Air to liquid intercooler to get your winter MPG back

2011tdiproject

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This is something I thought about a while ago, just wondering if you guys had thought of this or had any experiences or knowledge related to it.

As noted in my other thread about the winter fuel economy, my MPG in nice weather is about 42, but falls off like a rock when it's below 20 or so outside. 30mpg or less, making the difference in fuel cost negligible. I'd rather drive my gas powered car in the extreme cold, faster warm up time, etc.

So the first thing I thought of was to block the intercooler like all the semis do, but then I thought that probably wouldn't even be enough. Then I thought of temporarily replacing the intercooler piping with a direct pipe between the turbo and intake manifold, but that would be kind of a pain, switching it every winter.

So then I thought of using an air to liquid intercooler, like I did years ago on my turbo honda. The air to liquid unti would solve all these issues quite elegantly. I'd set it up to not turn on the coolant pump until the intercooler had reached a set temp, say 100 degrees. (So in the winter, the pump would basically never run, unless you're boositng 30lbs up a long hill) I don't know what the charge air temps would be at 0 degrees out, but I'd bet money they'd be warm enough to get the MPG back up, since the turbo would be adding a little heat to the air, and the intercooler in the engine compartment with the pump off wouldn't be taking any heat back out.

The air to liquid intercoolers also have better performance in certain ways, like pressure drop, durability, and volume of air in the intake tract.

What do you guys think? p.s. it's really not that hard to set up an air to liquid unit, and the racecar look is undeniable under the hood.
 

40X40

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When drivers block off the front of a TDI in cold weather, it is not the intercooler that they are trying to block... it is the whole engine compartment in order to conserve heat and allow the engine to warm up faster and stay warm during cruise when very little power is produced.

(Holy run-on sentence!)

Bill
 
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30_Yr_Dsl_Veteran

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So the first thing I thought of was to block the intercooler like all the semis do
You are incorrect on TWO accounts.

First, trucks don't block their intercooler; they block their radiator.

Secondly, ALL modern trucks specifically say in their MANUAL: DO NOT USE A WINTERFRONT. Such an item is a "relic of the past", and not needed, and is actual harmful. :eek:

 

2011tdiproject

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I think what they are blocking that has the most effect is the intercooler. Allow me to elaborate, if I may. When the motor is below the thermostat's set temp, the thermostat is blocking almost all of the coolant from flowing through the radiator. So at that point, the radiator's temp is more or less irrelevant. Then the operating temp becomes a function of the charge air temp and the load. On very cold days where I live, my tdi will reach operating temp going down the road, but if I let it idle, it will drop off. That is a good example of the effect of the charge air, since the thermostat is closed, the cooling fans are off, the car's not moving so there's no air going through the engine compartment, and the motor still won't get fully warm.

I'm sure there also is a cooling effect just from cold air physically blowing through the engine compartment against the motor, but I think that is small compared to the effect of the intercooler and the radiator.

I may be wrong that a liquid intercooler would reach a temp much above ambient just from being heated by an idling turbo adding heat to the charge air. I'll have to research that more, charge air temps before and after the turbo. But I still believe if you feed the motor warm air, it won't matter how cold the radiator is, or how cold the air blowing against the motor is.
 

jettawreck

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As in the other threads, most of the cold weather mileage loss is from increased tire rolling resistance, oils/greases in transmissions/axles, longer engine coolant warm up times, small loss from fuel changes, etc. The gains from warmer intake air would be very modest, I suspect, and not ever see a payback from the time and cost of doing such a conversion/mod. But, if you feel inclined to do some serious fabricating, give it a shot and see.
 

Vince Waldon

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And in actual fact the engine prefers breathing cold dense air...within limits, the colder the better...which is why there's an intercooler in the first place. :)

The colder and denser the air the more oxygen, and my car is the most fun to drive on a crisp -35C morning after the engine, tranny, etc are all up to temp but my IATs are still well below freezing. :) :)
 

Vince Waldon

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One more consideration is the Laws of Thermodynamics...specifically in this case, any heat you put into warming the intake air must remove at least an equal amount of heat from the engine...and as we all know these engines are already pretty miserly at coming up to temperature in the first place.
 

