Fuel Pump speed control
Discussion
Max_Torque said:
100psi is a walk in the park for my system (that runs up to 150psi, and thats just limited by the rail pressure sensor. (although std fuel injectors cannot open against much more than 10bar).
Certainly holding a rail at 80psi is easy, the only issue is if you were to sit with the system operational but not running the engine for ages (>30mins) the the pressure pumps do start to get a bit warm as no fuel is flowing through them to cool them.
There is really no advantage in keeping the mechanical pressure regulator, as you would have to set it above the max pressure you want to ever run. Once you have seen how well the electronically managed system works, you'll never want to go back to the mechanical version anyway ;-)
I slowly adding the diagnostic routines into my system for test, things like automatic leak detection, error limit flagging (identifies when the system is unable to maintain a suitable level of control of fuel pressure (sensor failure, lack of fuel, pump failure etc) and to act accordingly. So far i have a caution/warn led mounted in the dash, which buld checks on key-on, then goes out if all is well. Minor faults (like small pressure errors) set the led to slowly flash (and store a suitable code in volatile memory so you can interogate the unit for the cause of the error) Major faults (shorted pump, insufficent pressure, system leak etc) disable the system completely, turn the led on continously, and trigger another output that can be used to remove power from either the injectors or coils to stop the engine if required.
Faults are reset by power cycling the unit ie a key/ignition cycle, but are stored in memory until cleared by the cal tool program.
One thing rallying teaches me is that you never have time to look at the dash in a stage......... ;-)
That's my point though. Many injectors may not be happy at 100psi. Many fuel lines will be pushed at 100psi. Filters ?Certainly holding a rail at 80psi is easy, the only issue is if you were to sit with the system operational but not running the engine for ages (>30mins) the the pressure pumps do start to get a bit warm as no fuel is flowing through them to cool them.
There is really no advantage in keeping the mechanical pressure regulator, as you would have to set it above the max pressure you want to ever run. Once you have seen how well the electronically managed system works, you'll never want to go back to the mechanical version anyway ;-)
I slowly adding the diagnostic routines into my system for test, things like automatic leak detection, error limit flagging (identifies when the system is unable to maintain a suitable level of control of fuel pressure (sensor failure, lack of fuel, pump failure etc) and to act accordingly. So far i have a caution/warn led mounted in the dash, which buld checks on key-on, then goes out if all is well. Minor faults (like small pressure errors) set the led to slowly flash (and store a suitable code in volatile memory so you can interogate the unit for the cause of the error) Major faults (shorted pump, insufficent pressure, system leak etc) disable the system completely, turn the led on continously, and trigger another output that can be used to remove power from either the injectors or coils to stop the engine if required.
Faults are reset by power cycling the unit ie a key/ignition cycle, but are stored in memory until cleared by the cal tool program.
One thing rallying teaches me is that you never have time to look at the dash in a stage......... ;-)
And realistically, why would we want to run 100psi base pressure ?
And the issue you raise of working the pump to always generate 100psi regardless of flow. Surely that isnt efficient use of power as it will always be drawing a lot of current ? placing strain on wiring etc ?
So could the pump heating also be an issue at cruise ? Say driving at 60-70mph with relatively low fuel consumption for 2-3 hours ?
The difference is between "power" and "current". When fuel flows are low (or zero) the pump speed is also practically zero for any output pressure (it just slowly turns due to "leakage" around the pump elements (which is actually a good thing, because it means all "phases" of the motor's rotor get used, so it is not like a full "stalled" condition) Although the current can be high (and in reality it isn't that high even at high pressures, because there are no hydraulic system losses from moving massive volumes of fuel around the system (remmeber, on a conventional system, to get say 4bar in the rail requires a true pump output approaching 6 bar due to pressure losses at high flows)) the actual voltage supplied to the pump is very low. So the "power" of the system is minimal (Power = Volts x amps) this minimises any heating of the system.
