just wanted to know which i should order, and why the high pressure is the same price, is there a big difference?

Thanks,
Alex

 

I'm about to pick up a Walbro as well and have the same question. Anybody have some insight as to which pump is best for the evo?

 

You definitely want the HP (High Pressure) version.

Why?

Normally aspirated engines never see intake manifold pressure above ambient ("0"), so the pump never needs to provide greater than the base FP to keep the pressure across the injectors constant.

With forced induction engines, the fuel pressure must keep pace with the manifold pressure in order to keep pressure across the injectors constant, such that the rail FP is always equal to ambient + manifold pressure. In other words, for every psi of manifold pressure, the rail FP must be increased by a psi to keep the injectors going. This makes it more demanding on the pump.

Regular pump = NA engines

HP pump = forced induction engines

 

HP for the added insurance

 

Def high pressure, especially for the same price!

 

A regular Walbro 255lph at 30psi boost and 12.5V flows 147lph.

A Walbro 255lph HP at 30psi boost and 12.5V flows 189lph.

That is a 29% difference. For the mathematically challenged, that means one supports 550whp, and the other 390whp at that boost pressure. Which would you feel is more appropriate?

I think that should clarify the difference well enough.

 

good info ted. had to LoL at that though!

 

So, how do we know which WALBRO we have installed in tank? Is there a different part number for a HP vs. a non HP? TedB always gets me worried with his caveats, damn!

 

The part numbers are different.

GSS307, GSS315, and GSS317 are regular 255 lph models.
GSS340, GSS341, and GSS342 are high-pressure models.

The only difference between the three in each case are the connections.

 

Thanks, TedB

 

absolute?

 

Thanks TedB! High Pressure Walbro on order!