Help with fuel pump voltage (have I been misinformed?)
Discussion
Unless your pump is right on the borderline of what the engine needs this will make no difference. I think you are barking up the wrong tree. Unless you are also running injectors that are too small and hitting 100% duty cycle in which case a tiny drop in fuel pressure will matter. In that case the solution lies in fitting the right size injectors and addressing the fuel pump size/wiring so you have some overhead capacity without going lean.
fatjon said:
Unless your pump is right on the borderline of what the engine needs this will make no difference. I think you are barking up the wrong tree. Unless you are also running injectors that are too small and hitting 100% duty cycle in which case a tiny drop in fuel pressure will matter. In that case the solution lies in fitting the right size injectors and addressing the fuel pump size/wiring so you have some overhead capacity without going lean.
I have RC 650cc injectors, nowhere near the duty cycle unfortunately.I believe that my issue is twofold.
The voltage is too low to the pump, hence it not flowing enough fuel
The original fuel line is too small, as above.
Cheers
Yup, them are big injectors for a little OE fuel line. I have a twin injector setup and use a -6 for each bank but the fuel pumps share a 1.5mm cable without any problems. There is some volt drop so they usually see about 13.3 when running. If yours are pushing hard into a skinny fuel line they will take more current and consequently create more volt drop. Maybe the solution is in the fuel lines then? Quite easy to test just take a fat cable from the battery to the fuel pump and see if your problem goes away. If the pump is fed through a relay rather than directly switched by the ECU there's no chance of frying anything.
Butter Face said:
I have RC 650cc injectors, nowhere near the duty cycle unfortunately.
I believe that my issue is twofold.
The voltage is too low to the pump, hence it not flowing enough fuel
The original fuel line is too small, as above.
Cheers
Perhaps it might help if you explained what this supposed problem actually is ?I believe that my issue is twofold.
The voltage is too low to the pump, hence it not flowing enough fuel
The original fuel line is too small, as above.
Cheers
You seem to be blaming a voltage...but dont really understand how the system works in the first palce
You then say duty cycles are fine.....which implies there is no issue with fuel flow, voltage, line size or whatever
You make no indication there is a fuel pressure problem either.
So exactly what is the problem you're trying to fix even though all of what you are telling suggests no fuel flow problem ? Although there is a lack of proper information.
Hi mate.
The issue (as I understand it) is that the fuel pressure is dropping off at higher RPM, so at 5k+ RPM where my rising rate FPR should be upping the fuel pressure with the boost, the pressure is dropping off (I can't tell you exactly what it should be/is as TBH it's all been pretty confusing for me)
My understanding is that the engine is just not getting enough fuel at higher RPM, the pump is flat out but is restricted as to how much it can flow by the power it's getting/fuel pipe restriction.
I'm no technical expert at all, I am going by the information from various sources that tells me the pump isn't getting enough power and as such when the engine/injectors need it, it isn't there.
Hope that makes sense!
The issue (as I understand it) is that the fuel pressure is dropping off at higher RPM, so at 5k+ RPM where my rising rate FPR should be upping the fuel pressure with the boost, the pressure is dropping off (I can't tell you exactly what it should be/is as TBH it's all been pretty confusing for me)
My understanding is that the engine is just not getting enough fuel at higher RPM, the pump is flat out but is restricted as to how much it can flow by the power it's getting/fuel pipe restriction.
I'm no technical expert at all, I am going by the information from various sources that tells me the pump isn't getting enough power and as such when the engine/injectors need it, it isn't there.
Hope that makes sense!
Butter Face said:
Hi mate.
The issue (as I understand it) is that the fuel pressure is dropping off at higher RPM, so at 5k+ RPM where my rising rate FPR should be upping the fuel pressure with the boost, the pressure is dropping off (I can't tell you exactly what it should be/is as TBH it's all been pretty confusing for me)
My understanding is that the engine is just not getting enough fuel at higher RPM, the pump is flat out but is restricted as to how much it can flow by the power it's getting/fuel pipe restriction.
I'm no technical expert at all, I am going by the information from various sources that tells me the pump isn't getting enough power and as such when the engine/injectors need it, it isn't there.
Hope that makes sense!
Upload a datalog showing these items.The issue (as I understand it) is that the fuel pressure is dropping off at higher RPM, so at 5k+ RPM where my rising rate FPR should be upping the fuel pressure with the boost, the pressure is dropping off (I can't tell you exactly what it should be/is as TBH it's all been pretty confusing for me)
My understanding is that the engine is just not getting enough fuel at higher RPM, the pump is flat out but is restricted as to how much it can flow by the power it's getting/fuel pipe restriction.
