ULTM8Z

This has been an epic failure so far... looking for some insight...

So at the last dyno day here in SoCal, we found my 24 lb injectors were going static (if i recall) around 5000 rpm and up. I'm pushing ~400 hp at the crank. It seemed like I was max-ing out on the 24's.

Decided to get some 30lb injectors to give myself plenty of margin.

Figured I could swap in the injectors, change the injector constant to 30, and the VE tables would remain essentially unchanged.

WRONG!!!!!!

I got hold of two different sets of injectors from two different members here.

Holley (which I believe are Rochestor)

LSX from Fuel Injector Connection

I started with the Holley and had to completely recalibrate the VE tables. Values were way off, and it wasn't a simply a case of scaling the entire VE tables by some amount. I had to redo everything.

Played around with that for a while and they never seemed to run quite right (as compared to the 24's).

So I took those off and put on the LSX injectors. Now going from one 30lb set to another 30lb set, the VE table was way off AGAIN! The BLM's dropped down to between 108 and 112 all over the place.

How can this be? I thought the ECM would scale everything with a simple injector constant change.

Other pieces of info....

I measured the DC resistance of these injectors:

24's = 14.5 avg

30's (Holley) = 12.5 avg

30's (LSX) = 14.5 avg


Also, a curious thing happened a several weeks ago too (while running the 24's)... I had a faulty alternator connector (basically some corrosion on the terminals) that resulted in the system voltage spiking to around 16V. I took the car out for a drive (not noticing this initially) and coincidentally with a update on the tune and was shocked at the increase in torque. I thought I made a huge improvement in the tune, but I then noticed the voltage, pulled over, unplugged and reconnected the connector and the voltage returned to normal (14.5V). At that point, the power increase was gone and I've never been able to replicate it since.

Any thoughts? Is there some ECM parameter I'm missing here?

Orr89RocZ

iTrader: (20)

Injectors can have different spray patterns which require slight tuning changes. Surprised yours is that major.
Were the injectors rated at 43.5 psi or 58? Whats your pressure? Did you try messing with inj constant to see if that helps dial in the ve tables?

RBob

iTrader: (1)

The actual flow rates vary, they aren't all flowed at the same pressure and sometimes different fluids are used. So a Holley 24#/hr can flow more or less then a Delphi 24#/hr or a Bosch 24#/hr.

Best thing to do here is to adjust the injector flow rate in the calibration to center the majority of the BLMs around 128. For the most part that 'tweaks' in the actual flow rate, or at least to what the former injector flow rate seemed to be.

The remaining differences in the VE table is due to the injector opening & closing characteristics. This is the offset versus battery voltage and the short injector PW adder versus PW.

RBob.

ULTM8Z

Shoot, I didn't even think about the pressure rating. I'll have to look into that...

I can play around with injector constant, but how would that affected commanded AFR for open loop and PE?


I don't have this switch activated, should it be?

Not sure what this is??


Also, any thoughts on that incident with the 16V system voltage? I would LOVE to re-capture the torque I picked up from that.

Orr89RocZ

iTrader: (20)

16v would offset injectors more, decreasing pulswidth so leanin out the mixture. Plus increased ignition strength possibly? Sounds like your base tune at 14 v is not quite dialed in right. It may be 128 blm but motor may like it leaner or richer. Need to play with it

RBob

iTrader: (1)

It won't affect the commanded AFR, but it will affect the resultant AFR.

$8D right? IIRC, this injector offset compensation is switch/flag selectable to use either the ignition input (also called battery) voltage or the fuel pump monitor input voltage. Your choice.

It is an adder to the PW when they are lower then 3.9 msec:

Above 17.1 volts the ECM shuts down the quad-drivers, not sure if it was that high or not.

RBob.

ULTM8Z

Hmm... I know my fuel pump voltage reads out around 12-13V on the scanner even when the alternator is putting out 14.5. Maybe I need to switch to battery voltage on that one setting... Injectors seeing 14V when the ECM is basing pulse width calculation on a 12-13V system voltage. So maybe when the system hit 16V, it bumped the inj PW calculation to another range where the engine preferred that amount of fuel delivery? Hmmmm.....

ULTM8Z

I called around and looked online and all of my injectors are flow rated at 43 psi which is the pressure I'm running. So at least that's an eliminated variable in this.

1tpi

Very intresting

bladehand

interested as well

ULTM8Z

I contacted Fuel Injector Connection to see if they can supply the BPW vs battery voltage offsets.

BTW, does anyone know where I can get the voltage offsets for the blue top Bosch 24 lb injectors (I think they're the Ford Motorsports, but I've had them for so long, I can't remember where I got them from).