I have kinda been side tracked with the CIS-to-EFI project because I have been overhauling my 915 transmission. The following is some work I did on the EFI conversion I did in January.
I decided to measure the flow rate of the six injectors I had. They are the Rochester type part number #7151 17084888 and came off a V6 3.1L Lumina/Corsica. I originally thought that since the Lumina was a 3.1L and my 911SC is a 3.0L I would be OK. This was not the case.
I took my trusty 2L bottle and filled it up with some water. Then I compressed it to 50psi. The fuel regulators on fuel injection systems use 3atm of fuel pressure which is 44psi. I went with 50psi as it is easy to read on my gauge. Plus the pressure would drop a little as the water was removed from the bottle.
I connected the rubber hose from the 2L bottle to the injector. I turn the bottle upside down. I applied 12v to the injector and the water started to flow out the injector. I placed a container under the injector to catch all the water. I turned on the injector for exactly 3minutes. I repeated this a couple of times for each injector. The following were the results:
1) 357g of water
2) 351g of water
3) 367g of water
4) 358g of water
5) 356g of water
6) 357g of water
All the injectors were within 3% of each other, which is good. Calculating the flow of water resulted in an average of 15.8lbs/hr. Since water is heavier than gasoline, I could expect a higher flow rate with gasoline. I calculated that I should get about 12% more flow rate with gasoline than water. This results in a flow rate of 17.5lb/hr of gasoline.
Reading on the net I found that the flow rate of the injectors needed is:
flow rate = engine HP/ 2 / number of injectors / 85%
The 85% is the max duty cycle the injectors should be run to be on the safe side. I figured my 911SC has about 195hp with the backdated exhaust.
This gives me a required flow rate of 19.1lb/hr which is less than the 17.5lb/hr I was getting from my injectors. This means I needed higher flow rate injectors. I could probable use them and be OK as this estimate assumes a very rich running engine, however I have plans to increase power so I don't want to be on the edge with the injectors.
Looking on the net I found that the injectors from 5.0L mustangs are 19lb/hr. I though I should get 21lb/hr to be on the safe side, but they are very expensive. I also found out that the 3.2L 911 engines with EFI use 19lb/hr injectors, so I thought 19lb/hr should be OK. I picked up 8 of them for $15 + $15 shipping on ebay. The photos below shows the two. The injector in the left is the Rochester and the injector on the right is the Bosch one from the Mustang. The adapter I made for the Rochester injector to fit on my runners also works for the Bosch injector. I did a quick flow test on one Bosch injector using the same setup and found it had a 25% high flow. I will clean and flow test all eight injectors when I have time.