My 044 based system onyl requires 4.7A to make 5.7bar at zero flow, and with it's rotor resistance of 0.56Ohm, that means the IsquaredR loses are only 12.3Watts (which it easily radiates without significant heating)
On my car yesterday i left it with a 5.7bar rail demand, engine off for 30 mins, (i.e. worst case zero fuel flow to cool pumps) and the pumps were slightly warm to touch (i'd guess maybe 30 deg approx). At any point where system power is high, then you must also be moving a lot of fuel (because the pumps are only turning fast when actually moving fuel volume) and in this case the heat is carried away normally by the fuel, except in this case, it does not get returned to upheat your fuel tank etc (becuase it is all injected into the engine)
The beauty of the electronically managed system is it's flexibility, don't want 100psi, no probs, change on number in 2secs, and bingo, there's your new rail pressure set, no spanners required!
Regarding high rail pressures, really these are key to high specific power outputs. Most people run with std pressures for 2 reasons 1) mechanical pressure regs only work well up to about 4-5bar before you run into massive non linearity issues and 2) they don't understand the benefits of running with a high fuel pressure. (lets put it this way, F1 cars and WRC cars are both still port injected (ok, i know wrc 1.6 turbo's have just gone DI) and they run 100 bar and 16bar rail pressure respectively, and both engines have specific outputs that are very good (in terms of bhp/unit airflow) Higher rail pressures = better atomisation and crucially a shorter pulse width to get in the required fuel mass, so you have much more freedom to accurately control when in the cycle the injection event occurs (road cars, and especially tuned road cars typically run with >80 injector duty at peak power (a wrc car runs at ~35%........)
Now you could get short injector pulse widths by just fitting "large" injectors (i.e. injectors with large nozzles) but these suffer from 2 issues:
1) at low loads you can't get linear control of injected fuel mass, so idle and driveability suffer (probably not an issue for a race car etc)
but more critically:
2) the fuel atomisation is terrible. This means very poor mixture distribution (forcing you to run richer than strictly necessary to compensate (hence lots of "high boost tuned" cars seen with black smoke out the back..... (ever seen a wrc car smoke? even though they make >300Nm/litre? no, me neither.........) and worse still, it acts to quench the charges burn rate, forcing you to retard your ignition away from MBT and costing you power and reducing you specific output
The probelm of course it that "Normal" injectors simply fail to open much about 9bar (they become non linear above about 7bar). There are two solutions:
1) use TAG racing injectors, rated to >20bar, the downside being they are approx £480 an injector last time i checked (ouch! especially if you have a V12 lol)
2) do what i do, and use a "high voltage" (30V) peak and hold driver to slam normal injectors open, even at high fuel rail pressures. The downside, the pintle seats tend to wear after a bit leading to dribbling, and you can easily cook them your drive cal is not properly cal'd)
As with everything, speed costs £££, how fast can you afford to go??? ;-)
My 044 based system onyl requires 4.7A to make 5.7bar at zero flow, and with it's rotor resistance of 0.56Ohm, that means the IsquaredR loses are only 12.3Watts (which it easily radiates without significant heating)
On my car yesterday i left it with a 5.7bar rail demand, engine off for 30 mins, (i.e. worst case zero fuel flow to cool pumps) and the pumps were slightly warm to touch (i'd guess maybe 30 deg approx). At any point where system power is high, then you must also be moving a lot of fuel (because the pumps are only turning fast when actually moving fuel volume) and in this case the heat is carried away normally by the fuel, except in this case, it does not get returned to upheat your fuel tank etc (becuase it is all injected into the engine)
The beauty of the electronically managed system is it's flexibility, don't want 100psi, no probs, change on number in 2secs, and bingo, there's your new rail pressure set, no spanners required!
Regarding high rail pressures, really these are key to high specific power outputs. Most people run with std pressures for 2 reasons 1) mechanical pressure regs only work well up to about 4-5bar before you run into massive non linearity issues and 2) they don't understand the benefits of running with a high fuel pressure. (lets put it this way, F1 cars and WRC cars are both still port injected (ok, i know wrc 1.6 turbo's have just gone DI) and they run 100 bar and 16bar rail pressure respectively, and both engines have specific outputs that are very good (in terms of bhp/unit airflow) Higher rail pressures = better atomisation and crucially a shorter pulse width to get in the required fuel mass, so you have much more freedom to accurately control when in the cycle the injection event occurs (road cars, and especially tuned road cars typically run with >80 injector duty at peak power (a wrc car runs at ~35%........)
