Right now I am stuck at what injectors to use on my setup. I plan on running the LE2 setup (58mm tb and ported intake, le2 heads, le2 cam)....should be around 415rwhp. Right now I have a set of SVO flow matched 30# injectors at 31.3lbs. Will these be enough for my setup ( I may stroke it into a 383 ), considering I want to run a 75-125hp shot of dry nitrous too? I have a guy wanting to sell me Accel 36# injectors. Should I go with those to be safe, or stick with the SVO's I already have?! ( I heard the SVO's are the best, and can actually flow alot more than what they are rated at ). Let me know what you guys think, thanks ---

 

DO NOT USE ACCELS!!!PLEASE

 

Why are the Accels so expensive I wonder? What do they do that makes everyone hate them, lol?! ---

I was just reading on LS1.com that the 30# svo's run like 36# injectors because of the high fuel rail pressure. What pressure do I have to run to get these SVO's to perform right? ---

 

That is because the LS1's run at 58 psi. The LT1's run at 43.5 psi so they will run at 30#'s. You can always up the pressure with an adjustable fuel pressure regulator. The SVO's work well at higher pressures also. If all your fuel is being supplied through the injectors while running the nitrous, I don't know if they will be big enough.

 

Darn, I guess I will have to go for the 36-42lb Delphi ones?? They are better than the Accel right?? I heard the SVO's stopped being made in 36# ---

If I get a pressure regulator I should have no problem running the 58psi needed to push the 30# inj to work like 36# ones right? I read that the more precise the injector you use on your setup, the better your engine will react to the cam?? I know LLoyd recommends using 30 or 36#'s for the LE2, but that is without nitrous. Maybe I should go with a 75 shot instead of a 125?? ---

 

I'm no expert, but I think that on your setup N/A, that the 30's will be make the car a little more responsive down on the low end and mid range than 36's. Turning up the fuel pressure might also atomize the fuel better depending on the injector design.

Here are some formulas I found to determine injector sizing:

Max HP x 0.5 / 8 = lb/hr naturally aspirated
Max HP x 0.55 / 8 = lb/hr supercharged
Max HP x 0.65 / 8 = lb/hr turbocharged

I think you use the HP at the flywheel.

 

You can use rwhp in the formula and when you get an injector size, that is the size of the injector running at 80% duty cycle, which is around where you want to be. The 30's at 80% duty cycle will be 24.00. Your 415 rwhp would need 25.94 lb/hr, so that's a good match I think. With a 125 shot, that should be around 100 rwhp. 515 rwhp would need 32.19. If you ran 58 psi and made the 30's run like 36's, then the 36#'s would need to run at 90% duty cycle, which would be 32.40. 90% duty cycle is still acceptable.

 

Awesome, thanks, I will stay with the SVO's ---

 

For 415rwHP with an M6, you will be at about 475 flywheel HP.

475 X 0.07 = 33.25 #/HR

That assumes an efficient tune (0.47 #/HR/HP BSFC) and no more than an 85% duty cycle. A 36 #/HR injector would be a good choice. You aren't going to get a better low end with 30's, and they will be over 90% DC with your anticipated HP. The only place oversize injectors might hurt you is at idle, when the pulse width can not be turned down low enough to get the sub 1.0 mSec pulse widht required for idle, but there are people here running 42's with no idle problems. I run 78's.... idles fine.

Note that the SVO injectors are flow rated at 2.7bar (39.15psi), so they will flow about 5% higher than rated flow when used in a stock 3bar (43.5psi) fuel system like the LT1's.

 

I guess 42#'s it will be then, do you recommend Delphi or stick with the SVO??

That should cover me at 600hp (125 n20) x .07 = 42lbs OR is a nitrous equation different than the .07 used in the n/a equation?? I am using the ZEX lt1 setup with the fuel regulator box that adds fuel as the nitrous is added by reading the bottle pressure ---

Do you recommend I use an upgraded fuel pump....like the Walbro 205 or 255 lph one (205lph is good to 500hp n/a right....but if I stroke it I may be AT 500hp, so is a 255 lph better or overkill still)? How about an adj. fuel pressure regulator for anything, or is the stock pressure regulator fine? ---

I guess the SVO's would have been fine if I didnt want to go with the n20....that is some food for thought , thanks SO much for the help ---

 

Is the ZEX kit wet or dry? If its wet, the use of N2O does not affect injector sizing. If its a dry kit, it depends how it adds the extra fuel through the injectors. Some dry kits add the extra fuel by raising the pressure, which means you size your injectors based on NA HP. If the ZEX is a dry kit that alters the injector pulse width, it would affect the injector sizing.

You should go for the 255 LPH pump if you plan to increase NA HP and add nitrous in the future, or run a pair of 205 LPH pumps, and only activate the 2nd pump when you spray (which is the setup I have).

The stock FPR should be fine.

 

Its the zex dry lt1 specific kit # 82018. It says it "provides fuel enrichment by reading the bottle pressure and giving increased pressure to the fuel pressure regulator. This increase in pressure performs the function of adding fuel volume through the engines own injectors."

From that quote and what you said in the post above, I should plan my injectors to the NA hp and NOT the hp with the nitrous numbers included, right?!

Lets say I MAY get up to 500hp x .07 = 35lb injectors. Wow you just saved me from buying the wrong ones!!!(42lbs) ... back to the 36lb ones, lol ... THANKS ---

 

There would be nothing wrong with running 42's. Is the cost that much different?

 

Nope, they are about the same cost....AND I can find 42# SVO's....I just thought I would be overkilling it ... dont you want it as close to your hp setup as possible? I read in another of your threads that 42's will idle just fine in my setup and can be tuned down to my application. Wow, I am going to be a pro at injectors soon ---

 

If you plan to go stroker I think the 42's would give a little more breathing room. We installed the same zex kit on an lt4 (ported) headed, GTP6 cam with full bolt on's. It had the 255 pump with 36's and on the 125 setting the duty cylce was at 88%. This was a stock bottem end car also. The 42's can be tuned to run just fine and idle just fine. A little over kill won't hurt you. Just don't get excessive with it.