Trying to understand CP3 opperation (Elect.)
- Thread starter RPM Motorsports
- Start date
What is funny though, is Casper was holding full commanded rail pressure with duals on the dyno at ~750hp, then I put on a modified pump and it climbed to 800hp without any changes to the tune or settings.
Just because the reported rail pressure says it's 100% doesn't mean there is not more left.
Here is why I "think" that is: During a crankshaft revolution, the injector opens, rail pressure drops the whole time the injector is open. If the rail pressure falls sharply for the last 10% of the injector open time, sensors have a natural filtering effect to them, so it might not even "see" that minor of a dip in the reading, since that is only about .00025 seconds. But 10% more fuel is not minor on a dyno.
But I don't know for sure.
Just because the reported rail pressure says it's 100% doesn't mean there is not more left.
Here is why I "think" that is: During a crankshaft revolution, the injector opens, rail pressure drops the whole time the injector is open. If the rail pressure falls sharply for the last 10% of the injector open time, sensors have a natural filtering effect to them, so it might not even "see" that minor of a dip in the reading, since that is only about .00025 seconds. But 10% more fuel is not minor on a dyno.
But I don't know for sure.
And to top it off, 4 injectors open in one crankshaft revolution. It seems possible reported pw is not accurate at times. I only caught a glance with Jon's software and his pressure monitor but I could be wrong. Just saying the actual rail pressure may have the effects as you mention Pat.
The limited sample rate of the scan tool basicly averages things. Using a standalone datalogger with a higher sample rate has shown some interesting things about the fuel system. I still have not got my mind completely around it yet. Need more time to test.
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3 pumping pulses per rev versus 4 injections pulses per rev is going to create some interesting feedback.
At what Speed/RPM does the pump run at? Since its run off the cam gear, but its drive gear is smaller, does it run at crankshaft rpm? And on dual fuelers, by rough guess, they look to run at crank rpm right? Pulleys look like there about the size of the harmonic. I have noticed that not all dual fuelers have same pulley sizes. Any advantage to overdriving one or are we at there RPM limit as stock? Maybe we could put stronger element springs in the pump? There pretty stout stock though! My vocabulary was colorful trying to get the essentric/crank out
They run at crank speed.
The way the pump works, is that by restricting it's inlet supply, the stroke of the pistons in the pump is reduced. If you increase spring rate, it will affect low and medium pump output quite a bit.
The pumps fade rapidly starting at about 3800rpm. This is why dual fuelers or modified pumps show their biggest HP gains at higher RPM's.
The way the pump works, is that by restricting it's inlet supply, the stroke of the pistons in the pump is reduced. If you increase spring rate, it will affect low and medium pump output quite a bit.
The pumps fade rapidly starting at about 3800rpm. This is why dual fuelers or modified pumps show their biggest HP gains at higher RPM's.
Ahh, thanks Pat! I kinda forgot about the restriction/feed system. Ya, not a whole lot you could mess with. More and or bigger pumps are the best awnser huh. least with 2 pumps your having more frequent pressure pulses per crank rev to smooth it out aside from additional fuel volume