With 310cc Injectors running at 5psi, what should my idle and WOT fuel pressures be?

Also, what size disk are you guys using for this?

TIA

(Ryan's too lazy to search! ;-) )

Static fuel pressure to 30 psi. You'll want the rise to be somewhere around 4 or 5 to 1. 5:1 is probably better. Basically, you should be at 50-55 psi at 5 pounds of boost.


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

sorry to highjack the post, but i have a question. if you use bigger injectors, does your stock pressure drop? i am runnig 52-54psi on stock injectors right now. if i throw in bigger ones when i install my turbo, will the fuel psi drop because of this, thusly needing a bigger fuel pump? do i have this right?, or am i way off?

It doesn't automatically drop if thats what you're asking. You need to adjust the fuel pressure regulator to the proper pressure at idle. You can't adjust the fuel pressure on the stock N/T pressure regulator - because the FPR is non-adjustable.

The HRC and Star kits come with a rising rate fuel pressure regulators. These fuel pressure regulators raise the fuel pressure by X psi for every pound of boost it sees(the FPR has a boost/vacuum port in it). You can adjust the idle fuel pressure with these FPRs as well.

Our computers can compensate for a slight difference in injector output, but only a slight difference. Basically, when you run bigger injectors on our cars you need to lower the idle fuel pressure so that the injector output closely mimicks the stock injector output at the stock pressure. 310cc injectors will flow the same amount of fuel at 30 psi fuel pressure as the stock 235cc injectors flow at 50 psi.

If you want a more detailed description of how it all works - check out Corbin's explanation of MFI and choosing injectors.
http://www.2gnt.com/www/corbin/mfi.html
http://www.2gnt.com/www/corbin/chooseinj.html


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

many many thanx

Also you will not need a bigger fuel pump if you run bigger injectors. Since the PSI is dropped, there is no need to get a fuel pump that will flow at 100psi of fuel.


Nick
97RS
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Old: Custom IHI Stage2
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so you just change the disks out right for a star kit? You don't have to mess with any of the Fuel pressure stuff? You just drive it check AF ratio then change disks accordingly? Haha I got the engine out today and I'm gonna want bigger injector in the near future,

So, what size disc and ring do I need to use with the SFMU if I am running 310cc injectors? Anyone?

I used the 2.72" disk/ring combo, with the short, dark spring inside the SFMU. I also use the bleed valve to fine tune the boosted fuel rise rate if i was a bit too rich. The bleed valve is a very nice thing to have, if you dont have it yet. I ran a good 8 psi with this disk/ring and had enough fuel. For 5 psi, you should be fine. Run about 20-23 psi of fuel pressure at full idle vacuum (16-19 Hg's), and around 29-30 psi of fuel static (0 psi). At 5 psi boost, you should be around 50-55 psi fuel pressure. If the fuel pressure is too high, or you run way to rich, open the bleed valve until your EGT's and A/F look good. I like to have a max of 1550 EGT's and A/F o2's around .94-.96 in 4th gear WOT. For 5 psi, you can run a tad bit leaner than for 8 psi, so o2's from .92-.95 should be good.

GREAT -- Thank you very much.

>Also you will not need a bigger fuel pump if you run bigger
>injectors. Since the PSI is dropped, there is no need to get a
>fuel pump that will flow at 100psi of fuel.
>


Except for the fact that the Larger fuel pumps flow with not just a higher pressure but also more fuel volume which is important.


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im running 310s and i have the static set at 22 psi and i still get a check light for being to rich....also, in first gear i feel the car bog down but in second and on at 12 psi it clears up but is still too rich...not sure which disc im using..dont remember but which one are you supposed to be using? i know im going to about 70 psi at around 12 psi...thanks

Are you sure they are 310s? That just doesn't sound right at all.


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