Now you could get short injector pulse widths by just fitting "large" injectors (i.e. injectors with large nozzles) but these suffer from 2 issues:
1) at low loads you can't get linear control of injected fuel mass, so idle and driveability suffer (probably not an issue for a race car etc)
but more critically:
2) the fuel atomisation is terrible. This means very poor mixture distribution (forcing you to run richer than strictly necessary to compensate (hence lots of "high boost tuned" cars seen with black smoke out the back..... (ever seen a wrc car smoke? even though they make >300Nm/litre? no, me neither.........) and worse still, it acts to quench the charges burn rate, forcing you to retard your ignition away from MBT and costing you power and reducing you specific output
The probelm of course it that "Normal" injectors simply fail to open much about 9bar (they become non linear above about 7bar). There are two solutions:
1) use TAG racing injectors, rated to >20bar, the downside being they are approx £480 an injector last time i checked (ouch! especially if you have a V12 lol)
2) do what i do, and use a "high voltage" (30V) peak and hold driver to slam normal injectors open, even at high fuel rail pressures. The downside, the pintle seats tend to wear after a bit leading to dribbling, and you can easily cook them your drive cal is not properly cal'd)
As with everything, speed costs £££, how fast can you afford to go??? ;-)
Edited by anonymous-user on Wednesday 10th August 20:27
andygtt said:
how many road cars are going to be needing 100psi of fuel pressure... I know the modern direct injection cars are but the high powered modded cars are running less than that usually?
Mine runs 4bar constant, im pretty sure all the skylines etc run similar... why run more?
There wouldnt be many boosted setups that run a constant fuel pressure. 99% will rise roughly in line with boost.Mine runs 4bar constant, im pretty sure all the skylines etc run similar... why run more?
I really am curious as to what you use your car for Max ? On a technical level, you really do seem to go all out with everything you do. It surely must be more than a bit of fun ?
But back on topic. I'm still awaiting the simple version lol
If a dead end system can work, and also raise fuel pressure in line with boost, fair enough, it would be workable for most.
I myself on my own car wouldnt be happy running a base pressure of say 70-80psi base pressure all the time, to make up for the lack of a 1:1 reference with MAP.
Currently I'm on around 3.5 bar base + boost.
Although in essence, running 80psi wouldnt be a problem. It just seems wrong to do it ? and it wont really offer me any benefits, and it will mean I have to re-tune everything.
On the fuel temperature note. On a car that gets well used, perhaps fuel temperatures may remain cooler. However, for a car that gets used for drag racing. Sitting in the fire up lane, long queues in very warm weather. I can only see fuel temperatures at the rail soaring in a dead ended system. In those instances a full flow return will remain cooler.
Max_Torque said:
The only issue with running a "fixed" rail pressure is at idle (rather than any issue under load) as you end up with very short injector pulse widths to only supply small quantities of fuel.
As long as your fixed pressure is sufficient to flow the max quanity of fuel with the worst case injector delta pressure then you are fine!
I think that has answered my question as to why this system is better than a fixed rail pressure. So, by running a fuel pump controller opens the possibility of mapping fuel pressure to the engines requirements, so injector pulse width remains within a region that the injector is happy with.As long as your fixed pressure is sufficient to flow the max quanity of fuel with the worst case injector delta pressure then you are fine!
RE; My car, it was built to win the 2wd turbo class on single venue MSA tarmac rallies, but the MSA banned it before i could use it in anger........ So now, it's just a stupidly over-the-top trackday weapon ;-)
Regarding high fuel rail temps, as long as you have sufficient pressure to avoid vapourisation then having elevated fuel temps is no issue. In fact, it can help emissions due better atomisation and faster vapourisation in the intake charge! The change in density of the fuel over the range of temps seen (say -30 cold degC start to +100 degC after key off soak) doesn't change the fuel density that much (~0.1%/deg density coefficient). Of course, the real answer is to measure rail temp and correct for it. Most OEM rail sensors include a rail temp sensor with the pressure sensor, that was the fuel system can both correct for the density change, and know when it needs to use an "overpressure" at keyon to prevent boiling in the rail.
