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Flavio
Samba Member
Joined: May 14, 2008
Posts: 414
Location: Madeira Island, Portugal
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 Posted: Mon Dec 10, 2012 12:30 pm Post subject: |
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Glad you've solved your problem. The orifice thing makes sense.
Wondering if this device would work with an electric pump...
Considering that a mechanical pump sucks the fuel from the fuel suply line, (and you have the "T" connected to the suply line), probably the pump will also suck fuel from the "T" through the 125 jet.
BUT, an electric pump will push the fuel in the two lines (suply and "return") and probably this will not work...?
Have you some feedback from others about using this "T idea" with an electric fuel pump ?
Thanks in advance.
Note: I'm using a low pressure electric pump and regulator and the fuel always passes the needle valve when the engine is hot... |
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Altema
Samba Member
Joined: June 20, 2010
Posts: 2904
Location: Lower Michigan
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| Posted: Mon Dec 10, 2012 6:00 pm Post subject: |
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| Flavio wrote: |
Glad you've solved your problem. The orifice thing makes sense.
Wondering if this device would work with an electric pump...
Considering that a mechanical pump sucks the fuel from the fuel suply line, (and you have the "T" connected to the suply line), probably the pump will also suck fuel from the "T" through the 125 jet.
BUT, an electric pump will push the fuel in the two lines (suply and "return") and probably this will not work...?
Have you some feedback from others about using this "T idea" with an electric fuel pump ?
Thanks in advance.
Note: I'm using a low pressure electric pump and regulator and the fuel always passes the needle valve when the engine is hot... |
You are correct that the relief line will be under suction after the orifice. That, combined with the pressure before the orifice, helps with the fuel cooling process. As mine stands right now, the base of the carb is the coolest component in the engine compartment due to the pressure drop, and the fuel pump is the next coolest.
This setup is not intended for an electric pump, BUT, if you did want to use it, then the pressure relief line would need to T back into the supply line before the electric pump. Your regulator should be after both T's, but before the carb. That reminds me, someone else is waiting for a diagram!
Paul |
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Alpha_Maverick
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Joined: May 01, 2011
Posts: 626
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| Posted: Mon Dec 10, 2012 9:02 pm Post subject: |
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If you're using a regulator, just switch to a return-style, and have the return go back to the inlet of the pump. Done.
_________________
| Alstrup wrote: |
hmm well, wiggly  I like 5,5inchers in the rear at least. |
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Flavio
Samba Member
Joined: May 14, 2008
Posts: 414
Location: Madeira Island, Portugal
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| Posted: Tue Dec 11, 2012 7:44 am Post subject: |
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Thank you both for your informations.
Because I have the electric fuel pump under the fuel tank, I think, that in order to avoid running an extra return fuel line, probably I can do something simple and similar to the figure below ?
Just a short bypass between the pump inlet / outlet ?
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Dale M.
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Joined: April 12, 2006
Posts: 20379
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Tue Dec 11, 2012 9:05 am Post subject: |
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| Flavio wrote: |
Thank you both for your informations.
Because I have the electric fuel pump under the fuel tank, I think, that in order to avoid running an extra return fuel line, probably I can do something simple and similar to the figure below ?
Just a short bypass between the pump inlet / outlet ?
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Should work... Remember orifice in bypass setup is very small so it only drops off pressure over time (a minute or two) when pump is off....
Only problem I see is if regulator maintains pressure between itself and carb ( check valve or whatever in regulator) to prevent pressure in line from regulator to crab from bleeding back to supply side of regulator....
To big a orifice in bypass restrictor may cause fuel starvation at carbs because any fluids will flow through path of least resistance....
Also this is still at experimental stages, your results may be different from others...
Dale
_________________
“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.
"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
============================================================
All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ... |
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Altema
Samba Member
Joined: June 20, 2010
Posts: 2904
Location: Lower Michigan
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| Posted: Tue Dec 11, 2012 9:37 pm Post subject: |
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| Dale M. wrote: |
| To big a orifice in bypass restrictor may cause fuel starvation at carbs because any fluids will flow through path of least resistance.... |
Yes, especially with dual carbs and a performance build. The bypass orifice can be very small and still be effective.
| Dale M. wrote: |
| Also this is still at experimental stages, your results may be different from others... |
Always something to keep in mind. Although others have asked for information, I have not seen anyone post results with an electric pump, and it's not likely that an electric pump will benefit much from cooling. The primary benefit will be from preventing line pressure buildup regardless of the source, since the fuel pump will usually maintain pressure. Also as Dale mentioned, the pressure regulator will be an unknown factor... unless it's the return style. |
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Altema
Samba Member
Joined: June 20, 2010
Posts: 2904
Location: Lower Michigan
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| Posted: Tue Dec 11, 2012 9:41 pm Post subject: |
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| Alpha_Maverick wrote: |
| If you're using a regulator, just switch to a return-style, and have the return go back to the inlet of the pump. Done. |
Bingo! That would be the best of both worlds.  |
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Alpha_Maverick
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Joined: May 01, 2011
Posts: 626
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| Posted: Wed Dec 12, 2012 5:04 am Post subject: |
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flavio: just remove your deadhead regulator on the engine, and install a bypass regulator near the fuel pump. This way, the fuel line going to the carb has regulated pressure, and you have the bleed down you want when the pump is off.
