Injector Sizing

[Barbadian Camaro]

I see they is a Head and Cam Bible,and Cam Comparison and NO Injector sizing to suit your mods.

[techsan23]

Re: Injector Sizing

I think that is usually based on what kind of horsepower your pushing with your setup. If you are running forced induction with your head/cam combo you will be using a completely diff size injector, and even then it will be based on boost level.

[ssms5411]

Re: Injector Sizing

^ Yes it depends what your going to do, I'm running 36LB (33lb) GTP injectors on my car right now since I had a Powerdyne, then was running nitrous and will be turbo soon so I never swaped the old ones back in just a hazzle. With just my VS cam I'm still running 50%+ duty cycle with these injectors so I'm glad I left them in. I will be putting in 65LB injectors once the turbo goes in. So you just need to know what your final goal is and find the injectors to match, used 36lb GTP injectors are cheap around $60-$70 and are a nice upgrade depending what style injector you need.

[Barbadian Camaro]

Re: Injector Sizing

Well the same way you have head and cam combos they should be Injector size combos too,that's basically what I mean as SSMS5411 give just a brief description on what his set up is and include Injector size with his combo.

[mdenz3]

Re: Injector Sizing

No need for a Bible, just math. :)

To figure out how much horsepower these injectors can support. To do that we need to know about B.S.F.C. (Brake Specific Fuel Consumption). B.S.F.C. is the amount of fuel, in pounds, that the engine will use per hour, per horsepower it produces. The recommended levels of fuel consumption are; .45-.50 lbs per hr per hp for naturally aspirated engines, .55-.60 lbs per hr per hp for supercharged engines, and .60-.65 lbs per hr per hp for turbo charged engines. To determine what horsepower levels an injector will support use the fallowing formula:
injector size (in lbs / hr) X % duty cycle / B.S.F.C = Horse Power supported per injector
For this example:
34.327 X .80 / .50
27.4616 / .50
54.9232 hp per injector, or a 439 hp N/A V8

To determine what size fuel injectors your engine will need you would use the fallowing formula:
Horsepower X B.S.F.C / Number of injectors X Duty cycle ( 80% )
For example:
400 X .50 / 8 X .80
200 / 6.4
31.25 lbs / hr injectors

To determine what size fuel pump an engine will need you would use the fallowing formula:
Horsepower X B.S.F.C. + 15% (for recirculation and flow loss in piping)
For example:
400 X .50 = 200
200 + 15% = 230 lbs / hr, or 35.18 Gal / hr

To determine the increased flow rate of n injector at a greater fuel pressure use the fallowing formula:
√ ( new pressure / old pressure ) X old flow rate = new flow rate
For example:
√ ( 50 / 43 ) X 34.327
√ 1.1628 X 34.327
1.0783 X 34.327
37.015 lbs / hr @ 50psi (It would now support a 470 hp N/A V8 engine)

Conversions: (number used by GM in stock calibration)
1 Gallon = 6.538 pounds
1 Gallon = 3.785 liters
1 Gallon = 3785.411 ml
1 pound = .153 Gallons
1 pound = .5791 liters
1 pound = 579.1 ml

Important note, all HP numbers are at the flywheel.

[Fondle]

Re: Injector Sizing

i got a set of 28lb to sell, they should be big enough for what you want to do

[whitdog54]

Re: Injector Sizing

Are the GTP injectors dierct swap for 99+ cars? Also what year GTPs?

[97rs4life]

Re: Injector Sizing

Are the GTP injectors dierct swap for 99+ cars? Also what year GTPs?

no, the connectors are different for 00-02 cars. If a 99 then yes

[LETZRIDE]

Re: Injector Sizing

i got a set of 28lb to sell, they should be big enough for what you want to do

how can you say that when he hasnt said what he wants to do yet? if just a mild cam you can probably get away with 28#, if going cam and heads, or going with a pretty big cam, then I would go 36#

[Blizzard242]

Re: Injector Sizing

how can you say that when he hasnt said what he wants to do yet? if just a mild cam you can probably get away with 28#, if going cam and heads, or going with a pretty big cam, then I would go 36#

Not everyone is an amazing salesperson.

BTW, welcome mdenz3.

[BallerMaro13]

Re: Injector Sizing

BTW, welcome mdenz3.

damn, new guy just went all Good Will Hunting on this thread haha.

as Blizzard said, welcome aboard mang.

[ssms5411]

Re: Injector Sizing

damn, new guy just went all Good Will Hunting on this thread haha.

as Blizzard said, welcome aboard mang.

Damm Fondle , getting rid of members again........J/K with you man.LOL

[whitdog54]

Re: Injector Sizing

no, the connectors are different for 00-02 cars. If a 99 then yes

Yea I knew it was something like that.

So what would be a cheap upgrade for 00-02 cars. Will any year GTPs swap out? Or do you have to go aftermarket?