NLang

iTrader: (12)

I'm talking 450+RWHP w/ factory 26.4 and 28.8 fuel injectors on 100% N/A cars-no NOS and additional fuel. No offense, and considering where I stand w/ fuel experience (some-not my master in school...), I think it's safe to say that Mr. Endres has miscalculated to say the least. There's no way that's correct, sorry...
Accel, which I'm sure we all have heard of, said their 32's would work, but recommended their 36lb/hr injectors, which are rated @ 3 bar (43.51psi), for anyone reaching the 480-500RW mark. Those put out 41.54lb/hr @ 4bar (58.02psi). That's a lot of fuel. I know a lot of people running those injectors. They have a good rep. I thought they were all over doing it with the 36's. It turns out that is what I'll need myself within the next couple weeks...
Another thing...there are a lot of dealers offering different styles of injectors. All of them have different hp ratings per the style of injector or manufacturer. So, I guess that sort of kicks that that formula up there ^ out the window...It's recommended that everyone call the manufacturer of their choice now before choosing a size for their app. I was told this by four different companies.
I think many people's questions have been answered throughout this thread. It's too bad there really isn't a true answer OR equasion. The equasion could've gotten you in the ballpark some yrs back, but there are now just too many diff. styles to choose from-all having diff. HP ratings. Good luck everyone!

Racetronix

iTrader: (2)

Why worry about the bare minimum requirements?
Just get a set of Delphi 42's and tune them for the build of your motor.
Delphi 42's are more than enough for most LS1 motors and are just as manageable as the factory injector. They are quite affordable too!

Turbo Buick owners don't play the injector game every time they bolt another HP item on their motors. Many just buy 50's even for a fairly stock motor and just recalibrate the ECM as they build more power!

And yes... some of the injector info out there is a bit out of wack!

gametech

iTrader: (1)

I fully agree. Anyone into speed knows that they have never made their last mod. Why not just buy good size injectors to start with? You will find a few guys in the truck section using 43# asm injectors. The factory computer seems to have no problem controlling these, and it is nice to have the overhead for those smaller blower pulleys and bigger intercoolers that fedex always seems to be delivering.

ataylors

iTrader: (2)

You have to think of an injector like a scale, you dont want to get a 5000 lb scale to weight something that is 2 oz..

gametech

iTrader: (1)

It is true that you can get injectors that are too big, but the factory computer seems to have no problem controlling some fairly large injectors. As long as idle quality and light load performance doesn't suffer, why not just get plenty of injector to start with?

Racetronix

iTrader: (2)

That is a very poor analogy.
Besides, that is all relative to the resolution of the scale and how much FAT you might put on down the road.

In the case of an injector as long as the PW can be made stable and narrow enough to maintain the desired A/F at idle then there are usually few if any issues. The real problem is with tuners who have difficulty understanding and tuning larger injectors for good drivability and AE fueling. LS1 computers are very capable allowing them to support a wide range of injectors while still maintaining factory type mileage and drivability with increased HP.

As stated before an ECM from a Turbo Buick used in 1986 can be tuned to support injectors upwards of 86lb/hr on a small 231CI V6. Why do many V8 tuners fear large injectors so much and pray on a customer's fears with old school rhetoric??? A good tuner can work magic. A poor tuner will wield excuses.

NLang

iTrader: (12)

Well, first off, Those HUGE Delphi's you're speaking of are $80+ EACH. That's beyond ridiculous for someone who could NEVER use them. My worries were lack of fuel atomization at lower rpm with injectors that are too large, overcycling causing detonation with small injectors, and paying loads more for big injectors w/o needing them (I'm WAY over budget). I went with a set of 1k mile flow matched/balanced CPR Racing 'disk' type injectors. They'll spit out plenty for the 500RW combo(630hp max), and didn't cost me much (for their size and life-time guarantee anyway).
I've certainly appreciated all the input. Please keep it up as I'm not the only gear-head out there lacking in the fuel department. How about instead of 'sure, you can use them', conjure up some details explaining how, why, and any dissadvantages to going overboard or underboard. That's what this place is for, right?
Again, thanks guys.

dynocar

Don't be too big or too small. We all know that there are good formulas to help guide us for proper injector sizing for various applications. A fuel injector has to have enough time to fully open and close its valve (pintle, ball or disc) for accurate cyl to cyl fuel distribution. If the injector flow is too large, at idle and cruise, its valve's pulse width (time that valve is open) may not have enough time to fully open before it has to close again to limit fuel flow. With these valves uncontrollably floating with each injectors individual valve movement characteristics, each cylinder will receive a different amount of fuel, some too lean causing misfires and stumbling. For many styles of injectors we do not want to see less then approx. a 1.5 ms pulse width. At the other end of the scale, if an injector is too small, during high HP and RPM applications, the valve will stay open too long and not have enough time to fully close. This condition can cause cyl to cyl fuel distribution problems possibly damaging an engine because one or more cylinders are running too lean because again, each injector will flow dramatically differently. To prevent this we try to stay under 80%, some say 90% duty cycle. Injectors are not designed to run fully open all the time due to the possiblity of failure due to overheating and the lack of any flow control capabilities. Different injector types have better dynamic ranges then others, the disc usually the best and the ball type usually the worst because of their differing valve weights. Also, different engines require more or less fuel per HP, a term called BSFC (brake specific fuel consumption). Well designed engines have lower BSFCs then mismatched ones, thus require less injector per HP. Boost applications usually have higher BSFC, so more injector per HP. Varying charging voltages will also affect this issue. Recently we dialed in a trailored drag car without an alternator. He later decided to add one (EFI, 2 fans, electric water pump, huge electric fuel pump, lots of guages and lights) and car went much slower. No, it was not the extra HP to run alternator. His car went real rich because he went from approx 10 Volts to 13.5 Volts to the injectors causing them to fully open quicker. We recalibrated A/F and he went faster then before.

EJ