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"Aftercooler" vs. "Intercooler"
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"Aftercooler" vs. "Intercooler" - 08-26-2009

In researching the subject, with regard to losses in boost and the consideration of going to a smaller pulley to compensate, I came across the following article that I thought I'd share here... if for no other reason than to understand the two words better. As is pointed out in the article, though, "intercooler" has come to also mean "aftercooler" in the way "Xerox" has become just another word for "copy."

(Note: I checked last night and I'm pulling just a hair over nine pounds of boost with my 2.8" pulley, which seems fairly consistent with what other 2.8" users seem to be getting.)

Russ

***

(Online version, here.)

Let's Talk Intercoolers!
8/3/2001 9:37:00 PM


An intercooler (sometimes referred to as an aftercooler) is designed to remove heat from the compressed air coming from the supecharger (or turbo) before it enters the engine's induction system. An intercooler works just lie a radiator - air is cooled by fins, bars, louvres, and plates inside the intercooler that are cooler than the compressed air coming from the supercharger. The reduction in air temperature increases the density of the air (more air molecules per cupic foot), which consequently increases your engine's ability to make more horsepower and torque. The decreased air temperature allows you to run more boost on a given octane of fuel before detonation occurs.

What's up with the terms?

The term 'intercooler' comes from days when they were first used on twin turbo aircraft engines. With two turbos, the air charge would get VERY hot - it was heated by the first turbo, then heated again by the second turbo. To combat this double temperature rise they placed a heat exchanger in between the two turbos and called it an "intercooler" because of its location in between two turbos. When this same kind of heat exchanger is used on a single turbo or supercharger, it is located after the supercharger, and should technically be called an "aftercooler" because of its location after the single turbo or supercharger. These terms didn't seem to stick, though. The term 'intercooler' caught on and became almost universal for all heat exchangers regardless of their position. The term 'aftercooler' became synonymous with air-to-water coolers because this is the term Vortech uses to describe their coolers, which are water cooled. So while technically incorrect, we will still use the popular terms 'intercooler' to mean any air-cooled charge cooler and 'aftercooler' to mean any water-cooled charge cooler.

Why Intercool?

There are several important benefits to intercooling that have resulted in their increased popularity in recent years. The most significant advantage is that intercooling increases the detonation threshhold because of the cooler air charge, meaning you can run more ignition advance for higher performance, or run lower octane fuel before experiencing detonation. This makes intercoolers very desirable for those looking to get the most out of their street vehicles on pump gasoline. The cooler air also allows your engine to run slightly cooler, reducing the chances of overheating. Intercoolers also enable your engine to produce more horsepower because of the denser air charge being delivered to the engine's combustion chamber.

Don't assume, however, that you can simply bolt an intercooler on to your supercharged engine and expect power gains with no other changes to the system. Intercoolers do create some internal drag causing a slight reduction in boost, and can also cause the engine to run lean (knock) due to the denser air charge. These problems are easily corrected and should not cause concern, however they cannot be ignored. Boost pressure can be brought back up (actually you'll probably want to run substantially more boost than you did with a non-intercooled application) using a smaller supercharger pulley. The smaller supercharger pulley will spin the supercharger faster and increase its output. Make sure your supercharger is designed to handle these higher boost levels. Correcting the air/fuel ratio to compensate for the denser air charge can be done with larger fuel injectors, recalibrated FMU, larger fuel pump, adjusting the mass air meter, etc.

Intercoolers... Aftercoolers... What's the difference?

In order for an intercooler to effectively cool the air that passes through it, the intercooler itself must be cooled by some external means. Most intercoolers are cooled just like your engine's radiator - air flows over the outside of the intercooler's fins, which in turn cool the air inside the intercooler - hence the name Air to Air Intercooler. Some intercoolers, however, are cooled by water instead of air, in which case they are generally called aftercoolers, or Air to Water Intercoolers. The benefit to an aftercooler is that air passing through it can be cooled more than in a traditional air/air intercooler if very cold water and ice are used to cool the intercooler - in fact, some aftercoolers chill the air to below ambient air temperatures even after it has been compressed by the supercharger. The reason aftercoolers are more effective in cooling the air charge is because water is a much better conductor of heat than air - in fact water conducts 4 times as much heat as air! The obvious drawback is that with time, the water will heat up to the temperature of the air passing through it, and its ability to cool incoming air goes away. Some aftercoolers, however, use a small radiator to cool the water that runs through the system, making them ideal for street use as well as racing. For drag racing applications aftercoolers packed with ice work very well because they only need to work for around ten seconds or so (hopefully) before you shut down and head to the victory podium. For milder racing and street applications air/air intercoolers or aftercoolers with radiators are more practical as their ability to cool incoming air is not reduced with time.

When is it right to intercool?

Obviously, intercoolers only work with supercharged or turbocharged vehicles where there is a substantial difference in temperature between the air entering the engine and the cooling medium (the intercooler). Because superchargers heat up the air significantly as they compress it, it is possible for there to be a very large temperature difference between the intercooler (ambient air temperature - 80F degrees or so) and the compressed air (200F - 350F degrees). Superchargers with higher boost will create a hotter discharge, so as you increase your boost, the effects of the intercooler become more and more noticable. In general we would not recommend intercoolers on supercharged engines with less than 8-9psi of boost, as the benefits will not be substantial. Essentially, run an intercooler when only when you running peak boost (i.e. any more boost would cause detonation) for the octane of fuel you use. Intercoolers work well in both warm and cool climates and work exceptionally well on marine applications because of the easy access to cold water.

