To decap these injectors all you need is a dremel, a steady hand and a few minutes. I started by lightly clamping the injectors in a plastic jawed vice with the strainer facing horizontally towards me. With a cutting blade in the dremel (like a mini angle grinder) I ran a cut around the outside edge of the tip. You have to be careful not to cut too deep as the strainer is extremely thin. Once the cut is all the way around the "cap" falls off. After a quick tidy up and smooth off the first highflow injector was done.
The decapped injector is on the left:
With 8 decapped injectors in hand I took myself off to Fueltech Automotive. Big thanks to Pete and the boys for letting me loose on their injector
flow bench. Fuel pressure was initially set at 35psi. First off we checked the
flow by simulating 32ms injector timing and simulated 1600rpm. The photo gives a good idea of the spray pattern from the newly highflowed injectors.
Notice there is only 7 injectors fitted - well it turns out somebody had lost the 8th injector boss.
I'm no expert so I can't say for sure if these flows are what should be expected but I'm sure someone will let me know soon enough. According to the boys the spray pattern is a little "fluffy" but not as bad as they have seen from some other injectors.
Next up was the all important
flow test. The
test bench has a setting for
flow testing and some graduated tubes for reading off the
flow. This is where the fun started. The
test bench has adjustable fuel pressure but the
test cycle is locked at 15 seconds.
I hit the start button and was totally amazed to find that each injector had flowed roughly the same amount, the biggest problem was they had only flowed roughly 112mL each. Now if an injectors flows 112mL in 15 sec then it flows 448cc per minute. I was astounded, I thought decapping was supposed to increase the
flow when these things are 440cc to start.
Not being able to believe the results I decided to repeat the
test. This time I watched the pressure gauge and noticed it was dropping to around 18psi. Now that makes more sense. The injcetors now
flow as much as 18psi as a stock injector at 35psi.
It turns out the
flow bench isn't made for testing such high
flow injectors. The pump simply couldn't keep up with the
flow no matter how hard I tried. The decision was made to run one injector at a time.
After disconnecting six of the seven injectors I started the
test again. This time the graduated vessel overflowed after just 5 seconds of testing. When the injectors are run a fair amount of foam is made on the surface of the liquid. I believe this is something to do with the liquid the machine uses.
The fuel pressure was then reduced to 30psi to give a slight reduction in
flow to hopefully let me
test each injector. Because the
flow bench has a fixed 15 sec
test cycle I was forced to hand time a 5 sec cycle. The machine times down automatically but I stopped it manually so it didn't overflow - once stopped the machine displays the
test cycle time as a whole second value. This means I could be testing anwhere from 4.5-5.5 sec and still display 5 sec. As a result my overall
flow figures are just ballpark numbers.
Injector #1 - 66mL in 5 sec - 792cc
Injector #2 - 67.5mL in 5 sec - 810cc
Injector #3 - 66.5mL in 5 sec - 798cc
Injector #4 - 64mL in 5 sec - 760cc (I think these results are a mistake)
Injector #5 - 67mL in 5 sec - 804cc
Injector #6 - 67mL in 5 sec - 804cc
Injector #7 - 66mL in 5 sec - 792cc
Injector #8 - 66mL in 5 sec - 792cc
Looking back at the results we can see there is a spead of 50cc from least to most. Based on these poor figures there is 5.6% variation across all 8 injectors.
Once all the serious stuff was done I decided I'd wind the pressure up a bit. Thinking about it, most people are quite happy to run 15psi through their motors so I got to thinking 35psi base pressure + 15psi boost pressure gives a rail pressure of 50psi. What would these bad boys
flow
A 5 sec
test showed a
flow of 79mL or a total
flow of 948cc
That got me thinking - what if I wanted to run 20psi boost??? So the fuel pressure was increased to 55psi but a 5 sec
test was enough to overflow the 130mL graduated tubes . After a little juggling I settled on a 3 sec
test giving 58mL or a massive total
flow of around 1160cc
I've had fun, hopefully it's been a good read and hopefully it helps someone out.
