Intercooled 300DT Pictures - Page 6 - PeachParts Mercedes-Benz Forum

#76 10-21-2002, 07:41 AM

Ridge,

I don't doubt for a minute that there is an extreme heat loss across the heat exchanger as you explain. I also don't doubt the effectiveness of intercooling and turbocharging.

All I've been trying to say is that adding turbocharging and intercooling with no fuel system modifications will have minimal if any effect on power and little on fuel efficiency.

Once computerized fuel injection, such as that seen on most all gas engine cars today, comes to our diesels, then airflow improvements will be automatically compensated for. Until then we have to make it happen manually.

Adding the intercooler with no other modifications is much like going to a carbureted gas engine, adding a high flow exhaust, a good intake and porting the heads WITHOUT rejetting the carburetor. To take advantage of the additional air, you would have to add additional fuel to maintain the correct fuel/air ratio.

In a diesel there is no real 'fuel/air ratio" as in a gas engine because they are not mixed together before entering the cylinder. But, there is still an important relationship of the two elements.

I hope your paint job came out well.

Have a great day,

#77 10-21-2002, 08:18 PM

Quote:

Originally posted by LarryBible
Adding the intercooler with no other modifications is much like going to a carbureted gas engine, adding a high flow exhaust, a good intake and porting the heads WITHOUT rejetting the carburetor. To take advantage of the additional air, you would have to add additional fuel to maintain the correct fuel/air ratio.

Actually the main function of the intercooler is to cool charged air so that it expands more upon combustion thus creating more power.

Since an intercooler allows delivery of the same volume but %10+ greater air mass to the combustion chamber, the result upon heat of combustion is greater pressure forced against the pistons.

Like I said earlier, you could modify or build an engine to run on only supercooled air (say liquid nitrogen) with no combustion at all. So when you think 'intercooler' think 'cooled air expansion assist' rather than the conventional fuel/air mixture concept.
After that, think 'intercooler with ice water atomizer'; I know I am.

omegabenz · #78 10-21-2002, 09:00 PM

I believe the efficiency.

My friend turbocharges cars for a living, and I went down to him and he started up his diesel pick up truck that he made that has an intercooler, on the inlet side it will burn your hand, on the outlet it is slightly hotter than ambient.

On his biturbo car, same thing, hes got 14 psi running into the engine, and same thing, burn your hand on one side, and its fine on the other.

leathermang · #79 10-21-2002, 09:17 PM

I think there are two main questions here....

1. How much cooling does Ben's intercooler accomplish as measured in additional air entering the combustion chamber ?

2. Are the Mercedes Benz Diesels in question designed in a way which allows them to measure and respond to that extra air by injecting an appropriate amount of fuel into the cylinder ?

3. In other words, might the design of the load/altitude/etc compensation system require that the air be cooled before it enters the first sensor in order to effect an increase in power (as a result of fuel added to match the increase in air ?

I thought I would narrow and try to pin this down since the variables involved in " my friend's turbo " examples involve so many unknown factors....

#80 10-21-2002, 10:04 PM

1. about %10 more air by mass, same volume
2. no
Why keep bringing up air/fuel mixture? Increased O2 is not the key factor to intercooling.
according to howstuffworks.com:

Quote:

* Cool the incoming air - Compressing air raises its temperature. You would like to have the coolest air possible in the cylinder because the hotter the air is the less it will expand when combustion takes place. Therefore many turbo charged and super charged cars have an intercooler. An intercooler is a special radiator through which the compressed air passes to cool it off before it enters the cylinder.

leathermang · #81 10-21-2002, 10:41 PM

Dzldog, Since you don't know the ambient temp and the number of degrees of cooling which Ben's intercooler produces... How did you come up with 10% ?

They phrased that definition in a backwards manner ... The point is that cooler air is denser.. and thus into the same amount of space one can place more air AND FUEL in order to get more power out of the engine... that is if the system is designed where it can monitor and respond to the changes...

#82 10-21-2002, 11:09 PM

Leathermang:
Ridge claimed a 125F drop after intercooling; assuming pre intercooler charged air temp of about 275F, the increase of air mass would be about %10.
The main benefit of cooling the charged air will be the fact that it will expand more from combustion heat regardless of fuel increase.
We can only turn that little screw on top of the ip so far, so it is really a mute point. The installation of an intercooler will add more power to the 617 with an already tweaked turbo/ip because that cooler air will expand more.

leathermang · #83 10-22-2002, 12:20 AM

"The main benefit of cooling the charged air will be the fact that it will expand more from combustion heat regardless of fuel increase. "

Sorry, air does not spontaneously expand and produce more power by itself...

Oxygen won't even burn by itself....

It is only the ability to burn more fuel by putting more oxygen AND fuel into the cylinder that the intercooler causes an increase in power...

How did you get the 275 degree figure ?

The writers of that intercooler definition really did you a disservice by phrasing it that way...

Another way of questioning that concept is to try to explain where it could expand TO.... you have a certain size opening when the piston is at BDC and a certain size when it is at TDC... so the concept of it " expanding more" leaves the question of WHERE ? Whereas visualizing it as providing more oxygen to burn more fuel leaves you with the result of more power (BTU's) being produced in that same space....

mplafleur · #84 10-22-2002, 07:28 AM

Larry, leathermang,

Excellent responses. I do not say that you can't get more power and efficiency by intercooling a turbocharged system. I am saying that you won't realize any gain if the fuel system does not compensate for the denser air charge.