I'm no technical expert at all, I am going by the information from various sources that tells me the pump isn't getting enough power and as such when the engine/injectors need it, it isn't there.
Hope that makes sense!
What base pressure are you running and how well does fuel pressure rise with manifold pressure, and when it deviates...by how much ?
You've stated duty cycles are fine....so almost regardless of fuel pressure there doesnt seem to be a lack of ability to feed fuel to the engine. Unless fuel pressure is dropping insanely...in which case in injector duties could not be behaving normally. So there has to be a red flag here somewhere.
As with any remote diagnosis, proper information is needed. At the minute there is to a degree conflicting information.
Fuel pressure dropping a little on it's own is no big deal. Not always ideal, but no big deal. But as it depends on many other factors...far more information is needed here.
Exactly how much power is the car making ? ( although that could be another dyno debate in itself ) and what fuel ?
stevieturbo said:
Butter Face said:
Hi mate.
The issue (as I understand it) is that the fuel pressure is dropping off at higher RPM, so at 5k+ RPM where my rising rate FPR should be upping the fuel pressure with the boost, the pressure is dropping off (I can't tell you exactly what it should be/is as TBH it's all been pretty confusing for me)
My understanding is that the engine is just not getting enough fuel at higher RPM, the pump is flat out but is restricted as to how much it can flow by the power it's getting/fuel pipe restriction.
I'm no technical expert at all, I am going by the information from various sources that tells me the pump isn't getting enough power and as such when the engine/injectors need it, it isn't there.
Hope that makes sense!
Upload a datalog showing these items.The issue (as I understand it) is that the fuel pressure is dropping off at higher RPM, so at 5k+ RPM where my rising rate FPR should be upping the fuel pressure with the boost, the pressure is dropping off (I can't tell you exactly what it should be/is as TBH it's all been pretty confusing for me)
My understanding is that the engine is just not getting enough fuel at higher RPM, the pump is flat out but is restricted as to how much it can flow by the power it's getting/fuel pipe restriction.
I'm no technical expert at all, I am going by the information from various sources that tells me the pump isn't getting enough power and as such when the engine/injectors need it, it isn't there.
Hope that makes sense!
What base pressure are you running and how well does fuel pressure rise with manifold pressure, and when it deviates...by how much ?
You've stated duty cycles are fine....so almost regardless of fuel pressure there doesnt seem to be a lack of ability to feed fuel to the engine. Unless fuel pressure is dropping insanely...in which case in injector duties could not be behaving normally. So there has to be a red flag here somewhere.
As with any remote diagnosis, proper information is needed. At the minute there is to a degree conflicting information.
Fuel pressure dropping a little on it's own is no big deal. Not always ideal, but no big deal. But as it depends on many other factors...far more information is needed here.
Exactly how much power is the car making ? ( although that could be another dyno debate in itself ) and what fuel ?
Butter Face said:
Power is 320bho using Tesco Momentum 99. The rest of the questions I will have to clarify and update at a later date but I will come back ASAP.
Even at the lower voltage that pump should have no issue supplying only 320hp.In injector duties are behaving fine, if fueling is fine when you are driving the car, and it behaves in a consistent manner at all times then there is no real issue to be concerned with.
If you feel pressure is abnormal or there is some other problem, detailed information/logs are needed to even attempt to diagnose.
Butter face, I have followed your build thread from start to finish. Might be worth putting a link to your build on here. It highlights a lot of the technical issues you have had/solved/having.
Just a suggestion. I'm no expert but am mainly following this thread as I want to know how you solve the problem.
Good luck
Just a suggestion. I'm no expert but am mainly following this thread as I want to know how you solve the problem.
Good luck
Butter Face said:
Off the top of my head I believe that the anticipated fuel pressure at max RPM was wanting to be 4.5 bar but at the moment the pump is struggling to achieve 3.2 bar. I can't be sure and need to sit down with my guy and write it all down.
Appreciate the help so far!
Again, datalogs would be helpful.Appreciate the help so far!
If indeed there is a disparity of 1.3 bar....that is far from ideal. As to the cause, could be many things.
More detail on the fuel system needed. Size of lines, filters etc etc where is pressure being monitored and how ?
Bollah said:
I'd be also inclined to check the voltage when you have some load on the engine too. You may find that the voltage is dropping the more load you put on, which would be even more of a reason to run a feed from the battery through a relay as mentioned earlier
Some cars can do strange things under load, especially silly charge alternators on modern stuff. Again, datalogs of system voltage under load as you say would be helpful.Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff