Digital Tuning T4m0 - Dial In The Injectors

[lizzard]

hi dudes
I'd like to dial in the injectors properly:
I installed 19 lb/hr aftermarket injectors in my mustang GTS 95 and realized afterwards that their flow rate was tested @43.5 psi, not @39 psi

So make sure your injectors are dialed in properly (remember that many aftermarket injectors are flow-rated at 43.5psi, not 39 that you're getting at the fuel rail, which makes them act smaller than their rated flow so you should put in the REAL number for high & low slope adjusted for fuel pressure). This small tip was a source of much frustration and makes a lot of folks think the computer's impossible to tune. It's not.

So, @jozsefsz what are the REAL numbers?
39/43.5*19=17.03 lb/hr for high slope? (AHISL)
24.97 lb/hr for low slope? (ALOSL)
that's it?

 

[a91what]

Can't you just increase the rail pressure?

 

[jozsefsz]

Hey Mr. Lizzard!

This calculator is handy for flow rate change calculations (it's not exactly a 1:1 ratio to pressure):
RC Fuel Injection

To save you the trouble, 39psi is about 200cc/min, so 19lb injectors rated at 43.5psi will flow ~18 at 39psi.

So I'd go with 18psi hi, I'd use about 24-25 for lo myself. A lot depends on your specific injectors -- more modern designs are less sloppy at low pulsewidths. If they're a good brand (not some eBay injectors that have disappointed me before) go on the low side (24) for lo slope.

If you have an AFPR you could move up to 43.5, or even higher if your injectors support it, but if you don't those settings should take care of you.

Just a note, the difference between 18 & 19 is going to be pretty small, probably within the EEC's ability to adjust. So personally I wouldn't do too much other setting changes (breakpoint, min pulsewidth, battery offset) -- those are probably close enough.

 

[lizzard]

hey thanks for the calculations and for the link jozsefsz!
Actually I had a AFPR from BBK, but it was leaking like hell. So I sent it back with this useless liquid filled pressure gauge.