Fuel Pump speed control
Discussion
stevieturbo said:
Can you use a solid state relay to PWM the pumps ?
Not ideally, because you really need synchronous rectification at these currents, or the losses increase massively, as do the electrical noise/ EMC emissions (because of the sharp turn off during the reverse recovery of the passive freewheeling diode.Max_Torque said:
A genuine 400bhp fuel pump is going to be pulling 10A on it's own, and will be taking between 3A and 5A all the time.
Knowing the typical PWM Full and Half bridge drivers used in these devices, i would not want to source more than 5A continuous from the ecu itself.
Agreed, I think maybe even 7A continuous. So it sounds like the SQ6 can drive the system, but I need a separate PCB building to amplify the signal and take the high current requirement away from the ECU. Knowing the typical PWM Full and Half bridge drivers used in these devices, i would not want to source more than 5A continuous from the ecu itself.
That Infineon BTN7960 chip is not expensive, looks like I can buy it for £4! how many other components would I need? How straightforward is building the necessary board? something I can attempt myself or would I be better to ask one of our Electronic Engineers at work to help... (I have limited soldering experience! but I am enjoying doing as much as possible myself on this build)
Regarding a pressure transducer to stick in the fuel rail, I was thinking of sticking this in a T-piece where fuel line splits to go to each bank of injectors: http://www.ebay.co.uk/itm/170980134449
cheap and Chinese but I have used them for oil pressure measurement on racecars in the past with no issues.
And as an additional safety measure sounds like it will be worth putting one of these in the high pressure line shortly after the pump?
http://www.ebay.co.uk/itm/221483198900
Max_Torque said:
The Pierburg CWA200 only uses the PWM signal input to set it's target speed. It has it's own internal power drivers, so the PWM signal pin will only sink a tiny amount of current (<10mA) This means you can drive it with just about any PWM output. The only complication is that the input does NOT accept TTL logic levels, and requires >8Vdc to set a "high" state. This would require a simple voltage level conversion circuit (1 transistor, 2 resistors). However, if you drive it from the "PWM" outputs on the SQ6, these should put out Vbatt as their "High" logic level voltage. Because of the low currents and slow frequency (~100Hz means you can have nice slow rising/falling edges without loosing pwm resolution), you can run this signal line down a tiny "twisted" pair shielded cable and have no issues with noise over long cable runs.
Excellent, this does sound pretty straightforward. I'll do as suggested 
if you want a cheap and easy fuel pump amplifier you could easily unsolder the controller chip from an secondhand OEM pump driver module, and apply a pwm generated by your ECU directly to the driver IC mounted in that nodule.
See here for a perfect candidate: Helbako_EKPM2
See here for a perfect candidate: Helbako_EKPM2
Max_Torque said:
I would suggest using an OEM differential pressure sensor like this:
You will need that to report the injector differential pressure to your ecu, so you can use a lookup table to modify injector pulse width to maintain a constant fuel mass delivery.
I've been looking at these. Any part number and cal values available anywhere. I'm struggling.You will need that to report the injector differential pressure to your ecu, so you can use a lookup table to modify injector pulse width to maintain a constant fuel mass delivery.
Sorry OT
stevesingo said:
yeah, that would be fine, but being a Motec part, i bet they charge you for it!Something like this:
VDO_pump_driver_on_ebay
Is almost certainly a lot cheaper!
Max_Torque said:
stevesingo said:
I've been looking at these. Any part number and cal values available anywhere. I'm struggling.
Sorry OT
The one i can find at the moment is Ford number 3R3E9F972AA, iirc they are a 5bar range over 0-5v ratiometric output.Sorry OT
I also like the look of this one, with temperature sensor
Your fuel injectors are effectively just a fixed orifice. The mass of fuel that flows through that orifice depends upon the pressure acting across it. Clearly, one end of your injector is fixed to the fuel rail, that has, statically speaking, around about 4bar(gauge) in it. However, assuming your injectors are not remote (ie mounted up above the inlet trumpets) then the other side of them has inlet manifold pressure acting on them, which for an NA engine, varies between around 0.3bar(abs) to 1bar (abs).