Windex

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As Vince puts it, colder air is more dense, and allows the engine to work most efficiently. What you propose by warming the intake air would have the (albeit very small) opposite effect.

I work in heavy trucks up here in the north. The rad covers are for the radiator only, not the air-to-air / intercooler.

You are correct that the t-stat keeps the coolant from (mostly) flowing though the rad, but there are bleeds in the system to allow some circulation - Radiators in heavy trucks need the rad covers or they don't fully warm up, and fuel economy will suffer.
 

40X40

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I don't know if a 2011 golf has both a high AND low pressure EGR, but I understand my 2013 Passat does and it recycles a huge amount of exhaust gas under light load (cruise). It has a water/air intercooler as well.
Will the parts fit? IDK. What about the ECU programming? Looks like a lot of work for little gain to me.

Bill
 

2011tdiproject

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The Passat has an air/liquid intercooler? I did not know that. Hmm.

Well, it might be a while before I can get back to this forum with any results here, as it looks like the winter is Finally coming to an end where I live. Also, I think I'm going to sell the VW for a 335d, so maybe I will build it on that car instead. In my other field, (the one that makes me money rather than wastes so much of it), a surprising amount of what people say, theorize and repeat is absolutely incorrect, and/or misinterpreted. So, I have gotten completely used to doing my own experiments, and cars/engineering is a lot more my passion, so I'll probably end up doing this experiment at some point though.
 

nicklockard

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At others: This myth of "cold air = best efficiency" is totally unfounded and goofy. Where do these (wrong) over simplifications come from?

Run some models to test your hypothesis--you can prove or disprove them easily. Follow the road load link in my signature below.

At the OP: I think your intuitions are on the right track, but perhaps you can get most of what you're after with blocking alone, if cost is a factor for you.

OP, pm me if you want some tips on making winter FE optimizations.
 
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mtbmaniac

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Don't forget about the cabin heater core. That is a "radiator" that is not thermostatically controlled. It circulates coolant directly from the engine. If you turn off the cabin fan completely while at idle with a warm engine, the coolant temp in the car will not drop. I dont think you would see any gain from sucking in warm air.
 

jettawreck

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First off, what's your definition of "cold"? I seem to see a drop off as intake temps drop below about 20*F. Meaning that at normal driving the ambient temp would be around 10*F or a bit colder. That's not yet very cold really. Most of that drop is from other factors.
This winter for me there were many days of driving in sub -20*F temps and not many with temps above 0*F. Most all my tank averages still maintained 48 mpg, only about 7 mpg off my warm weather normal average. Take the increased warm up time, rolling resistance of the tires, etc out of the equation and I don't think there is much to attribute to real cold intake air temps.
Extremely cold intake air in a compression ignition engine is counter productive for best efficient operation, of course, but, I think the gains beyond simply covering the IC would be very minimal and as mentioned before, would not return much savings. Even though this winter was far from the normal cold even around here, how much time do you really normally spend driving in sub 0*F temps?
Tire heaters, wheel bearing/cv joint warmers, might be about as practical and as productive as heated wintertime IC. You would have a complicated system that would only see limited time of usefulness and minimal returns.
.02 mine.
 

Windex

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At others: This myth of "cold air = best efficiency" is totally unfounded and goofy. Where do these (wrong) over simplifications come from?
Um, then I guess all these intercoolers (providing cooler intake air) our cars come equipped with are unnecessary?

Colder air is more dense. Denser air carries more oxygen, more oxygen means an ability to combust more fuel = bigger bang per displacement volume.
 

40X40

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Cold air = More power does not mean Cold air = Best efficiency

Does best efficiency mean best MPG? My MPG goes down when it is either TOO cold or TOO hot....

If a 'little bit is good, then too damn much is better' is rampant on these forums.

