How much increase in air input would 100 degrees F decrease cause ?
How much resistance to air flow does that intercooler produce ?
Is it really important to anyone who drives a heavy luxury vehicle to have that increase in power... and how much decrease in fuel mileage would it cost?

You would only decrease milage if you spent a lot of time with it floored, steady state milage would not change, only full load milage.

Gale Banks limited its 6.2 GM sidewinder kit to 9psi due to charge heating at higher boost. The Forced induction Honda crowds know anything above 9psi intercoolers are needed due to temps of the incoming charge.

A cooler charge of 15psi at 200 degrees F has far higher density of oxegen than a 15psi charge has at 300 degrees F. And with the denser charge you can run more fuel and get lower EGT than you would have at the same boost but higher ( uncooled) temps.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

The temperature rise of the compressed air does not depend on the quantity of air. It is determined soley from the compression ratio of the engine. Colder air in = colder compressed air. And it follows that the colder the air is, the colder the exhaust is, for the same quantity of fuel burned.

__________________
'83 240D with 617.952 and 2.88
'01 VW Beetle TDI
'05 Jeep Liberty CRD
'89 Toyota 4x4, needs 2L-T
'78 280Z with L28ET - 12.86@110
Oil Burner Kartel #35

http://i16.photobucket.com/albums/b1...oD/bioclip.jpg

Now, you have finally hit on a valid question. Yes, absolutely, the intercooler must be sized to accept the volume of air that the turbo can put out. Otherwise, you will get a turbo that can put out 15 psi and a manifold, on that same engine, that reads 6 psi. Of course the 6 psi is a cooler charge, but, the performance of the engine will actually decrease because there is less air in the cylinders. If you have turned up the fuel delivery on such an engine.............. can anybody say BLACK SMOKE? ?

I think some of you guys are trying to blow smoke up my pants leg....

for instance...

Take the concept of Kindling temperature...and combustion temperature...

Take some wood and freeze it...

then put some kind of ignition source to it...

it will not burn until it reaches kindling temperature...

and when it does burn , if it has the same amount of oxygen available as the same amount of unfrozen wood... it will burn at the same temperature...

you have reached OVER a threshold....

the idea of cooling air in order to put more into a given space is fine...

but I am pretty sure that , for example, if you put twice the air into the same bore and compress it to the same final volumn... that it will be hotter.... because it takes more force to compress it...and that is what is manifested in the heat of compression....

But at the same time... once it has passed that threshold at which it ignites the fuel sprayed into it... I really don't think the temperature of the exhaust is going to be cooler...

The exhaust temp is mostly going to be determined by the amount of fuel injected into the hot air......

Then there is this other problem...

Does everyone agree that an intercooler is a moot point on a non turbo engine ?

In other words....... an INtercooler is only needed to try to take away the heat ( and expansion ) caused by the compressing of the air by the turbocharger.... ????????????

So lets take the following example...and use a figure mentioned as a goal earlier...

You have a turbo MB diesel engine in the middle of Texas....the ambient air temperature is 100 degrees F.... just to make things simple....

How much does the air temp rise as a result of the turbocharger compressing it ?

Does everyone agree that if all things were perfectly designed and installed.... that the lowest temperature which the intercooler could possibly provide is that of the ambient air temp of 100 degrees F ? Because this is the air which the intercooler is using to cool the air which had its temperature increased by being compressed by the turbocharger.... ?

Now usually the temperature and amount of air flowing in a heat exchanger situation is pretty much an inverse relationship with reference to the changes one air mass can effect upon another one..

For an example... if you have 100 degree air trying to cool 200 degree air.. a one to one relationship between flow rates will mean the exhausting air on the cooler will be at 150 degrees......and the cooled air at 150 degrees if the volumn is equal...

To get another half step.... to 125 degrees in the cooled air you would need to provide twice the flow of ambient air......

So you see that soon you have a power problem in moving that much air past the cooling fins of the intercooler.... which of course would need to be figured in when computing the net increase of power produced by intercooling....

And then there is another problem most easily described as this :

GEARING IS EVERYTHING.

If you put more fuel into your engine... but have no way to change the way in which that power can be turned into a different ratio between piston travel and travel across the road... then you are going to burn more fuel per distance traveled....

Whoooooooooooooooo. Whooooooooooooooooo. Whooooooooooooooo.
That's smoke, Greg.

You are correct. Once the charge reaches the threshold at which it ignites the fuel sprayed into it, the exhaust is not going to get any cooler. This is the case in a naturally aspirated engine. However, in a turbocharged engine, the charge is at least 200 degrees hotter than the threshold at which the fuel will ignite. If you can lower this temperature by 100 degrees, or so, then you absolutely will lower the exhaust temperature. I'm not sure of the exact amout, so I cannot quote it to you, but, it will be lowered by a measurable amount.

No smoke here, Greg, just the facts.

General rule of thumb is 2% power increase for every ten degrees of inlet temp decrease...

This intercooler will provide a 1 or 2 psi pressure drop through the core which will have to be compensated for with a wastegate adjustment.

People do spend big bucks for luxury car power. Why is there a demand for gasoline Mercedes cars?

There will be no decrease in mileage unless your foot is in it all of the time and steady state cruising will see a mileage increase.

