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  #1  
Old 12-03-2002, 07:41 PM
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vkykam vkykam is offline
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Fuel Mileage Increase

This is the strangest way to increase fuel mileage that I've personally experienced...

About 4 weeks ago, during a heavy downpour, I drove the car through a flooded road at a good speed; saw the water pond too late to slow down. Anyhoo, check engine light came on, and as I put it in diagnostic code, I saw MAF, Idle Air, and both the O2 sensors reporting errors. Car would have severe loss of power, and would stall out. I drove the car for another 20 or 30km before getting home. Car had essentially swallowed some water. Gulp.

I found the next morning that the air filter was still fairly wet, and was deformed from the suction of the engine. So off I went to the local parts store, and replaced the air filter.

This is where it gets interesting. Prior to the incident, I would get consistantly 240-260 miles before the fuel warning light comes on. After the water ingestion, I've gone thru 5 tanks of gas, and each I've been able to drive to 260-285 miles before the light comes on. That's a 10% improvement in mileage. WOOHOO! No driving habit change, nothing else has changed. Didn't even reset the computer by disconnecting the battery.

I asked my mechanic last week, and he told me that the water could have cleaned out some of the carbon buildup inside of the engine. He tells he occasionally he will inject water into the throttle body just prior to a car going for emissions test, to, um, steam cleain it.

Weird.

Remember, Your Mileage May Vary. LITERALLY.

VK
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  #2  
Old 12-03-2002, 08:41 PM
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Yeah, we used to do the same many moons ago on carbureted cars. Cold water hitting hot carbon would cause the deposits to fragment and blow out the exhaust. Typically fuel injected cars don't collect as much dry carbon as the older carb cars though. Most EFI cars collect gooey deposits in the manifold but little, if any,deposits in the cylinders. Water has little effect on the (relatively) cooler, gooey deposits. May be that you needed a new air filter or possibly it rinsed your MAF out?

BTW - besides the ongoing debate over the viability of a 'million mile' reusable filter, we've been finding that cheap air filters and/or those that aren't changed often enough are sending fibers downstream to the MAF and causing problems, as the fibers wrap themselves around the sensor wire.
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  #3  
Old 12-03-2002, 09:23 PM
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Beav,

Please correct my stream of misunderstandings and tell me where I'm wrong ('cause I'm pretty sure I am).

I thought MAFs heated up the wire to work, but then I also seem to remember only some kinds used heat? If they heat, how hot?

For some unknown reason I thought they would get hot enough to burn off paper (Farenheit 451), but of course paper air filters probably aren't really just paper either??
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  #4  
Old 12-03-2002, 09:55 PM
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They do heat up, but I think of the heat as a by-product of the process. I seriously doubt that the sensor gets anywhere near hot enough to ignite anything. Wouldn't that be a nice bit to have, the sensor sending little flaming balls of filter debris straight through the manifold to a bunch of injectors burping up gas?

The change of resistance in the wire is what determines the mass of the air flow (tricky, eh? The voltage signal returned to the computer will increase as more cooling air flowing across the wire reduces the resistance. Five volts in and .7 returning generally indicates idling flow at a reasonable air temp and baro pressure. Drop the temp and more volts, Increase the baro pressure and the same occurs. When using a scanner, many newer cars show both voltage and grams/second readings, the latter obtained from a look-up table in the computer.
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  #5  
Old 12-04-2002, 06:54 AM
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I know on the 928 the MAF was self cleaning because the wire would get red hot (I think on shutdown, but I'm not sure) to burn off deposits.

CJ
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  #6  
Old 12-04-2002, 08:00 AM
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Beav,

I've ruled out the filter. The filter was less than 3 months old, and the MAF was from Harry's wreck, which I installed at the same time as the filter, and at that time it yielded no improvement in mileage. The filter is paper, and the old and new are the exact brand.

I guess with 185k miles, it'll collect a few bits of carbon?

VK
Quote:
Originally posted by Beav
Yeah, we used to do the same many moons ago on carbureted cars. Cold water hitting hot carbon would cause the deposits to fragment and blow out the exhaust. Typically fuel injected cars don't collect as much dry carbon as the older carb cars though. Most EFI cars collect gooey deposits in the manifold but little, if any,deposits in the cylinders. Water has little effect on the (relatively) cooler, gooey deposits. May be that you needed a new air filter or possibly it rinsed your MAF out?

BTW - besides the ongoing debate over the viability of a 'million mile' reusable filter, we've been finding that cheap air filters and/or those that aren't changed often enough are sending fibers downstream to the MAF and causing problems, as the fibers wrap themselves around the sensor wire.
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  #7  
Old 12-04-2002, 09:08 AM
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Another thing I thought I'd mention: Ever heard of water-injection? Essentially, you shoot some water into the intake manifold. Since water doesn't compress, it raises your compression a tad, cleans the cylinders a tad, and cools your engine a tad. It was used on quite a few WW2 airplanes actually, it really helped at high altitudes. I had a kit for my neon but threw it away due to no instructions. >shrug<

- Ca$h
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  #8  
Old 12-04-2002, 09:57 AM
Green1995SVX
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I have 133,000 miles and have never run through any carb cleaner. Do you think this is something I should do, Beav? (sorry, kinda OT)

Mike
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  #9  
Old 12-04-2002, 04:19 PM
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Quote:
Originally posted by Beav
Wouldn't that be a nice bit to have, the sensor sending little flaming balls of filter debris straight through the manifold to a bunch of injectors burping up gas?
Makes sense & you have a great knack for expressing things - I'm jealous.

And of course enough patience - or whatever - to actually think thru things before I post. Alas, at 51 I think I'm on the down slope, not likely to get any better.
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  #10  
Old 12-04-2002, 09:39 PM
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Mike: Are you having any problems? You can't fix what isn't broken, but you can break what already isn't.

Lee: You've only got a few years on me. And sometimes it takes me an hour or two to edit my responses. (this is known as the martyr pitch - is anyone buying it? )
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  #11  
Old 12-05-2002, 09:38 AM
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Quote:
Originally posted by lee


Makes sense & you have a great knack for expressing things - I'm jealous.

And of course enough patience - or whatever - to actually think thru things before I post. Alas, at 51 I think I'm on the down slope, not likely to get any better.
At our ages, with as little time as we may have left, we can't afford to be patient.
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  #12  
Old 12-05-2002, 09:54 AM
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Quote:
Originally posted by Beav
Lee: You've only got a few years on me. And sometimes it takes me an hour or two to edit my responses. (this is known as the martyr pitch - is anyone buying it? )
Not for a second!

Don't let the Beav kid you. He cheats. He has this brain with this humonguous, massive IQ - and he uses it! Not Fair, Beav!
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  #13  
Old 12-05-2002, 10:40 AM
LarryIII LarryIII is offline
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Quote:
Originally posted by lee


Makes sense & you have a great knack for expressing things - I'm jealous.

And of course enough patience - or whatever - to actually think thru things before I post. Alas, at 51 I think I'm on the down slope, not likely to get any better.
Lee,

That slope gets alot steeper at 58 where I am.
I hope I don't get real old like Ron.
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  #14  
Old 12-06-2002, 08:52 PM
SVXnCO
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It's all rather similar to the Bessemer process in making steel. Cold air blown on the carbon in the steel causes it to ignite, which in turn cleans out the impurities in the metal.
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  #15  
Old 12-06-2002, 09:14 PM
Ron Mummert Ron Mummert is offline
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Quote:
Originally posted by LarryIII


Lee,

That slope gets alot steeper at 58 where I am.
I hope I don't get real old like Ron.

I hope I get real old like Trevor.

Ron.
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