I’ve been doing a lot of reading and research on injectors and their duty cycles. What I’ve stumbled upon may be totally incorrect, but I may have a way to get an estimate of HP based on how much flow my injectors are putting out under WOT and no KR. Now, this is by no means a scientific method to calculate HP, but I figure it may be close. Here’s what I’ve put together:

If the max flow rate for a given injector is known and….

You have your readings for injector Pulsewidths at WOT

Then based on formulas which I’ve found on this and other sites we can get an approximation of FWHP

Injector PW calc
2*60/rpm = maxpw at given rpm – this is the maxpw the injector is rated at for this rpm
So 2*60/6000 = .020 or 20ms so at 6Krpms, this injector has a max pw of 20ms

So we then take our given pw at that moment and
Pw/maxpw (ie, 17/20) = current duty cycle
17/20 = .85 or 85%

Now that we have duty cycle for the injector (28.4lbs/hr stock ’98 injector rating) we calculate for hp by
504*currentdc
504 is the max fwhp a 28.4lbs/hr injector can supply given reasonable figures
504*.85 = 428hp at current injector pw and rpm

So, in this case, given 6000rpm and a current injector pw of 17ms, I’ve derived that I’m putting out 428fwhp

I don’t know if hp ratings are linear for a given injector based on max duty cycle, but according to the numbers I’ve seen, they appear to be. I don’t know if this is even in the ballpark, but it would seem that it’s a decent estimation of fwhp at that given moment. Now, one thing I’ve thought about is that if there is any KR at that moment, the computer may be slowing down the flow of fuel to compensate for the KR, so, make sure you don’t have any KR and that you are taking readings from your WOT fuel cell because under these conditions, the computer is going to be supplying the max amount of fuel for the given conditions.

If someone has a dyno sheet and a scan log, they can verify how close my calculations are. I haven’t dyno’d my car yet, so I have no clue how close these approximations are.

So, what do the gurus think?

<small>[ September 07, 2002, 10:19 PM: Message edited by: Badazzvette ]</small>