump and regulator, $500)

- Connect a fuel pressure switch with warning light between the OEM tank and the surgetank. When the light is on you have about 0.5 gal (finish the lap and pit or cruise in 5th).

- Leave the OEM tank alone and just cut the rubber hose from the tank and feed it into the surge tank 

- Connect the surge tank "out" to the engine and fuel rail  

- Connect the surge tank overflow to the fill tube (cut and add a T connection, avoids drilling in the tank)

 

Do you think the above would be safe? The surge tank would sit in the trunk, we already have isolated the trunk from the cockpit (since the filler tube is there).

 

It's a lot of money for just a tiny bit of fuel but I think the key is that we can really use all the fuel instead of guessing and it should reduce the risk of runnnng out of fuel. 

Link to comment
Share on other sites

53 minutes ago, turbogrill said:

- Use a Radium FST-R (integrated pump and regulator, $500)

 

I saw a post a few months ago where @Hi_Im_Will was offering a ready made surge that looks like this one, his might save you some money and he is a fellow champcar racer.  Just something to check before you sink $500 in that one.  Do a search on his user name, it will probably show up.

Link to comment
Share on other sites

1 minute ago, Burningham said:

 

I saw a post a few months ago where @Hi_Im_Will was offering a ready made surge that looks like this one, his might save you some money and he is a fellow champcar racer.  Just something to check before you sink $500 in that one.  Do a search on his user name, it will probably show up.

 

Awesome! thanks

Link to comment
Share on other sites

This has been in our car for 5 years now. You'll need an external high pressure fuel pump and a fuel pressure regulator for the returnless system, so factor those into the total price.

 

https://www.ebay.com/itm/2L-Aluminium-Universal-Complete-Fuel-Surge-Tank-2-Litre-Swirl-Pot-System-kit-BL/271611587297?epid=24008368668&hash=item3f3d4feae1:g:lw0AAOSwEK9UHCTJ

Link to comment
Share on other sites

13 minutes ago, enginerd said:

This has been in our car for 5 years now. You'll need an external high pressure fuel pump and a fuel pressure regulator for the returnless system, so factor those into the total price.

 

https://www.ebay.com/itm/2L-Aluminium-Universal-Complete-Fuel-Surge-Tank-2-Litre-Swirl-Pot-System-kit-BL/271611587297?epid=24008368668&hash=item3f3d4feae1:g:lw0AAOSwEK9UHCTJ

2 liters is over the rules capacity 

Link to comment
Share on other sites

Can you just run a low pressure pump from the surge tank to the main tank?  When the car skips you need to turn on the low pressure pump, let it transfer 1/2 gallon to the main tank and get you into the pit?

 

I haven't read the rules on this, but it seems simpler.

Link to comment
Share on other sites

20 minutes ago, MMiskoe said:

Can you just run a low pressure pump from the surge tank to the main tank?  When the car skips you need to turn on the low pressure pump, let it transfer 1/2 gallon to the main tank and get you into the pit?

 

I haven't read the rules on this, but it seems simpler.

You have it backwards. Low pressure (or high pressure) from main to surge. Pump surge to fuel rail. 

Edited by enginerd
Link to comment
Share on other sites

43 minutes ago, hotchkis23 said:

Could have got him a year ago....2L came into the rules last year....

Unless I had some form of displacing block in there....

 

Or perhaps a cautious engineer would measure the exact capacity of the tank rather than relying on the listed capacity from an eBay seller....

  • Like 1
Link to comment
Share on other sites

1 hour ago, MMiskoe said:

Can you just run a low pressure pump from the surge tank to the main tank?  When the car skips you need to turn on the low pressure pump, let it transfer 1/2 gallon to the main tank and get you into the pit?

 

I haven't read the rules on this, but it seems simpler.

 

How would you get fuel into the surge tank? It would work very well for the first stint but then you would have to fill both of them.

I guess you could tap of a little from the fill tube some how.

 

Or you have two pumps, one to prime it after you fueled (would suck fuel from main) and one to move it when empty. 

 

The benefit would be you don't have to fiddle with any of the existing pluming, you would just tie into the overflow / vent hose.

 

54 minutes ago, enginerd said:

You have it backwards. Low pressure (or high pressure) from main to surge. Pump surge to fuel rail. 

 

He is thinking of it as a second tank, when the main tank is empty you move fuel from surge tank to main tank.

 

Could even have my race capture pro turn on the fill pump when fuel pressure is low.

Edited by turbogrill
Link to comment
Share on other sites

4 hours ago, turbogrill said:

He is thinking of it as a second tank, when the main tank is empty you move fuel from surge tank to main tank.

Yes, but that is absurd. The main benefit of a surge tank is that it keeps you fueled in corners. Maybe he’s got a really good fuel setup that draws every drop of fuel even while cornering until the tank is completely dry. For the rest of us, we have 2L surge tanks to be a buffer when the main tank still has some fuel but it isn’t being sucked up by the pump. 

  • Like 2
  • Thanks 1
Link to comment
Share on other sites

On 4/16/2020 at 4:25 PM, enginerd said:

This has been in our car for 5 years now. You'll need an external high pressure fuel pump and a fuel pressure regulator for the returnless system, so factor those into the total price.

 

https://www.ebay.com/itm/2L-Aluminium-Universal-Complete-Fuel-Surge-Tank-2-Litre-Swirl-Pot-System-kit-BL/271611587297?epid=24008368668&hash=item3f3d4feae1:g:lw0AAOSwEK9UHCTJ

You are forgetting that his factory returnless system doesn't have a provision for the surge tank "overflow" back to the main tank.  Hence the name ;)

Link to comment
Share on other sites

On my system, "returnless" refers to the fuel rail, not the surge tank plumbing.