Bill
 

jettawreck

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Really cold air doesn't compression ignite as efficiently as it does when it's warmer. There are trade offs when it gets to a point. 50*F air is better than 180*F air, but doesn't mean -30*F intake air will be even better.
Sort of like 190*F coolant temp is good, but 250* not so much.
The equipment is for a broad range of operating conditions and most of the time the IC helps keep intake temps from getting too high. When it's below freezing temps it's not really needed, but doubtful if it's worth disabling it.
 

uturn

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I'm thinking if you could rig a bypass in winter months that would be a quick install it would be worth it. But only if you live in the mid west/ canada/ alaska where you know for sure its going to be 25 f or below for months. Even better I think if you made a quick change block off plate that would install in place of the intercooler opening in the bumper that would be even easier. Easier than switching over the intercooler bypass pipe twice a yr.
 

VWBeamer

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Already tried this and researched why it failed to produce better fuel economy.

I experimented on my own car with the inter-cooler blocked off, thinking warm air would produce more efficient combustion. My fuel economy decreased with the blocked inter-cooler, and I noticed a decrease in power also.

Why?

Cold air is more dense, containing more molecules and can therefor expand more. Thus it delivers more torque for a given amount of fuel. Warm air can not expand as much, because it's in effect already partially expanded.

Also( as mentioned )cold air contains more Oxygen. So cold air will produce better fuel economy, power and lower emissions for a given amount of fuel burned by producing more complete combustion. Even though diesels run lean, you bring air fuel ratios closer to spectrometric under acceleration and combustion benefits from the extra available oxygen.

As far as cold air being less efficient in igniting compression ignition engines, that is true, but the air would have to be very cold, well below freezing, for it to offset the gains of the denser cold air, with it's higher oxygen content. As long as there is enough heat in the cylinder to start the combustion process you will see gains from colder air.

So unless you live in a very cold climate, your better off leaving your air to air inter-cooler functional.
 

jettawreck

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Already tried this and researched why it failed to produce better fuel economy.

I experimented on my own car with the inter-cooler blocked off, thinking warm air would produce more efficient combustion. My fuel economy decreased with the blocked inter-cooler, and I noticed a decrease in power also.

Why?

Cold air is more dense, containing more molecules and can therefor expand more. Thus it delivers more torque for a given amount of fuel. Warm air can not expand as much, because it's in effect already partially expanded.

Also( as mentioned )cold air contains more Oxygen. So cold air will produce better fuel economy, power and lower emissions for a given amount of fuel burned by producing more complete combustion. Even though diesels run lean, you bring air fuel ratios closer to spectrometric under acceleration and combustion benefits from the extra available oxygen.

As far as cold air being less efficient in igniting compression ignition engines, that is true, but the air would have to be very cold, well below freezing, for it to offset the gains of the denser cold air, with it's higher oxygen content. As long as there is enough heat in the cylinder to start the combustion process you will see gains from colder air.

So unless you live in a very cold climate, your better off leaving your air to air inter-cooler functional.

At what temps did you block off the IC? That's the big question.
As mentioned, there will probably be no benefit to this above freezing, and maybe 0F. In very cold temps I think there will be some minimal gains. DrivebiWire did a write up about it a long time ago, I can't find it.
Anything above freezing temps would probably be foolish to defeat the IC, but the biggest reason for the IC is to reduce intake air temps due to the heating effects of the turbo compressing air (compressed air gets hot) in the intake. Diesels w/o turbos genearlly don't need/have IC as intake temps don't get high enough, even where it gets pretty hot, to warrant the use/cost.

Lots of things affect fuel economy when the temps (intake, ambient, coolant, fuel) change. The ECU advances timing less as most all these variables get warmer. We cann't just say cold air is flat out better across the board w/o knowing how cold we are referring to. 50F is cold to some, but 50F is a pretty nice day around here and haven't seen it since Oct.