BTW, Deltahawk has a two-stroke turbocharged/supercharged diesel aircraft engine that is ready for flight testing. This is the one I am interested in. I was first intrigued by the Zoche radial, but he doesn't seem to be getting anywhere. He's been tinkering around with that engine for about 20 years now and I think now that it's only a hobby to him. He wasn't even at Oshkosh this year.

http://www.deltahawkengines.com/

Ridge,

I really would like to see it. It looks like a great example of engineering work. I like to see this kind of stuff and highly encourage it.

#85 10-22-2002, 07:44 AM

leathermang offers a great response.

So much for the credibility of: "howstuffworks.com." I can't believe that they think that the advantage of an intercooler has to do with the exansion of the air rather than its effect on combustion.

leathermang is absolutely right. The effect of cooled air is that the air is more dense. Air that is more dense HAS MORE OXYGEN!

If the concept of cooling the air with no other changes were true, we would have a good start in eliminating our need for fossil fuel.

Have a great day,

BlueBabyBenz · #86 10-22-2002, 01:29 PM

Quote:

Originally posted by Leathermang;

Another way of questioning that concept is to try to explain where it could expand TO.... you have a certain size opening when the piston is at BDC and a certain size when it is at TDC... so the concept of it " expanding more" leaves the question of WHERE ?

I have to disagree with this logic. You are using the fact that at a given rpm, the engine is a strain controlled load device to conclude there is no possible increased expansion, and hence no benefit to intercooling without additional fuel. But even before assessing the argument of whether or not we NEED more fuel to create more horsepower, we can't ignore the law of gases.

When dzldog asserts that the `cold air will expand more', that is another way of saying for a given volume, the pressure is greater.
The whole point of creating combustion is to increase the downward pressure on the piston head during the power stroke, and if you do that, you are creating more horsepower.

I'm not saying it does, or it doesn't, I'm just saying that the fact that at a fixed rpm the engine has a given volume for any given crank angle is not proof that it doesn't.

I agree that the BTU's available are derived from the fuel quantity, but only about 35% go into work done by the engine. That leaves a great deal wasted that go into the cooling system, friction, exhaust heat and unaccounted losses. It is not inconceivable that intercooling could nudge that figure upwards.

We can speculate forever on this, but I for one want to see the results on a dyno. Anybody have anything like that?

Thank you, all of you, btw. Ridge, LarryBible, Leathermang, mplafleur, dzldog, omegabenz and others I may have temporarily forgotten. Each of you has made excellent contributions to this board in general, and this thread in particular and inspired us to learn so much more.

leathermang · #87 10-22-2002, 02:33 PM

Saving this space so my response will be next to the questions...when I get it composed...

BlueBabyBenz · #88 10-22-2002, 05:56 PM

Man. This thread has become an obsession for me!

I've been reading everything I can get my hands on about the chemistry of combustion, because I can't rest until I know the complete answer.

I'm at the point where I can see that;

a) combustion energy, for all intents and purposes comes from the BTU's available in the fuel. What I'm saying here is that we can ignore any BTU's that exist in the compressed and cooled air that ends up in the chamber just prior to the power stroke. BTU's are BTU's, and the increased expansion of cooler air is possibly offset by the greater BTU's required to get it to the same temperature.

b) There is a fixed amount of oxygen that is required for the complete combustion of the carbon atoms in the fuel. The ratio is 2.67 pounds of oxygen for every pound of carbon atoms in the fuel.

c) Engine designers have attempted to deal with the difficulty of making sure the carbon atoms have access to enough available oxygen atoms, by designing various prechambers etc.

I do wonder about the following.

Given that we don't have computerized fuel delivery systems (I think I remember reading something like that), is it possible that during a great deal of the rpm range, more than adequate fuel is being delivered, but some fuel remains unburned because of inadequate oxygen supply? If this is true, then intercooling would help, and result in a broader power band, and increase in the Ridge seat-of-the-pants dyno results.

leathermang · #89 10-22-2002, 07:39 PM

LOL, you are not the only one checking out this thread... have you looked at the number of times it has been downloaded ?
Again I am saving this space for responding..

Once the valves close on the cylinder and the piston heads up on its compression stroke the equation on the compressing/heat formation etc.... are determined by the gas laws you mentioned earlier.... since the mechanical force from an explosion in another chamber is pushing the piston... and its travel is predertimined by the length of the crank stroke... then there is a very good chance that having put more , even though cooler, air into the cylinder will result in higher temperature being produced at full compression.... this would result in higher working pressure for the entire equation...

Thus, I have no idea where you get the concept about ignoring what gets into the cylinder just prior to the compression stroke...

I still say that the phrasing " increased expansion" from that definition is hurting your analysis... it is not really expanding if you don't put any fuel in there... it is just DE COMPRESSING from being squeezed by the piston with no place to escape...

BlueBabyBenz · #90 10-22-2002, 08:19 PM

Originally posted by Leathermang:

Quote:

Thus, I have no idea where you get the concept about ignoring what gets into the cylinder just prior to the compression stroke...

Actually, what I said was

"a) combustion energy, for all intents and purposes comes from the BTU's available in the fuel. What I'm saying here is that we can ignore any BTU's that exist in the compressed and cooled air that ends up in the chamber just prior to the power stroke....

Big difference between that and saying I'm ignoring what gets into the cylinder just prior to the compression stroke....

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