I built this setup to measure the minimum pulsewidth for various injectors. By minimum pulsewidth I mean the shortest pulsewidth that results in enough fuel flowing through the injector for an engine to idle.

http://para.noid.org/~lj/InjectorPulseTest.jpg

I've only looked at three part numbers so far, all made by Siemens-Deka, and all tested at 43 psi fuel pressure. Here's what I found:
60 lb/hr high impedance: 1.5 ms (this injector has a "Mototron" part number in ink)
72 lb/hr low impedance: 0.8 ms
83 lb/hr low impedance: 0.9 ms

As expected, the high impedance injector had a fairly broad transition from no flow at all to a reasonable stream, whereas the low impedance injectors had a sharper cutoff. I'm convinced that is why guys have a hard time getting the big high impedance injectors to work well at low loads.

 

sweet setup! thanks for sharing the data. are you able to do more testing for other popular sizes, like svo 30/42s?

 

Anything you want to send me! I have Delphi 65, 75, 85, and 95s plus Bosch 160s in stock that I'll be testing over the next week or so.

 

ah damn, should've told me last week, i just put mine in. a friend of mine has an extra spare, i'll ask him.

 

ahhhhhhhh i should have sent u mine out, i am having troubles low load getting my racetronix 38's to idle, i threw the cam in to try and make it need more fuel. but if i get to low levels of fuel needed the car has a hard tiem running. awesome man!!

 

nice work.

Your values for 60's are very close to some I have for those injectors as well.

I don't know why people have trouble making them work, I use them for fords all the time with no real issues, but I have full batt comp tables as well.

Ryan

 

Yes this is why for years guys go to a low Z injector with big pound hour stuff. Factory cars (german stuff etc) have been running lowZ stuff form the facotry even for years

 

I've got the Motron 60's running well at 1.8-1.9 ms on my combo listed in my sig...

 

I truly don't mean this as any kind of slam: A piece of research I'd really like to see is for someone who has big high-z injectors working well to switch to low-z injectors. Maybe the Motrons really work as well as low-z 60s would, or maybe you would notice a real performance difference if you switched.

BTW, CHarris, do your injectors say Mototron on the body? Or Motron?