Engine/Transmission (1994 - 1998) Intercooler efficiency?

[JGK]

Does anyone know, either by direct measurements, or by published specs, what the average cooling efficiency is of the stock intercooler in a '98 12-valve truck? It would likely be stated as a percentage, perhaps at some given ambient temperature.



Thanks,

-Jay

 

[JGK]

TTT



What, no takers?!

 

[Bob4x4]

Manufacturers do not like to publish any numbers they can be held to. Bob

 

[Matthug]

It's pretty good thats all I know, practically no one upgrades it under 800 HP so I'm not worried about it LOL.

 

[Bob4x4]

It's pretty good thats all I know, practically no one upgrades it under 800 HP so I'm not worried about it LOL.

That is not the best criteria... ... ..... The dyno doesnt last long enough to worry about. Pull a 12k trailer up a long grade and try to use all your power,that is the test.



Bob

 

[Jim Fulmer]

It's pretty good thats all I know, practically no one upgrades it under 800 HP so I'm not worried about it LOL.

That's just because they haven't blown it up yet and there pouring there money into other places on the truck. I did this very thing then got the prototype intercooler from Piers and I've been running it since. It's a much more efficient cooler and built to stand our abuse.



The last time I check they were on sale.



Jim

 

[JGK]

The reason for my inquiry is due to a page I found on this site, which is dedicated to the Dodge Stealth and Mitsubishi 3000GT VR4. The page is a technical discussion of adiabatic processes relating to turbos. Below is a copied section of the page. The last line is what caused me to ask my question.





Many people think that 12 psi in the manifold is a moderate boost level so I'll use that as an example. If we can assume there is a 2 psi pressure loss from the turbo to the manifold, then the PR at the compressor is about 1. 95 ( (14 +14. 7)/14. 7). Let's also assume we manage to keep the intake air temperature down to 80ºF (or 540ºR). The air temperature leaving the compressor, due to adiabatic heating only, would be 194ºF which is 654ºR = 540ºR x (1. 95)0. 286. This is an increase of 114ºF! But the air is actually hotter than that.



Turbochargers compress the air by increasing the velocity of the molecules. When the air molecules don't move in a direction toward the intercooler (IC), they serve only to heat the air. The more the air is heated above that predicted by adiabatic compression, then the less efficient the turbocharger is. Compressor flow maps usually show at various flow amounts and pressure ratios the measured efficiency of a turbocharger. Compressors usually operate in the 55-75% efficiency range depending on engine load, pressure ratio, turbine speed, and compressor size (65-70% is average, 75% or more is where we would like to be).



When we factor in compressor efficiency (CE) the final temperature of the air leaving the compressor is



T3 = T1 + (T2-T1)/CE.



If compressor efficiency is 70% in the above example, then the final temperature is 242ºF, more than hot enough to boil water. If we increase the PR to 2. 36 (18 psi manifold and 2 psi IC loss), the temperature would increase to 295ºF. These high temperatures explain why intercoolers are so important when boost pressure is above a few psi. You can use my client-side JavaScript calculator to interactively determine turbo outlet temperature.



The intercooler of course is supposed to cool the air. Intercooler efficiency, IE, can be calculated by measuring the air temperature going into the intercooler, Tin, the air temperature leaving the intercooler, Tout, and the ambient air temperature, Tamb.



IE = (Tin-Tout)/(Tin-Tamb) or Tout = Tin - IE x (Tin-Tamb)



High efficiency levels are near 90% and lower levels are toward 50-60%. If an 80% efficient intercooler had been used in the above example, then manifold air temperature at 12 psi boost would have dropped to about 104ºF = 242ºF – 0. 8 x (242-70)ºF. Intercooler air cooling by the way is not an adiabatic process. Ideally, heat is removed from the air without a corresponding decrease in pressure. If you think about it, you'll see that intercooler efficiency is far more important than the efficiency of the turbocharger.