I think what we are looking for is the aproximate point where cold air is too cold to be a benefit. It might be a benefit to the small percentage of those that live/drive where its really cold quite a lot of the time.
But, for the minimal gains I would expect, I doubt it would get me to go thru the bother of making/using an IC cover.
 

nicklockard

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Closer to spectrometric, huh? Lol. You could be be dangerous if you read actual books! Keep it up :D
 

steve05ram360

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I have found that with the grille block and monitoring the IATs that intake temps higher than 75* gets the best mpg. I have my fuel lines and canister insulated to prevent heat soak and have the canister t-stat valve bypassed and continued to see sumer time mpg numbers.

You guys who are still seeing cold temps, block the front grille and track your mpg before & after and you will see an increase. MK5 & 6 owners can remove the top off the small airbox that feeds the air filter box or the plastic u shaped hose feeding the airbox and also see an improvement in mpg. My best mpg during the commute was 49.0 mpg and achieved recently in late January/early February.

Temps have started to climb here into the 70s on a regular basis so my grille blocks will have to come off. Anything 70 & below is fine, no overheating or any problems, commute was flat with only 1 hill climb on the way home, steep and maybe 1/2~3/4 mile. Again, no heating issues.

That grille block of mine cost all of $10 bux... plastic & zip ties.



 

VWBeamer

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The spell checker in my browser changed "stoichiometric" to spectrometric.

I have a theory that one can always spot a person who lacks the technical knowledge to carry on a useful debate when they disagree. The person lacking knowledge will resort to correcting spell mistakes and dealing personal insults because those actions are in the domain of a lower IQ.

Your post accurately reflects my theory in action.


Closer to spectrometric, huh? Lol. You could be be dangerous if you read actual books! Keep it up :D
 

VeeDubTDI

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The Passat has an air to water intercooler and the MPGs still suck in cold weather. Sorry, I don't think this is a solution to this "problem."
 

Diesl

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Warming your intake air is counterproductive, as the turbo will then have to work harder to get the same mass of oxygen into the cylinders (warming the air decreases its density; already explained here).

The same density effect means your engine has to work harder to push the car with the same speed through colder (denser) air. The density increases about 8% going from 70°F down to 30°F, so this is a sizeable effect; the effect on your diesel mileage will vary depending on your average speed. (The faster you go, the higher the fraction of your total losses that is due to air drag.)

Blocking off the grill will help improve the aerodynamics of the car, independent of any effect on intake air temperature.
 
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2011tdiproject

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I'm happy to see you guys are still discussing this. I'm trying to think through a fog of distraction, drug use, and the quandary of my f'd up life right now, so I may not be the most articulate here, but I'll try my best anyway.

I'm just going to try to use basic logic to illustrate why I believe the number one factor dropping my wintertime fuel economy is charge air temp.

To you guys who keep repeating that cooler air is more dense, and saying "why did they put an intercooler on the car in the first place then", well, I live in South Dakota. At least I do currently. It gets Very cold here. It can hit -20 in January. That is 52 degrees below freezing. That is cold enough that if you throw a glass of hot water into the air, it turns directly into snow and falls to the ground. I don't think the VW would be able to start without glow plugs at that temp.

jettawreck, you say you average 49mpg in the same type of extreme cold, well, I can't argue with that, but your car is older/different than mine. Mine is an mk6, 2011. I really don't know why my car loses mpg like it does and yours doesn't. But they have completely different injection, computer, and emission controls.

Okay, so here's my attempt at using solely logic to illustrate what I think is going on.

I would say that above about 25 degrees, my mpg is fairly good. Like 36, 37mpg. This obviously varies a bit. Variables influencing this are drafting other cars, crosswinds, 10 degree or so temp variations as I drive along between the tiny towns in the middle of nowhere where I live.

But, when it gets down to somewhere below 20 out, my mpg really starts to drop. On days when it is 0 out, I only get about 30mpg.

