how to figure injector constant?
Thread Starter
Joined: Nov 2001
Posts: 7,903
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From: Cleveland, OH
how to figure injector constant? I have msd 50# rated at 43.5 i believe it is.
I am running with 50 psi static fp. That is without the vacuum hose attached. At idle with the hose attached my fp drops to 42 with 18" vacuum. I'm using a vacuum/boost reference regulator. I cam up with 7.31 as a constant but that didnt work too well. What is the proper number to use? I insert the same number all the way across the injector constant scale i believe.
I am running with 50 psi static fp. That is without the vacuum hose attached. At idle with the hose attached my fp drops to 42 with 18" vacuum. I'm using a vacuum/boost reference regulator. I cam up with 7.31 as a constant but that didnt work too well. What is the proper number to use? I insert the same number all the way across the injector constant scale i believe.
Re: how to figure injector constant? Using Chris B's spreadsheet, assuming a constant FP of 50, I get:
At MAP = 0, 6.75
At MAP = 40, 7.14
at MAP = 80, 7.50
Use of the same number all the way accross is probably not correct.
I'll send you the spreadsheet, as I'm not 100% confident that I manipulated correctly for your situation.
BTW, I got it from a thread started by GodSpeed in this forum.
At MAP = 0, 6.75
At MAP = 40, 7.14
at MAP = 80, 7.50
Use of the same number all the way accross is probably not correct.
I'll send you the spreadsheet, as I'm not 100% confident that I manipulated correctly for your situation.
BTW, I got it from a thread started by GodSpeed in this forum.
Re: how to figure injector constant? yea the pressure does rise, but if it rises one psi per psi boost, then the relative pressure of the fuel pushing into the intake is still the same.
TECH Fanatic
Joined: Nov 2001
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From: Las Cruces, NM
Re: how to figure injector constant? For FI the number stays the same across the board, because the pressure difference is the same. You need to post the size of the original injectors. But any way there probably 28 lb at 58 psi or so and you new ones flow 50lb at 43 psi.
So you only have roughly 1.78 times the flow going into the engine as stock. Even if you had the 50 lb injectors running at 58 psi they would flow ~57 lb, so that would give you 2.06 times the flow.
Gary
So you only have roughly 1.78 times the flow going into the engine as stock. Even if you had the 50 lb injectors running at 58 psi they would flow ~57 lb, so that would give you 2.06 times the flow.
Gary
