Injection Perplexion!?!

[pbsch]

So my new set of 21# injectors came in today. Before even installing them in the car I wanted to know how closely balanced they were. So, I installed them on my fuel rail and tested them one by one.

Based on the conversion program from witchhunter.com my stock 17# injectors should flow 178cc/ml per minute at 100% duty cycle.


Using fairly scientific process - stopwatch on my cell phone and a good controller switch. I ran each injector for darn near to a minute (well within 1%) at 43# fuel pressure
When I initially tested the injectors that were in the car I got 85, 90, 130, 150, 150 and 150ml. odd.

I assumed that, therefore, I had four relatively good injectors and two really bad ones.

I started looking for two more 17# injectors and located delco brand ones at a reasonable price. Brand new out of the box, they flowed 85ml hmmmm

I had also ordered a complete set of 21#ers. The first three I tested all flowed 100ml!!!

I decided to verify the part numbers on the injectors that came with the car and interestingly the ones that flowed 150 had a part number that correlated to a 25# injector from a four cylinder. So, here is what I see so far

Injector rating Should flow Flows
25# 262ml 150ml
21# 208ml 100ml
17# 178ml 85ml

I'm going back out to check the pressure on my fuel rail, but otherwise I am perplexed.
I also verified that my measuring container was properly calibrated

Anyone flow tested any of their injectors and gotten the ml that they should?

[pbsch]

On a percentage basis, these all represent somewhere between 47 and 57% of expected which is statistically interesting

[pbsch]

OK, I'm almost embarrassed to admit this, but I just rechecked fuel pressure and the pump that was rock solid at 45# is now at 20#. pinched the return line and it didn't improve, so I don't think it is regulator related...

[unchained01]

They might have been tested/rated at 55psi instead of 43.5 And i hope some else chimes in and sheds some light on it also

[Superdave]

you need constant pressure to test them reliably, i used a large tank filled with WD-40 tied to an air compressor regulated down to 45 PSI.. then just my phone and a micro switch to open/close them.


That's from back when i was cleaning them in the ultrasonic cleaner. I usually got consistent results after cleaning.. before was a different story.

[pbsch]

Mystery solved. The hose between my fuel pump and the lid to the surge tank had split - guess just cause the auto parts store says it is FI rated doesn't mean it is... Fortunately I had some leftover hose from the drag shop I bought to do the jump from the surge tank to the steel fuel line and the fuel line to the fuel rail, so it was a 20 minute fix. Back to rock solid 45 psi at the fuel rail! New injectors 210ml old 17# injectors 175ml, mystery 25# injectors 250ml. All is right with the world again. Got too late to fire the car up and blast it around the neighborhood so I'll have yet another day at the office to think about getting home and seeing how the car runs. Off to reset the fuel injector scalar for the new squirters and burn a new prom.

[pbsch]

I now have four extra 17# injectors(3 that are brand new) and four 25# injectors that are volume verified if anyone is in the market for some proven good ones, shoot me a PM.

[robertisaar]

crazy that someone had apparently replaced the factory injectors with some significantly oversized injectors....

happen to know what the 4 banger injectors are from? and if they're low-impedance?

also: i'd check your plugs to make sure they aren't completely flooded with fuel on those cylinders and oxidized on the cylinders that didn't have the 4 cylinder injectors.

[pbsch]

I believe they came from the 2.3 and 2.4 GM motors of a similar vintage part number 17091654. They are typical impedance 13.6 ohms.

Spark plugs are like new clean and shiny - I haven't run this more than twenty minutes and only drove it around the block a couple of times

[robertisaar]

odd.... i'm finding those listed as both LT4 corvette injectors and as 2.4 injectors....

the bad part is that the LT4 application, i KNOW are high impedance and the 2.4 is listed as low impedance....