Begi Shimless Fmu

[kamikazi89]

I am ready for tuning my gen 1 stage 1 custom build turbo kit in the next 2 days and i have a question for the experts here as in my country tuners is not familiar with fmu tuning so as the title says i run on my bike the begi shimless fmu and i set the idle pressure at 43-44 psi and the bleed screw at 1 full turn out from closed and when i boosted the bike to test it my bike goes to 3-4 psi of boost and at this time the fmu raise the fuel pressure is that right or the raise of fuel pressure is late?and the other is that the fmu boost is feeded from 2 throttle bodies and the boost gauge is connected to the plenum.sorry for my bad english

 

[kamikazi89]

Another think is that i twist the throttle to the 1/2 and 3/4 not full throttle

 

[Boosted Cycle Perf]

On a gen 1 with 8 psi you want 80-90psi of fuel pressure.

 

[kamikazi89]

On a gen 1 with 8 psi you want 80-90psi of fuel pressure.

The fuel pressure is okay but it have a little delay to raise if you compare it with the boost gauge

 

[Boosted Cycle Perf]

The fuel pressure is okay but it have a little delay to raise if you compare it with the boost gauge

That's normal. A small light needle is gonna react faster then building and additional 40-50psi of fuel pressure. You're good.

 

[kamikazi89]

That's normal. A small light needle is gonna react faster then building and additional 40-50psi of fuel pressure. You're good.

Thank you man!

 

[kamikazi89]

Dyno day today and with 7.5psi boost afr at 10000rpm was 12.2 100% tps and the injectors maxed out and the base fuel pressure was set at 48 psi any advice?

 

[Boosted Cycle Perf]

Dyno day today and with 7.5psi boost afr at 10000rpm was 12.2 100% tps and the injectors maxed out and the base fuel pressure was set at 48 psi any advice?

That's lean. What's the boosted fuel pressure? Meaning during the pull at full boost, what is the fuel pressure?

If the injectors are at 100% duty cycle and is still lean I'd put money on your boosted fuel pressure is too low.

 

[POWERHOUSE]

First off, if your signal hose to the FMU is coming off the small ports on your throttle bodies, you need to run a check valve so the FMU does not see vacuum. Alternatively, you can run your signal directly from the plenum. Once you have this correct, set your idling fuel pressure anywhere from 42-45 pounds. Put your bleed screw on the FMU at 1/2 turn, and leave a fuel pressure gauge connected when you make your full dyno pulls. I agree with Rob that your fuel pressure at full boost must be low, so you need to check it even after you set the FMU up correctly.

 

[kamikazi89]

Yes my fuel pressure at boost was low max 80 psi and i start to think if my fmu is 3:1
I connect the regulator on 2 throttle bodies as you said before Frank in the pm and it has a check valve on it and the bleed screw is set at 3/4 of a turn out

 

[kamikazi89]

That's lean. What's the boosted fuel pressure? Meaning during the pull at full boost, what is the fuel pressure?

If the injectors are at 100% duty cycle and is still lean I'd put money on your boosted fuel pressure is too low.

Yes sir you are right

 

[OZBooster]

Did you log boost pressure or read a gauge , any chance at boost creep ? , dyno graph will show torque leveling or dropping slowly after 8500rpm , it should drop off reasonably quickly
is your fuel pressure gauge accurate ?, fluid filled ? not getting buzzed by vibration
base fuel at 43psi with key on not running and 7.5 boost should get you ~88, you could turn the needle valve in another 1/8 and see if that helps
in later yrs of using FMU i ended up putting the supply to the plenum and forget about the check valve complications,

 

[kamikazi89]

I reed the gauge as the tuner make the run and the gauge is liquid filled and checked with another gauge and is accurate
The bike goes Steaty 6psi to the 9500 rpm mark and from there the boost spikes and stay at 7.5 psi and i am worried about that btw i run full exhaust with the external gasses in the exhaust is that a bad idea for the boost jump at high rpms?

 

[OZBooster]

The wastegate mount angle will not help , i had one come here with steeper angle than that that made boost with the wastegate removed
porting the turbo may help, cut in and radius the upper edge and knife edge the lower so the exhaust gets turned otherwise the speed of the exhaust gasses dont let them change direction easily
and the extreme case like i had here it acts like a venturi
better to build it with a bend so it sweeps out of the housing

 

[kamikazi89]

The wastegate mount angle will not help , i had one come here with steeper angle than that that made boost with the wastegate removed
porting the turbo may help, cut in and radius the upper edge and knife edge the lower so the exhaust gets turned otherwise the speed of the exhaust gasses dont let them change direction easily
and the extreme case like i had here it acts like a venturi
better to build it with a bend so it sweeps out of the housing

I port the wastegate hole and inside of the cast i also fabricate dumps to test for boost creep and my last think to check is how to check my fmu if its 6:1 or 3:1 because on the dyno i saw the fuel press gauge from 54 psi base fuel press goes to about 78 psi and that says its a 3:1 or dont works well any advise how to bench check?

 

[POWERHOUSE]

I port the wastegate hole and inside of the cast i also fabricate dumps to test for boost creep and my last think to check is how to check my fmu if its 6:1 or 3:1 because on the dyno i saw the fuel press gauge from 54 psi base fuel press goes to about 78 psi and that says its a 3:1 or dont works well any advise how to bench check?

You can check it right on the bike, without the bike running. Put a fuel pressure gauge on, and hook up a hand pump with a gauge (like a suspension pump) directly to the signal port of the fmu. Run a positive lead to the fuel pump and note the pressure. With the fuel pump running, pump up your hand pump while looking at both gauges - you will see exactly what the fmu is doing and what the rate of gain is . . . post the results.

 

[kamikazi89]

You can check it right on the bike, without the bike running. Put a fuel pressure gauge on, and hook up a hand pump with a gauge (like a suspension pump) directly to the signal port of the fmu. Run a positive lead to the fuel pump and note the pressure. With the fuel pump running, pump up your hand pump while looking at both gauges - you will see exactly what the fmu is doing and what the rate of gain is . . . post the results.

I check the fmu and my results is
Base fuel pressure is 50 psi and at 8 psi of boost the pressure goes to 76 psi so my fmu rate of gain is 3.25:1

 

[POWERHOUSE]

I check the fmu and my results is
Base fuel pressure is 50 psi and at 8 psi of boost the pressure goes to 76 psi so my fmu rate of gain is 3.25:1

Over the years we have modified standard 5:1 fmus to make them 3:1, like the one you have. This was done to accommodate larger injectors, like 65# and it worked out great. That is one choice you have. . . the other is to get the proper 5:1 regulator with the setup you have. RCC's "shimless" version (which we have in stock) is exactly what you need.

 

[kamikazi89]

My fmu is the shimless also and i notice that bleeds boost not only from the needle vent hole but also from the needle body and if you touch it bleeds more

 

[POWERHOUSE]

My fmu is the shimless also and i notice that bleeds boost not only from the needle vent hole but also from the needle body and if you touch it bleeds more

That is not good! Tighten the needle valve body up into the fmu more, make sure it does not leak. Re-test. Leaks are the enemy! Lmk how you make out . . .