I've been working on scaling for a set of 950cc injectors ... they are acting a little funny ...

Scaling is set around 630cc I believe with the latency increased a little. This puts the low trim at about +6 and the mid trim around +2. Acceptable IMO for that size injector, but it seems very low for a 950. He even checked the part number to verify the injector size.

But the fuel map is very strange. It seems that the injectors spray a ton more as load/RPM rises. For instance, 12.2 might give me 11.5 @ 4000 and 180, but it takes 13.2 to get the same 11.5 @ 4000 and 220. The same goes for increasing revs at the same load.

So, the act like 780's at idle/cruise, but like 950's in boost.

Is this common, or is it maybe a fuel pressure issue?

 

630 scaling is abysmally low for 950s. Something is definitely not right.

Have these injectors been spray/flow tested, by any chance? Can you log (or observe) fuel pressure on this car, preferably post-filter? Low-hanging fruit: have you tried changing the fuel filter?

Just a couple of ideas off the top of my head.

 

The car is 2 states away ... I'll see if he's checked the filter though.

 

Wait, they behave normally under boost, ridiculous at idle/cruise? Vacuum leak, maybe? Problem with the intake snorkel? Venting? Now I'm thinking an air metering problem; does airflow at idle look normal?

It's a couple more ideas, anyway.

 

Which injector brand?

If you are getting +6 FT at idle it needs more latency. It also needs more scaling if you are both +6 and +2 at mid.

Are they Low Impedance?

 

What fuel pump?

 

What i found with my limited experience scaling injectors is the global value is relative to the actual latency values. You could get trims to plus or minus 2 with a lower global right now but the ratio of mid to low trims being off means that you need way more latency to get a higher global more in line with your injector size. as you raise the global the ratio of low to mid changes when it fuels the car. If your 950's have a global of high 7 or low 8 hundred range with the right latency values then your fueli map will more accurate IMO .

Hopefully this makes sense.

Good Luck