i would like to know what size you use in your primary rail, and secondary rail.
also people who use stock idle fuel pressure, is it pretty loud or not even?
people with 252cc in primary rail how loud is it for you at 26-30psi?
one reason i wish to do the 8-injector setup is because it wont be as loud as my #30 injector at idle or even 440cc if i only do the normal way later
thanks

Michael 99gs
HRC Stage 2 @12psi :D
Stage 3 process begins gathering parts for rebuild
2GNT Member #32

http://www.dreamwater.net/purplebeast

>i would like to know what size you use in your primary rail,
>and secondary rail.
>also people who use stock idle fuel pressure, is it pretty
>loud or not even?

Mine's not loud. I know Ryan's got louder when he went to 30# injectors.

Mine's not together yet, but it'll have stockers in the primary rail and Accel 30 pounders in the secondary giving me 550cc/min per cyl. It'll have -6 AN lines all the way around(except between the rails which will be -8 AN), and a Walbro 255hp intank. I have the pump installed right now and with the stock injectors/lines/pressure and it seems a bit loud at idle.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

I have stock primary and 440cc secondary. You can't really hear the injector tick unless your head is by the back of the motor. If that's what you mean by loud.

Oh, I was talking about the pump.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

yah the pumps...hehe
Michael 99gs
HRC Stage 2 @12psi :D
Stage 3 process begins gathering parts for rebuild
2GNT Member #32

http://www.dreamwater.net/purplebeast

mines not in the car yet, but ill be using 270cc primaries and 315cc secondaries

i was thinking, between using say stock 235cc injectors and 252cc injector (accel) difference is just you can lower your idle/static fuel pressure, newer injector thats really all. oh yah, even if you got the 252cc compared to the stock 235cc to get your car to run correct you would have to get around the same fuel trims, so even if you did get the 252cc its not like your running any safer right?
today, i was thinking... i will just get my stock 235cc cleaned etc by rc and put that in my primary rail, and in my secondary rail either put 420cc (accel) or 441cc ford injectors and i know i will love to drive my car more without those super loud pumps..hehe
Michael 99gs
HRC Stage 2 @12psi :D
Stage 3 process begins gathering parts for rebuild
2GNT Member #32

http://www.dreamwater.net/purplebeast

my Accel inline pump is damn loud at 20 psi of fuel pressure. Although, it wasnt much louder when i went from stock fuel pressures to the lower fuel pressures. Just a bit louder. I'm gettin really tired of everyone asking me "what's that noise" every time they get by my car or go for a ride in it haha.. I need that Walboro intank

>oh yah, even if you got the 252cc compared to the stock 235cc to
>get your car to run correct you would have to get around the
>same fuel trims, so even if you did get the 252cc its not like
>your running any safer right?
Thats correct. The primaries are there to give the base amount of fuel and the pressure should be set to give decent fuel trims. All of the safety(being rich in boost) comes form the secondaries. As long as the secondaries+primaries can provide enough fuel at maximum boost you should be safe - but its the adjustment on the secondaries that work the a/f under boost.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

thanks
Michael 99gs
HRC Stage 2 @12psi :D
Stage 3 process begins gathering parts for rebuild
2GNT Member #32

http://www.dreamwater.net/purplebeast

wait, i know we just dont get the total CC's from adding the 2 sets. anyone can give me the quick math for this? or is it on corbins page? thanks. oh sorry for the hijack

>i was thinking, between using say stock 235cc injectors and
>252cc injector (accel) difference is just you can lower your
>idle/static fuel pressure, newer injector thats really all. oh
>yah, even if you got the 252cc compared to the stock 235cc to
>get your car to run correct you would have to get around the
>same fuel trims, so even if you did get the 252cc its not like
>your running any safer right?



pretty much, but remember you are running a rising rate fpr, so at full boost, the pressure across the primaries will increase, and they will provide more fuel. so say you have 235 primaries at 43psi @ idle, you run 17lbs of boost and the fuel pressure goes to 60psi, so the primaries are providing more fuel.

However, your secondaries are what are doing most of the leg work in boost.

