how do i know if i need a high or low pressure fuel pump? and also if i need high or low impedence fuel injectors? do i just need to match the two or what. also is 42# injectors too much for my car. heres the mods: RGR stage 2 heads, SLP CAI, BBK 52mm....soon to be 58mm, hooker long tubes w/ y-pipe, msd wires, been bore out to a 355 with keith black internals, and im sure i missed a few things. any info helps. thanks

 

When I replaced my fuel pump the cost difference for a heavy duty pump (maintains flow rating under higher pressure) was very little. Go with the Racetronix setup as it is easy to install and quality parts. Your setup doesn't need high pressure, but give yourself some margin.

The stock PCM will only drive high impedance injectors (stock injectors are 24# high impedance). 42# injectors will give you room to grow and the tuners I've spoken with feel they're easy to tune.

 

[QUOTE=OBE1 95Z28;4424492]When I replaced my fuel pump the cost difference for a heavy duty pump (maintains flow rating under higher pressure) was very little. Go with the Racetronix setup as it is easy to install and quality parts. Your setup doesn't need high pressure, but give yourself some margin.[QUOTE]


what is the advantage of going with the racetronix set-up from thunder racing over the walbro pump kit from new era performance? their both 255 lph walbro pumps. thanks

 

you should be fine with the stock system if your staying N/A at 355ci. now if your boosting, stroking, etc. the stock system needs to be upgraded, bigger injectors, higher volume fuel pump....

 

[QUOTE=97ramairta;4424511][QUOTE=OBE1 95Z28;4424492]When I replaced my fuel pump the cost difference for a heavy duty pump (maintains flow rating under higher pressure) was very little. Go with the Racetronix setup as it is easy to install and quality parts. Your setup doesn't need high pressure, but give yourself some margin.I made the mistake of buying the Walbro 255lph HD pump. It doesn't fit properly in the fuel bucket located in your gas tank. Racetronix modifies the Walbro pump to properly use the fuel bucket.

 

ok i was just curious because for having the same exact pump the prices are extremely different. thanks

 

A "low pressure pump" (7-10psi) is used with a carb. A "high pressure pump" (40-80psi) is used with fuel injection. You need a pump capable of pushing at least 190 LPH at 43.5psi to support 500 flywheel HP, for example.

Your stock injectors are high impedance (12-15 ohms). Your stock PCM can not drive low impedance (2-5 ohms) injectors, unless you add an external box to drive low impedance injectors. If you aren't going over 42#/HR, you don't need to complicate things with low impedance conversion.

Get a good estimate of your flywheel HP (or what you expect it may be in the future with additional mods), and multiply it by 0.07 That will get you in the ball park on the required injector size.

 

He was referring to the "high pressure" and standard pressure capable Walbro pumps. The HP version having a high relief valve setting that makes it suitable for forced inducted applications, especially situations where an FMU is used. The standard pump is fine up to about 60 psi.

 

the guy i bought the car from said it dynoed 426 FWHP. im going to be upgrading a few things like the headers, TB, intake, new tune, and what not so i want to make sure im getting enough fuel. i did the math and 42 lb injectors should support about 600 fwhp. so im guessing them are a safe bet to use so i can have some room to grow on w/o changing injectors 10 times. thanks for all the info guys.

 

Would have been nice if he actually said that.