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Old 04-18-2012, 10:50 PM   #11 (permalink)
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On further reading in that last pdf i noted that with every 10 degree Celsius increase in turbo inlet air causes a reduction in fuel economy by 0.7%

I think that paper did not help my theory !
it did say that -10 to 45 c was their diesel motors optimal running temperatures. It could be they will perform poorly and use more fuel outside of those best working conditions.

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Old 04-19-2012, 12:32 AM   #12 (permalink)
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Quote:
Originally Posted by ecomodded View Post
And Stan WOW that is encouraging and actually sounds like proof of the benefit.
Good stuff. I enjoyed the article...thanks! I don't know that it really "proves" anything, but I DO think it hints this line of research is worth looking into. Small, high-speed diesels aren't MAN ship engines (80cm bores...300 RPM ), and they certainly aren't gas turbines, but there may be benefits to FE from running under near isothermic conditions.

An easy-to-do first-order swag might be to rig a "hot air intake" by drawing intake air past the exhaust pipe and by routing the fuel line past a hot water line. Anybody ever tried this?
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Old 04-19-2012, 01:16 AM   #13 (permalink)
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Quote:
Originally Posted by Stan View Post
An easy-to-do first-order swag might be to rig a "hot air intake" by drawing intake air past the exhaust pipe and by routing the fuel line past a hot water line. Anybody ever tried this?
Nope and I don't plan on it.
Unless I move to AK or ND.
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Old 04-19-2012, 02:06 PM   #14 (permalink)
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After some more thought, it dawned on me that the 10 degree increase at the the turbo that would increase fuel usage by 0.7% was just that at the turbo.
I am more concerned with fuel usage when not using the turbo.
Means that the turbo's extra hot air after it has been compressed and heated by the turbo will not like to be increased without loss of economy. When cruising and not using the turbo the inlet temperature is cool to cold on most driving conditions and may very well benefit from a warmer intake temp. In the dead of summer, the road baking hot, air being sucked into the intake is hot, being sucked from 6 inches off the hot pavement(my car) it is hotter then one would suspect,my car gets its best mpg during the summer.
Here's a idea Stan, run a hair dryer on high heat and med heat into
your cars intake, say after the air filter, and note any changes to your {if you have one, i don't) fuel economy device with the car at idle.
Piwoslaw or Diesel Dave or anyone else if you have a fuel economy gauge and a hair dryer or as Stan suggested, run a heat safe hose from over your exhaust to your intake and note any differences
for the good or bad by preheating the air.
If I had a gauge I would be doing the test myself.
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Old 04-19-2012, 02:16 PM   #15 (permalink)
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Quote:
Originally Posted by ecomodded View Post
When cruising and not using the turbo the inlet temperature is cool to cold on most driving conditions and may very well benefit from a warmer intake temp. In the dead of summer, the road baking hot, air being sucked into the intake is hot, being sucked from 6 inches off the hot pavement(my car) it is hotter then one would suspect,my car gets its best mpg during the summer.
Hers a idea Stan, run a hair dryer on high heat and med heat into
your cars intake, say after the air filter, and note any changes to your {if you have one, i don't) fuel economy device with the car at idle.
Piwoslaw or Diesel Dave or anyone else if you have a fuel economy gauge and a hair dryer or as Stan suggested, run a heat safe hose from over your exhaust to your intake and note any differences
for the good or bad by preheating the air.
If I had a gauge I would be doing the test myself.
Good idea. I have a VAG-Com. Anybody know off hand if that will work?
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Old 04-19-2012, 09:37 PM   #16 (permalink)
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Here is a link to the Vag Com website.
Ross-Tech: VAG-COM: Fuel Trim Info
where it talks about fuel trim, I am thinking maybe looking at these numbers before heating the air and after heating the air. There could easily be a better method for Vag Com to be used for reading any changes. I am not familiar with
vag com.
Anybody have the knowledge?
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Old 04-20-2012, 05:57 AM   #17 (permalink)
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My winter MPG losses at last winter were because of winter diesel, because engine could not reach optimum temperature in cold, I needed cabin heater which took so much heat that even with grill blocks it was too cold wind under the hood for engine to stay warm, also because most of driving was in deep snow, sometimes more than 4 inches and they are now going to reduce road upkeep further...

It might be even worse with warmer air, cold air probably helped a bit as cold air has more oxygen.

Boost gauge did sit at 0.2-0.3bar when driving on snow, while normally it is at 0bar mark, maximum is around 1bar.

With petrol car that had been given bit more aggressive cam etc. it was interesting to note that during the summer at cold places (temperature sensor at intake pipe and laptop logging / instruments), car did go easier, throttle position must be lowered to not increase speed, injector open time was then shorter.

Of course there must be the limit for that, if we think about ethanol, it has trouble making good mixture with cold air, which partly leads poor starting below zero, maybe there are such points for diesel too, glow plugs are there because of reason, if colder would always be better surely glow plugs would not be needed.

Compression makes diesel and air hot, so that it does ignite, if air is so cold that compression does not reach enough heat, then igniting will be poor, so surely there is optimal temperature and too cold will not be good.

Some effects are of course because of cold fuel, which makes it bit harder to find out which is what.

I vote for 10C or around there, purely a guess, but I would consider that being good one.

Then think about humidity in air and how water increases efficiency, in cold air there is less water, what that might affect? I know that after the rain when weather is damp car likes to fly
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Old 04-20-2012, 03:49 PM   #18 (permalink)
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Quote:
Originally Posted by ecomodded View Post
After some more thought, it dawned on me that the 10 degree increase at the the turbo that would increase fuel usage by 0.7% was just that at the turbo.
I am more concerned with fuel usage when not using the turbo.
Means that the turbo's extra hot air after it has been compressed and heated by the turbo will not like to be increased without loss of economy.
Sounds like you want to know what happens with a normally aspirated diesel then. The results of temperature and atmospheric pressures are discussed in this NACA paper from 1937 (Note the discuss both fuel economy and power at variable loads). http://aerade.cranfield.ac.uk/ara/1937/naca-tn-619.pdf
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Old 04-20-2012, 04:51 PM   #19 (permalink)
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That has a lot of information in it ConClark. I am finding it hard to get any usable data from. It mixes altitude and air pressure in the data that in my opinion renders the results unfit for comparisons purposes with a road car. If you feel I missed something from the paper that you feel is important please post up with it. I am not not trying to learn from the paper it just seems to be data of another direction, aircraft to be exact.
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Old 04-20-2012, 09:00 PM   #20 (permalink)
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If you feel I missed something from the paper that you feel is important please post up with it. I am not not trying to learn from the paper it just seems to be data of another direction, aircraft to be exact.
Figure 14 has data in it to where atmospheric pressure is held at sea level and air inlet temperature is varied along with the quantity of fuel injected. If you look at the bottom of that figure you will find that they give chart fuel consumption in lbs of fuel per hp per hour.

The trends in the data for the sea level test results is directly applicable to an auto diesel with similar intake temperatures and fueling.

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