OK, I just might be nuts, but my thinking was:
If a CTD runs empty most of the time, so that extra cooling is of no big concern, then would it be advantageous to bypass the intercooler?

Some members report an increase in mpg when they change the air filter.
That's no big surprise. Then, of all things that restrict the airflow, the intercooler has to be a major cause, for passing all that air through such small tubes must create a few psi pressure loss...

Just wondering: has anyone bypassed their IC and did they get any mpg improvement?

 

The intercooler serves the purpose to be a heat exchanger between the hot compressed air from the turbo to the cooler outside air. When air cools down, there are more O2 molecules at a higher density per unit. So the more O2 you can get into a unit, the more theoretical combustion power you have. Since diesels love a lean environment for combustion, the more O2, the less fuel.

 

Im purty sure the turbo will be pulling in the engines air through the air filter regardless if it got an i/c or not.

Best way to get good miliage is to adjust the ding bat behind the wheel.

 

I find it hard to believe that an air filter could make a perceptible difference in fuel mileage under normal conditions.

At low boost, the air coming out of the turbo is pretty close to ambient air temp, so the intercooler isn't doing much. I'm sure that eliminating the pressure drop across it would improve efficiency slightly, but I'm not sure you'd see enough gain to make it worth it.

 

Actually the pressure drop, if there is any, is because of temperature difference. The air becomes more dense after being cooled, thus taking up less space, less restriction=less pressure.

 

Keep the cooler.

 

If it gets used in a dusty environment, it could make a difference. I know of a 6 liter that wouldn't run under half throttle, until they pulled the air filter and blew it out.

 

There's pressure drop because of flow through the tubes. It's probably not significant enough to justify the extra complexity of an intercooler bypass, but it's there.

EDIT: In fact, the way I understand it, pressure drop is caused solely by aerodynamic drag. I'm not sure exactly how to explain it, but pressure drop and temperature drop are relatively independent in an intercooler. The temperature drops because of heat transfer, not pressure drop; if the pressure didn't drop, the intercooler would still transfer heat, drop the temperature, and increase density.

Another way to look at it: running 14.7 psi boost pre-intercooler (pressure ratio of 2) the temperature out of the turbo is at least 186°F. Let's say it's 200. Say the intercooler drops the temp to 100°F. If the pressure dropped only because of temperature drop, you'd lose 12.9psi across the intercooler. The more the temperature dropped across the intercooler, the more the pressure would drop. This obviously isn't the case.

Good point. I was talking about changing from a stock filter to an aftermarket filter - a clogged filter is a different story.

 

Why not put two identical pressure gauges on it, one on each side of the intercooler and find out for us?

 

Good idia!

 

Done this and temperature probes on aircraft engines for high altitude testing. No exact numbers could be extrapolated because conditions varied, but the average temperature and boost pressure was lower.

 

Aint that the truth......

 

While the IC does offer resistance to flow, which equates to pressure drop, there is also pressure drop associated with the decrease of charge-air temperature.


In other words,

Ignoring the resistance to flow, and working with constant flow, one will still see an apparent pressure drop due to the increasing density of the charge-air with the decrease in temperature. (Comparing the IC's inlet to it's outlet).


Keep the IC. You'll enjoy an increase in mpg due to the denser charge-air. After all, it is the charge-air that is expanding, pushing the piston with the addition of heat from the fuel.

 

Is our exaust gases hot enough to recirulate to our breathers to be reburned?, and keep your ic.

 

Can't "reburn" exhaust gasses . . . . . ? I don't follow the question.

Exhaust Gas Recirculation (EGR) is done for emission control reasons as it fouls the incoming air so as to reduce combustion temperatures. This in turn reduces the formation of oxides of nitrogen (a pollutant). Dodge actually added the IC for the same reasons (reduced combustion temps, therefore reduced oxides of nitrogen)