Regarding high fuel rail temps, as long as you have sufficient pressure to avoid vapourisation then having elevated fuel temps is no issue. In fact, it can help emissions due better atomisation and faster vapourisation in the intake charge! The change in density of the fuel over the range of temps seen (say -30 cold degC start to +100 degC after key off soak) doesn't change the fuel density that much (~0.1%/deg density coefficient). Of course, the real answer is to measure rail temp and correct for it. Most OEM rail sensors include a rail temp sensor with the pressure sensor, that was the fuel system can both correct for the density change, and know when it needs to use an "overpressure" at keyon to prevent boiling in the rail.
Max_Torque said:
RE; My car, it was built to win the 2wd turbo class on single venue MSA tarmac rallies, but the MSA banned it before i could use it in anger........ So now, it's just a stupidly over-the-top trackday weapon ;-)
Regarding high fuel rail temps, as long as you have sufficient pressure to avoid vapourisation then having elevated fuel temps is no issue. In fact, it can help emissions due better atomisation and faster vapourisation in the intake charge! The change in density of the fuel over the range of temps seen (say -30 cold degC start to +100 degC after key off soak) doesn't change the fuel density that much (~0.1%/deg density coefficient). Of course, the real answer is to measure rail temp and correct for it. Most OEM rail sensors include a rail temp sensor with the pressure sensor, that was the fuel system can both correct for the density change, and know when it needs to use an "overpressure" at keyon to prevent boiling in the rail.
So while we strive to keep intake temperatures low, you would see no issue with injecting fuel at 60, 70, 80degC ? If indeed it would even remain as liquid at those temperatures ?Regarding high fuel rail temps, as long as you have sufficient pressure to avoid vapourisation then having elevated fuel temps is no issue. In fact, it can help emissions due better atomisation and faster vapourisation in the intake charge! The change in density of the fuel over the range of temps seen (say -30 cold degC start to +100 degC after key off soak) doesn't change the fuel density that much (~0.1%/deg density coefficient). Of course, the real answer is to measure rail temp and correct for it. Most OEM rail sensors include a rail temp sensor with the pressure sensor, that was the fuel system can both correct for the density change, and know when it needs to use an "overpressure" at keyon to prevent boiling in the rail.
The latent heat of evapouration is so much higher than the fuels specific heat energy stored as it's basic temperature that varriations in fuel temp really make little difference to intake manifold volumetric efficiency. And of course, where you care about charge temps,at WOT etc, then your fuel rail is not hot, because it is being supplied by nice cold fuel from your tank (that hasn't been upheated by being cycled through your engine bay etc!)
In fact, from an emissions and driveability perspective, hot fuel is an advantage to mixture preperation at low loads!
The only time when you get a significant upheat on a returnless system is on a start after a proper hot soak, where at keyon you do not get the nice cooling rush of "new" fuel around the rail as the pumps prime. Here, where rail temps exceed 120degC, the returnless systems will "overpressure" to approx 6 bar (less pressure than i run normally lol) to prevent vapourisation in the rail. it's a very simple piece of control strategy
eg:
[code]
if(RailTempDegC > 100) then FuelPressureTarget = OverPressureSetpoint;
else FuelPressureTarget = NormalSetpoint;
[/code]
Fuel temperatures below approx 80degc really have no measurable effect on the performance of the system or BMEP
(we run tests up places like gross glockner, Sierra Nevada's, and Italian alps etc where the car is driven agressively up the pass, key'off immediately at the top (usualy with a top hose temp >110degC) and left till engine bay temps have peaks (typically 15-20mins, usually at ~160degC air temp peak underbonnet), then restarted. The systems must be able to cope with severe tests like this
Sounds like a good excuse for a pic, here's one i did earlier:
In fact, from an emissions and driveability perspective, hot fuel is an advantage to mixture preperation at low loads!