Hence the pressure ratio across you injectors, not including dynamic effects such as standing pressure waves in the fuel rail, will change significantly with throttle position. To correct for this, the EMS system will measure the actual injector differential pressure, using the sensors pictured above, with one side of the DP sensor having fuel rail pressure acting on it, and the other side being connected by a short tube, to the inlet manifold.
This means the EMS system can have a lookup table that corrects fuel injector pulse width vs IJDP (InJectorDifferentialPressure) to account for the flow rate differences.
If you have a very fast and properly calibrated returnless pressure control system, you can attempt to hold a constant IJDP, but you will find that inertial and dynamic effects during rapid load changes, make this somewhat un-obtainable, especially for port throttled systems where the downstream "throttled" volume is small (and hence can rapidly change pressure)
On my returnless system i have a sort of halfway house, where i measure IJDP in real time, use the EMS to correct the fuel mass, but have the returnless pressure control target follow a slower, non linear low pass filted IJDP target. This reduces the control effort the fuel pressure system has to conduct, but still allows dynamic IJDP control in order to maintain injector headroom (vital on my heavily boosted engine, but still useful on an NA one)
ETA: this^^ is of course what a conventional mech fuel pressure regulator does, with one side of the diaphram referenced to intake manifold pressure. You can run with a fixed rail pressure, and accept that the effects of IJDP varrying with manifold pressure will just be "baked" into your main fuel map. However, if you main load determination is just throttle angle, you tend to get relatively big changes in post throttle pressure for tiny changes in throttle angle, especially on port throttled engines where the "curtain area" of the throttles is large and the area gain vs Throttle plate angle big.
It will certainly work, and if you have a baro sensor, at least you can get the fuel mass correct when close to WOT (although effective WOT angle is of course engine speed and air density dependent). The problems tend to come at light loads (small throttle angles)
Hence the pressure ratio across you injectors, not including dynamic effects such as standing pressure waves in the fuel rail, will change significantly with throttle position. To correct for this, the EMS system will measure the actual injector differential pressure, using the sensors pictured above, with one side of the DP sensor having fuel rail pressure acting on it, and the other side being connected by a short tube, to the inlet manifold.
This means the EMS system can have a lookup table that corrects fuel injector pulse width vs IJDP (InJectorDifferentialPressure) to account for the flow rate differences.
If you have a very fast and properly calibrated returnless pressure control system, you can attempt to hold a constant IJDP, but you will find that inertial and dynamic effects during rapid load changes, make this somewhat un-obtainable, especially for port throttled systems where the downstream "throttled" volume is small (and hence can rapidly change pressure)
On my returnless system i have a sort of halfway house, where i measure IJDP in real time, use the EMS to correct the fuel mass, but have the returnless pressure control target follow a slower, non linear low pass filted IJDP target. This reduces the control effort the fuel pressure system has to conduct, but still allows dynamic IJDP control in order to maintain injector headroom (vital on my heavily boosted engine, but still useful on an NA one)
ETA: this^^ is of course what a conventional mech fuel pressure regulator does, with one side of the diaphram referenced to intake manifold pressure. You can run with a fixed rail pressure, and accept that the effects of IJDP varrying with manifold pressure will just be "baked" into your main fuel map. However, if you main load determination is just throttle angle, you tend to get relatively big changes in post throttle pressure for tiny changes in throttle angle, especially on port throttled engines where the "curtain area" of the throttles is large and the area gain vs Throttle plate angle big.
It will certainly work, and if you have a baro sensor, at least you can get the fuel mass correct when close to WOT (although effective WOT angle is of course engine speed and air density dependent). The problems tend to come at light loads (small throttle angles)
Edited by anonymous-user on Wednesday 26th November 18:36
stevesingo said:
Would that be 0Bar=0v, 5Bar=5v?
