I just had my 9lb pulley and aftercooler with front mount installed. My tuner tried to put the 650cc injectors on and they basically wouldn't fit. He called Tech2 where I got them and they basically didn't know anything and told him to call Russ Collins (RC injectors?). Well to make a long story short, with the stock injectors there is plenty of fuel. I really don't understand that, but I did see my A/F chart and it was 12-12.4, give or take. The car runs great even on the shitty 91 octane that we have.

 

What was your duty cycle on the stock injectors at WOT?

 

That's a good question, is there something on the chart that says duty cycle? He told me it would make no sense to put in bigger injectors and have them run at 40% duty cycle.

 

The EMS should indicate duty cycle. I would ask your tuner for the reading.

 

stock injectors can not handle 9 psi at WOT with a safe injector cycle duty (80-85%)


Juan

 

My stock injectors max out with stock vortech and VAFC!!! Still a little lean with high flow exhaust!
What is your troque?

 

I've seen other posts indicating the stock injectors pooped out at 350-360 RWHP (100% duty cycle). You don't want to run at 100% duty cycle for very long, it's harder on the injectors and doesn't leave any room to compensate for lean conditions (colder air than when tuned, higher baro, etc). Staying under 90% is a good idea.

I can see a few reasons to go to bigger injectors:
1. You want more HP than you can get with the stock injectors.
or
2. You want more adjustability when tuning with an after-market ECM or add-on box.
or
3. You have FI and don't want to run the rising-rate fuel pressure regulator, so the only way to get more fuel is larger injectors.

I am by no means a "tuner" but I have worked on two FI cars, my '00 (stock Comptech SC) and a friend's '04 (Comptech SC with 4" pulley), and we ran 304 and 310 RWHP while staying under 85% duty cycle and maintaining a safe (12.50) A/F ratio. In both cases the "tuner's recommendation" was to go with bigger injectors and an after-market ECM or VAFC. We did neither.


I don't think torque (or troque) matters per se. Generally speaking, output HP and fuel flow go hand-in-hand. If you do a rough calcualtion of my above results (304HP / 85%), you get about 360HP at 100% duty cycle, same results as others on this board found when dyno testing.

.

 

[QUOTE]Originally posted by modifry

I am by no means a "tuner" but I have worked on two FI cars, my '00 (stock Comptech SC) and a friend's '04 (Comptech SC with 4" pulley), and we ran 304 and 310 RWHP while staying under 85% duty cycle and maintaining a safe (12.50) A/F ratio.

 

Yes, but the pressure is dramatically higher.

 

Comptech FRP is maxed at 80 psi

stcok injectors and 80 psi fuel preassure can not deal with 300 WHP @ 85% injector duty cycle.

At 100% of duty cycle is possible but not at 85%. or it runnig more than 12.5 A/F at higher rpms




Juan