The only time when you get a significant upheat on a returnless system is on a start after a proper hot soak, where at keyon you do not get the nice cooling rush of "new" fuel around the rail as the pumps prime. Here, where rail temps exceed 120degC, the returnless systems will "overpressure" to approx 6 bar (less pressure than i run normally lol) to prevent vapourisation in the rail. it's a very simple piece of control strategy
eg:
[code]
if(RailTempDegC > 100) then FuelPressureTarget = OverPressureSetpoint;
else FuelPressureTarget = NormalSetpoint;
[/code]
Fuel temperatures below approx 80degc really have no measurable effect on the performance of the system or BMEP
(we run tests up places like gross glockner, Sierra Nevada's, and Italian alps etc where the car is driven agressively up the pass, key'off immediately at the top (usualy with a top hose temp >110degC) and left till engine bay temps have peaks (typically 15-20mins, usually at ~160degC air temp peak underbonnet), then restarted. The systems must be able to cope with severe tests like this
Sounds like a good excuse for a pic, here's one i did earlier:
Edited by anonymous-user on Thursday 11th August 13:59
Edited by anonymous-user on Thursday 11th August 14:03
stevieturbo said:
andygtt said:
how many road cars are going to be needing 100psi of fuel pressure... I know the modern direct injection cars are but the high powered modded cars are running less than that usually?
Mine runs 4bar constant, im pretty sure all the skylines etc run similar... why run more?
There wouldnt be many boosted setups that run a constant fuel pressure. 99% will rise roughly in line with boost.Mine runs 4bar constant, im pretty sure all the skylines etc run similar... why run more?
I really am curious as to what you use your car for Max ? On a technical level, you really do seem to go all out with everything you do. It surely must be more than a bit of fun ?
And yes it is just a bit of fun for me... I was gutted fighting torque was cancelled as I wanted to take me car along to see how it performes after all thats what its all about.
Surely coping and what is optimal are two different things ?
I wouldnt want to start a race with fuel being injected at 100degC ? Surely nobody would, especially in a boosted engine ?
As I say, we all, yourself included strive to keep intake temps as low as possible. Hot fuel would be counter productive ?
So yes the engine may be able to run, but it's performance must be compromised by this heat ?
When people fit fuel coolers, if engines are happy running very high fuel temperatures, why would they bother ?
Is it simply the pump that doesnt like the temperature ?
I have asked plenty of times before from various sources and never got an answer.
What sort of fuel temperatures are considered too high ? Unless I'm reading wrong, you dont seem to suggest even very hot temperatures are bad at all ?
I also thought one of the reasons for wanting a pump controller, was to reduce fuel temperatures ?
I wouldnt want to start a race with fuel being injected at 100degC ? Surely nobody would, especially in a boosted engine ?
As I say, we all, yourself included strive to keep intake temps as low as possible. Hot fuel would be counter productive ?
So yes the engine may be able to run, but it's performance must be compromised by this heat ?
When people fit fuel coolers, if engines are happy running very high fuel temperatures, why would they bother ?
Is it simply the pump that doesnt like the temperature ?
I have asked plenty of times before from various sources and never got an answer.
What sort of fuel temperatures are considered too high ? Unless I'm reading wrong, you dont seem to suggest even very hot temperatures are bad at all ?
I also thought one of the reasons for wanting a pump controller, was to reduce fuel temperatures ?
Edited by stevieturbo on Thursday 11th August 18:22
stevieturbo said:
Surely coping and what is optimal are two different things ?
I wouldnt want to start a race with fuel being injected at 100degC ? Surely nobody would, especially in a boosted engine ?
As I say, we all, yourself included strive to keep intake temps as low as possible. Hot fuel would be counter productive ?
So yes the engine may be able to run, but it's performance must be compromised by this heat ?
When people fit fuel coolers, if engines are happy running very high fuel temperatures, why would they bother ?
Is it simply the pump that doesnt like the temperature ?
I have asked plenty of times before from various sources and never got an answer.
What sort of fuel temperatures are considered too high ? Unless I'm reading wrong, you dont seem to suggest even very hot temperatures are bad at all ?
I also thought one of the reasons for wanting a pump controller, was to reduce fuel temperatures ?
Ok, let me try and reiterate a few points for clarity:I wouldnt want to start a race with fuel being injected at 100degC ? Surely nobody would, especially in a boosted engine ?
As I say, we all, yourself included strive to keep intake temps as low as possible. Hot fuel would be counter productive ?
So yes the engine may be able to run, but it's performance must be compromised by this heat ?
When people fit fuel coolers, if engines are happy running very high fuel temperatures, why would they bother ?
Is it simply the pump that doesnt like the temperature ?
I have asked plenty of times before from various sources and never got an answer.
