Return line to surge tank, or cell?
#1
Mad Man
Thread Starter
Return line to surge tank, or cell?
I know nearly everyone returns their fuel to the surge tank, but to me this is counter-intuitive. That is the hottest fuel, and much of it goes straight back to the engine. Other than not scavenging the last the drop of fuel, why not return to the cell instead? Thanks, Carl
#2
If your high-pressure pump outflows the lift pump, your surge tank will always be empty. Also, if the lift pump inlet is uncovered for some time, the high-pressure pump would quickly drain the surge tank. Better to return the fuel to the surge tank. And have an overflow line from the surge tank that returns the fuel to the main tank (replacing hot fuel overflowed back to the main tank with cooler fuel provided by the lift pump).
-Max
-Max
#3
Mad Man
Thread Starter
O'K, Don't you think it would be nearly impossible for a 255lph pump @~5psi to get outflowed by an Aeromotive A1000 @ ~75psi?
Seperate question. If I am running parralel -6 lines out of a Y block, can I use -8 for the main line (main external pump to rails), or do I need a -10? Also, Can I use a -6 return, or do I need to go up to a -8.
Third question, I am using one port on the FPR(aeromotive) for a FP gauge. Can I feed both rails back into a single port on the FPR, or should I use one for each rail, and then tee off one line for the gauge?
so, are -6 sufficient for the feeder pump, or do I need -8.
I ask these questions due t having everything to run the set-up as follows.
Bosch in tank(911 turbo pump)/-6 to surge, -6 back to cell
-8 out of surge to -10 to Big SX filter
-(?) to front, Y block to (2)-6 to rails
Y block(or two seperate lines) to FPR all -6
-6 return to surge.
I can do -10 to the rails, and -8 return with seperate -6 to the FPR. I can also do all -10 surge/pump/filter/front to rails/ -6 to Y block-6 to FPR--8 return to surge. Max what whould you do?
Seperate question. If I am running parralel -6 lines out of a Y block, can I use -8 for the main line (main external pump to rails), or do I need a -10? Also, Can I use a -6 return, or do I need to go up to a -8.
Third question, I am using one port on the FPR(aeromotive) for a FP gauge. Can I feed both rails back into a single port on the FPR, or should I use one for each rail, and then tee off one line for the gauge?
so, are -6 sufficient for the feeder pump, or do I need -8.
I ask these questions due t having everything to run the set-up as follows.
Bosch in tank(911 turbo pump)/-6 to surge, -6 back to cell
-8 out of surge to -10 to Big SX filter
-(?) to front, Y block to (2)-6 to rails
Y block(or two seperate lines) to FPR all -6
-6 return to surge.
I can do -10 to the rails, and -8 return with seperate -6 to the FPR. I can also do all -10 surge/pump/filter/front to rails/ -6 to Y block-6 to FPR--8 return to surge. Max what whould you do?
Last edited by Carl Byck; 03-13-05 at 08:28 PM.
#5
Originally Posted by Carl Byck
O'K, Don't you think it would be nearly impossible for a 255lph pump @~5psi to get outflowed by an Aeromotive A1000 @ ~75psi?
I understand the concern about hot fuel, but I think if you setup the surge tank properly, it will get a continuous supply of cool(er) fuel from the lift pump to keep the temps in check. Routing the return line back to the main tank just seems like a recipe for certain starvation of your high-pressure pump to me.
-Max
#6
Mad Man
Thread Starter
Good enough for me Max, I plan on monitoring fuel temps anyway, fuel coolers are cheap enough, they just strike me as vulnerable to damage. Any thoughts on the myriad of line size variations?
#7
Originally Posted by Carl Byck
Seperate question. If I am running parralel -6 lines out of a Y block, can I use -8 for the main line (main external pump to rails), or do I need a -10? Also, Can I use a -6 return, or do I need to go up to a -8.
Here are the cross-sectional areas for different line sizes (IDs from my Pegasus catalog for Goodridge or Aeroquip lines):
size, ID, flow area
-6, 0.34", 0.09"^2
-8, 0.44", 0.15"^2
-10, 0.56", 0.25"^2
So, two -6 hoses are a little bigger than one -8, and are a good bit smaller than one -10. My guess is that feeding the y-block with a -8 hose would be fine, but it probably depends on how much total flow you need. I have heard that using very large (-10) supply lines can itself cause some problems due to the voluminous (and heavy) column of fuel in the line when you accelerate. I'd try the -8 supply line.
One issue that you can run into if the return line is restrictive is that you'll get elevated fuel rail pressures when the injectors aren't flowing much (like at idle). I would be inclined to use a -8 return line to match the supply line for this reason.
Third question, I am using one port on the FPR(aeromotive) for a FP gauge. Can I feed both rails back into a single port on the FPR, or should I use one for each rail, and then tee off one line for the gauge?
so, are -6 sufficient for the feeder pump, or do I need -8.
I ask these questions due t having everything to run the set-up as follows.
Bosch in tank(911 turbo pump)/-6 to surge, -6 back to cell
-8 out of surge to -10 to Big SX filter
-(?) to front, Y block to (2)-6 to rails
Y block(or two seperate lines) to FPR all -6
-6 return to surge.
I can do -10 to the rails, and -8 return with seperate -6 to the FPR. I can also do all -10 surge/pump/filter/front to rails/ -6 to Y block-6 to FPR--8 return to surge. Max what whould you do?
I ask these questions due t having everything to run the set-up as follows.
Bosch in tank(911 turbo pump)/-6 to surge, -6 back to cell
-8 out of surge to -10 to Big SX filter
-(?) to front, Y block to (2)-6 to rails
Y block(or two seperate lines) to FPR all -6
-6 return to surge.
I can do -10 to the rails, and -8 return with seperate -6 to the FPR. I can also do all -10 surge/pump/filter/front to rails/ -6 to Y block-6 to FPR--8 return to surge. Max what whould you do?
-Max
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#8
Mad Man
Thread Starter
Your final thought is where I really thought I would start. I have a couple different FPRs, I'll see if one has a fourth port. Thanks for your thoughts, Carl
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