what does meziere waterpump help with?
5/11/08, 11:18 AM
#41
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Join Date: November 27, 2004
Location: Albuquerque, New Mexico
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SoundGuyDave,
Once more unto the breach....
No problem. While focusing point by point, I tend to get a bit TOO focused at times.
Let's see if I can do a better job of summing this up this time. The electric pump has bearings and it has a shaft seal, just like the mechanical pump. The ONLY difference is the drive system. The pulley on the electric pump is just an idler pulley to keep the accessory drive belt routed correctly and it WON'T add much load.
In short, the biggest statement I have been arguing against is "electric water pumps are more EFFICIENT than mechanical pumps". Don't confuse "efficiency" with "power draw". Efficiency is simply work out divided by work in. Due to all the additional losses generating the electricity that drives the pump, the electric pump CAN'T be more EFFICIENT than the mechanical pump.
Power draw is a different question. I have never stated that an electric pump would put less of a LOAD on the engine. I just said it was not as efficient. I also went into WHY an electric pump was less efficient and why it would put less of a load on the engine (it's moving much less water at higher engine speeds than the mechanical pump). Heck, I even covered a few of the pros of the electric pump..
There is nothing wrong with my logic. Just my English language skills!
I kind of doubt the PCM will be dropping the charge rate at high RPMs. These systems are VERY sensitive to voltage drops and that actually hurts performance on an EFI engine much more than on a carb engine. There are a LOT more electrical systems drawing power. One item that REALLY gets hit with different voltages is the fuel injector duty cycle. More specifically, the turn on time of the injector.
That changes dramatically as the voltage drops. They ECU has algorithms that try to correct the pulse width based on how long it thinks it will take the injector to open, but it isn't perfect.
But who knows? They have done some pretty weird things with this ECU, so until I have looked at the whole program for the ECU, I sure wouldn't say "no way!". Let's just leave that one as a possibility.
See above for my explanation of efficiency and power draw. I THINK I suitably beat this idea down.!
I agree completely. I only included that wiring loss to be (somewhat) thorough. But you are right. It's not much in the grand scheme of things.
I don't have any links. I have read a few articles on the subject over the years (the first one I read was back in 1990 or so in Mechanical Engineering). Fuel efficiency is one reason they are pursuing it. Unlike the water pump, you only need to provide steering boost when someone is trying to steer the car, so there is a LOT of time when the mechanical pump is wasting gas and not doing anything productive.
The other reason people were looking at going electric is the ability to tie the steering system into the vehicle's dynamic stability control system. We already have a "throttle by wire" system and there are some cars out now that not only will act to prevent wheel lockup during hard braking, but will actually do the braking FOR the driver if they don't stop soon enough. Adding active steering is just the next step to full drive by wire systems.
We are definitely trying to do SOMETHING here! I'll leave it up to the readers to decide what! 
Once more unto the breach....
RRRoamer,
You are absolutely right, my comment was NOT overly clear... The "spin by hand" was in an attempt to demonstrate frictional losses, not anything else. If you read my other posts in this thread, you will have noticed repeated references to magnetic flux and increased horsepower losses due to draw. Anybody that has ever run a lift-gate on a truck knows how the alternator loads up the engine when the gate compressor is running. I apologize for lack of clarity on that point.
You are absolutely right, my comment was NOT overly clear... The "spin by hand" was in an attempt to demonstrate frictional losses, not anything else. If you read my other posts in this thread, you will have noticed repeated references to magnetic flux and increased horsepower losses due to draw. Anybody that has ever run a lift-gate on a truck knows how the alternator loads up the engine when the gate compressor is running. I apologize for lack of clarity on that point.
With respect to your position that the electric pump is roughly a 1/4HP device, I will agree that sounds about right. I think the bulk of the additional losses from the stock pump come from bearing and seal friction, in combination with flow resistance at higher RPM. The pulley on the electric pump is a simple free-wheel, and imparts almost no load to the engine. There is ample proof that the electric setup does free up HP, so something in your logic chain is obviously incorrect.
In short, the biggest statement I have been arguing against is "electric water pumps are more EFFICIENT than mechanical pumps". Don't confuse "efficiency" with "power draw". Efficiency is simply work out divided by work in. Due to all the additional losses generating the electricity that drives the pump, the electric pump CAN'T be more EFFICIENT than the mechanical pump.
Power draw is a different question. I have never stated that an electric pump would put less of a LOAD on the engine. I just said it was not as efficient. I also went into WHY an electric pump was less efficient and why it would put less of a load on the engine (it's moving much less water at higher engine speeds than the mechanical pump). Heck, I even covered a few of the pros of the electric pump..
There is nothing wrong with my logic. Just my English language skills!
One thought that I did have, is that the field coil is actually controlled by the PCM, and not a stand-alone regulator. I would say that it's distinctly possible that at higher RPMs, the PCM is commanding a lower charge-rate, thus reducing the magnetic drag effect on the engine. Thus, the pump is actually drawing down on the battery during WOT or near-WOT conditions, but as the RPMs and engine load drops, the PCM commands a higher charge-rate, replenishing the battery. I don't know for a fact that this is what the PCM is doing, but it is well within the realm of possibility. We've already seen a LOT of PCM-based electronic trickery to get higher fuel efficiency, lower emissions, and more HP from this platform, so I could easily see this as another part of that overall strategy.
That changes dramatically as the voltage drops. They ECU has algorithms that try to correct the pulse width based on how long it thinks it will take the injector to open, but it isn't perfect.
But who knows? They have done some pretty weird things with this ECU, so until I have looked at the whole program for the ECU, I sure wouldn't say "no way!". Let's just leave that one as a possibility.
Oh, and you were worried about wire-loss earlier? The resistance of 10ga multi-stranded wire works out to be approximately 1.2 ohms per 1000', or .0012 ohms per foot. Given the average 6' of cable for an electric pump installation, the net wire resistance is 0.0072 ohms. With a circuit voltage of 14.2V, and a circuit draw of 15A, the wire would dissipate approximately 1.62 watts. Not enough to worry about.
The electronic steering control you referenced earlier, do you have any links for info? I am going to ASSUME that you're talking about electronically controlled assist levels, where there is higher assist at lower road-speeds (one-finger wheel turning for parking) and lower-assist at higher road-speeds (higher effort with more feedback). That can be done quite easily with electronically controlled valving in the rack, but does not necessarily imply electric fluid pressure generation. Our 5R55 trans works much the same way... The pump is mechanically driven (from the flats on the torque converter snout), but ALL of the solenoids, actuators and valves in the trans are electronically controlled, to alter shift points, speeds, and pressures. One thing most people don't realize about power steering systems is that there is a pressure bypass valve at the output of the pump, and that that pressure is reached at very low engine speeds, usually only slightly above idle.
The other reason people were looking at going electric is the ability to tie the steering system into the vehicle's dynamic stability control system. We already have a "throttle by wire" system and there are some cars out now that not only will act to prevent wheel lockup during hard braking, but will actually do the braking FOR the driver if they don't stop soon enough. Adding active steering is just the next step to full drive by wire systems.
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