TonyMR2
I found the online fuel calculators such as Raceworks and Injector Dyamics, along with the walbro fuel pump flow charts with pressure drop, very helpful to calculate maximum possible fuel pump flow (at applied pressure).

Claimed pump rating at 500hp rating is basically zero fuel pressure, 8an line matching outlet minimal length, no fuel filter, and no boost pressure... that’s not real world 3sgte....

Use the calculators for you own application :)

Not planning to go over 475hp this is the limit of the turbo, so realistically any where between 400 to 475hp. This fuel pump is good enough to achieve this.

Just so any enthusiast is following this doesnt misunderstands - even at fuel, the walbro 255 (linked) will not flow enough for 500hp.

Very quick check...

If you are running just 17psi boost from your 43psi base pressure, the 255 is now running maximum 180 (12v)-230 (13.5v) litres at best case scenario (no other restrictions). At stoich you need 259 litres of fuel to 500hp.

Walbro 255 is a great / safe selection of pump based on the small turbo and fuel combination for 300hp (240rwhp).

Maximum flow cross over of the pump 255, without restriction (big issue in a stock fuel lines/system in mr2) with fuel is at 400hp / 24 psi (12v). 13.5v flows more though my recommendation is go no where near “maximum flow ratings” at 12v as that is best case scenario flow of the pump (which it won’t live up to in the fuel system due to line restrictions and voltage/amps). Read the manufacture information and online calculators for cross referencing.

Robk is correct. He described what I experienced. You will need a bigger pump well before you get to 500Bhp. Please play it safe and use a pump that has a lot of head room for the power that you are making. Cutting corners always ends in tears, and more expense. Do it right the first time.
I have learnt this the hard way.

Had to buy an other 3sgte head as it was to soft due to overheating. I practice porting on the old head. Here are photo of my porting on the new head.
Seats have been enlarged for 1mm oversized Valves. Once porting is finished, back to shop for head facing etc.
Before and After 
It's not smooth for a reason. It will increase power as it will created more turbulence mixing fuel in the chamber better.
Before intake

After intake

Before intake
 
 

After intake
 

Exhaust Before

After this is smooth done with 80 grit
 

exhaust before

Exhaust after 80 grit

 
 
 

My last SW20 put down 316RWKW (424 wheel HP) at 22psi running on 98ron with a single Walbro 255, 1000cc injectors, Wolfkatz top feed rail and Turbosmart Regulator set at 43psi. I'm not sure how close the pump was to its limit but must have been fairly close. 

Head finish 1mm over sized valves installed 6 thou shaved all ported. What a job to fit double valves springs in. Waiting on cams then I will shim it. Got Cometic Head ready for fitting.

Pickup cams today.
Shimming next.

Butterfly's removed holes welded. Now waiting for my solid over bucket shim order to arrive, then degree the new cams.
 


Sent from my SM-G930F using Tapatalk

Solid light weight over bucket shims done. Cams have been degreed.

Had to get a new tuned length extractor as the old one had to many cracks.