I recently made an order for a walbro hp pump and didn't think much about it vs. a lp pump. I did a little research and seems like this may be a problem. From what I understand having a high pressure pump when your not under high boost applications can supply to much fuel. I'm only running 21-22 psi tops right now. I plan on going with a meth kit so I ordered the hp pump figuring it would be good for the future. Any insight? Thanks

 

EVO's have a set up where the voltage that goes to the pump is in two stages. The first stage is low voltage and the pump only works at a certain percentage, then when in high boost the voltage is kicked up and the pump works harder.....

If you are tuned for the pump even at 21psi you will be fine....

 

Cool, I appreciate the help. I'm still learning very much about my car. I'm not installing it until right before I get tuned so that should work out fine.

 

At 20 psi, the 'LP' pump flows about 10% less than the HP pump. As the manifold pressure is increased, the disparity becomes larger.

http://www.lightningmotorsports.com/walbro.htm

Always be sure to get the 'HP' pump.

 

Thanks ted the write up really helped a lot, I'm not so worried I ordered the HP pump now.

 

I was to understand that the LP and HP pumps flowed the same untill higher pressures.

The only difference in the pumps a valve is crushed. And from what I understand is a fire hazard.

Theres a pretty big thread on nasioc about it. DB was buying the pumps from another vendor and reselling so the story is. I believe its just the pressure release valve is crushed.

I look for the pumps to be taken off the market soon.

 

Walbro makes these pumps in two different versions, the "LP" and the "HP". The "HP" pump is intended for forced induction applications, and when one purchases a "Walbro 255 lph pump", he wants the Walbro "HP" version.

Neither of these refer to the modified pump sold by BR, which is not something Walbro makes or advocates. Don't get confused.