Now you are way over your head. If you increase the horsepower output of the engine, via the use of a turbocharger and an intercooler, you will see the ET to any distance decrease, if, and only if, you use that available power.

It is no different than taking a naturally aspirated diesel and comparing it to a turbocharged diesel with the same displacement. Both will burn the same amount of fuel if you do not ask any more horsepower from the turbocharged engine than the naturally aspirated engine can put out. Now, if you step into it and use the available horsepower from the turbocharged engine, of course you are going to get less fuel economy when you do it.

You would only need to change the gearing of the rear axle if you wanted to take advantage of a huge power increase across the rpm range. If you could get 250 hp from a 617, you probably do not need 3.07 gears in it anymore and could benefit from gearing that would be somewhere around 2.50. This would allow the engine to run slower. Since it has considerably more torque across the range, it can do this without the need to run it up to such high speeds, as we currently do.

The whole point is moot, however, becasue the kit could only achieve another 25-30 hp or so. It is meaningless to even discuss different gearing for such a small increase in power.

Gearing isn't relevent to making more power but it is something that will transform a car. The SD is geared too low in the differential. I'm going to put a 2.46 diff (380 SEL) in there after I dyno the intercooler since the torque peak will be in the 2500 rpm range. I put a taller fifth in my VW TDI and suffered no discernible acceleration reduction since I dropped the rpms at cruise 300 rpm closer to the engine's torque peak. There is a NVH and mileage benefit to be had in doing this as well.

Jim
dieselgeek.com

Just ordered a VDO pyrometer for baseline measurements. Will start collecting them this weekend.

Jim
dieselgeek.com
'82 300SD stopped counting at 307K

Lets use Turbo and TurbowithIntercooler for the current part of the discussion... which was the original comparison asked about...

But keep in mind that when the factory did that change to turbo they DID change the gearing.

Other factors are also at play... and one does not want to wear out the engine due to " Lugging"... being out of the correct rpm range and proper section of the power curve.... and that can also affect fuel useage differently at different rpms....much more than a properly geared machine.

That way we are starting with one of the most efficient machines produced... and wondering if Retro Intercooling would be a reasonable thing to attempt.

Ok,, I concede the point about using the same fuel if the engine is not asked to produce more hp per distance traveled...

This of course assumes correct settings of the Injection pump and air mass sensor or whatever system is used to compensate... not just cranking up the screw so that more fuel is being administered to the bore...

Diesel Geek, Ok.. if that is all the drop due to friction... and is compensated at the wastegate then that is good...

Ok,,, " 200 degrees hotter than needed to ignite the charge"..
... lets look at that....Do you mind posting the actual temps we are talking about ? What are the typical combustion temps ?

But the main question is not the temp in a turbo unit after compression.... but whether lowering the temp of the air BEFORE compression significantly ( or any )will produce a difference to the after compression temperature.....

Is anyone factoring in the additional absolute pressure reached due to the cooling effect of the intercooler causing more air to be in the bore prior to compression stroke ( assuming it can get anywhere near 100 degrees F drop).... ?

Lets also address the fact that a lot of ambient air is going to have to be moved across this intercooler in order to get a 100 degree drop...
Have yall crunched the numbers on that amount of air ? What is the number?
How is it going to be produced in the available space in these old Diesels ?

Diesel Geek, Look around at the people here on the Diesel Forum.... what do you see ? People who typically bought 15 year or older Automobiles THAT ONLY HAD 120 HP WHEN THEY WERE BRAND SPANKING NEW... So that " some people will pay for Power...." I don't think is THIS GROUP of GUYS.... LOL

JIM, I am just 25 miles from you... and clearly you need a dyno for what you are wanting to do... why don't you design and make one... if you don't have room to store it at your place you can put it out here in the country...
You two eager Beavers ( Randy and you ) could really go to town with a Dyno....

I don't wish to ignore you on this one, that is for sure, but, I don't have the hard numbers for you and I don't have my textbooks available (I'm not at home) to do the calculations.

It has already been shown to you that lowering the charge air temperature will lower the exhaust temperature, provided that you do not increase the fuel. This is the sole purpose of the intercooler. You now can increase the fuel and get additional power while maintaining the same EGT's as the engine without the intercooler. It is quite simple to document this and I'm sure it will be confirmed.

The turbocharged air will suffer a pressure drop across the intercooler. The absolute pressure in the intercooled engine is lower than the absolute pressure in the non-intercooled engine. The turbo will need a boost adjustment to return the manifold pressure to the level it was prior to the intercooler installation.

Quite true. I'm sure that no numbers have yet been crunched, Greg. That is what the prototype is all about. Can the intercooler provide enough of a temperature drop to achieve a gain in HP of 25-30 or so? Where to put a decent sized intercooler, and have sufficient airflow through it, is definitely a problem.


LOL. Well, Greg, you probably are quite right here. I'm not sure that I wish to spend $700. to get 25 hp out of the 617. But, the entire concept is very interesting and I will follow the prototype very carefully to see how he does with it. Maybe he can get 50 hp from the mod? Maybe he will only get 15 hp? Nobody knows until he does it. We are all, as you put it, blowing smoke