Do I need an inline fuel pump also?
- Thread starter taylorsomero86
- Start date
nosmatt
Founding Member
I WOULD say nope. but maybe........ really depends. but, with gt40 heads, and a b303.... you will probobly be fine. i would not run it at 11 psi tho..... not long for this worl with that much strain on the belt.
i would invest in a boost a pump... after using one, i have come to really appreciate em....
good luck
i would invest in a boost a pump... after using one, i have come to really appreciate em....
good luck
You've got to be careful when you're talking about adding an inline pump. Most of them are not capable of producing volume in excess of the intank pump unless fuel pressures get to the point where the intank is unable to keep up. In other words: a 255L intank fuel pump will flow more gas at stock fuel pressures than an inline T-Rex will at stock fuel pressures. It's only when fuel pressures are significanlty above normal (usually the result of using an FMU) that most inlines have any real effect other than just heating the gas. With your 42s, I doubt that you will run into that problem. A 255 at or near stock fuel pressures should be plenty for what you're trying to do providing you plan a custom tune with your combo.
89MustangGX
I have nothing productive to add!
I have been looking into this off and on, and there is a High Pressure version of the 255 pump that seems to be a better way to go for not running an inline pump. 
This may help some:
Flow rates--
13 volts
psi --------------------- 40----- 60-- -- 80
255 low pressure in LPH---233-----199----162
255 High pressure LPH ----244-----217----180
T-Rex LPH----------------162-----137----108
Keep in mind that the T-Rex is a 'flow through' pump. It will run but will not provide much in the way of increased fuel flow until the backpressure starts to overcome the in-tank pump's ability to keep up with volume demand at increased pressures. Even with the two pumps working together, you shouldn't expect much more flow than what you see for the T-Rex. The big advantage and why folks use the T-Rex is that it, in conjunction with the in-tank pump, do not loose as much flow as the pressure increases compared to the intank pump on it's own. They're sharing the load and are better able to keep a more elevated flow when the pressure rises.
You can also see that the high pressure 255s provide a little bit more flow at a given voltage and pressure but that they loose just about as much as the low volume pumps do as pressure increases. To me, they're not worth the extra expense unless your ability to flow the correct amount of fuel is JUST under what it needs to be and a hair more volume will do it for you. If you need more gas than that, you might want to consider a remote pickup in the tank and an Aeromotive (or similar) stand alone external line pump. The Holley inline pumps a bit more gas (about 30 lph @40 psi) and don't fall off as much as the typical intank pumps do but... keep in mind that two fuel pumps typically add more heat to the fuel than a larger more efficient single pump.
Edit: I should also note that with a T-Rex... until you start getting to the point where the flow rates get close to the inline pumps max output volume, that it's usually ends up being an inline restriction for your intank pump.
Flow rates--
13 volts
psi --------------------- 40----- 60-- -- 80
255 low pressure in LPH---233-----199----162
255 High pressure LPH ----244-----217----180
T-Rex LPH----------------162-----137----108
Keep in mind that the T-Rex is a 'flow through' pump. It will run but will not provide much in the way of increased fuel flow until the backpressure starts to overcome the in-tank pump's ability to keep up with volume demand at increased pressures. Even with the two pumps working together, you shouldn't expect much more flow than what you see for the T-Rex. The big advantage and why folks use the T-Rex is that it, in conjunction with the in-tank pump, do not loose as much flow as the pressure increases compared to the intank pump on it's own. They're sharing the load and are better able to keep a more elevated flow when the pressure rises.
You can also see that the high pressure 255s provide a little bit more flow at a given voltage and pressure but that they loose just about as much as the low volume pumps do as pressure increases. To me, they're not worth the extra expense unless your ability to flow the correct amount of fuel is JUST under what it needs to be and a hair more volume will do it for you. If you need more gas than that, you might want to consider a remote pickup in the tank and an Aeromotive (or similar) stand alone external line pump. The Holley inline pumps a bit more gas (about 30 lph @40 psi) and don't fall off as much as the typical intank pumps do but... keep in mind that two fuel pumps typically add more heat to the fuel than a larger more efficient single pump.
Edit: I should also note that with a T-Rex... until you start getting to the point where the flow rates get close to the inline pumps max output volume, that it's usually ends up being an inline restriction for your intank pump.
1of2000
New Member
very interesting... i had to upgrade my intank to a 255lph when i added 42# inj but i left the T-rex from vortech in place.
Should I have removed it? Is it doing nothing?
Idle FP = 31psi
11#boost = ~40ish psi
Should I have removed it? Is it doing nothing?
Idle FP = 31psi
11#boost = ~40ish psi
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