Don't intercoolers restrict the flow of air into the engine?

Yes. Any time there is an obstacle in the way of the air flowing into the engine (like an intercooler fin or louvre), a pressure loss will result. Today's intercoolers are very effective in minmimzing this pressure loss so that the benefits obtained by cooling the discharge temperature normally outweigh the 1-2psi (approximate) loss in air pressure, which can be regained by running a smaller pulley and increasing the output of the supercharger.

The final word!

So while intercoolers work well on higher output superchargers, they are not recommended for lower boost level kits, like an average 6psi street kit. If you're looking for exceptional performance from your engine, consider adding an intercooler to your engine, or consider purchasing a supercharger kit that comes with an intercooler. Most ATI ProCharger systems include intercoolers and still remain very reasonably priced. Paxton has also recently introduced several intercoolers to fit their more popular supercharger systems, while Vortech already includes intercoolers with several kits. Good luck with your intercooling endeavors, wherever they may take you!


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08-26-2009

Yeah we all use the term 'intercooler', but in most cases it is technically an 'aftercooler', cooling temps AFTER the compressor. And a well-designed system really works well for after-cooling the heated air :-)


Mike - "Sally", The Beast: 2005, 5.0L V8 stroker, forged/cammed, KB 2.6 blower @18psi w/GT500 h/e; ARH LT's; 4r70W full-auto trans, CircleD converter; Shaftmasters driveshaft; GT500 8.8 w/3.73's; VEI digital gauges, PLX widebands; full suspension. Current best 1/4: 10.7 @ 128, on 93 octane
(Formerly a V6 Automatic with Vortech SQ supercharger & a/a intercooler -- 310 RWHP, w/best 1/4: 12.79 @ 107)

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08-26-2009

Yeah, I'll probably keep calling it an intercooler... but at least I'm smarter about it now. If my boost gauge is right and I'm running nine pounds of boost... and that drops one or two pounds after the intercooler goes on... I'd probably be fine running a 2.6". Giving it some thought.

Russ


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08-26-2009

Only problem with the 2.6 pulley is it really pushes the limits as far as running it and not getting any belt slippage. Hopefully all the pulley, tensioner and belt research helps prevent that as much as possible.



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08-26-2009

With the pulleys and belt I just bought (your setup, Gaylon), would a different tensioner take care of it?

Russ


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08-26-2009

Quote:
Originally Posted by Sniper308
With the pulleys and belt I just bought (your setup, Gaylon), would a different tensioner take care of it?

Russ
I don't think you need a different tensioner as long as you are getting the most you can from the stock one. In my case that required going to the slightly larger tensioner pulley. I think the system will work OK with the 2.6. My plan is to stick with the 2.8 however and eventually the R1900 supercharger which is going to be out a ways yet.



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sticky material perhaps?


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Quote:
Originally Posted by Nice Pony
I don't think you need a different tensioner as long as you are getting the most you can from the stock one. In my case that required going to the slightly larger tensioner pulley. I think the system will work OK with the 2.6. My plan is to stick with the 2.8 however and eventually the R1900 supercharger which is going to be out a ways yet.
It would be great to go to a TVS system eventually.

With your current exhaust and other mods, Gaylon, what horsepower do you think you might see with the 2.8" and, I presume, a custom tune?

Russ


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2005 Mustang ~ V6 Automatic ~ Performance White
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Custom 2.6" Pulley from South Florida Pulley Headquarters (Pulley Anti-Slip Coated by Carbinite Metal Coatings)
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08-26-2009

We should be able to get 300RWH or a little more out of the current M90 supercharger with the 2.8 pulley esily with the intercooled system. Doug was able to get 306RWHP out of a bone stock V6 that had the stock exhaust, was an automatic and had the stock 3:31 gears on the prototype intercooled system with a 2.6" pulley. He said at the time if he had time he could have even got more but our dyno time was up and he met the main goal of proving that over 300RWH was possible with the current M90 supercharger with an intercooler.



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08-26-2009

Well, the goal is to do what you've been doing lately, road racing and such. If you're running around nine pounds of boost like I am, and without water/meth injection which I currently have, and you're not blowing anything up at sustained speeds and higher RPMs... all on a 2.8" pulley... I'm thinking, with the average drop of one to two PSI I've been reading about by adding an intercooler (aftercooler), I'd be back to where I am now by going to the 2.6" pulley. I've really wanted to hit 330 RWHP, which I've always felt to be a reasonable goal for the X-Charger and my other mods, but maybe that's how guys blow things up -- by chasing numbers. I did talk to Matt down at BamaChips about a month or so ago, before ordering my 2.6" pulley, and he felt I'd be fine using my Mustang as a daily driver with the smaller pulley (and an intercooler). Had no reservation about it at all and Dave flat out said (wrote) to me he'd run a 2.6" on a daily driver. Decisions, decisions.

Russ


"Putting performance into PERFORMANCE WHITE!"

***
Orders I will NOT obey!

2005 Mustang ~ V6 Automatic ~ Performance White
X-Charger #28 ~ Hi-Po ~ Explorer Express (Xtreme Intercooler #01)
Custom 2.6" Pulley from South Florida Pulley Headquarters (Pulley Anti-Slip Coated by Carbinite Metal Coatings)
Custom JDM Tune for XCal2 Tuner with 93-Octane
Zabteck Throttle Body

View My Garage for a list of all mods to date.
   
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