450 injectors pressure?

[minimoose]

Hi everyone! I am confused and figured id ask. What do the stock fuel injectors run at. I have a walbro 255 fuel pump aermotive fuel pressure reg. and 450 injectors. The car is running rich I have not done a blt I am wanting to do one I just do not have a tester as of right now. Car has a apexi safc but is not tuned with it as im retarted and afraid to mess with something I do not understand.

 

[steve]

What do the stock fuel injectors run at.

From the 91 Factory Service Manual (FSM):

NA - 240cc injectors at 47.6 psi
Turbo Automatic - 390cc injectors at 42.7 psi
Turbo Manual - 450cc injectors at 36.3 psi

 

[9!'clipseDOHC]

To set the fuel pressure:

1. Get your car idling at normal operating temp,
2. Pull the vacuum line from the AFPR and cap it with your thumb,
3. Loosen the retaining nut,
4. Turn the adjustment screw to raise or lower your fuel pressure to 36 psi,
5. Tighten the retaining nut,
6. Reinstall the vacuum line (secure it with a zip tie),
7. Enjoy.

 

[kmetiuk]

36.3? Really? Sounds low....I believe you. Just saying thats the lowest Ive heard in a car. Doing my fuel system in a few weeks so thats good to know.

 

[bertrenolds]

Most people will say 37psi for a 1g turbo dsm. Set your base FP to 37psi and then learn how to tune with the safc. There really isint alot you can do with stock injectors with the safc, probably get bigger injectors then learn how to tune.

 

[Bud92gsx]

36.3? Really? Sounds low....I believe you. Just saying thats the lowest Ive heard in a car. Doing my fuel system in a few weeks so thats good to know.

For you on the 2g is 42psi..

Only 1g's have different fuel pressure, from auto to manual..Just like the wisemen just posted..

 

[steve]

I wish we had access to the engineers who designed the cars so we could get real answers to the why questions but the best we can do at this point is look at the factory specs and guess why they chose to run the injectors at less than the industry standard.

There is a lower bound to injector pulse width in the ECU, consistency between pulses and between injectors at short pulse widths is a key parameter for both emissions and idle quality. They may have dropped the base pressure to hit a sweet spot with the original injectors. As noted the 2G turbo cars all run 43 psi, have newer 450 cc injectors with a dual spray pattern and have a faster ECU.

 

[Bud92gsx]

I wish we had access to the engineers who designed the cars so we could get real answers to the why questions but the best we can do at this point is look at the factory specs and guess why they chose to run the injectors at less than the industry standard.

Like when you did the math and figured out at 36-38 psi..The 1g 450's don't even flow 450CC's....

But the 2g cars at 42 ish psi do actually flow 450 cc's..I thought that was funny, I could be the only one though..

 

[steve]

Right. By changing the base fuel pressure you change the injector flow rate.
If you drop the base pressure the injector pulse width has to increase to provide the same amount of fuel.
The shorter the idle injector pulse width the more slight differences impact the result.

On the other side of the trade offs you need to make sure you have enough flow so you don't max out the injector in normal operation. You really want the injectors to stay below 85% DC so there is a bit of balancing between idle and WOT going on.

 

[minimoose]

Ok thanks all for the info. Im going to try setting it againand see what I get. As of right now it hardly smokes at idle, really hard to see. But once you rev it, it blows a black cloud out.

 

[moving-violatio]

minimoose I looked at your profile and before you mess with that safc I would make sure you had some kind of monitering device. I use wideband to tune with but you should also have some sort of logging software to use. The safc is actually very user friendly, I am using it with 650cc injectors right now, still working on a perfect tune but that comes with time. As for the 450cc thats where I learned how to actually use it. very small measurements make big changes to your afr with the 450cc injectors.

P.S. Im working on getting the loggin software myself just havnt had the money.

 

[minimoose]

Yea I want to get link eventually so I didnt want to waste money on a logger. I know I need a wideband I just havent got it yet kinda a work in progress on the side.

 

[moving-violatio]

I understand trust me. You can pick up a brand new wideband from summit racing for 200 or find a used one with everything on it for between 100-150. Just have to look around. Also I would look into which one of the loggers will work the best for you. I have seen that a lot of the people with 1gs go with ecu link.

 

[minimoose]

Yea I have seen them in summit for 200. As far as the logger are you talking about the hand held palm style?

 

[kmetiuk]

Haha....ya didn't notice the 91 in that post.