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Old 10-13-2009, 07:53 PM   #1 (permalink)
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Greetings from Maryland!

Hello!

I own a '96 Geo Metro LSi 1.3L. I'm interested in trying to make it more efficient. I have a routine 4.2 mile run at about 50 MPH that I run two to six times a day, and would like to use to judge city mileage based off of one month of these runs.

-S-

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Old 10-13-2009, 09:41 PM   #2 (permalink)
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Hello and welcome to the site. Is that LSi equipped with an automatic or manual trans?
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Old 10-13-2009, 09:58 PM   #3 (permalink)
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Old 10-13-2009, 11:30 PM   #4 (permalink)
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Quote:
Originally Posted by Johnny Mullet View Post
Hello and welcome to the site. Is that LSi equipped with an automatic or manual trans?
Auto. I know, I know. The Domestic Car snob at work has already been up on my case about not having a manual. For the amount I paid for it, and for the work that went into it before I got it, (Read: Branded title, everything in front of the firewall.) I'm not going to complain about something I can deal with myself with a quick trip through Craig's List, eBay, or most expensive case... a rebuild.

I'm still processing a good amount of the information on this site. The BlackFly has raised an eyebrow in the tests that have been run on it so far. Once I get instrumentation installed I am going to start baselining and modding. Nothing too exotic, looking to remove the battery and replace with a 500F 16V ultracap at first.

I read something in here about possibly installing an electric water pump. I have a question about that. Wouldn't the electric pump be less efficient? You would be doing two or three energy conversions and losing part of the energy to heat generation at each conversion. What is the thought process behind the swap?
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Old 10-13-2009, 11:51 PM   #5 (permalink)
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The cool part about water pumps is that they don't actually need to be driven at a variable speed, and they really don't need to be driven all the time. Sure, the electric pump is slightly less efficient, because of the conversions that need to take place. Unfortunately, there are also losses in belt-driven pumps, since it's more mass that the engine has to accelerate, and that mass is under increasing load, making it even harder for the engine to accelerate that mass.

With an electric pump, it's a bit different. Once the mass has been accelerated, it's up to speed, and can now be driven under constant load at constant speed, without variation. Constant load, of course, takes less energy than acceleration and deceleration, which means that the electric water pump is actually more efficient, if you view it as simply being less "lossy".

Back to the point of the water pump not needing to be driven all the time;

Someone will disagree with me on this, but the water pump DOESN'T need to run all the time. The cooling system was designed for "worst case scenario", remember? That means the OEM water pump flows more than is actually necessary, which is a waste of energy in most cases. Slowing the speed of the water pump, or leaving it off and running it on a thermostatic control will actually decrease warm-up times, and you can turn it off for short periods of time while driving on the highway, as well.

I don't think I'd necessarily turn it off, but I would love to have one set up on a thermostatic speed control that would slow down to keep coolant flow, but as the engine got warmer, it would speed up to increase cooling capacity, reaching full speed at something like 205*, still well inside the "danger" zone. (I'll run as high as 212*, never over 215*). With the OEM cooling system on Cara, it takes my driving up a mile long hill in 1st gear floored, approaching/maintaining high engine speed and nearing redline several times to get to 215*, and then only after heat soak takes effect.
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Old 10-14-2009, 07:47 PM   #6 (permalink)
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Quote:
Originally Posted by Christ View Post
The cool part about water pumps is that they don't actually need to be driven at a variable speed, and they really don't need to be driven all the time. Sure, the electric pump is slightly less efficient, because of the conversions that need to take place. Unfortunately, there are also losses in belt-driven pumps, since it's more mass that the engine has to accelerate, and that mass is under increasing load, making it even harder for the engine to accelerate that mass.

With an electric pump, it's a bit different. Once the mass has been accelerated, it's up to speed, and can now be driven under constant load at constant speed, without variation. Constant load, of course, takes less energy than acceleration and deceleration, which means that the electric water pump is actually more efficient, if you view it as simply being less "lossy".
I see. This actually makes sense to me. You might be able to drive that off a separate electric circuit that charges off of a solar panel if you don't drive more than a few hours a day. You could also put in a relay failover to power it off of the alternator if the power source discharges.

Quote:
Originally Posted by Christ View Post
Someone will disagree with me on this, but the water pump DOESN'T need to run all the time. The cooling system was designed for "worst case scenario", remember? That means the OEM water pump flows more than is actually necessary, which is a waste of energy in most cases. Slowing the speed of the water pump, or leaving it off and running it on a thermostatic control will actually decrease warm-up times, and you can turn it off for short periods of time while driving on the highway, as well.

I don't think I'd necessarily turn it off, but I would love to have one set up on a thermostatic speed control that would slow down to keep coolant flow, but as the engine got warmer, it would speed up to increase cooling capacity, reaching full speed at something like 205*, still well inside the "danger" zone. (I'll run as high as 212*, never over 215*). With the OEM cooling system on Cara, it takes my driving up a mile long hill in 1st gear floored, approaching/maintaining high engine speed and nearing redline several times to get to 215*, and then only after heat soak takes effect.
A thermistor with a cut off relay might do what you're looking for. Do you have an idea how much current draw the electric water pump would take? Or is there a running thread somewhere I just missed?

-S-
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Old 10-14-2009, 10:05 PM   #7 (permalink)
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I don't remember a thread on this, but you can find the current draw of electric water pumps as a unit on SummitRacing and other websites that sell them.
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Old 10-14-2009, 11:47 PM   #8 (permalink)
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