Fuel Pressure?
Furyous - 7/9/15 at 06:37 AM
While moving cars around today I took my Fury for a quick blast up and down the road (still not registered!). It would trundle along ok but when I put
my foot down it had a burst of power before bogging down. It's kind of like it had power until the fuel pressure dropped off.
I checked the fuel pressure with a gauge on the regulator. Without the engine running it was about 3 BAR. I didn't get a chance to check the
pressure with the engine running. All the time I've had the regulator it's made a whistling/tooting sound under pressure, kind of like
stretching a balloon neck while letting air out.
Could it be a faulty FPR or should I be looking somewhere else? I seem to have always had running problems with this Duratec but I haven't been
able to drive it more than a couple of hundred yards to check things out properly. It's on GSXR1000 throttle bodies with Microsquirt.
adithorp - 7/9/15 at 07:30 AM
Could be FPR... but could be a lot of things and apart from the noise you have no evidence that it is the FPR. How's it been mapped? How good a
quality is the FPR?...
Furyous - 7/9/15 at 08:22 AM
I probably should have mentioned that I've given it a quick drive a couple of times before and it's picked up ok aside from some pops and
bangs. Running the engine on the driveway is a bit hit or miss. It's sometimes smooth and sometimes rough as an old dog. What makes me think of
the FPR is the way it had a burst of power before dropping off, rather than bogging down as soon as the throttle was opened.
The FPR was about £120 from Demon Tweaks. Not sure which brand/model.
The map I'm using was set up on another car with an identical set up. The idea was to get a tune that was "nearly there" to get it
going.
britishtrident - 7/9/15 at 11:14 AM
The steps to check the FPR are...
(1) Switch on and check fuel pressure engine not running.
(2) Start engine, pressure should drop to compensate for manifold vacuum.
(3) Disconnect vacuum line fuel pressure should rise back to very close to pressure when engine not running.
(4) Reconnect the vacuum line with engine at idle snap the throttle open and closed. As the throttle snaps open (ie.low manifold vacuum) the fuel
pressure should rise to just below the pressure at before starting engine. As the throttle snaps shut (ie high manifold vacuum) the fuel pressure
should drop to below idle pressure then quickly stabilise when engine rpm settles at idle.
(5) Switch the engine and (pump off) and observe how low it takes for the pressure to return to zero (atmospheric). A rapid fall back indicates a
leaking injector or regulator.
[Edited on 7/9/15 by britishtrident]
Furyous - 9/9/15 at 04:50 AM
I think I might need to clarify something.
If I want 3 BAR, how do I set that? Engine off? Engine running with/without vacuum connected to FPR?
I had a little play and set it to 3 BAR with the engine running and vacuum connected. It seemed to idle much more smoothly and revs picked up straight
away when I snapped the throttle open. But that was about 4 BAR without the engine running.
If I set it to 3 BAR with the engine off, it would drop to about 1.75 BAR with engine running and vacuum connected. It hesitated when I snapped the
throttle open.
Haven't driven it with the different settings, though.
britishtrident - 9/9/15 at 05:43 AM
Atmospheric pressure is 1bar above complete vacuum inlet manifold pressure varies greatly but fuel normally pressure at idle would be about 0.6 bar
lower than with the engine not running.
I have no idea the pressure your engine map was calibrated for but.
Most tinntops run at around 3 bar with the engine at idle but some manufacturers run 4 bar.
Furyous - 9/9/15 at 06:05 AM
I know it was mapped for 3 BAR. I'm just not sure at what point it should be showing 3 BAR.
quote:
Originally posted by britishtrident
Most tinntops run at around 3 bar with the engine at idle but some manufacturers run 4 bar.
So, this and the way it was running better when it was set to 3 BAR while the engine was running makes me think I had it set too low before-hand.
It seems like it WAS a pressure problem but it was user error rather than a faulty FPR.
Thanks for the help. 
britishtrident - 9/9/15 at 07:05 AM
quote:
Originally posted by Furyous
I know it was mapped for 3 BAR. I'm just not sure at what point it should be showing 3 BAR.
quote:
Originally posted by britishtrident
Most tinntops run at around 3 bar with the engine at idle but some manufacturers run 4 bar.
So, this and the way it was running better when it was set to 3 BAR while the engine was running makes me think I had it set too low before-hand.
It seems like it WAS a pressure problem but it was user error rather than a faulty FPR.
Thanks for the help.
3 bar at idle should be fine.
There good videos on YouTube on testing fuel pressure regs, ISTR there is one on the Schrodingers Box channel the guy (Matt) that runs it is pretty
good at presenting reliable info.
Link to Schrodingers Channel Box on YouTube