Fuel system and fuel pick up questions.
08-02-2012, 09:36 PM
#1
Fuel system and fuel pick up questions.
Looking to upgrade my fuel systems, who has been through this before? The boat has always had decent sized engines to my knowledge. The pick ups look to be 1/2" but unsure of that, the rest of it is all 3/8 and #6. The plans are to ditch the holley electrics and goto SX pumps and boost reference regulaters. After speaking on the phone to the shop where I would purchase it all through, I was told i need at least 5/8 pick ups, then after that I can go #8 all the way to my fuel logs. Drilling and tapping on the tank maybe a option, I dont think I want to weld new bungs in the tank with it in the boat, that sounds like a bad combo. What are everyones thoughts on this? Engines are BBC with 8-71s and dual pro systems, they are pretty mild and detuned currently down to 700ish. Future plans will be to add intercoolers and better heads, but I just want reliable, not any more serious HP. Will the 1/2 inch pick ups work? The shop told me it would wear the pump out faster, thanks!
08-02-2012, 09:40 PM
#2
Registered
I think 1/2 should be fine, I run about 700hp in a procharged HP500 use a 1/2 pickup, into #10 braided, H/P filter, aeromotive A1000 pump, A1000 boost referenced regulator, #6 to carb, and #8 return to tank, running a return system is the key...Rob
08-03-2012, 02:17 AM
#3
That setup should be plenty for 700 hp. Also look to keep the fuel lines as short as you can. I can't believe some of the rigging I have seen, with like -6 running all over the boat to transfer valves, etc. On my new setup, I went -12 straight up out of new 5/8 pickups, and have only about 4' of USCG Parker hose to get to Hardin 3/4" filters mounted on the engines. It is aeroquip -12 out of the filter to the Aeromotive pump, and -10 from there to the rails. Return is a -8. This is an EFI system that supports just over 1000 hp.
08-04-2012, 11:59 AM
#4
I have most of the parts ready to rig this new fuel supply, however the instructions for the boost reference regulator say it should NOT come off the intake port. I had the understanding that was where it would go from. Where else would it come from? 8-71 roots with dual prosystem carbs? Anyone? Thanks!
08-06-2012, 05:59 PM
#6
Platinum Member
Platinum Member
Whoa!
Do not use a boost referenced regulator for a drawthru carb system (supercharger BETWEEN the carbs and motor).
You run 5-7 psi of pressure to the carbs whether you're on boost or not. All you need to do is make sure you are able to maintain 5-7 psi at full load and wide open throttle.
You don't need nearly as much pump as you would if your pressure requirements were higher. The A1000 I hear mentioned flows enough fuel for 1,100 hp in a carb motor with 7psi requirements, but only 800hp for an EFI motor with 35+psi requirements.
If you boost reference your carbs, then that has nothing to do with feed line pressure. And if your carbs are not yet set up for boost referencing, and you don't understand boost referencing any more than it appears, then you either need to run them "as is" or send them to somebody to have them prepped and rejetted for a boost reference signal - they will also give you instructions on how to plumb the reference port.
As far as the pump and regulator, if you go with "huge pumps" then you will have to run a bypass back all the way to the tank. If you run "enough" pump without overkill, then you may be able to bypass back to the pump inlet if you add fuel coolers. This reduces the need to add more ports to your tank.
AND if you run a good mechanical pump on the motor, then you can run a small electric booster instead of a power hungry, heat generating, plumbing nightmare of a pump.
Make sure you get your ducks in a row before you go spending money on things that cause problems you don't currently have.
MC
Do not use a boost referenced regulator for a drawthru carb system (supercharger BETWEEN the carbs and motor).
You run 5-7 psi of pressure to the carbs whether you're on boost or not. All you need to do is make sure you are able to maintain 5-7 psi at full load and wide open throttle.
You don't need nearly as much pump as you would if your pressure requirements were higher. The A1000 I hear mentioned flows enough fuel for 1,100 hp in a carb motor with 7psi requirements, but only 800hp for an EFI motor with 35+psi requirements.
If you boost reference your carbs, then that has nothing to do with feed line pressure. And if your carbs are not yet set up for boost referencing, and you don't understand boost referencing any more than it appears, then you either need to run them "as is" or send them to somebody to have them prepped and rejetted for a boost reference signal - they will also give you instructions on how to plumb the reference port.
As far as the pump and regulator, if you go with "huge pumps" then you will have to run a bypass back all the way to the tank. If you run "enough" pump without overkill, then you may be able to bypass back to the pump inlet if you add fuel coolers. This reduces the need to add more ports to your tank.
AND if you run a good mechanical pump on the motor, then you can run a small electric booster instead of a power hungry, heat generating, plumbing nightmare of a pump.
Make sure you get your ducks in a row before you go spending money on things that cause problems you don't currently have.
MC
08-06-2012, 07:06 PM
#7
Mcollinstn, Thank you! I bought all this from a local shop(they recommended the reg.), so now I have some very expensive and fancy regulators I probably do not need. I have no provisions for a mechanical pump on my blocks, or else I would have already went that route. Electric is all I can run. The holley pumps were not worth a ****, and they were falling off pressure. I may have more pump than I need now but I am plumbing in a #8 return line from the bypass regulator. So with all that being said, I should just put the plug in the regulator where the boost reference port is, I may return them for another bypass regulator, or just use them in case of future upgrades where I might need it, again, thank you.
08-07-2012, 04:44 PM
#8
Platinum Member
Platinum Member
Decent regulators start at $60. Great ones can be had for $90. If you spent a lot more than that, you might consider trading them back in for credit and saving cash.
But if you want to keep them, there is nothing wrong with running them. You just don't connect the reference line to anything. You do need to keep it open to atmosphere, though, as plugging it can cause some variation of pressure with elevated temperature.
Technically, that open port on the regulator does not satisfy the USCG regulations for a fuel device in an enclosed engine compartment - you would have to run a long hose to one of several acceptable locations - AND it still wouldn't be USCG approved since it has no approval tag on it.
BUT
You can run it with nothing on it, or you can cut a piece of sock and wrap it over the barb and zip tie it. If you got nice regulators with 1/8" female threaded ports on them for reference, you can install a pneumatic muffler which looks nice, serves the purpose, and is cheap.
With big pumps, you will be diverting a LOT of fuel back thru the return almost ALL the time.
The fuel picks up a significant amount of heat through the pump, and long runs at low cruising speed will cause the fuel in your tank to get hotter than you probably want - especially the "alcohol enriched" crap we have these days which is on the edge of vaporlock even on a mild day.
The best solution would be a variable speed controller for your pump. You can use a PWM electronic pulse controller without harming your pump, but you cannot use a rheostat or something like that.
Keep tabs on your fuel temp in the tank.
MC
But if you want to keep them, there is nothing wrong with running them. You just don't connect the reference line to anything. You do need to keep it open to atmosphere, though, as plugging it can cause some variation of pressure with elevated temperature.
Technically, that open port on the regulator does not satisfy the USCG regulations for a fuel device in an enclosed engine compartment - you would have to run a long hose to one of several acceptable locations - AND it still wouldn't be USCG approved since it has no approval tag on it.
BUT
You can run it with nothing on it, or you can cut a piece of sock and wrap it over the barb and zip tie it. If you got nice regulators with 1/8" female threaded ports on them for reference, you can install a pneumatic muffler which looks nice, serves the purpose, and is cheap.
With big pumps, you will be diverting a LOT of fuel back thru the return almost ALL the time.
The fuel picks up a significant amount of heat through the pump, and long runs at low cruising speed will cause the fuel in your tank to get hotter than you probably want - especially the "alcohol enriched" crap we have these days which is on the edge of vaporlock even on a mild day.
The best solution would be a variable speed controller for your pump. You can use a PWM electronic pulse controller without harming your pump, but you cannot use a rheostat or something like that.
Keep tabs on your fuel temp in the tank.
MC
08-14-2012, 12:43 PM
#9
Well I returned the regulators today, what would you or anyone recommend for a good regulator that i can run a #8 return off of? Looking at the CP performance site and I am not sure what I should order. The past holley black pumps would fall off at cruising speed. The boat seems to like cruising at around 3600 rpm, the engines just run perfect there and the boat runs nice at that speed. But after 33-3400 it appears to fall off fuel pressure when trying to cruise there for any extended time. All my wiring to feed the pumps is short and minimum of 10 gauge, if need be I can increase that too.
08-15-2012, 05:39 PM
#10
Platinum Member
Platinum Member
Holley "Blacks" are good for 120 GPH with a fuel path that has minimal restrictions.
75 GPH "at the carb" is good for around 800 hp so if you are running out of fuel, then it's likely an obstruction in your fuel path (filter/separator may be too small, pickup may be too small, etc).
If this is the case, then a giant fuel pump will only incrementally improve your situation.
You may have to play DR Frankenstein on this setup.
Add a tee after the pump before the regulator.
Add a tee between the regulator and the filter/separator.
Add a tee between the filter/separator and the carbs.
Plumb in a fuel pressure gauge at the first tee and watch it as you speed up the boat, and go into fuel starvation. See if the pressure drops below your regulator setting.
Then move to the second point and repeat. Keep doing this until you find the place where the pressure drops. The restriction is between the test points.
MC
75 GPH "at the carb" is good for around 800 hp so if you are running out of fuel, then it's likely an obstruction in your fuel path (filter/separator may be too small, pickup may be too small, etc).
If this is the case, then a giant fuel pump will only incrementally improve your situation.
You may have to play DR Frankenstein on this setup.
Add a tee after the pump before the regulator.
Add a tee between the regulator and the filter/separator.
Add a tee between the filter/separator and the carbs.
Plumb in a fuel pressure gauge at the first tee and watch it as you speed up the boat, and go into fuel starvation. See if the pressure drops below your regulator setting.
Then move to the second point and repeat. Keep doing this until you find the place where the pressure drops. The restriction is between the test points.
MC