This is what makes me think. I want all you guys to see exactly what I'm getting at here. It's not a linear drop off. If you graphed it, it's not a smooth line gradually going down. It goes smoothly at first, but then as the temp goes down, it hits a point where it drops off really quickly. It drops off so quickly that on the really cold days, it's not even saving me money to drive this diesel vs my old 2002 grand prix, with its supercharged gas v6. I do not see any type of significant dropoff in mpg with that gas powered car. It does drop off to some degree, but it's not significant like in the diesel VW.

Using logic, that tells me it is not stuff like the tranny fluid being thicker, oil being thicker, increased wind resistance with the slightly more dense colder air, stuff like that. If that were the case, both cars, my gas powered car and my diesel VW, would drop off equally as a percentage. But they don't.


That tells me it's the temp of the air the diesel is breathing that is affecting this, more than anything else. I don't know Why exactly, I can't say that. Maybe the design of the motor just doesn't like cold air, maybe it also has something to do with how the computer is programmed. I would love to be able to experiment with that aspect of this, but I can't. I would love to be able to go into the programming and open that high pressure EGR valve more as a function of the cold, but I can't do that.

Nicklockard, you sound like you're holding back some knowledge, drop it on me here!

And to the couple comments saying that adding an air to liquid intercooler is major fab work, you should see my chevy pickup, or my honda. My pickup was 2wd, now it's 4wd, sitting on 37s with a solid front axle, divorced transfer case, etc. Little kids point and stare when they see it, "look dad, it's a monster truck!" It's pretty funny. I lost count of how many nights I stayed up until 4 am working on that thing.
 

2011tdiproject

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Another comment here. Since I have this addiction to modifying everything I own, if I do keep the VW, it will see a ton of upgrades, much bigger turbo, all the supporting mods, including of course, the intercooler. So the air to liquid intercooler could give me the option of killing 2 birds with one stone, so to speak. Support more hp in the summer when the tires actually hook, and not chill the charge air to insanely cold temps in the winter.
 
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Diesl

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I'm happy to see you guys are still discussing this. I'm trying to think through a fog of distraction, drug use, and the quandary of my f'd up life right now, so I may not be the most articulate here, but I'll try my best anyway.
OK...
I'm just going to try to use basic logic to illustrate why I believe the number one factor dropping my wintertime fuel economy is charge air temp.
very good. Basic logic. Still following.
To you guys who keep repeating that cooler air is more dense, and saying "why did they put an intercooler on the car in the first place then", well, I live in South Dakota. At least I do currently. It gets Very cold here. It can hit -20 in January. That is 52 degrees below freezing. That is cold enough that if you throw a glass of hot water into the air, it turns directly into snow and falls to the ground. I don't think the VW would be able to start without glow plugs at that temp.
And it does have indeed glow plugs. So far the basic logic is working out. Very cold, glow plugs, it starts. I also like that you refrain from claiming that colder air is not more dense in South Dakota. Even though it is very very cold there.
[Deleted part with jettawreck's car being different from yours.]
Okay, so here's my attempt at using solely logic to illustrate what I think is going on.
Basic logic. Very good.
I would say that above about 25 degrees, my mpg is fairly good. Like 36, 37mpg. [...]
But, when it gets down to somewhere below 20 out, my mpg really starts to drop. On days when it is 0 out, I only get about 30mpg.
This is what makes me think. I want all you guys to see exactly what I'm getting at here. It's not a linear drop off. If you graphed it, it's not a smooth line gradually going down. It goes smoothly at first, but then as the temp goes down, it hits a point where it drops off really quickly.
I can almost see it. The only thing that would be better than almost seeing the plot is seeing the plot. If you could post a plot of your diesel mileage against temperature, that would really help.
Using logic, that tells me it is not stuff like the tranny fluid being thicker, oil being thicker, increased wind resistance with the slightly more dense colder air, stuff like that. If that were the case, both cars, my gas powered car and my diesel VW, would drop off equally as a percentage. But they don't.
Just like with that graph that your are so vividly describing, actually seeing these numbers, in this case for you gas car that doesn't suffer worse mileage in winter, would really help.
That tells me it's the temp of the air the diesel is breathing that is affecting this, more than anything else[...]
Dang so close! I was following and following, and then you lost me.


