Fuel Pump speed control
Discussion
Max_Torque said:
I'm afraid to say that if you change your fuel delivery volume you will be forced into a remap. All the mechanical pressure regulators i have tested have had a significant pressure "slope with flow". In order to keep the reg compact, manufacturers of said eveice use short stiff springs to load the control orifice. This means, that at low fuel consumption conditions, where the control orifice needs to be lifted a large distance off its seat to allow sufficient fuel to return to the tank, the spring load is significantly higher than when the control orifice is almost shut.
Hence, your actual fuel rail pressure will vary with return flow rate............
(on the worst cheapy reg i testes, it varied by 2 bar over the flow rate of an 044......)
Dont quite follow ?Hence, your actual fuel rail pressure will vary with return flow rate............
(on the worst cheapy reg i testes, it varied by 2 bar over the flow rate of an 044......)
Surely if I have 3 bar in my rails now. Then fit a pump controller and run the pumps more efficiently, but still see 3 bar in the rails. Surely fuelling should remain the same ?
stevieturbo said:
Dont quite follow ?
Surely if I have 3 bar in my rails now. Then fit a pump controller and run the pumps more efficiently, but still see 3 bar in the rails. Surely fuelling should remain the same ?
I think thats the theory - but MT is saying that the regulators he's tested are not very good at actually regulating.Surely if I have 3 bar in my rails now. Then fit a pump controller and run the pumps more efficiently, but still see 3 bar in the rails. Surely fuelling should remain the same ?
I've got a billet TAG regulator here if you want to test a high end one.
Its a bit like this one, but more of a conventional in/out layout.
http://www.eettaiwan.com/ARTICLES/2002MAY/PDF/2002...
Edited by eliot on Sunday 14th August 21:10
stevieturbo said:
Dont quite follow ?
Surely if I have 3 bar in my rails now. Then fit a pump controller and run the pumps more efficiently, but still see 3 bar in the rails. Surely fuelling should remain the same ?
1st assumption, you have 3 bar in rails with just the pumps running but the engine using no fuel.Surely if I have 3 bar in my rails now. Then fit a pump controller and run the pumps more efficiently, but still see 3 bar in the rails. Surely fuelling should remain the same ?
under this case, the regulator is returning the entire flow of the pump, hence the control orifice will be at maximum lift (because several hundred l/hr of fuel will be flowing through it). Most people "set" there regulator at this condition.
However, as your engine uses a larger and larger proportion of fuel, the regulators control orifice will have to move towards the closed position. As it has a spring inside it, this movement will by necessity cause a reduction in the force on said control orifice (because it is a spring, and hence has a "spring rate"). That reduction in force results in a low pressure being required to balance it, so ultimately, rail pressure falls as return flow reduces.
Most people never spot this, because they never look at fuel rail pressure at peak fuel consumption etc.
if you use a pump speed controller to reduce the return flow at all times, then you WILL also reduce rail pressure by some amount. That amount depends upon the design and "linearity" of the pressure regulator. Hence, you will need to increase fuel pulse width at low loads/rpms to account for the reduced rail pressure (your "mapping" will already have this compensation in it at high load, and i'm sure that this is the reason a lot of people find there injectors are at maximum duty suddenly whilst seeming to be plenty large enough at medium loads etc (ie the closer return flow falls to zero the lower rail pressure actually gets on a std mechanical reg)
eliot said:
I think thats the theory - but MT is saying that the regulators he's tested are not very good at actually regulating.
I've got a billet TAG regulator here if you want to test a high end one.
Its a bit like this one, but more of a conventional in/out layout.
http://www.eettaiwan.com/ARTICLES/2002MAY/PDF/2002...
Note the gradient of the pressure slope as return flow falls below approx 50l/hr on that reg. It will be lot steeper on a cheapo regulator.I've got a billet TAG regulator here if you want to test a high end one.
Its a bit like this one, but more of a conventional in/out layout.
http://www.eettaiwan.com/ARTICLES/2002MAY/PDF/2002...
Edited by eliot on Sunday 14th August 21:10
Still dont quite follow...or maybe I do.
If anything, using a pump controller will make the rail pressure easier to maintain, and give the FPR and easier life too.
As in an ideal world with a very well programmed controller, you could in theory have the FPR deal with a fixed return flow all the time. So the internal spring or whatever isnt really doing much work at all.
So surely it's all good ?
Run the pumps at a minimum work load to maintain your desired pressure at the rails. But this wouldnt necessarily require very technical controls ?
So the FPR return is always doing the least amount of work to maintain your pressure. The spring is never at one extreme or the other ?
You could say it's operating in the same way it would be at maximum engine effort.
If anything, using a pump controller will make the rail pressure easier to maintain, and give the FPR and easier life too.
As in an ideal world with a very well programmed controller, you could in theory have the FPR deal with a fixed return flow all the time. So the internal spring or whatever isnt really doing much work at all.
So surely it's all good ?
Run the pumps at a minimum work load to maintain your desired pressure at the rails. But this wouldnt necessarily require very technical controls ?
So the FPR return is always doing the least amount of work to maintain your pressure. The spring is never at one extreme or the other ?
You could say it's operating in the same way it would be at maximum engine effort.
stevieturbo said:
Still dont quite follow...or maybe I do.
If anything, using a pump controller will make the rail pressure easier to maintain, and give the FPR and easier life too.
As in an ideal world with a very well programmed controller, you could in theory have the FPR deal with a fixed return flow all the time. So the internal spring or whatever isnt really doing much work at all.
So surely it's all good ?
Run the pumps at a minimum work load to maintain your desired pressure at the rails. But this wouldnt necessarily require very technical controls ?
So the FPR return is always doing the least amount of work to maintain your pressure. The spring is never at one extreme or the other ?
You could say it's operating in the same way it would be at maximum engine effort.
First with the controller you would not need a mechanical reg but if you decided to leave it in then yes it should sit in about the same place through the whole power range.If anything, using a pump controller will make the rail pressure easier to maintain, and give the FPR and easier life too.
As in an ideal world with a very well programmed controller, you could in theory have the FPR deal with a fixed return flow all the time. So the internal spring or whatever isnt really doing much work at all.
So surely it's all good ?
Run the pumps at a minimum work load to maintain your desired pressure at the rails. But this wouldnt necessarily require very technical controls ?
So the FPR return is always doing the least amount of work to maintain your pressure. The spring is never at one extreme or the other ?
You could say it's operating in the same way it would be at maximum engine effort.
Second, as you say, the whole system is now running at a constant pressure despite flow rate. What Max is saying is that you have never had that constant rate before so your maps will have been unknowingly tweeked to compensate for the low fuel pressure at high demand.
Steve
Steve_D said:
First with the controller you would not need a mechanical reg but if you decided to leave it in then yes it should sit in about the same place through the whole power range.
Second, as you say, the whole system is now running at a constant pressure despite flow rate. What Max is saying is that you have never had that constant rate before so your maps will have been unknowingly tweeked to compensate for the low fuel pressure at high demand.
Steve
My rail pressure is almost 1:1 with boost at all operating ranges though ? Perhaps maybe not keeping up to the tune of about 0.2-0.3 bar at the top end. Whilst I doubt it, the 044's may be struggling, or may simply be the normal operation/abilities of my FPR.Second, as you say, the whole system is now running at a constant pressure despite flow rate. What Max is saying is that you have never had that constant rate before so your maps will have been unknowingly tweeked to compensate for the low fuel pressure at high demand.
Steve
On a side note to Max and steve.... there has been a question asked about turbo comparisons on the noble forum that has actually been something I have been wondering myself.
Basically if boost was set the same and inlet air temp, rpm etc the same... would a large turbo and a small turbo make the same power?... wondered if you guys had any input?
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Basically if boost was set the same and inlet air temp, rpm etc the same... would a large turbo and a small turbo make the same power?... wondered if you guys had any input?
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
stevieturbo said:
My rail pressure is almost 1:1 with boost at all operating ranges though ? Perhaps maybe not keeping up to the tune of about 0.2-0.3 bar at the top end. Whilst I doubt it, the 044's may be struggling, or may simply be the normal operation/abilities of my FPR.
