lake speed

unless you are blocking the pv's off I would run boost reference power valves as well as a boost reference fp regulator. it takes a little time but this set up can be tuned to idle around the dock as well as run wide open. make sure you have enough pump to supply enough base fuel psi and 1 pound of fuel per 1 pound of boost. I have a lot of experience with the blow through stuff on both cars and boats and it does and will work if set up properly.

Fenderjack

iTrader: (2)

Thank you.. The carb will most def be done by somebody who is FAMILIAR doing these style carbs.. The pump shouldn't be a problem( big bosch pump) My main concern was with the way I had the pic drawn up.. Just wanted to be sure it will work this way before we start gather parts and all.. I still run a vacuum line into the blower box/ intake manifold, not to the carb itself, or can it be done any one of them ways..


John jr

tinman565

Well...I guess I was sorta right (my setup was for a traditional blower)...lol.

lake speed

I always ran c and s specialties carbs. I made 1249 rwhp with an 8.2 deck height sbf with a 106 mm turbo with one of their carbs the car was occasionally street driven and ran 5.0's in the eighth on 325 radials. all of his was done with no intercooler. the way that you have drawn the fuel system will work but are you running the procharger carb box or a hat on the carb? how much boost do you plan on making?
this may help you in making sure that you have enough pump.

First, you'll need to calculate how much pressure you need. You'll need to know a few things first: 1) Max boost you plan on running, and 2) Regulator type. Why does the regulator type matter? Because if you are using a dead-head style regulator, you must have an additional pressure differential across the regulating orifice to be able to control fuel pressure. Generally, this will need to be 10-15 psi. If you’re running a bypass or return style regulator, you will not need this extra pressure, because the regulating orifice is on the return side of the system. There will also be losses in the system from fuel lines and fittings, as well as acceleration losses. You’ll need more pressure at the pump to account for these losses. You can generally assume these losses to be around 5 psi. If there are a lot of bends in the system, your losses may be more. With these things in mind, let’s calculate how much pressure we need.




P = (base fuel pressure) + (boost pressure) + (line losses) + (10-15 psi if running a dead head regulator)




So, for a blowthrough engine with a bypass regulator making 20 psi boost and a base fuel pressure of 7 psi we have:




P = 7psi + 20psi + 5psi = 32 psi





If we ran a dead-head regulator, we would need 10-15 psi more than that to have adjustability at the regulator. So if we run a bypass regulator, we’ll need 32 psi and if we run a dead-head regulator, we’ll need at least 42 psi. Now lets figure out how much fuel flow we’ll need.

How much fuel we need will be dictated by how much Horsepower we plan on making. In our case, lets say we are shooting for an even 1000 Hp. This number needs to be the Hp at the crank. At this point, I need to introduce some IC engine fundamentals. Every engine has what is called a BSFC, or Brake Specific Fuel Consumption. This number is the amount of fuel it takes, in pounds, to support 1 Hp for 1 Hour. The units for this number is (lbs/hr)/Hp. For a naturally aspirated engine, the BSFC will be around .45-.55 (lbs/hr)/Hp. For a turbocharged engine it will be around .55-.6 (lbs/hr)/Hp. A supercharged engine will be around .6-.65 (lbs/hr)/Hp because of the added Hp it takes to spin the supercharger.

To determine how much flow we need, we simply take our target Horsepower and multiply it by the corresponding BSFC. I generally use the high end of the scale just to get a conservative estimate. So, for our 1000 Hp turbocharged engine we have:




Fuel required = (target Hp) * (BSFC)

Fuel required = 1000 Hp * .6 (lbs/hr)/Hp = 600 lbs/hr



Note: Many fuel injection pumps use lbs/hr as a measure of flow. If you want to know the flow in gal/hr, simply divide the lbs/hr figure by 6, since gasoline weighs about 6 lbs/gal.

At this point, we need a pump that flows 600 lbs/hr (or 100 gal/hr) at 32 psi with a return style regulator or a minimum of 42 psi with a dead-head regulator. Now we need to start looking at fuel pump performance curves to see what they flow at specific pressures. For example, If you look at the flow curve for the Aeromotive A1000 pump below, we can see that at 32 psi the pump flows ~600 lbs/hr at +12V. This pump would work on a system with a bypass regulator. However, at 42 psi, the pump only flows ~550 lbs/hr, which is not quite enough at +12V for a dead-head setup. The pump will work for either system at +13.5V, but you would need to be sure the pump was running at 13.5 volts at WOT, which may not be possible if you’re running a lot of electrical accessories, like electric fans, electric water pump, fuel pumps, etc. It’s best to err on the side of caution with fuel systems, so if you were to run a dead-head regulator, a larger pump would be in order.

MILD THUNDER

iTrader: (3)

Your sketch should work fine. I would lose the red and yellow fuel lines though. not uscg approved.

Fenderjack

iTrader: (2)

Thank you, still app your input...

yah I kinda thought it might be a issue with them too..

THANK YOU..

As in bypass regulator you are referring to a return( fuel return line out of the reg)??? excellent info.. The fuel pump used will be a bosch pump, will flow ruffly 75gph.. Boost will be 12-14 psi.. The fuel line routing it self will be a pretty strait shot, with the only fittings going into the reg, then out then into the box, then Y into each side of the carb...

John jr

tinman565

75 gph ????? Thats gotta be a typo.

Fenderjack

iTrader: (2)

Is that not enough??? I am using this same pump on my vehicle, it makes well into the 5xx whp range?? Does a crab'd set up need that much more pump over a fuel injected set up???


John jr

ezstriper

not sure about the bosch pump, I run the aeromotive A1000 pump, their regulator that is boost referenced for that pump, #10 line from tank, thru fram H/P filter, regulator, #6 lines to box, #8 return as speced by aeromotive, my carb is a 950 from prosystems, the regulator increases fuel pressure 1lb for each psi of boost...vacume line to carb box

Scarab28

I still run a vacuum line into the blower box/ intake manifold, not to the carb itself, or can it be done any one of them ways..

The vacuum line MJSTcome from the Box. The box willl generally have approx 3 more lbs boost than the intake.