Flow-matched Fuel Injectors

If you’ve ever done research into upgrading your fuel injectors, and are looking for a used set, you’ll occasionally see someone saying, “make sure they’re flow-matched”.

Were you ever curious as to what that means?

Look at this video:

In the above video, initially, the spray pattern is being observed, with the injector on the far right turned sideways to see the spray pattern at a different angle.  These are Subaru WRX injectors (so said the author).  The injectors are being run at different RPMs and are not yet clean.  At the end of the observation, the injectors were statically tested.  At the end of that test, 3 of the injectors were flowing 95-96cc while one was flowing 92cc.  3 are within flow specification while the other is not.  His plan is to apply a 20-minute ultrasonic soak to the set in the hopes that the injector with the lower flow will increase it’s flow (the soak would probably clean out any build-up/gunk in the injector).

The above video shows the results of an ultrasonic cleaning and a back-wash to remove any build-up within the injectors from the first video.  Notice that after the static flow test, the injector with the hangup now has a measurement of 96cc, matching at least 2 of the other injectors (the last one is still at 97cc but is probably within spec).

Yes, I saw that he quoted the measurement of the 2nd injector being 92cc in the first video and 93cc in the second video.  Probably a (small) gaff on his part.

I thought these two videos were pretty cool.  I’m a geek like that!

I found the videos while trying to find videos on how to perform an injector swap on GR/GV STIs.

Oh, and by the way, going big on injectors….requires a tune.  The stock ECU cant calibrate itself to adjust for larger injectors — source is here, under the “Questions” tab, and is the answer to Question #3.

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