What sort of fuel temperatures are considered too high ? Unless I'm reading wrong, you dont seem to suggest even very hot temperatures are bad at all ?
I also thought one of the reasons for wanting a pump controller, was to reduce fuel temperatures ?
Edited by stevieturbo on Thursday 11th August 18:22
1) Fuel temperatures in the rail can reach over 120 degC without significant effects, as long as the rail pressure is maintained sufficently to prevent boiling in said rail
2) Fuel temperatures have very little impact on volumetric efficiency and hence engine performance. I was unable to measure (using circa £2M worth of engine dyno kit) any significant change in BMEP for fuel temps up to approx 85 degC. On the 2.0 turbo i was testing, temps above 85degC "may" reduce BMEP by a couple of % (even post processing the results we struggled to demonstrate a significant reduction in performance)
Even when running rich for peak power, there is approx 8x as much air by mass as fuel being injected, and the latent heat of evapouration of the fuel is the dominating factor in determining charge temperature variations due to liquid fuel temp. Also, for most engines (and see my previous posts about injector duty cycle maximums) at high power you have a high injector duty cycle. This results in you injecting most of your fuel quantity on a closed valve, at which point it just sits around absorbing all the heat from the (usually alluminium) intake runner walls. So your fuel rail temps might only be say 30degC, but the fuel just gets heated by the nearly 100degC ally walls all around it anyway........ )
3) On returnless systems, you can have a high rail temperature for a few seconds after start (because the hot fuel is not "flushed out" by new fuel like in a return system). But, for all other operating points rail temperature is lower than for a return system (because the bulk tank temp stays lower and the fuel pumps are putting much much less heat into the system (std 044 at full flow = 12v x (approx)15A = 180W of heat all the time + all the heat picked up by the fuel passing at high velocity through the hot rail!). Regarding "starting a race with hot fuel". by the time you have done your sighting lap, then rev'd the engine for 5 sec before the green light, the rail will not have any hot fuel in it ;-) It really is only during key-off hot soaks where any significant temperature increase is measured (and of course depends on the physical layout of your fuel system. i.e. plastic/stainless fuel rails mounted well off the cylinder head don't suffer from nearly as much upheat as an aluminium rail bolted directly to the head etc)
TBH, i'm not really sure why people fit fuel coolers? I have never found the requirement in any car i have ever been involved with. Generally, the bulk fuel mass in the tank coupled with said tanks large surface area have the same effect. I do wonder if people fit pumping systems with such terrible efficiency that they then require a cooler to take out all the heat they have put in via the pumps?
(perhaps "sprint" cars running with say only 5L of fuel might need one etc??)
the reason i'm worried about fuel temp is that the tank on a noble is in the engine bay around 6 inches from one of the turbos.
but if I read what you are saying correctly, high fuel temp will disapear when mixed with the air anyhow (assuming the air is cool), the actual fuel system itself isn't effected much by fuel temp... therefore it has very little impact on the engine performance?
my rail gets very hot as its steel, intakes are plastic but there is just a lot of heat generally in the engine bay that heats everything in the bay.
but if I read what you are saying correctly, high fuel temp will disapear when mixed with the air anyhow (assuming the air is cool), the actual fuel system itself isn't effected much by fuel temp... therefore it has very little impact on the engine performance?
my rail gets very hot as its steel, intakes are plastic but there is just a lot of heat generally in the engine bay that heats everything in the bay.
6" is huge.......... (no, lets not have any unecessary phalic jokes here, oh, ok, just one then ;-)
Seriously, 6" with a suitable heat sheilding systems is no problem what so ever, most OEM's call 10-12mm a critical clearance these days!
You don't really want your bulk fuel temps to be too warm, Bosch only spec their pumps to 80degC and you get massive vapour pressure from hot gasoline.
Seriously, 6" with a suitable heat sheilding systems is no problem what so ever, most OEM's call 10-12mm a critical clearance these days!
You don't really want your bulk fuel temps to be too warm, Bosch only spec their pumps to 80degC and you get massive vapour pressure from hot gasoline.
Thanks for that. It is the first time Ive ever heard anyone give definitive info about fuel temperatures.
But....I was of course referring to drag racing. There is no sighting lap. You queue, you heat up, you race.
