[codyace]

Originally Posted by jspaeth

Haven't rewired the pump, but here is an interesting tidbit, which may be relevant.

We did this forever ago with DSM's and small wired jap cars, so it's something I just natrually do on new cars.

Super easy to do as well. Use the factory fuel pump 'power' wire as the trigger for the relay, battery for power in, ground to the chassis, and run a new power out wire. Easy Peezy. This way you know FOR SURE you'll have good voltage going to the pump at all times.

Originally Posted by jspaeth

Checked voltage from hot side of pump to ground side of pump and hot side of pump to chassis, and both give 12 V.

Another thing to check (being you're not rewired) is alternator output at WOT. Not sure if the ApexI unit does this or not...I know I can log it though with my Conzult.

Originally Posted by jspaeth

as for the weak pump....I am saying if the pump is weak up top to the point where it is unable to still provide enough flow/pressure to keep the pressure in the rail at say 62 psi, then you will have to use more injector duty than you thought you would have had to.

I can see your train of thought, but to me, 62 psi from the pump is 62 psi from the pump...and shouldn't require any more fuel in the grand schme of things...what you're describing would be in the event the pump is weak, and the regulator is only persay putting 55 psi at WOT to the car...which would then make sense (higher duty cycle) as the injectors are being asked to work faster.

Originally Posted by jspaeth

This might be wrong, but it seems like a possibility to me. I really need a digital FP gauge, but don't feel like spending the $$$.

For what? Just put a T in your fuel line, run it up to the window under the wiper. At the other end of the line, just put a gauge in. Crude? certainly...but it's mechanical, and it works.

Originally Posted by jspaeth

You say power is based on tune, but given a perfect tune and reasonable AFRs, you should again be able to CALCULATE how much fuel you require for an engine to put out XXX whp.

Another crude mathematical forumula I've used is the following...it's oddly dead on.

Desired whp (or actual whp) X 1.15 (drivetrain loss) = Crank Power
Crank Power/2 = Number then take Number /4 (4 cyl) = Injector size minimum required to run for the power

For example (my car)

400 x 1.15 = 460 415/2 = 230 230/4 = 57.5 lbs (603.75 cc)

THis is about damn near dead on for my car. I have 615's, and my car run low 90% duty cycle for the power at WOT.

It's funny to see how this works on 'most' cars. I'm not sure where I initially learned this little trick (I think it was a street racing thing we used to do, as you'd ask for injector size to determine the cars potential power output...this way you could gauge a cars pwoer without asking hhaha)

Originally Posted by slider2828

Yeah that is really weird.... but.... At the top end, I get about 10.7 AFR.... Now I believe it should be closer to the 11.5, but I measure pre cat, so its about 11.5 post cat. I think that is most important to keep in mind.....

I think pre cat measurements would be the one I'm looking for...this way the actual outside air can't change the measurement. 10.7 is very rich IMO.

Originally Posted by slider2828

Just for kicks, try putting in the stock fpr... I seen some weird things happen with adjustable fprs....

Agreed. This is why I like Nismo ones.





This has become quite the troubleshooting thread Nice to see some civilized car discussion going on