I also like the look of this one, with temperature sensor
yeah, there ar a few to choose from, mostly from cars between approx 2003 to 2008, when everyone went returnless on the Port Injected Gasoline engines, but before it all went DI.I also like the look of this one, with temperature sensor
I stuck the sensor i have on the Druck Pressure calibrator we have at work, and iirc it was 0v = 0bar, 5v = 5bar, but at the moment i can't find the spreadsheet i stuck the numbers into....... (must be on my backup harddrive somewhere). The zero offset is at least easy to work out/measure!
Max_Torque said:
Your fuel injectors are effectively just a fixed orifice. The mass of fuel that flows through that orifice depends upon the pressure acting across it. Clearly, one end of your injector is fixed to the fuel rail, that has, statically speaking, around about 4bar(gauge) in it. However, assuming your injectors are not remote (ie mounted up above the inlet trumpets) then the other side of them has inlet manifold pressure acting on them, which for an NA engine, varies between around 0.3bar(abs) to 1bar (abs).
Hence the pressure ratio across you injectors, not including dynamic effects such as standing pressure waves in the fuel rail, will change significantly with throttle position. To correct for this, the EMS system will measure the actual injector differential pressure, using the sensors pictured above, with one side of the DP sensor having fuel rail pressure acting on it, and the other side being connected by a short tube, to the inlet manifold.
This means the EMS system can have a lookup table that corrects fuel injector pulse width vs IJDP (InJectorDifferentialPressure) to account for the flow rate differences.
If you have a very fast and properly calibrated returnless pressure control system, you can attempt to hold a constant IJDP, but you will find that inertial and dynamic effects during rapid load changes, make this somewhat un-obtainable, especially for port throttled systems where the downstream "throttled" volume is small (and hence can rapidly change pressure)...
ETA: this^^ is of course what a conventional mech fuel pressure regulator does, with one side of the diaphram referenced to intake manifold pressure. You can run with a fixed rail pressure, and accept that the effects of IJDP varrying with manifold pressure will just be "baked" into your main fuel map. However, if you main load determination is just throttle angle, you tend to get relatively big changes in post throttle pressure for tiny changes in throttle angle, especially on port throttled engines where the "curtain area" of the throttles is large and the area gain vs Throttle plate angle big.
It will certainly work, and if you have a baro sensor, at least you can get the fuel mass correct when close to WOT (although effective WOT angle is of course engine speed and air density dependent). The problems tend to come at light loads (small throttle angles)
I get all of this, and I can absolutely understand why OEMs do it, especially for the low throttle angles where as you say small angles give large flow area increases. And also it must be of big benefit for altitude compensation?Hence the pressure ratio across you injectors, not including dynamic effects such as standing pressure waves in the fuel rail, will change significantly with throttle position. To correct for this, the EMS system will measure the actual injector differential pressure, using the sensors pictured above, with one side of the DP sensor having fuel rail pressure acting on it, and the other side being connected by a short tube, to the inlet manifold.
This means the EMS system can have a lookup table that corrects fuel injector pulse width vs IJDP (InJectorDifferentialPressure) to account for the flow rate differences.
If you have a very fast and properly calibrated returnless pressure control system, you can attempt to hold a constant IJDP, but you will find that inertial and dynamic effects during rapid load changes, make this somewhat un-obtainable, especially for port throttled systems where the downstream "throttled" volume is small (and hence can rapidly change pressure)...
ETA: this^^ is of course what a conventional mech fuel pressure regulator does, with one side of the diaphram referenced to intake manifold pressure. You can run with a fixed rail pressure, and accept that the effects of IJDP varrying with manifold pressure will just be "baked" into your main fuel map. However, if you main load determination is just throttle angle, you tend to get relatively big changes in post throttle pressure for tiny changes in throttle angle, especially on port throttled engines where the "curtain area" of the throttles is large and the area gain vs Throttle plate angle big.