Ok, enough with the joking. Are you actually keeping track of your diesel and gas mileage? By that I mean writing down the mileage and the number of gallons for each tank. This forum is full of posts and whole threads actually of people posting anecdotal evidence (aka 'stories') about winter this and mileage that, but too few seem to keep track of their numbers. Great entertainment, but it's very hard to learn anything from it.
 
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VeeDubTDI

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I have a factory liquid charge air cooler and it does not make winter time MPGs better, despite very tight regulation of the charge air temperature by the ECU.
 

roadhard1960

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In days of old engines did not have much control using sensors. Both for gas and diesel engines. On a modern computer controlled diesel you have throttle position, water temp, mass air flow, oxygen, fuel temp, intake air temp, boost pressure, rpms and probably some other sensors. For a diesel, timing and injection quantity can change a lot with all these variables. For the poster who mentioned his mileage drops when it gets cold, but when it really gets cold, maybe the computer hits a point where it is doing all it can just to run. See the Cummins forum article about intake temp affects combustion temp by a factor of almost 3.

Blocking the radiator vents off in cold weather (not 40F, but cold weather) helps that engine warm up faster by letting less cooling air in the compartment. Not all the cooling happen via water. Sure the engine has a water thermostat but you can lose a lot of engine heat by running the cabin heater at full blast. I had a thermostat get stuck closed last summer. I opened all my windows and turned my heater on full hot and full speed. I was able to drive home at moderate speeds. It is not so easy to do that on some gasoline engines as they seem to make a lot more heat. Lots of those sensors say "Hey, I am comfortable, how but letting me run at a more optimum setting." Of course actually not. The computer sees this value and that value and adjusts IQ and timing. If the engine sensors report "normal" values the computer simply tries to work on its optimum settings. Keep that engine cold and it will never get in to the optimum settings.

You still have tires that have more rolling resistance when they are cold. Transmission oil as well as bearing grease is also thicker.

As others have mentioned, the intercooler helps cool the compressed air down. Not an issue when it is colder than a witches .... but it is an issue when it is 60F outside and you are driving 100 mph.

There have been some discussions over at ecomodder and cumminsforum about how they baseline off 32C. http://www.cumminsforum.com/forum/9...emp-whats-too-high-too-low-2.html#post2995916

Various threads also talk about blocking the grill off in a Cummins is doable up to about 70F. Of course this assumes that you are not driving the truck hard driving it real fast or pulling a lot of weight or a lot of air dragging trailer. The guys that are blocking off the grill are reading the torque reported from the computer (more torque equals more fuel used) as well as intake air temp and coolant temp.
 

robnitro

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In gas cars, warmer air helps economy. Warmer air being less dense, you need to open the throttle more for the same fuel. Less pumping loss due to less restriction from the throttle being more open when warm.

In a diesel, it is not always that smart. In the VE and PD ecu's there is no correction for boost with temperature (or so I haven't found to be in effect UNLESS you run a MAP based tune). So, the ecu will ask for the same boost pressure, even though the maf is reading much higher. The ecu will determine max fuel allowed for that airflow (smoke map), but it doesn't reduce fuel usage. The boost setting is based on how much you push the pedal (IQ request), and that smoke map is the top limit of fueling for your current airflow. Colder air will just make the engine respond quicker, as you have more airflow for the same boost. Perhaps if it is that way off, like running super high IAT, you may be pushing the pedal more for the same fueling- making the boost spike too much (more exhaust manifold pressure from that).

But in general, no on a diesel it will not help economy, UNLESS the ecu drops boost x% knowing that colder air is x% denser (which the map based tune does do- but it has its other inefficiencies- mostly assumptions of VE to estimate expected airflow).

In my other thread, based on observations from many on ecuconnections forum and my own testing... dropping low IQ request boost request does help economy. Less exhaust manifold pressure, the turbo is doing less work- which means less energy taken.
http://forums.tdiclub.com/showthread.php?t=409852
 
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