if your pushing 8-9 lbs of boost do you absolute have to upgrade your injectors. ive searched and only found 50/50 yes & no on this. is there anyone on here who has a more definitve answer on this?

 

I would PM/ask jproy, he seems to be the supercharger expert on here

 

No, you do not have to upgrade the injectors! If you are at 3-5 psi with the stock blower you will see about 100psi on the stock fuel rail with the Comptech 8:1 FPR(fuel pressure regulator) , with the HB pulley at 6+psi you will probably see about 105-120 psi depending on how you are tuned, with the 9psi pulley on the jackshaft you will probably be looking at as much as 130+psi depending on tune. Those numbers are rough estimates and someone can jump in if they want to correct.

The point is, several people have run the HB and 9psi kit here and used the stock injectors at those high as hell fuel pressures. I don’t know of one injector failure or seizure that caused an engine failure, but at those pressures it is likely. IT IS NOT NECESSARY to run larger injectors but you run the risk of injector failure at those high pressures the injectors were never intended to run at.

What I am about to say is not perfect science but is what I know, have read, and been told by experts. Apparently Injectors lose their atomization efficiency to spray the fuel as a fine mist when the fuel pressure goes above 70psi and it comes out as more of a stream and less of a mist the higher you go pressure wise. Obviously it works at 130psi but the fuel does not combust as well as it would with the finer mist of the lower psi injector. 100+psi on a fuel system is very high but it does work.

I am running 440RC injectors. The purpose of doing that was so I could deliver the fuel necessary at 10psi of boost to the engine at no more than 65psi. This is how any car manufacturer or good tuner would have done it. I have the Walboro 255 lph pump in the tank and have upgraded the Comptech 8:1 FPR to the Aeromotive 1:1 unit and set the base fuel settings on the high side of the stock FPR operational window. 54psi with vacuum removed. Additionally, myself and others have proven the Comptech FPR to be VERY inconsistent with repeating identical fuel pressures for WOT. The fuel pressure is never the same each time you floor so you are getting different amounts of fuel to the cylinders and the tune is never the same and could lead to going lean even if you are tuned with a piggyback.

So I will be running a much lower pressure system at 54psi static. I see 44psi at idle with vacuum and should see 64psi at 10psi of boost. I will get awesome spray characteristics and that should (in theory) help with atomization and more complete combustion which will give more power. Who knows? I won’t be able to prove it since so many things have changed on the car at once. But I will also have the rock solid repeatable WOT fuel pressure every time I stab the throttle and will know that aspect of my tuning will remain consistent and repeatable every time.

 

with that being said i think i will upgrade the injectors, fuel pump, and fpr. im dropping 2k for this blower so i want to make sure i do this right the first time. i dont want to half ass it just so i can put it now just for shit to go out on me later. ill have to push the install date back since i have to order more stuff but its worth it.

 

Just make sure that crank pulley you are using with the supercharger is the stock size. I just noticed it in your sig.

 

I already told you that you would need bigger injectors and pump. Good luck with the project bro.

 

yes i would upgrade injectors on anything running over 6 lbs of boost in my opinion some 440's should be sufficient, my buddy with his turbo miata is running 330's i believe on his 4 banger and he never sees over 70 percent duty cycle, but i do think a 255 lph fuel pump would be overkill, you could drop down to a slightly lower size.
and he is usually running anywhere from 10-14 lb's

 

anybody know whats the part number or the application (car) that will work for a 2003 cl-p for the walbro 255 lph fuel pump

 

The LPH on the pump name is the max flow.

http://shopping.lightningmotorsports...ails/d_885.gif

440cc/min = 42GPM

 

So regulating the fuel manifold to ~64 psi is just about perfect (looking at the pump curve)

Now the fuel injectors. Since they rate fuel injectors at 43 psi, you are looking at 516cc/min @64psi. (http://www.rceng.com/technical.aspx)

The S2K injectors rated at 360cc/min running @ 64psi give you 436cc/min. These don't require fuel rail mods.

That flow rate of 436cc/min will support over 360hp, which is in the ball park of what I am expecting with 6psi boost.

(I used BSFC of 0.55 and 0.8 duty for all calcs)

My conclusion. ThinJim's 440 injectors are a bit overkill for my application @6psi. However, they look perfect for him. The 516cc @ 64psi will support up to 430hp.

I am going to use the 360 injectors and aim for a manifold pressure in the 60s. That should be sufficient. Worst case scenario, it ends up in the low 70s and I am okay with that.

P.Diddy - If you are looking at 8-9psi. the 440s will work for you. But also, it seems like the general consensus is that those pressures will require intercooling.

I sort of forgot the point of me writing all this. I guess I was just trying to convince myself that the S2K injectors will in fact work for my application without elevating the manifold pressure above 70psi.

Thoughts?

 

IF 550's are the same price and would relieve some pressure off the FPR, fuel pump, and not run so close to max duty cycle then why not just get the 550's?

 

I'll buy that.

 

your can always use the rdx injectors which are 410cc. i made a diy on how to make them fit, takes a little trimming and switching the o-ring from the cl-s/tl-s to the rdx injectors

 

Also not a bad idea at all. Post up the link to the DIY please.

 

Here it is.

https://acurazine.com/forums/showthr...=rdx+injectors

I just pulled the trigger on some RDX injectors.