How important is it to say have the BPC tweeked for PSI and DC max...?

Say I have the PSI pretty high and DC is not hitting more than 60 and car is screaming pretty good should I lower PSI and retune? I understand this can open up other issues in the tune.... but what is the better way to go?

In a round about way I am trying to figure out with the above tune do we have the best possible PW values being used or if we lower PSI and get DC around the 85% range will the PW be better and get better fueling more so better fuel milage this way?

 

I would say the injectors are sized for the CID displacement and or horsepower at 85% duty cycle at 13 lbs FP. Too small and they go static. Too large and they have has too small a pulse width at idle. I suspect there is a minimum PW. We know there is a maximum as well. I think I experienced too small a PW idle so I needed to go to a VAFPR to clean up idle.

 

Best is to have the largest possible injector PW. This provides the best fuel distribution. Which is why a VRFPR works so well.

First data log some throttle stomps from a low to medium RPM. This will use the injectors to a maximum due to the AE. Can then base a lower fuel pressure (injector flow rate) based on that and the high RPM DC%.

On the TBI engine here there is an RPM area that a throttle stomp causes the DC to go a little above 100%. This is due to the AE event. At 6K RPM WOT the DC is about 82%, so I just leave the injector flow as is.

I could reduce the AE to prevent the DC from going over 100%. But it really doesn't make a difference.

RBob.

 

Ok so I am gonna guess then that 80 pound injectors at 23 psi are better than 90's at 18psi? A higher PSI gives a higher PW? It appears the 90's have a much wider cone and they seem to be a better MIST type of pattern, call me crazy... they just seem to be a much better spray vs the 80's.

I'm off to read more on PW...

 

The flow rate between the 80's at 23 psi and the 90's at 18 psi is nearly the same. So from a PW standpoint there is no difference.

For the cone width, observe the injector spray while the engine is idling. It should strike the TB bore just above the throttle plates. Then run down the sides of the bore and disappear.

RBob.

 

check this out. keep in mind 65 lb and 55 ld injectors exist as well and the biggies.

http://www.users.bigpond.net.au/ben_...ctorsizing.xls