osti33

At what point do fuel system upgrades become needed? I just finished a small build on my 99FRC.

Build includes:
LS6 intake
CNC Ported 862s loaded with stock size LS1 valves
Texas Speed Cam
XS Long tube headers
Blackwing air intake
Borla cat back

Obviously the car isn't built to be a world beater. Just a fun little street car.

I just got it back together yesterday. I haven't had it tuned yet.

Full system is 100% stock. Injectors, pump, etc. Will the stock system support this build or are pump and injectors going to be needed? I can find out on the dyno if it runs out of fuel up top but I hate to pay for dyno time twice.

I figure you guys probably already know if the stock fuel system can support it. Otherwise I would like to upgrade it before going to the dyno.

Thanks in advance.

neutron82

I would at least get a 255 in tank pump and probably a slightly bigger injector... if I remember correctly the duty cycle on my z06 was in the 90% range with 420rwhp with the stock injectors

osti33

Thanks neutron.

Are the LS6 injectors(your zo6) bigger than the LS1 injectors(my 99 FRC)? I'm just trying to figure out how much bigger injector I need along with the pump.

I'm not real sure what to expect power wise. Like i said, I know it won't set the world on fire but it should make a fun daily driver.

Thanks

neutron82

I believe they are both 28lb's but I could be wrong... you would probably be good with a 32lb injector or something around there, you could go even higher if you want to leave yourself some room to grow in the future

LoneStarFRC

IIRC, the '99s were 26 lbs.

OP, with those mods, you should be just fine with 28 lbs. A lot of folks underestimate the 28 lb injectors, but if it makes you feel any better, buy some 30s. You're going to need a tune either way and your tuner can tell you your injector duty cycle numbers. Keeping the IDCs in the 80 to 85% (max) range at WOT is where you want to be. Also make sure that whatever size you get, they have the EV1 style (also called "minitimer") connections, unless you are willing to buy eight connector adapter harnesses. A lot of the later design injectors on the market use EV6 style. Not a major problem, but just something to be aware of.

I agree with Neutron on the fuel pump swap. As long as you're going to have the pump module out anyways, replace the fuel level sender as well. Easy to do both at the same time. Lots of '99s (other years too) had fuel sender issues. If you haven't already, you may even have to deal with the right side siphon jet/sender unit as well.

www.racetronix.com click on "web store". Happy shopping.

neutron82

you might be able to pinch by with the stockers, I did for awhile on my setup with them almost maxed out before I opted for more power... one thing I have learned though is that with fuel it's better to have more than you need than not enough, that's why I recommended a slightly bigger injector along with the upgraded pump to leave you a little wiggle room to grow... if you want to perfectly match the injector to your setup then the tuner will be able to tell you exactly what size you need for your power level

osti33

Thanks for all the great info guys. I really appreciate it.

What do you guys think about the Fast/Bosch 36# part 303608 that Hinson, Summit, etc sell?

Seem like they would be more than enough injector for what I'm doing plus have room to grow. Also it looks like their is plenty of tuning info out there for them in both EFI live and HP tuners. Price seems reasonable too at ~300 shipped.

Thanks.

LoneStarFRC

There's also some website calculators people can go to and plug in their information and it'll tell them what size injector to consider.

The main thing I think it's important for people to keep in mind is, be HONEST with yourself and be as accurate with your info as possible. IOW, don't go into it with some pre-conceived, offhand notion of what you THINK the size should be (usually based on your buddies, or internet chatter, etc). Let the info speak for itself.

For the most part, I think people will be pleasantly surprised by the fact that they can use either their stockers, or if an upgrade is indicated, it does NOT need to be some God-awful, huge, MEGA injector. There just seems to be a lot of misinformation out there with regard to injector sizing. It's like carburetors, more is not always "better".

HTH

osti33

Thanks for the help guys. I'll keep my eye out for some 28s or 30s.

I appreciate all the help.

Bill Curlee

Just remember,,,,,,, You CANT just pop a new set of LARGER injectors in and run them. They have to be scalled in the PCM for the proper duty cycle.

The best thing to do is, purchase you injectors and when you tune the car, install the new injectors so they can be scalled by the tuner. Your NEW injectors wil or should come with paperwork on the flow data and everything the tuner needs to properly scale them in the tune1



BC