>pretty much, but remember you are running a rising rate fpr,
>so at full boost, the pressure across the primaries will
>increase, and they will provide more fuel. so say you have 235
>primaries at 43psi @ idle, you run 17lbs of boost and the fuel
>pressure goes to 60psi, so the primaries are providing more
>fuel.
Not exactly. The primaries will provide the same amount of fuel at 0 boost as they will at 17lbs of boost. The rising rate is 1 to 1 so the fuel pressure will go to 60, but you have to remember that the intake manifold pressure also goes to 17psi - so the pressure differential(rail pressure - manifold pressure) between the fuel rail and the intake manifold is constant. At 0lbs of boost the pressure differential is 43psi(43 - 0). This differential remains constant no matter what amount of boost you run. At 17lbs of boost the pressure differential is still 43psi(60 - 17). Basically, the pressure differential for a 1:1 riser system like this is always equal to the static fuel pressure.

>However, your secondaries are what are doing most of the leg
>work in boost.
It's because of this constant pressure differential that the secondaries do all of the boost work.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

>Not exactly. The primaries will provide the same amount of
>fuel at 0 boost as they will at 17lbs of boost. The rising
>rate is 1 to 1 so the fuel pressure will go to 60, but you
>have to remember that the intake manifold pressure also goes
>to 17psi - so the pressure differential(rail pressure -
>manifold pressure) between the fuel rail and the intake
>manifold is constant. At 0lbs of boost the pressure
>differential is 43psi(43 - 0). This differential remains
>constant no matter what amount of boost you run. At 17lbs of
>boost the pressure differential is still 43psi(60 - 17).
>Basically, the pressure differential for a 1:1 riser system
>like this is always equal to the static fuel pressure.


really? how does this pressure differential work? I dont understand how 60psi of fuel pressure doesnt create more flow than 43psi with the same injectors. how does the pressure in the intake track matter in this regards, since the fuel is isolated from the intake until after it leaves the injectors?

im not arguing, i just didnt know this ;)

It's cool.

>...since the fuel is isolated from the intake until after it leaves the injectors?
This is the part that's not exactly right. It should be - The fuel is isolated from the intake, until the injectors open.

When the injectors open, the fuel pressure pushes fuel into the manifold. At 0lbs of boost there is 14.7 psi of natural atmoshpere(0 psig or gauge pressure) to push against inside the manifold. It goes without saying pretty much that as boost increases, so does the pressure in the manifold. So at 10lbs of boost there is 24.7 psi(or 10 psig - gauge prssure) to push against inside the manifold.

I think it would be easier to explain with a lab example instead of an engine example. Our lab rig is a fuel injector mounted to a container that we can pressurize. Lets set the fuel pressure to 10psig and start the container pressure at 0psig. The injector will squirt a certain amount. As we pressurize the conatiner the injector will sqirt less and less, because the pressure differential becomes less and less. Once we equalize the pressure in the container with that of the fuel rail(both at 10psig), the injector won't squirt anymore. It' might leak into the container depending on how the injector is mounted, but since the fuel pressure and the pressure in the container are equal - it will not squirt. If we increase the pressure in the container to more than whats in the fuel rail - all of the sudden the flow will reverse. Now we're putting air in the rail instead of fuel in the container. Ok, lets reset the test - back to 0psig in the container and 10psi on the rail. We're back to putting a certain amount of fuel in the container, lets call it X cc/min. This time as we increase the pressure in the container, we'll also increase the pressure in the rail by the same amount at the same time. At 10psig container pressure the fuel pressure is at 20psig BUT because the pressure differential is the same(10psig) - we're still getting X cc/min. You could bump it as far as you want. Lets say the container has 80psig. The rail would have 90psig and we'd still be getting X cc/min out of our injector - because there's still only a 10psig pressure differential.

Ok, out of the lab and back in the garage. Pressure differential is why all factory turbo cars use a 1:1 fpr - to make the Boost and fuel pressures rise together.

If you want to play with some numbers you should check out Corbin's injector page. http://www.2gnt.com/www/corbin/chooseinj.html I've also made a spreadsheet with all of the equations buried in it if you want to play around with that http://www.users.fast.net/~metaljim/garage/TurboCalc.xls


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

Cool, your example explained it well :thumbsup

Thanks for helping yet again Jim :) if i could give ya more points, i would, heh

Whoah, does this translate into vacuum too?

Like, If I'm running -20inHg (for simplicity sake, lets say -20psi) and 20psi fuel pressure, my differential pressure at idle is 40psi at the injectors?

Is this why some people measure a/f as an actual ratio, and try to get it constant across the board?

Geez I really need to read Maximum Boost. :rolleyes

Yep it still applies. Even our non-turbo cars have a 1:1 regulator - at least the 95s do - the ones with a vacuum line run to the regulator. Not sure about the returnless systems.

2 inHG is about 1 psi.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html