Do you like your Diesel warm or cold ?

[ConnClark]

Part load efficiency data is kind of hard to find.
But it stands to reason that it too will follow the basic trend of the Carnot efficiency equation of Nth= 1- (Tmin/Tmax)


Attached is results of an experiment of adding an intercooler to a turbocharged engine and keeping fueling the same.

and finally here is a link to a book on diesel engines. If you want to do a detailed analysis or partial analysis of how intake air temperature will effect things by plugging in numbers to equations this book will show you how.

http://www.dieselbookmarks.com/bombe...nce%20Book.zip

I can dig up some further studies and papers by NACA that show a similar trend if you like.

Edit: added the words "the same" after the word fueling

[ConnClark]

Figure 14 in this NACA report shows how intake temps effect efficiency at variable loads. Note: Colder is better



http://aerade.cranfield.ac.uk/ara/1937/naca-tn-619.pdf

[Olympiadis]

Originally Posted by Daox

I'd like to see any SAE (or other) testing that shows how IAT effects diesel efficiency.

I looked up some SAE papers, but it seems they want some money before they are willing to share.

There are some others I found that seemed very limited or incomplete, or just not applicable.

Here's some good information here:
http://rds.yahoo.com/_ylt=A0oGdHhPiU...el_ENVIRON.pdf

LINK

^The above paper is also not completely applicable for the following reasons:

1. It primarily highlights NOX production at a fixed load for the purposes of maintaining emissions compliance, not overall fuel efficiency of a road-going vehicle.

2. Though BSFC and NOX production are linked in that a faster burn rate can increase NOX, and also increase BSFC up to a point, BSFC is not directly linked to fuel economy in a road-going vehicle.

You can see by this that in fact both air temperature and water content do change the burn rate of the fuel, and therefore the emissions and power output of the engine.

I'm not really sure why, or if this was even in question though.
At least in my own company it is common knowledge that cooler, dryer, and more dense air will increase the maximum power output of an engine by increasing available oxygen, speeding up combustion under high load, and often increasing the VE of the engine as well.

[Olympiadis]

Originally Posted by ConnClark

Part load efficiency data is kind of hard to find.
But it stands to reason that it too will follow the basic trend of the Carnot efficiency equation of Nth= 1- (Tmin/Tmax)


Attached is results of an experiment of adding an intercooler to a turbocharged engine and keeping fueling the same.

and finally here is a link to a book on diesel engines. If you want to do a detailed analysis or partial analysis of how intake air temperature will effect things by plugging in numbers to equations this book will show you how.

http://www.dieselbookmarks.com/bombe...nce%20Book.zip

I can dig up some further studies and papers by NACA that show a similar trend if you like.

Edit: added the words "the same" after the word fueling

This looks correct to me, and verifies what I said.
Thank you.

[ConnClark]

Originally Posted by white2001s10

If you always hypermile with very light engine loading, then the warm air will help your fuel efficiency.

And it verifies that how?

[Olympiadis]

Originally Posted by ConnClark

And it verifies that how?

Oh I see now that your goal was clearly to discredit my original post.
You have picked out the other side of the coin, - the part that your posted link definitely does not verify.

None of the information found at any of the links either of us has posted even allude to increased fuel mileage in a road-going vehicle.

What the information does show is that when/if more power is needed, then cooler air is the way to go.
It also shows that intake air temperature and water content inversely affect the burn rate of the fuel.

No disrespect intended, but if you think this discredits what I posted, then it seems to me that you are confusing engine fuel efficiency (BSFC) with vehicle fuel efficiency.
Brake specific fuel consumption - Wikipedia, the free encyclopedia

If you are bent on discrediting that one part of my post, then please do it via controlled testing as I suggested, because your links do not.

I will grant that given a multitude of variables and different states of starting conditions, that there will necessarily be times when, even at very light loads, vehicle fuel efficiency will not increase by increasing the intake air temperature over ambient.

