Hot 4 Teacher

What is the best way to tap a mechanical gauge into the fuel system on an 03 496? I picked up a FAST AF ratio gauge and can now measure both manifolds at the same time, but I'd like to measure the fuel pressure also. Speaking of AF ratio, my engine shop suggested that I didn't go over 12.4:1 anywhere in the rpm range, but I know it makes the most power @ 13:1. What do some of you guys run? I'm going to take some data and send the ECU back to Dustin for some fine tuning and I'd like to nail down an appropriate ratio somewhere in range first. Any help would be greatly appreciated!

Also, what is the sweet spot for this set up? I'm currently turning almost 5,000 rpms @ WOT with my 28's. I know if I change back to my 26's, I'll be up to 5,300 rpm, but don't want to burn more fuel for the same speed.

Raylar

There is a schraeder valve fitting on the right side of the facotry fuel rail on a stock 496 right at the rear of the white coolant bottle. Make your fuel pressure guage connection there for a testing location only. I would never recommend running a fuel line from a pressure fuel system to a boats guage location, TOO LONG, TOO DANGEROUS. As for a snding unit on the motor with wiring to an electrical fuel guage on the dash, to unreliable from a calibration standpoint. Why are you monitoring fuel pressure on your 496?

Regards,
Ray At Raylar

Hot 4 Teacher

Earlier this summer, I didn't monitor anything and fried #3 because of it. I figure if I can monitor my manifold pressure, fuel pressure and AF ratio, I should reduce the chance of a repeat. My high pressure braided fuel line will run along the side and the gauge will mount on my windshield (not in the dash or close to other gauges). Another thing, do you offer a larger throttle body?

Raylar

Sorry to hear about your fuel pressure problem. Was it a problem with the adjustable fuel pressure regulator not staying at the new set pressure or did you have a delivery, fuel filter, screen problem which lowered fuel pressure? Its very unusual to have a fuel pressure problem on the 496 and most times the motor starts knocking quite a bit and sets of the "guardian" system in the ECM. You might want to make sure also you don't have a problem with the actual injector that was in #3 hole.
Yes we do offer a polished billet Raylar 80mm throttlebody to replace the stock 75mm unit. The cost is $486 each plus shipping. Hope everything is ok with your engine now.

Best Regards,

Ray @ Raylar

Rage

Mercury advised c/o Dustin Whipple that the PCM555 does not go into Guardian Mode when there is a detonation event. The PCM555 will only retard the ignition timing (8* max) when a detonation event is detected. Hence there is also no detonation / knock event fault recorded in the PCM555 either.

Hot 4 Teacher

Thanks guys. I concur with the no detonation warning. I already have the mechanical fuel gauge and braided fuel line (which cost more than the gauge) and can't find the valve. Does anyone have a picture that I could look at to see where the valve is? Ray, is it relocated with your intake?

Wild Card 09

I was able to hook up a matching Gaffig monster electrical fuel pressure gauge up to my ´06 525EFi can bus 14 pin harness. The signal wire is already included in the installation kit for the motor, together with one for oil temperature (and for all other electrical gauges).

On a 496, the ECU has the fuel pressure parameter as part of its metering basis. It must be possible to tap off that info somewhere on a 10 pin 496 harness, as well.

Plane Silly

The schrader valve is inboard and below the coolant res. The res. is notched out around it.

Hot 4 Teacher

Okay, I've got all the gauges working properly. Thanks for the help! With a 496 bored 30 over, a Raylar 103K and Whipple Stage I upgrade, I set the fuel pressure @ 50 lbs and the AF ranges from 12.6 to 13.5 with the highest readings between 3,000 and 4,000 rpm. I also had to unplug the vacuum regulator (it's much more even without it being plugged in). My question: Is it a bad idea to run more than 50 psi with the stock injectors? In order to be in the mid 12's (on the high side), I have to run 55lbs. If I have to turn these up close to 60psi to be in the low 12's, I may give my engine builder some credit, as he told my my injectors were too small last month. Any thoughts?

Rage, what is your current fuel pressure vs AF @ 3,500?

Hot 4 Teacher

The injectors were tested and came back "good". see post above about the injectors...

Is the diameter of your intake already sized to accept an 80MM, or do I need to hone it out some? Do you feel 80 is all you need for maximum performance? Do you, or does anyone else offer a 90MM?