 

I have the overflow from my surge tank going back to the fuel cell, keeps the surge tank topped up. I use a vent off the top of the surge tank to a vent back into the cell.

Link to comment
Share on other sites

7 hours ago, ABR-Glen said:

You are forgetting that his factory returnless system doesn't have a provision for the surge tank "overflow" back to the main tank.  Hence the name ;)

I wasn't forgetting this. You have a high pressure pump, then a FPR. FPR branches to rail and back to surge tank. Surge tank has two inlets and two outlets (in from tank, in from FPR excess, out to high pressure pump, out to return to main tank).

 

On 4/16/2020 at 10:19 AM, turbogrill said:

- Connect the surge tank overflow to the fill tube (cut and add a T connection, avoids drilling in the tank)

I think his original post with the idea of the overflow from surge tank (return to main tank) is good. A 'T' connection to some part of the tank filler system could work. 

Link to comment
Share on other sites

6 hours ago, enginerd said:

I wasn't forgetting this. You have a high pressure pump, then a FPR. FPR branches to rail and back to surge tank. Surge tank has two inlets and two outlets (in from tank, in from FPR excess, out to high pressure pump, out to return to main tank).

 

I think his original post with the idea of the overflow from surge tank (return to main tank) is good. A 'T' connection to some part of the tank filler system could work. 

OK, I thought you were proposing an alternate design, not just a cheaper surge tank.

 

7 hours ago, mender said:

On my system, "returnless" refers to the fuel rail, not the surge tank plumbing.

 

I have the overflow from my surge tank going back to the fuel cell, keeps the surge tank topped up. I use a vent off the top of the surge tank to a vent back into the cell.

I don't know if there is any standard definition of what a "returnless" system is. I think all the systems in the scope of this discussion use bypass style regulators to set the fuel pressure, and of course that regulator can be located anywhere after the pump it just changes how the bypassed fuel is routed.

 

I am not familiar with the NC Miata fuel system, but I assume based on his description that the regulator is located inside the tank and therefore there is no return line and no associated penetration in the tank to send bypass fuel to if the regulator was moved outside the tank. Such a system would be more "returnless" than the one you describe which still has all the same components as a "return(?)" fuel system, just re-arranged. Maybe yours should be called a "short-return" or a parallel system vs. a serial system of having the regulator after the rail?

Edited by ABR-Glen
Link to comment
Share on other sites

The older fuel systems circulated fuel through the fuel rail and returned the excess fuel back to the tank. The newer ones don't, hence the returnless moniker. The location of the bypass fuel mechanism is before the fuel rail, so as you noted can be anywhere including in the fuel tank.

 

I made my surge tank using the top of an Astro fuel tank (recirculating system). I cut out the part that the cartridge slips into and fabbed my 2 litre tank around that. That is fed with a low pressure lift pump and has a simple overflow back to the fuel cell via the vent tube that normally receives the return fuel from the fuel rail.

 

The high pressure pump in the surge tank goes to a Corvette regulator/filter which has a return line to the surge tank. The line from the regulator/filter feeds the fuel rail with no return/recirculating fuel.

 

Edited by mender
  • Like 1
Link to comment
Share on other sites

2 minutes ago, turbogrill said:

Why did you use a Corvette regulator and not something aftermarket and adjustable/easy to use.

 

I find all OEM stuff to be in odd shapes and difficult to use out side of it's intended use case.

55 psi output, small and reasonably priced. Not adjustable but cheaper because of that. The ECU was programmed to use a constant 55 psi.

 

WIX 33737.

  • Like 1
Link to comment
Share on other sites

5 hours ago, turbogrill said:

Why did you use a Corvette regulator and not something aftermarket and adjustable/easy to use.

 

I find all OEM stuff to be in odd cool shapes and difficult giving choice how to use out side of it's intended use case.

Fixed to reflect differing build styles.

 

Similar to Mender, we used most of a factory Infiniti sending unit and duplicate factory lines on our surge tank, in a strategic layout, this leaves some redundancy if the swirl pot pump fails, the original lines can be quickly moved back to the tank skipping the surge. 

  • Like 2
Link to comment
Share on other sites

5 hours ago, Team Infiniti said:

Fixed to reflect differing build styles.

 

Similar to Mender, we used most of a factory Infiniti sending unit and duplicate factory lines on our surge tank, in a strategic layout, this leaves some redundancy if the swirl pot pump fails, the original lines can be quickly moved back to the tank skipping the surge. 

 

I like that redundancy!

  • Like 1
Link to comment
Share on other sites

2 hours ago, ABR-Glen said:

If i moved my OEM regulator from the outlet of the fuel rail to the inlet end, but still had a return hose running the length of the car, you would call it a returnless design?

I would, because the fuel doesn't return once it gets to the fuel rail. The early EFIs used the recirculating fuel to cool the fuel rail and to reduce the effect of heat soak on hot starts.

https://www.aa1car.com/library/returnless_efi.htm

Third paragraph.

 

That's the way I look at it 'cause I'm an engine guy, and when I plumb a new fuel system in an old vehicle I do an external (to the tank) pressure regulator and non-PWM pump. :)

Edited by mender
Link to comment
Share on other sites

19 minutes ago, mender said:

I would, because the fuel doesn't return once it gets to the fuel rail. The early EFIs used the recirculating fuel to cool the fuel rail and to reduce the effect of heat soak on hot starts.

https://www.aa1car.com/library/returnless_efi.htm

Third paragraph.

 

That's the way I look at it 'cause I'm an engine guy, and when I plumb a new fuel system in an old vehicle I do an external (to the tank) pressure regulator and non-PWM pump. :)

How well does it recover from a gulp of air when its real low?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...