Fuel System technical specs

[Project Zero]

I\'ve done a search and can\'t find anything.

What is the stock fuel rail pressure, I think I read somewhere that it\'s 43PSI, I\'m tring to do some BHP/Injector type maths stuff so if anyone knows off the top of their head I would be V grateful.

Thanks in advance PZ

[Project Zero]

Thought I\'d post this seeing as no one knew.

The stock fuel pressure regulator maintains a constant pressure difference between intake manifold and Fuel rail pressure of 38 psi.
So stock supply at 12 psi boost is 38+12=50 psi

You can raise the pressure with an ADJUSTABLE fuel pressure regulator, which increases the pressure all the time and matches boost pressure with a 1:1 increase in fuel pressure. For example, if you have an adjustable regulator and you set it to 55 psi, you will get 55 psi at zero manifold pressure, and 65 psi at 10 psi of boost. A change like that will deliver SQRT(55/38) = 1.20 times the fuel delivered at the stock pressure, a 20% increase.

A different approach to raising fuel pressure is to use a RISING-RATE fuel pressure regulator (RRFPR). These are often confused with ADJUSTABLE regulators, but they are different in operation. RISING-RATE regulators add fuel pressure in some multiple of the boost pressure. If you add a RISING-RATE regulator and set it to a 3:1 ratio, you will get 38 psi at zero manifold pressure (stock pressure). At 10 psi of boost, you will get [38+10 psi from stock regulator] + [3*10 psi from RRFPR] = 78 psi. A change like that will deliver SQRT[(78-10)/37] = 1.36 times the fuel delivered at the stock pressure, a 36% increase. (Note that the increase is the square root of the new over old fuel pressures relative to the manifold)

And the horsepower value of your injector would increase by the same amount if all other engine management systems remained unchanged.

[clive]

Hiya,

Real sorry nobody came up with answers you needed, but you have done a fine job yourself.

Many thanks for the info as l have just found out a couple of things.

Well Done:)

[paul C]

Hi,

I came across this a while ago it may help.

HTH

Paul

http://www.maxcooper.com/rx7/how-to/fuel_system/index.html

[Project Zero]

Nice one Paul,

Thats what I was looking for all along.