Assuming this isn't a straw to pick due to something personal against me, I have to conclude some sort of misunderstanding.

Are you suggesting any of the following?

a. The BSFC is directly linked to vehicle fuel efficiency.

b. A variable like "air temp" will either increase or decrease vehicle fuel efficiency no matter the loading conditions (type of use of the vehicle).

c. Intake air temperature does not affect the burn rate of the fuel.

d. Warmer intake air will slow the burn rate of the fuel.

e. There is no need to match fuel burn rate to the loading of the engine.

I just want to be clear on where you stand before possibly taking a wrong turn here on this site.

[ConnClark]

The purpose of this thread is whether a warm air intake improves the fuel economy of a diesel. I cannot find any scientific studies that indicate that one will under any circumstance. I'm not trying to attack you personally but the only evidence I can find (both theoretical and experimental) points to the contrary.

An engine having its efficiency manipulated by intake air temperatures can't tell whether its on a test stand or in a vehicle. Unless conducted in a controlled blind study over a significant number of tests, over a period of time, and with a large number of tests subjects, road tests are not real proof that something works because you can't duplicate the conditions. A test stand allows repeatability and precise measurements of conditions and results which is why they are used in scientific studies.

for a.
An engine operating in a set of conditions that improves its efficiency does have a direct impact on the mileage that a road going vehicle can achieve.
That said I can get better mileage out of a 1912 steam tractor than I can out of a geo metro if I want to providing I'm driving both vehicles for the comparison.

for b.
yes it can

for c.
No, air temperature does effect the burn rate of the fuel.

for d.
No, warm air tends to increase the burn rate of the fuel.

for e.
optimal burn rate for a diesel is determined by rpm of the engine, the quantity of fuel injected, and the ratio of the connecting rod length to the crank throw not the load on the engine.


Now tell me isn't the limiting factor on an atomized fuel droplet's burn rate determined by the number of O2 molecules it passes by while burning?

[Olympiadis]

Originally Posted by ConnClark

for a.
An engine operating in a set of conditions that improves its efficiency does have a direct impact on the mileage that a road going vehicle can achieve.

for b.
yes it can

for e.
optimal burn rate for a diesel is determined by rpm of the engine, the quantity of fuel injected, and the ratio of the connecting rod length to the crank throw not the load on the engine.

There's our problem.
In my world you are wrong on these three counts.
I don't see my further posting in this thread as being productive anymore.
A debate of engine theory and vehicle efficiency is off topic and can be a separate discussion if you like.

[Arragonis]

I think I followed that exchange - so basically the warm air is for quicker warm up at start. OK. But for efficiency cooller air is better. Does that fact I hardly use full throttle affect this at all ? I give it a blast every now and again to shift any crud but usually its light throttle except for close to peak BSFC (around 1800 I think).

So if I need to go for cooller air but still have perhaps a grillblock for aero I need to find a shape which allows air to flow in but doesn't create too much disturbance to the (hopefully) better flowing air over the grill. The air intake is just behind the grill on the left hand side (from the driving seat). My thought is to upgrade the intake to the PD160 version which is larger :



and then experiment with the best intake opening - perhaps a large hold or better maybe a smaller set of holes of slots cut vertically.

The grill comes apart easily



and mine is quite 'scabby' so I don't mind experimenting with blocking it.

My car has an intercooller but its located inside the front, right (from the seat) wheelarch with air flowing through an opening in the bumper there around a foglight and then exiting through a small grill in the arch itself. There are FMC kits but they are spendy, too spendy for me.

All of this may seem like cunning design but its a car the size of a Polo with the wacking great 1.9 TDi in it. And yes it does feel very nose heavy

[ecomodded]

I read the thread and it is inconclusive at best and in my favor. I would only be heating the air by a limited amount its not as severe as a increase as you may think. Enough to aid in low demand combustion,Warm air is more explosive then cold air..