antballs420

i searched for stuttering and no good. well my bros car has a jdm b18c all stock internals with a turbo. heres the components.
t3/t4 turbo.
turbonetics evolution external wastegate
dsm bov
walbro in tank 255 lph fuel pump
blox 12:1 FMU
blox map bypass
and i retarded the timing 2 degrees to start. and then another 2 degrees, and still the same problem. it runs perfect all through the rpm range when the car is cold, up untill like 15-20 minutes when the car gets fully warm, then its stutters past 4k rpm with no power.

any ideas.

thanx

StolenTeg

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by antballs420 &raquo;</TD></TR><TR><TD CLASS="quote">i searched for stuttering and no good. well my bros car has a jdm b18c all stock internals with a turbo. heres the components.
t3/t4 turbo.
turbonetics evolution external wastegate
dsm bov
walbro in tank 255 lph fuel pump
blox 12:1 FMU
blox map bypass
and i retarded the timing 2 degrees to start. and then another 2 degrees, and still the same problem. it runs perfect all through the rpm range when the car is cold, up untill like 15-20 minutes when the car gets fully warm, then its stutters past 4k rpm with no power.

any ideas.

thanx</TD></TR></TABLE>

The problem is your running a FMU

antballs420

should that matter at 6psi.?
revhard kits come stock with them. dont think they have this problem.

BlueShadow

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by antballs420 &raquo;</TD></TR><TR><TD CLASS="quote">should that matter at 6psi.?
revhard kits come stock with them. dont think they have this problem.</TD></TR></TABLE>


The problem is you're running a FMU with an intank pump. The stock revhard kits come with an inline pump which can better withstand the high pressure that you see with an FMU. Below is a chart of the fuel flow for a regular 255 and a 255lph. At 6psi your fuel pressure is (6x12=72)+44=116psi of fuel pressure. Neither pump will flow fuel with that much fuel pressure. What you are probably seeing is onset of fuel pump starvation from too much pressure. The chart is in GPH, but to convert GPH to LPH I believe you multiply GPH by 4.54.

EDIT: try throwing an inline pump in there and see what happens. You should be able to leave the intank pump in place.

antballs420

i always thought that a walbro 255lph intank pump was pretty capable. and could feed 500hp motors. so ur saying that when the regulator and fmu are keeping all fuel(basically cutting off return) in the rail that the pump cant handle that?. i guess it makes sense but it would be a surprise.

BlueShadow

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by antballs420 &raquo;</TD></TR><TR><TD CLASS="quote">i always thought that a walbro 255lph intank pump was pretty capable. and could feed 500hp motors. so ur saying that when the regulator and fmu are keeping all fuel(basically cutting off return) in the rail that the pump cant handle that?. i guess it makes sense but it would be a surprise.
</TD></TR></TABLE>

Fuel pressure and voltage to the pump are two things that affect how much fuel the pump will actually put out. The Walbro pump is rated for 255lph at 43.5-45psi of fuel pressure and 12 volts. However an increase in fuel pressure decreases the amount of fuel it will flow, will a decrease in fuel pressure increases the amount of flow. And also if your fuel pump is experiencing voltage drop from bad wiring, then that will affect fuel pump flow as well. The more voltage your pump gets, the more fuel it will flow. If your pump is getting less voltage, then it will flow less.

If you are using a regular 255lph pump (non high pressure) then I'm pretty sure that's what's happening to you. Had that pump been a 255lph HP it might have been able to deliver the needed fuel for 6 psi. The HP stands for high pressure, and it is able to deliver more fuel at higher pressure, as you can see by that chart I posted above. Probably the easiest thing to do is just install an inline fuel pump along with the intank.

EDIT: if you were running a non-fmu setup then the pump can handle quite a bit of power/flow a lot of fuel. If you are not using an FMU then you would be using a 1:1 ratio FPR. so for every 1 psi of boost the fuel pressure goes up 1 psi. So say you were running some sort of EMS (not an FMU) then at 6 psi your fuel pressure is (6x1=6)+45=51. So at 6 psi your fuel pressure would be 51 psi, if you look at the chart above you'll see that at 51 psi the 255 lph and lph HP pumps can still flow a lot of fuel.

antballs420

thanx for the help, and not flaming me
anyway I was gonna just install the original pump and get the pump that comes with the revhard kit, being its meant to go with the 12:1 fmu. thinking it would give me the correct pressure. no?
i have an extra set of obd1 h22 injectors, would these help?

nickromeo

holy **** BlueShadow that is some DAMN GOOD information,

M4d pr0ps 2 u b!

honestly thats some really important good information to know!

StolenTeg

Why run the fmu and risk the motor while there is so many affordable tuning software

BlueShadow

Going back with the stock pump and inline pump is a good idea. However I dont think having the 255lph and inline pump will hurt. It just meants you wont have to worry about any fuel shortages. I believe as long as your fuel pressure is where it's supposed to be for 6 psi with the 12:1 FMU (which is 115-116psi at WOT) then you dont have to worry about it running rich. If your base/idle fuel pressure is at the stock levels with an inline pump, 255lph, and the FMU installed then you *should* be ok. I only say this because in some cases I've heard of peoples fuel pressures rising as much as 10 psi after installing a 255lph pump (usually the HP version).

just something to think about

BlueShadow

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nickromeo &raquo;</TD></TR><TR><TD CLASS="quote">holy **** BlueShadow that is some DAMN GOOD information,

M4d pr0ps 2 u b!

honestly thats some really important good information to know!

</TD></TR></TABLE>

thanks y0!

antballs420

after checking. i have the HP version. part #GSS-342. and the graph shows this pump supporting 150 psi, which is much higher than my needed 117psi. the pump should be able to support this,no??

D@nnY

gap the plugs smaller and put a wideband on the car for godsake before it blows up...if the plugs are black it may just be running to rich hot

HiProfile

And if the plugs are shot, no good pump would help. IMO there's more than just the pump becoming the issue. At 117psi, the injectors will have a hard time opening when the need too, closing and leaking.