Injector size/BPC Calculation

[MOPAR]

Could someone tell me how to calculate the Base Pulse Constant for the $12ose xdf.

I've just done a delco conversion on a 318cu chrysler V8 using Throttle body injection of a EA falcon and need to adjust the BPC to suit the different injector's. The injectors are bosch 0280 150 608, spec's I found on the net state the flow is 350 g/min @ 100kpa. The engine seems to run not to bad at the moment with stock VR V8 bin, by memory the BPC is around 130 but im sure it will need to be adjusted.

[delcowizzid]

try this sucker if you have excell little something holden202 made up the other day or if you know the lbs an hour and cylinder size you can do it with a calculator post up your cylinder size of one cylinder in CC's and the injector size in Lb's/hr and ill work it out its pretty easy

[VL400]

If your using throttle body injection $12S is not going to work that well, it does not support TBI It will only fire the injectors once per rev.



For calculating BPC there are a couple of ways, as far as I can tell the injector calc is supposed to be as follows...
BPC = L Per Cyl Disp / (Grams Per Sec * Number Of Inj Pulse Per Cycle)

However GM has used some fudge factors in there as it does not work out 100% accurate. I think VR V8 injectors are around 19lb/min (or 2.45g/s)



Another way is to use this when adding larger injectors...
(Old Inj/ New Inj) * Current KINJFLOW = New KINJFLOW

Or this if the displacement changes...
(New Disp/ Old Disp) * Current KINJFLOW = New KINJFLOW

[delcowizzid]

ah i didnt even read the throttle body injection part wondered why the low fuel pressure theres the answer

[MOPAR]

How many times does it fire the injectors per rev in say the $5D xdf when TBI is selected? Is it possible to add this option to the $12s if so how hard would it be to do?. The reason im using the $12s is for the high speed comm's and realtime capabilities, does anyone know of any other definition's I could possibly use?

[VL400]

TBI fires the injectors on every ref pulse - so a injector pulse for every cylinder. If you use a TBI memcal you will get the fuel injected on every ref pulse using 12S, so the sync fuel will be ok.

But I think the issue will be the async fuel pulses. This is the fuel thats injected when you hit the throttle, like a accel pump on a carby. On a PFI car its injected between the normal pulses and the fuel essentially sits waiting behind the valve. On a TBI car (using PFI settings) if you give this big hit of fuel it will drown some cyl and lean out others.

Give it a go but if throttle response is average this may be the reason, I have not had much to do with TBI but hopefully others on here who have will be able to offer some ideas.

[MOPAR]

Thank's for the reply. The car isn't drivable yet so im not sure what the throttle respose is like under load but it seem's to run & rev pretty well at the moment. I may have fluked it as the memcal I am using is out of an old camira ecu so it may well be a TBI one. I will put the tekscope on it tomorrow to check the injector frequency compared to the RPM.

Cheer's