Engine performance is expected to be as close to 100% right from the word go, right after that very hot start.
And many people who do run small swirl tanks, and perhaps small main tanks, and recirculate fuel back into that tiny tank could well see highish fuel temperatures. But again....until now nobody has ever really gave any specifics as to how hot is too hot.
I dont really have any issue on mine, as fuel temperatures rarely go above 40degC, except when the pumps are not running and heat soak kicks in. That said, I do have a large tank, and I also have a fuel cooler albeit a very badly placed one.
But as Andy experienced before, and I and many other 044 users after extended usage. What's the score with that damn noise they make ? Others have alleged it causes them running problems, although Ive never experienced any myself even when the pumps are noisy as hell.
This was one of the reasons I started logging fuel temps. But really...the pumps just seem to get noisy regardless of fuel temperature.
Back on the controller. I think, that running without an FPR, but with fuel pressure based on MAP electronically may be the easiest way to go ? And so hot fuel in the rails is never a concern. Leave them as a full flow system, but with a small bleed orifice in the return line instead of a FPR ?
This will always ensure there is some flow
But....I was of course referring to drag racing. There is no sighting lap. You queue, you heat up, you race.
Engine performance is expected to be as close to 100% right from the word go, right after that very hot start.
And many people who do run small swirl tanks, and perhaps small main tanks, and recirculate fuel back into that tiny tank could well see highish fuel temperatures. But again....until now nobody has ever really gave any specifics as to how hot is too hot.
I dont really have any issue on mine, as fuel temperatures rarely go above 40degC, except when the pumps are not running and heat soak kicks in. That said, I do have a large tank, and I also have a fuel cooler albeit a very badly placed one.
But as Andy experienced before, and I and many other 044 users after extended usage. What's the score with that damn noise they make ? Others have alleged it causes them running problems, although Ive never experienced any myself even when the pumps are noisy as hell.
This was one of the reasons I started logging fuel temps. But really...the pumps just seem to get noisy regardless of fuel temperature.
Back on the controller. I think, that running without an FPR, but with fuel pressure based on MAP electronically may be the easiest way to go ? And so hot fuel in the rails is never a concern. Leave them as a full flow system, but with a small bleed orifice in the return line instead of a FPR ?
This will always ensure there is some flow
Simple fact of the matter is that there is NO requirement to ever have any return flow!
In your drag race example, by the time engine has been held "staged" for say 3 secs at high rpm, the engine will have easily used all the "hot" fuel in the rail. (especially with drag race fuel consumption......) Remember "cold" fuel, even after a prolonged hot keyoff soak is only a fuel rail plus a little bit of fuel pipe "voulme" away (lets say ~50cc).
In reality of course, drag racing is not the ideal environment to use a returnless system, as they do very short runs entirely at WOT, meaning all the fuel sent to the engine is pretty much used anyway. The return is probably at zero flow anyway for the run!
i believe the 044 noise issue to be due to pump inlet cavitation when warm/hot. As fuel temp increases it's vapour pressure increases, meaning at the low pressures found on the inlet of a large powerful pump (like an 044 etc) when it is moving a high volume of fuel (which it is doing continuously with a return system), then cavitation occurs. (a side effect being that the one way relief ball valve in the pump also chatters back and forth as it occurs, making NVH even worse).
I try to keep my pressure pump inlet at a slightly raised pressure to help prevent this, by having a restriction on my swirl pot return to the fuel tank. That way, the lift pump generates approx 5kPa of positive pressure on the inlet of the 044's.
In your drag race example, by the time engine has been held "staged" for say 3 secs at high rpm, the engine will have easily used all the "hot" fuel in the rail. (especially with drag race fuel consumption......) Remember "cold" fuel, even after a prolonged hot keyoff soak is only a fuel rail plus a little bit of fuel pipe "voulme" away (lets say ~50cc).
In reality of course, drag racing is not the ideal environment to use a returnless system, as they do very short runs entirely at WOT, meaning all the fuel sent to the engine is pretty much used anyway. The return is probably at zero flow anyway for the run!
i believe the 044 noise issue to be due to pump inlet cavitation when warm/hot. As fuel temp increases it's vapour pressure increases, meaning at the low pressures found on the inlet of a large powerful pump (like an 044 etc) when it is moving a high volume of fuel (which it is doing continuously with a return system), then cavitation occurs. (a side effect being that the one way relief ball valve in the pump also chatters back and forth as it occurs, making NVH even worse).