This would suggest that your fuel supply system is more than capable of supplying sufficient volume of fuel (at the required pressure) and that even with the maximum amount of fuel being injected into your engine (injectors at what ever there max DC is), there is always sufficent "extra" being supplied to the rail to keep the mechanical regulator in it's linear region (for the graph shown for that TAG FPR that is above approx 50l/hr). This is of course a good thing (with regard to keeping your injector delta pressures constant) but would lead me think that you are using a lot of unecessary power and producng a lot of heat and noise to move fuel around the car that is never used by the engine ;-)My setup will be the same, ie I run 2 044's and its the amp draw that makes me want a speed controller as 044's use a large amount of amps... my headlights now flicker below 2000rpm... not helped by me putting an underdrive pulley on the alternator as they were failing at the extra 1000rpm that I am running.
Max_Torque said:
This would suggest that your fuel supply system is more than capable of supplying sufficient volume of fuel (at the required pressure) and that even with the maximum amount of fuel being injected into your engine (injectors at what ever there max DC is), there is always sufficent "extra" being supplied to the rail to keep the mechanical regulator in it's linear region (for the graph shown for that TAG FPR that is above approx 50l/hr). This is of course a good thing (with regard to keeping your injector delta pressures constant) but would lead me think that you are using a lot of unecessary power and producng a lot of heat and noise to move fuel around the car that is never used by the engine ;-)
Pressure does tail off slightly at the top end, but nothing bad. IDC's generally dont go over 75% with approx 1200cc per cylinder available, albeit also using slightly higher base pressure.But yes, this does mean a huge volume of fuel is getting circulated at low operating loads. Hence why I would consider a SIMPLE controller lol
And one that could also perhaps up the voltage if needed to say 16v ?
yes pumps can be heard as they work hard on idle unlike the engine... and 044's take a lot of current, 2-3times a normal fuel pump and I have 2 of them, coupled with the fact I geared down my alternator as it was overcharging and destroying itself at the extra revs my engine runs therefore it provides less charge below 2k rpm now... although I should be clear they dont go off or anything, just get a little brighter at 2k were most cars only suffer this on idle (if you turned everything on).
Max_Torque said:
probably the only correction that you would want the controller to do automatically is to adjust for battery (supply) voltage (which it measures internally). That way it would maintain the pump speed independant of battery voltage.
That should already be taken into account by the ECU by increasing injector pulsewidth, so if your pump controller is using injector pulsewidth as a control parameter it should automatically compensate for battery voltage as well.one eyed mick said:
A couple of things baffle me ! you can hear the pumps over a v8?--,if the pumps are taking so much current to effect the lighting system there is an issue with either the pumps or charging system ? yours baffled
lets put it this way:Say your upstairs bath hot tap has stopped working, and you need to fill the bath with hot water from a downstairs tap using a bucket, would you put the bathplug in place before starting to cart buckets up the stairs or not?
one eyed mick said:
A couple of things baffle me ! you can hear the pumps over a v8?--,if the pumps are taking so much current to effect the lighting system there is an issue with either the pumps or charging system ? yours baffled
That would depend on the V8, the pumps, how they are mounted etc etcAnd if they are affecting the lighting system, you need to wire them correctly.
I tested mine recently, and both pumps with the engine at idle are sitting at 21.5amps and 14.0v with 3.2bar pressure.
I did squish the return, although obviously this caused the engine to try and stall. But at around 5.5 bar, current rose to about 26amps. It was hard to watch pressure gauge, ammeter and squash the return line all at once without letting the engine stall too.
stevieturbo said:
I tested mine recently, and both pumps with the engine at idle are sitting at 21.5amps and 14.0v with 3.2bar pressure.
so your pumps are using 301W to do 3.2bar at idleMy two 044's are using a total of 53W to provide 5.7bar at idle.
When you consider that a typical claw pole alternator is only ~60% efficient, that means your engine is required to provide an extra 413W (29.5A @ 14V) or about 0.5bhp (of course, at idle, you have a few bhp spare ;-)
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