Only downside is that the reg is hard to adjust, but that's not something you should do frequently. 
_________________
| Alstrup wrote: |
| hmm well, wiggly I like 5,5inchers in the rear at least. |
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Flavio
Samba Member
Joined: May 14, 2008
Posts: 414
Location: Madeira Island, Portugal
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| Posted: Wed Dec 12, 2012 5:17 am Post subject: |
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Thanks Maverick. That's a very good idea.
Is it dificult to find a good quality Low pressure regulator (2 or 3 psi) with a return port ? |
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Alpha_Maverick
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Joined: May 01, 2011
Posts: 626
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| Posted: Wed Dec 12, 2012 10:08 am Post subject: |
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In portugal, I have no idea. In the US, I'd just use Summit Racing.
_________________
| Alstrup wrote: |
| hmm well, wiggly I like 5,5inchers in the rear at least. |
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Flavio
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Joined: May 14, 2008
Posts: 414
Location: Madeira Island, Portugal
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modok
Samba Member
Joined: October 30, 2009
Posts: 26785
Location: Colorado Springs
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| Posted: Wed Dec 12, 2012 12:29 pm Post subject: |
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| Flavio wrote: |
Thank you both for your informations.
Because I have the electric fuel pump under the fuel tank, I think, that in order to avoid running an extra return fuel line, probably I can do something simple and similar to the figure below ?
Just a short bypass between the pump inlet / outlet ?
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Many electric fuel pumps (such as the carter rotary/cb) already HAVE a dump regulator built in, so there is no need for this.
This bypass idea is only needed with diaphragm type pumps that are pressure regulated by spring pressure. A dump type regulator also does not need this. |
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Flavio
Samba Member
Joined: May 14, 2008
Posts: 414
Location: Madeira Island, Portugal
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| Posted: Wed Dec 12, 2012 4:04 pm Post subject: |
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So, I'm in need of some clarification here, my ignorance.
Modok: By "dump regulators" do you mean the ones that have some kind of pressure relieve/return (opposite to the ones named "dead head regulators") ?
My car has a Carter "Carotor" fuel pump and a low pressure "dead head Holley regulator". |
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modok
Samba Member
Joined: October 30, 2009
Posts: 26785
Location: Colorado Springs
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| Posted: Wed Dec 12, 2012 5:32 pm Post subject: |
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Ok. Carter makes 50 different pumps under the name "carotor" Some have regulators built in and some do not. I expect your does, since otherwise a deadhead reg would not make any sense.
Anyway, whatever pressure the fuel pump says it puts out is.... what the max pressure should be. If the pressure is higher the fuel will flow back to the tank.
If you have a type of pump that has no regulator built in, that's not gonna work! it will either burn out or the hoses will explode.  |
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Flavio
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Joined: May 14, 2008
Posts: 414
Location: Madeira Island, Portugal
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modok
Samba Member
Joined: October 30, 2009
Posts: 26785
Location: Colorado Springs
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| Posted: Thu Dec 13, 2012 2:09 am Post subject: |
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If yours has the attached fuel filter I'd expect it has a regulator, but I am not sure.
You must check the part number to see what it is for sure.
The one usually sold for VW use puts out 3-4 PSI, and is # P60504
They also sell one that puts out 6 PSI that looks exactly the same. |
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krp33
Samba Member
Joined: December 28, 2009
Posts: 11
Location: South Jersey
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| Posted: Thu Dec 13, 2012 8:41 am Post subject: |
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| I don't understand. If the car has an operational fuel tank vent, there should be no pressure build uo in the fuel system after shut down? I bet the tank vent is plugged. |
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Dale M.
Samba Member
Joined: April 12, 2006
Posts: 20379
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Thu Dec 13, 2012 9:33 am Post subject: |
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| krp33 wrote: |
| I don't understand. If the car has an operational fuel tank vent, there should be no pressure build uo in the fuel system after shut down? I bet the tank vent is plugged. |
Think of mechanical pump and [check]valve in pump and fuel between pump and carburetor....
Dale
_________________
“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.
"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
============================================================
All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ... |
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Altema
Samba Member
Joined: June 20, 2010
Posts: 2904
Location: Lower Michigan
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| Posted: Sat Dec 15, 2012 9:48 am Post subject: |
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So, with the light shed here by others, I have learned that:
1. An electric pump with a built-in dump regulator makes this mod un-necessary.
2. A return style regulator used with any type of pump makes this mod un-necessary.
3. This mod will not help with fuel percolation caused by the carb fuel bowl(s) being too hot.
4. This mod is most effective with mechanical pumps, or electric pumps with no dump regulator.
5. This mod will also provide some benefit when placed after a deadhead style regulator.
Thanks again guys for all the input and info  |
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Altema
Samba Member
Joined: June 20, 2010
Posts: 2904
Location: Lower Michigan
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| Posted: Sat Dec 15, 2012 10:09 am Post subject: |
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And for future reference, here's a diagram of how the mod was installed for daily use. Remember that this only affects the line from the fuel pump to the carb, not the line from the tank to the pump.
For those requesting info on dual carb setups, remember that the pressure regulator mentioned in the below diagram is a deadhead.
The mod is not necessary with return style regulators.
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