GT ALLEY Side-Mount Intercoolers
and Intercooler Pipe Kit

by Jeff Lucius

The custom side-mount intercoolers I purchased from GT ALLEY look very similar to what Alamo Motorsports (AMS) and Cartech offer (except for end caps and connectors). Supposedly, the intercooler cores were designed by Cartech. According to Alamo, each intercooler, with dimensions of 8.5"h x 6.5"w x 5.75"d, has about 19 square inches of internal flow area. Each intercooler should flow at least 300 cfm (remember that is compressed air; uncompressed air could have a volume twice that or more). Two of these intercoolers are more than adequate for the flow demands of our 3.0 L engine.

Corky Bell (when was active) recommends 6 or 7 square inches of internal flow area for every 100 HP. Therefore, with 38 square inches of internal flow area total, these two intercoolers can efficiently support 540 to 630 HP. Because these intercoolers are at least twice the size of the stock intercoolers, pressure loss across the intercooler should be significantly reduced. Unfortunately, I do not have measurements at this time to confirm this. I do have air temperature probes at the entrance to and exit from the driver's side IC (2-autometer3373.htm). A few preliminary measurements suggest efficiency of these intercoolers is around 75% to 85%, with good heat-sink capabilities.

Turbulent air flow (when the Reynolds number is over 4000; and it is over 100000 in our IC pipes) is the normal condition in IC piping. Using standard calculations such as those found at and , the following estimates can be used to determine the effects of changing IC piping diameter and flow rates. These are just rough estimates, require that the piping be fairly smooth on the inside with no sharp bends, and ignore the effects of the intercoolers themselves.

where Flow1, Diam1, and Pres1 are the reference (or starting) flow rate, pipe diameter, and total pipe pressure, respectively, and Flow2, Diam2, and Pres2 are the new flow rate, pipe diameter, and total pipe pressure, respectively.

For ten feet of 1.5"-diameter smooth pipe, calculations using the web pages noted above suggest that pressure loss should be about 1.2 psi at 15 psi boost (near sea level), 360 cfm (before compression) flow (in each half of our IC system), with an air temperature of 200F.

If the 10' pipe diameter increased to 2", at the 360 cfm (before compression) flow mentioned above the pressure loss would only be about 0.26 psi. A substantial improvement. With a 2.5" diameter, pressure loss would be reduced to about 0.090 psi; and at 3" diameter pressure loss would be only about 0.034 psi. So at the same flow rate the 2-inch pipe will have a pressure drop that is less than 25% of the 1.5-inch pipe pressure drop([2/1.5]-5.2 = 1.3333-5.2 = 0.224).

A 2"-diameter pipe could flow about 720 cfm (before compression) with a pressure drop of about 1.1 psi, about the same as a 1.5"-diameter pipe flowing only 360 cfm (before compression). So at the same pressure loss the 2-inch pipe will flow about twice as much air as the 1.5-inch pipe ([2/1.5]2.5 = 1.33332.5 = 2.053).

The pictures below are of the kit sold to me by GT ALLEY (Brian LaFuente is now with GT PRO) as part number GT-368I (intercoolers for use with GT-368R turbos). This kit, including polished aluminum intercoolers, chromed steel pipes, chromed steel Y-pipe, and standard radiator hose (later replaced with blue silicone hose), sold for about $2650 (July 1998). As of July 2005, Cartech sells their kit for about $1700 and AMS wants about $2500 for their kit (they both use the same picture to showcase their kits). The $1700 price includes the intercoolers and pipes. The $2500 price adds a new oil cooler. The pipes alone are $800.

For more pictures of this kit mounted in my car, go to my Gallery web page.

Here is a pic of a left HKS IC installed. The HKS core has dimensions of 8" wide by 8.5" high by 2.5" thick. The IC pipes have a nominal 2" diameter. Thanks go to Blue94V4R on the message board for this information.

Here are two pics from AMS comparing their left IC to the factory left IC.


Here is the picture from the Cartech web site. Picture credits and copyrights for the AMS and Cartech pictures go to them, of course.

Below are some pictures of DSM Eclipse/Talon intercoolers compared to our factory ICs and installed on a 1994 Dodge Stealth TT (thanks to AlmosN8kd on the 3SI.ORG message board). The size of the DSM IC is a bit larger than stock or the HKS, while still smaller than the AMS/Cartech IC and so the stock location of the oil cooler can be kept. This setup retains the factory nominal 1.5" diameter IC pipes.

DSM and stock left IC    DSM and stock right IC

DSM left IC installed 1    DSM left IC installed 2

DSM right IC installed 1    DSM right IC installed 2

Bob (oohnoo on the message board) welds stock-sized (a little larger than 1.5"), 1.75", and 2" pipes to DSM ICs so that they can be bolted right in on our 3000GTs and Stealths. See the pictures below (copyright to Bob) and more information on this thread at 3SI

DSM left IC, adappted for installation in 3S car    DSM right IC, adappted for installation in 3S car   

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Except for the small gif and jpg images, the content, images, photographs, text, and multimedia displayed are Copyright©2000-2006 by Jeff Lucius and K2 Software. All rights reserved. No part, section, image, photo, article, or whole of this site may be reposted or redisplayed without permission of the author.
Page last updated February 8, 2006.