Injectors?

[Devin Smith]

Here is my set up its a 1989 lx coupe. i need to know if i have to bump up to 24lb injectors im currently running stock 19lbs? The closest dyno is 8 hours away.

· 4.10 ford racing gear
· Lakewood 50/50 rear shocks
· C4 transmission with tsi reverse manual valve body, PA servos and Coan 3000 stall
· Hurst quarter stick shifter
· Cold air Intake
· 76mm C&L mass air
· 70 mm BBK throttle body and egr spacer
· MSD coil
· MSD cap and rotor
· MSD 8mm spark plug wires
· BBK shorty headers 2.5’
· BBK off road H Pipe 2.5’
· Flow Master super 44 mufflers 2.5’

· Energy suspension poly motor mounts
· Centerline warrior rims with MT skinny’s and MT 26x10.5x15 cheater slicks
· Ford racing Ac delete
· Smog pump delete
· Front sway removed
· Timing bumped to 14 degrees
· Electric fan
· BBK under drive pulleys
· Frame connectors
· Hurst roll control
* Summit racing aluminum Rad
* 3 inch harwood fiberglass hood
* 2 Carbeau forza seats
* Pro Comp upper and lower intake Gasket mached
*GT40X aluminum heads
*1.7 roller tip rockers Comp Cams

 

[Mr. Snrub]

I'm gonna say the 19s should be fine.

 

[Devin Smith]

thanks for the reply. with out the heads and upper and lower intake i was running 1.559 60 foot and 8.353 @ 82.28 mph 1/8

 

[Devin Smith]

mr. snrub what injectors are you using and your set up?

 

[Mr. Snrub]

mr. snrub what injectors are you using and your set up?

Edelbrock Performer heads - 2.02" intake and 1.60" exhaust, E-Cam, 1.6rr, gt40 tubular intake. 65mm throttle body, BBK maf, longtubes, prochamber, mac catback, 24lbs injectors.

 

[Devin Smith]

what made you switch to 24lbs injectors

 

[A5literMan]

You should only need 19's. If you had more cam,bigger heads,etc(made more power) you could step up the injector size. Right now you're probably still only in the 260rwhp range (or a little less). Check your plugs after a pass and see if they're showing any lean condition. If not keep rocking the 19's

 

[jrichker]

Stock heads , stock intake and stock cam will run fine with 19# injectors. here's why...

Fuel injector sizing & injector photos

Revised 26-Dec-2014 to add statement about figures are for flywheel HP and not rear wheel HP

Injector HP ratings: this flywheel HP, not rear wheel HP.
Divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines at the flywheel.

Example:
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP
36/.5 = 72, 72 x 8 = 576 HP
42/.5 = 84, 84 x 8 = 672 HP

The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.

19/.5 = 38, 38 x 8 = 304 HP x .85 = 258 HP
24/.5 = 48, 48 x 8 = 384 HP x .85 = 326 HP
30/.5 = 60, 60 x 8 = 480 HP x .85 = 408 HP
36/.5 = 72, 72 x 8 = 576 HP x .85 = 490 HP
42/.5 = 84, 84 x 8 = 672 HP x .85 = 571 HP

Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.

See Stan Weiss' - Automotive Performance Software / Interactive JavaScript to Calculate Change in Fuel Injector Flow from change in Fuel Pressure to get the calculators used in these examples.

Here's the duty cycle explanation. Duty cycle is how much of the time the intake is open the injectors are turned on. The 85% figure means that for 85% of the time the intake valve is open, the injectors are spraying. The idea is that you want some percentage of the duty cycle left over so that you have some room to grow the process.

If you are at 100% and you need more fuel, all you can do is turn up the fuel pressure. That means the whole fuel curve from idle to WOT is affected. Maybe you are already too rich at idle, and turning up the fuel pressure makes it worse. If you had some injector duty cycle left to play with, a custom tune could use that where it is needed. That would not over richen the whole range from idle to WOT.

If you did turn up the fuel pressure, you might be able to change the injector duty cycle to get the air/fuel mixture ratio you want since the injectors will have extra fuel delivery capability.

With larger than stock injectors or higher that stock fuel pressure, you will need an aftermarket MAF that matches the injector size. The MAF “lies” to the computer to get a fuel delivery schedule that meets the engine’s needs and isn’t too rich or too lean. The best strategy is an aftermarket MAF and a custom tune to insure the best air/fuel ratio over all the RPM range.

Don't forget to increase the fuel pump size when you increase injector size or significantly increase the fuel pressure



Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Wiring & Engine Info Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif[/b]

 

[RangerJoe]

Nice track times for such a mild combo.

Joe

 

[Devin Smith]

ya we couldn't believe i was getting those times. hoping to be in the 7s with the new intake, heads and 1.7 rockers. it leaves hard that c4 and sticky mickeys.

 

[Devin Smith]

heres a slip

 

[FastDriver]

Is everyone else missing the GT40X heads? He was running 82mph BEFORE the heads and intake. That's showing some decent power. I think you should upgrade the injectors, and I would base the upgrade on planned mods so you can grow into them. 24lbs would work well if you'll stay N/A.

 

[Devin Smith]

i ordered the tube for my c&L and accel 24 lbs injectors to be safe.

 

[Devin Smith]

do you guys think i need to upgrade my fuel pump its stock right now. i prefer if i can hold off for a bit.

 

[A5literMan]

Definetly upgrade the pump! If no power adders are in the future I recommend a 155-190lph pump. If you're going to be adding a bigger motor or forced induction go with at least a 255lph.

 

[FastDriver]

Don't skimp. Use a Walbro GSS 340. You can get them for $90 or less new.

 

[Devin Smith]

i ordered the 190 for now should be plenty for this set up cause i have bigger plans in the future. plan on going carbed.

 

[FastDriver]

Suit yourself, but there's no reason not to run a 255. I doubt you save any money going with the 190, and a 255 will last forever, too.