C5 for life

My research indicates the stock injectors are good up to 400 HP. I’ve also seen guys upgrading injectors with mild upgrades. With my car going under the wrench shortly to install :

Comp cams 54-444-11 cam
BTR trunion upgrade
spring upgrade
under drive pulley
Ls2 timing chain
1 7/8 inch headers/X pipe/ Ti axle back, already on
follwed by a dyno tune

I should be around 400HP. As I’m trying to make the best of my first upgrade, will I benefit from injector upgrade ?

04 6 speed 50k miles

Interestsd in the most aggressive daily driver. No auto cross. Couple passes down the track for results.

Thanks guys

Russ K

The stock injectors will support ~ 440 RWHP. That's assuming your not using E85 fuel.

Russ Kemp

aaronc7

Headers/tune, 390whp on a C5Z, I was around 85-90% injector duty cycle IIRC.

Probably not worth upgrading at this point, unless you think you'll add more down the road.

Or another way to look at it is you'll already be getting the car tuned/re-tuned, putting injectors in now would be a good time to do it.

I ran the GTP 36 lb/hr injectors on my NA setup.

Gordy M

A lot depends on what you want the car to do. If you are into autocross/HPDE/drags then you will be in the upper range of the injector duty cycle and 36 lb injectors would be of use. If it is for occasional fun driving/ canyon runs etc., then you can get by with the stock injectors.

JHrinsin

That is what the PO was seeing on his setup before switching to FAST 36 lbs/hr injectors. That maybe okay for street driving - you can argue just how long do you keep it at WOT down the freeway entrance ramp? But if you do track events you really don't want to see duty cycle much over 80% for any "extended" time frame. What exactly is "extended" period of time you ask - believe it or not just a few seconds. It would be better to switch to say 36 lbs/hr units so as to keep the duty cycle under the 80% threshold during WOT runs down the front or back straights or at the drag strip.

C5 for life

All good feedback guys. I want this car to make the best out of the upgrades. I drive it the same everyday. Translation, she gets a workout every time I turn the key. Without seeing over 6k RPM and fanning the clutch. I pretty much wash my day off between 2nd and 3rd and start my day with a decent rip on my way to work.

91BlueZ

The way to determine what size injectors you need, is to run the numbers through a fuel injector size calculator. A web search will turn up several calculators.

Assuming 400 HP on a naturally aspirated engine, and a max duty cycle of 85%, the smallest injector you can run works out to 31.3 lb/hr. That would mean you need 32 lb injectors or larger.

aaronc7

Online calculators are great for getting you in the ballpark..........end of story. BSFC is a ballpark guess at best.

0JUICED1

Once you start passing that 90% duty cycle range it would be wise to upgrade. We have tons of options and some great deals. We also have a injector tech page that shows all the injector calculator math and some break downs on how it all works.

91BlueZ

While I agree with you, I'm not aware of a better way to figure what size you need. Using a calculator requires you to guesstimate 2 things, HP and BSFC. Naturally aspirated will typically get you between .5 and .55 BSFC. You would need to dyno the engine to determine both BSFC and HP exactly.

neutron82

you could also raise the fuel pressure to get more flow out of your injector assuming you have enough pump for it and an adjustable regulator