It will certainly work, and if you have a baro sensor, at least you can get the fuel mass correct when close to WOT (although effective WOT angle is of course engine speed and air density dependent). The problems tend to come at light loads (small throttle angles)
But I'm building a trackcar, and I can put up with "character"
So because I'll be mapping every load and throttle line, surely the changes in inlet port pressure (between 0.3-1.0 bar abs.) and the subsequent change in AFR this would give for a given injector open time for a fixed fuel rail pressure will come out in the wash so to speak.
i.e we'll be mapping for MBT where possible, at a (hopefully fixed & stable) 3.6 bar fuel rail pressure and tweak the injector open time to give 12.6:1 AFR everywhere.
If it's a bit crap under 10°THM it won't be the end of the world. The main downside of this I can see with my method is that without the ECU knowing about baro it would be rubbish with altitude changes?
O/T
Injection phase angle with a port mounted injector - better over an Open or Closed inlet valve? (for torque - I guess other OEMs might prioritise raw emissions or something?)
Max_Torque said:
yeah, there ar a few to choose from, mostly from cars between approx 2003 to 2008, when everyone went returnless on the Port Injected Gasoline engines, but before it all went DI.
I stuck the sensor i have on the Druck Pressure calibrator we have at work, and iirc it was 0v = 0bar, 5v = 5bar, but at the moment i can't find the spreadsheet i stuck the numbers into....... (must be on my backup harddrive somewhere). The zero offset is at least easy to work out/measure!
Found it.I stuck the sensor i have on the Druck Pressure calibrator we have at work, and iirc it was 0v = 0bar, 5v = 5bar, but at the moment i can't find the spreadsheet i stuck the numbers into....... (must be on my backup harddrive somewhere). The zero offset is at least easy to work out/measure!
http://www.askatech.com/AskATechLive/forums/Resour...
Looks like a 20kohm pull up on the temp side.
this looks ideal for PWM signal amplification from ECU to fuel pump, just need to confirm a price...
http://www.hella.com/microsite-electronics/157.htm...
http://www.hella.com/microsite-electronics/assets/...
http://www.hella.com/microsite-electronics/157.htm...
http://www.hella.com/microsite-electronics/assets/...
Max_Torque said:
yeah, there ar a few to choose from, mostly from cars between approx 2003 to 2008, when everyone went returnless on the Port Injected Gasoline engines, but before it all went DI.
Apart from potential cost/weight/space savings, does a return-less system actually offer any performance benefits?Mr2Mike said:
Apart from potential cost/weight/space savings, does a return-less system actually offer any performance benefits?
Yes. Less fuel heating = colder, denser intake charge. (and reduced fuel evap for OEMs)
Less fuel pump current draw = lower alternator load on engine.
Potentially less noise from fuel pump as others have stated.
The wieght, space and electrical load benefits are what attracts me. I'm trying to keep the car under 750kg, and aiming to use a tiny 45A alternator.
Pat_T said:
this looks ideal for PWM signal amplification from ECU to fuel pump, just need to confirm a price...
http://www.hella.com/microsite-electronics/157.htm...
http://www.hella.com/microsite-electronics/assets/...
You will struggle to buy that amplifier from Hella, as it's am OEM part. You'll probably have to find to what car it is fitted and buy one from the manufacturer of that car.http://www.hella.com/microsite-electronics/157.htm...
http://www.hella.com/microsite-electronics/assets/...
Max_Torque said:
You will struggle to buy that amplifier from Hella, as it's am OEM part. You'll probably have to find to what car it is fitted and buy one from the manufacturer of that car.
M_T, correct, I'm an OEM powertrain engineer, it was recommended to me by one of our electrical engineers. You may be right though, I'll see what I can do..This one is available to the masses by the looks of it:
http://www.amazon.com/Dorman-590-001-Fuel-Driver-M...
Cheaper option, could this be modified to acheive the desired outcome?
http://www.ebay.com/itm/40A-9-40V-DC-PWM-Motor-Spe...
Edited by Pat_T on Friday 5th December 12:48
I'd use the widely available VDO amplifer, used on Fords, Jags and Astons (for which it should be easy to find the wiring diagram etc)
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