sl2ner

ive seen several builds with less supporting mods than i have running in the mid 400s and using #52 injectors.

Paulyy

I doubt that.

http://fuelinjectorclinic.com/flow-calculator

Cylinders: 4
Fuel pressure: 3bar fpr + boost (25 psi) = 68psi
Engine aspiration: Turbo charged
Horsepower: wheels
Duty cycle: 90

pole position

If you go with Precision try the 5862

blown 944

OK, I haven't seen too many mid 400's builds. But that's just me..

Have fun

blown 944

You can't add the boost in. It's pushing against that pressure. You use the base pressure.

sl2ner

on lindsey racings dyno page they have the following results with injectors...

458hp with #72
415hp with #48
463hp with #55
479hp with #72
461hp with #55
401hp with #48
416hp with #55

5 of these are still 2.5L as well so why cant i make the same power as these guys with the same or better supporting mods?

Paulyy

what do you mean? the pressure is from the fuel pressure regulator + the boost your running as it's a rising rate FRP.

blown 944

It's not really a rising rate FPR. It's 1-1

When dealing with pressure, it's about the pressure differential. The MAP cancels out the added pressure.

Imagine 0/0 nothing comes out. Same happens when 25/25. The base pressure is the only real pressure.

A rising rate uses a different rate ie 2:1 etc

Paulyy

Those numbers seem optimistic.

it's not about the supporting mods with choosing injectors.
Injectors can only give you so much fuel. with so much fuel, you get only so much power. or you'll just run out of injector

Rogue_Ant

Most fuel pressure regulators are a 1:1 rate (not rising-rate). This keeps the pressure delta across the injectors the same regardless of boost pressure, or vacuum.

I.E. At 0psi of boost, the fuel pressure is, say, 43psi. The injectors have 0psi on one side, and 43psi on the other. So the pressure drop across the injectors is 43-0=43psi.
At 10psi of boost, the fuel pressure is 43+10=53psi. The injectors see 10psi on one side, and 53psi on the other. So the pressure drop across the injector is 53-10=43psi.
During vacuum, say -5psi, the fuel pressure is 43+(-5)=38psi. The injectors see -5psi on one side, and 38psi on the other. So the pressure drop across the injector is 38-(-5)=43psi.


Now a rising rate regulator is going to be something other than 1:1, such as 1:4. In this case, fuel pressure increases 4psi for every 1psi of boost.
So, at 0psi of boost the fuel pressure is 43psi. But, with the 1:4 regulator, at 10psi of boost, fuel pressure is now 43+10*4=83psi.

Paulyy

Oh! all this time i never took into account that the injectors had pressure on the other side. I thought rising rate FPR is when it raises with the boost? that's what every one seems to say in australia.

So regardless, this guys injectors are to small.

Paulyy

Didn't see this. But after the explanation from josh and you, under stand now. It's possibly people that talk cars around here in australia (people who pay to get their engines built) are clueless

Penguinracer

I think it's important not to get too hung-up on a particular figure.

I'm trying to optimise a 2.5 litre - but within set parameters i.e boost pressure which is comaptible with pump fuel & good reliability & retaining the stock RPM range so as to ensure valve-train life.

I'm aiming to maximise the VE within those constaints - the ultimate power figure will be whatever it turns out to be, but the driveability has to be top notch - minimal lag, a widish torque/power band and a strong top-end.

Forget shooting for a specific number - it can result in making some unacceptable compromises.

I'd have thought 400 rwhp for a 2.5 would be a very impressive figure! Not that it matters!

333pg333

+1. Couldn't agree more. The figures bandied around may be optimistic, may be also bhp. Then what's the correction %? Do a bit more research rather than reading marketing blurb and build something reliable. It will be a fast car nonetheless. A totally subjective power number for street cred is just that.

sl2ner

well those numbers came off of dyno charts so they either got the correction screwed up or they lied about the mods on several of their customers cars for some reason. i definitely see what your saying but i dont see why i cant get similar if not the same or better with what i have done. seeing as its more then a lot of those had listed. would like to make 500hp but would be plenty happy in the 400 range like those dyno charts show.