I've got a 351w with h/c/i and a s366, fuel system is a walbro 255lph intank, stock lines and rails with 42lbs injectors. I'm only running 4 psi right now and I've already maxed my injectors. Does this sound right? I knew it wasn't the best set up, but figured I would at least be able to make it to 8-9 psi. I've heard a 255 pump and 42lbs should be able to make 500hp, I dont think I'm even at that. Any ideas?

 

255 lph pump is good for about 550hp MAX. I would suggest doing a fuel pump rewire if your going over 450hp,

You need atleast 50# injectors for 500hp,

It seems that alot of ford 42# injectors only flow 34.5#


I sourced this info from: http://www.efidynotuning.com/pre.htm

 

What is your base fuel pressure? With 2 255's and only 9psi desired, you can crank the base pressure way up to make the injectors flow more. I'd start at 60psi and see what the inj duty cycle looks like.

 

Base pressure is 43 psi, and I only have a single pump. I'm gonna try the hammer trick on the regulator tomorrow to see if that helps. I just bought a areomotive fpr and aftermarket rails from someone on another forum. Think at this point I'm gonna upgrade the pump, fuel line diameter, and injectors. Do you think 60lbs injectors would be enough?

 

425-450rwhp tops.

 

I've made 500rwhp on a 255 and 42's, but I was about out of injector. 60's would get you further, but the 255 will be running out soon. You could either drop in a 340 or 380lph pump, or go twin 255's.

 

I've ordered a 340 pump, rails, and regulator. Just need to order injectors, should I get 60's or go higher? Don't think I've mentioned it but it's only ever gonna get pump 93.

 

I made 500 hp with 44pph and a single 255.
now i have close to 700 with twin walro 255 intank and the same 44 injectors at 55 psi but that is the limit, soon i need bigger injectors.

 

60s be fine with that turbo.

 

So I ordered some Siemens Deka 60lbs on Sunday, and just got a email saying they are out of stock. They said they'll upgrade to 80lbs at no charge. Can I use the 80lbs injectors with my setup, or will they be too much? This is a mostly street driven truck and I've heard too large and injectors can cause idle issues.

 

I would have the same dillema here in our country we have to pass the sniffer test at idle.

 

HI-z 80lb injectors will idle just fine. It's mainly the large low-z injectors (120lb+) that have issues getting the pulse width low enough to idle well. My 160's for example won't idle well on pump fuel. The 80's I've tuned idle great.

 

Good info there

 

Cool, thanks 80's have been ordered.

 

Where was this from? I need some 80's and would like to get them at 60's price.

 

Lethal performance. Looks like they're the same price on the website.

 

Just something I read.
Injector Size = (Engine HP x BSFC) / (# of cylinders x duty cycle)
Seemed to give good results for me.