Well I upgraded from the stock TBI injectors (40#) to 55# 350 injectors today and I'm a little confused with respect to the BPW Constant. The formula that I've found for it is:

1461.5 * (Displacement of one cylinder in liters)
------------------------------------------------------------
Injector flow rate in grams/sec.

Using this, the stock BPW would be:

1461.5 * .6247 liters
------------------- = 181.7
5.040 grams/sec

But it's not, in my bin, and every other LO3 bin I've seen, it's been 134. So when I changed my fuel pressure a while back from 12 psi to 14.5 psi, I changed my BPW to:

Old BPW * Sqrt (12/14.5) = 122

And tuned from there

So for the new injectors:

BPW = 1461.5*.6247/ ( 6.9299 * sqrt (14.5/12)) = 120.2

Or I could take the old BPW * multipy it by .727 (ratio of the injector flow rates) and use that (88.72)

There's a big difference between the two (duh). Where am I going wrong? Is the stock BPW way off or am I missing something in the math?

Tony

 

The regular 350 injectors are closer to 61#/hr, so I'll use that.

61#/hr = 7.686 gms/sec

bpc = (1461.5 * .6247) / 7.686

bpc = 119

RBob.

P.S. Flow rate conversion: gms/sec = (lbs/hr / 3600) * 453.6

 

Thanks Rbob, but is the stock BPW way off?