94-95 Mustangs Tuning Injectors

From Mustang-Tech

1 Injector Parameters
2 Pintle Caps
- 2.1 Pintle Cap Part #s and Stores
- 2.2 Replacement Instructions
3 Choosing the Proper Sized Injectors
4 Links
5 Photos
6 Notes

Injector Parameters

Slopes, Breakpoints and Minimum Pulsewidths ^[1]

Injector Size	High Slope	Low Slope	Breakpoint	Minimum PW
19lb	19.5	26.5	0.00001725	0.00000750
24lb	24.5	30.5	0.00001925	0.00000500
30lb	30.5	38.5	0.00001975	0.00000500
36lb	36.5	42.5	0.00002025	0.00000400
38lb	38.5	45.5	0.00002250	0.00000400
42lb	42.5	50.5	0.00002500	0.00000400
50lb	50.5	60.5	0.00002500	0.00000350
55lb	55.5	66.5	0.00002500	0.00000350
83lb	80.5	100.5	0.00003000	0.00000300

Injector Offset vs Battery Voltage ^[1]

Injector Size	10	11	12	13	14	15
24lb	1.350	1.150	1.000	0.925	0.750	0.750
30lb	1.300	1.110	1.000	0.900	0.725	0.725
36lb	1.250	1.075	0.975	0.825	0.700	0.700
42lb	1.150	1.000	0.925	0.750	0.500	0.500
83lb	1.000	0.950	0.700	0.500	0.250	0.250

Crank Fuel Pulsewidth

If your larger injector car has hard starts, edit the function "crank_fuel_pulsewidth" and reduce the values by the ratio of your injector change. This will get you close - you may have to fine tune the calculation for your specific implementation.

Ex. 19lb to 42lb. 19/42 = 0.432

Crank ISC Duty Cycle

This may also have to be adjusted for larger injectors

Pintle Caps

The pintle caps will get brittle and break over time. It's a great idea to replace both the caps and the o-rings while you're at it.

Pintle Cap Part #s and Stores

NAPA Part #2-12085 (pic below)
Borg Warner Part #??? (Found at Pepboys)
Ebay
injector.com

Replacement Instructions

Boil new caps in water
Carefully remove old caps, o-rings and plastic spacer
Install the new spacer and o-ring on the bottom of an injector.
Place the new pintle cap in the circular end of a 10mm wrench on your workbench and press the injector straight down into the cap, careful not to bottom the injector out on your workbench.
Install the top o-ring

Choosing the Proper Sized Injectors

Injector Flow Rates at Various PSI

Typically you do not want to go over 80% duty cycle - this means you want a 20% safety margin on your injectors.

Increasing the fuel pressure from stock (39PSI with vacuum line unplugged) is a crude method to make your injectors perform like larger ones. Upgrading to larger injectors and having a custom tune done is a much more precise way to get exactly the right amount of fuel throughout the RPM band.