I try to keep my pressure pump inlet at a slightly raised pressure to help prevent this, by having a restriction on my swirl pot return to the fuel tank. That way, the lift pump generates approx 5kPa of positive pressure on the inlet of the 044's.
Max_Torque said:
.....I try to keep my pressure pump inlet at a slightly raised pressure to help prevent this, by having a restriction on my swirl pot return to the fuel tank. That way, the lift pump generates approx 5kPa of positive pressure on the inlet of the 044's.
Good call. As I'm converting from carb to EFI I already have a 6psi pressure regulator I can bring into play.Steve
you are actually slightly better off using an orifice to control swirl pot pressure, rather than an actual pressure regulator. Because when the system is not bled, or you have been picking air up from the main tank, an orifice is seen as "much bigger" to air, than it is to fuel (air is much less dense than fuel obviously) Hence, said orifice allows the system to prime or blead easily, without putting too much head across the lift pump, but when competely full of fuel, acts as a suitable restriction to put some positive pressure on your swirl pot.
The downside to an orifice is that is can become blocked, unlike a pressure reg that can simple lift off it's seat to clear any debris etc. Assuming you have an in-tank mesh sock on your lift pump (which you should anyway ;-) then a 2mm orifice is not an issue wrt blocking etc
The downside to an orifice is that is can become blocked, unlike a pressure reg that can simple lift off it's seat to clear any debris etc. Assuming you have an in-tank mesh sock on your lift pump (which you should anyway ;-) then a 2mm orifice is not an issue wrt blocking etc
This is exactly what I have done with my swirl pot... I have 2 litters feeding it constantly ( they are cheap and quite in the tank and can run dry without damage)... This means my 044s have a pressure as well as a 400mm head of fuel.
After 5000 miles with the new setup and the pumps in a position were they are very close the the manifold ( so hotter) they are no longer noisy even after 6 hours of constant driving to spa and the ring :-)
After 5000 miles with the new setup and the pumps in a position were they are very close the the manifold ( so hotter) they are no longer noisy even after 6 hours of constant driving to spa and the ring :-)
Edited by andygtt on Saturday 13th August 14:58
As my maths is crap. It's a fair point that fuel in the rails may get used up staging and waiting to race.
Although TBH, I dont think mine uses that much fuel at idle etc ?
Although me being daft. I actually have my primary rails dead ended and only my secondary rails are full flow. Was much easier to plumb them this way, and the primaries are always injecting fuel, so never gave much concern about heat. When in fact of course they will get heated a lot before racing.
In my case due to lack of foresight many years ago, my tank only has a single gravity fed 5/8" BSP outlet to feed the 2 x 044's
So that certainly wont help any noise. But 85% of the time it isnt a problem.
Either way, bottom line is the folks want a controller where they can retain a FPR or return line.
How that pump is then controlled is the thing. A returnless, fixed pressure setup could work, but for many it will take some re-engineering, and full remapping.
I know I cant be bothered with that. I'd like a setup to make life easier for the pumps, to make wiring easier ( ie less fuses and relays ) and relatively easy to install. ie, it will mirror current fuel pressure patterns.
Although TBH, I dont think mine uses that much fuel at idle etc ?
Although me being daft. I actually have my primary rails dead ended and only my secondary rails are full flow. Was much easier to plumb them this way, and the primaries are always injecting fuel, so never gave much concern about heat. When in fact of course they will get heated a lot before racing.
In my case due to lack of foresight many years ago, my tank only has a single gravity fed 5/8" BSP outlet to feed the 2 x 044's
So that certainly wont help any noise. But 85% of the time it isnt a problem.
Either way, bottom line is the folks want a controller where they can retain a FPR or return line.
How that pump is then controlled is the thing. A returnless, fixed pressure setup could work, but for many it will take some re-engineering, and full remapping.
I know I cant be bothered with that. I'd like a setup to make life easier for the pumps, to make wiring easier ( ie less fuses and relays ) and relatively easy to install. ie, it will mirror current fuel pressure patterns.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff