Intercooler Upgrades

[ Stock Intercooler | Relocation | Improvments | Intercooling a Turbo I | Sprayers ]

Description

This is page describes how to improve the efficiency of your turbo by installing or upgrading your intercooler. Whether you are installing an intercooler on a Turbo I, or moving or upgrading the intercooler that is already on your car, you will find the answers here. Most of these mods require varying degrees of modification to and fabrication for your vehicle. I hope to add several picture to this page in the future to aid the explainations.

What is an Intercooler?

An intercooler is a component that is usually located between turbo output and the engine. It functions the same as a radiator by removing heat from the air put out by the turbo. When the turbocharger pumps air into the engine, it adds a very significant amount of heat through the compression of the air and through heat transfer from the turbo's casting. When air is heated it becomes less dense and so fewer air molecules can fit into a given volume. The intercooler removes some of this heat, which makes the air denser, and so more air can enter the engine. The ECU adds more fuel as a result, and the engine puts out more power. Most intercoolers are air-to-air, which means the heat is transferred from the air from the turbo to the air outside the intercooler. These intercoolers are usually mounted next to or in front of the engine's radiator. Some are even mounted just behind the front bumper facia. The amount of heat that the intercooler can remove (its efficiency), is directly related to how much air passes through the radiator and what the temperature of that outside air is.

To learn more about the types of intercooler setups found on these cars, see the Turbocharger Concepts page. I recommend that you read that page so that you know some of the terminology that is used in the remainder of this page.

The Stock Intercooler

Vehicles that come equipped with intercoolers (Turbo II, III, and IV) have the intercooler located right next to the engine's radiator. Intercooled engines have a special radiator that is narrower but thicker than the stock radiator. Since both the radiator and intercooler are mounted behind the A/C condensor coil, intercooler efficiency is lower when the A/C is on. Also, air flow to the intercooler is restricted by the condensor coil and by the fact that part of it is usually blocked by the underbody of the car. Even with this and the fact that the intercooler is not very large, these intercoolers are suprisingly efficient. An stock intercooled turbo (Turbo II) engine gains about 30 hp and about 7 ft-lbs of torque over the stock Turbo I. Here is what the stock intercooler/radiator assembly looks like:

Relocating Your Intercooler

One trick to increasing your intercooler's efficiency is to move it behind the front bumper facia. You can disconnect the intercooler from the radiator brackets and leave the radiator where it is. You will probably have to fashion some sort of mount to support that half of the radiator.

Then you need to decide how you are going to mount the intercooler. Depending on the vehicle, it is usually necessary to mount the intercooler somewhat low, but sometimes it can be mounted higher. You will have to turn it sideways, of course. If it can be mounted directly behind the front grill, that may be best, depending on how large the grill is. An AA-body (Dodge Spirit) has a large grill while a G-body (Dodge Daytona) has a very small or no grill. When it must be mounted lower (behind the bumper), it is usually best to mount it at a downward-facing angle to pick up the high pressure are coming around the bottom of the front bumper/air dam. A 15 to 30 degree angle is about right. You will also have to fashion some mounting brackets for the intercooler when mounting it behind the facia.

The most difficult part of this modification is routing the air hoses between the turbo, intercooler, and throttle body. If you don't have A/C and keep the stock Turbo II radiator, you can route them right through the hole where the intercooler was. Otherwise, you will either have to route them under the front crossmember, or cut holes in the front underbody panel. Use 2 1/4" exhaust pipe and 2 1/4" I.D. truck radiator hose. Be sure to have your routing all planned out so that you know what types of bends you need. You can buy smooth-bent exhaust pipe at various angles and connect them with short pieces of radiator hose, or you can try to find a pre-molded truck radiator hose that already has the angles you want and cut it up. Call up some local truck parts stores and see if they have anything in stock. Most will have the straight hose, but it is often more difficult to find a store that will let you look through their pre-molded hoses. Also, you can buy silicone hose from many performance catalogs in various sizes and angles, though they are a bit pricey ($30 to $50 each). Try Pegasus Auto Racing.

You now have a more efficient intercooler. The additional length of plumbing usually has very little, if any, effect on turbo lag. Do not exceed 2 1/4" diameter hoses and pipes. Larger diameters will only increase the volume of the system which will increase lag. There would be little to no improvement otherwise. You may be able to use 2" pipe and hose, but it is not recommended for these long runs.

Installing a Better Intercooler

If you are going to relocate your intercooler anyway, why not install a better one? The stock intercooler has a lot of surface area inside for heat transfer. While this is good for efficiency, it does restrict the air flow. At stock boost levels, the stock intercooler works well. For higher boost levels, a better flowing intercooler will help greatly.

One common upgrade is to find an intercooler from a Dodge Conquest or Mitsubishi Starion at a salvage yard. These cars are not all that common anymore, so you may have to do some searching. You will find the intercooler behind the front facia, angled downward. It may also be helpful to take the brackets to aid your installation. Though the intercooler is somewhat larger and is freer-flowing, the does have small diameter hose connections (about 1 7/8"). You can either make an adaptor with a 2 1/4" to 1 7/8" exhaust pipe coupling, or you can remove the connections entirely and install your own 2 1/4" connections. Since the intercooler is aluminum, you will probably want a machine shop to do this for you since welding aluminum is very difficult and requires special equpiment. If you are lazy like me, you can cut out the old connections with a hack saw, widen the holes, mount a steel pipe in there with some screws and seal it up with RTV, JB Weld, epoxy putty, or whatever. It's not pretty or durable, but it does work.

Another popular intercooler is a new one from Spearco. Though they are expensive, they come is just about any size or form you could want and they are efficient, well made aluminum designs. For these, you have the opportunity to install the largest intercooler you can fit.

See Gary Donovan's Intercooler Indentification Page for some pictures of intercoolers.

Intercooling a Turbo I

If you own a Turbo I engine, one of the best performance enhancements you can make is to install an intercooler. You will see an immediate gain in torque and power, even at stock Turbo I boost levels.

The procedure used to install an intercooler depends entirely on what type of Turbo I engine you have. Intercooling a 1988 or later turbo I engine can be rather simple, while intercooling an 1987 or earlier Turbo I engine is significantly more complicated. This is because of the intake arrangement change that was made in 1988 from the pull-through setup to the blow-through setup. See the Turbocharger Concepts page for more details. Basically, the blow-through setup was just a non-intercooled Turbo II engine with a smaller turbo. The pull-through setup was a completely different design. I have broken down the information based on the intake setup:

The Blow-Through Setup

The easiest engine to intercool is the 1988 or later Turbo I engine. This is because all of the hardware you need for the intercooler is already there. No disassembly of the engine is necessary. If you are just going to install a stock intercooler in the stock Turbo II location, then the installation is a bolt-on no-brainer. All you need is any year Turbo II intercooler/radiator assembly, a Turbo II airbox, the upper and lower intercooler hoses from a Turbo II, and the lower radiator hose from a Turbo II. Look for most of these parts at a salvage yard. Just replace the stock Turbo I radiator and air box with the Turbo II components. The Turbo II radiator is narrower, so that is where the lower radiator hose comes in. The Turbo II airbox has the built-in duct for the upper intercooler hose. If you can't find a Turbo II airbox, you can cut out the upper corner of your Turbo I airbox and install a 2 1/4" piece of exhaust pipe in its place. be sure to seal it up with RTV since this is the clean side of the airbox. You can also use straight, 2 1/4" I.D. truck radiator hose for most of the upper intercooler hose, if necessary (you will need part of a bent pipe for the hose connecting the intercooler to the air box). The lower hose has several bends in it, so it is best if you can find this hose somewhere or buy a new one from Mopar (about $95). No Turbo II engines came with a BOV, for some reason. You will either have to disregard the BOV, or find a way to install in into the system. If you had to use a bent exhaust pipe on the upper hose, you can have a short, 5/8" steel pipe welded on the bottom or the side and install the BOV there. Alternatively, you can cut a hole on one of the hoses and somehow seal it there. Having the barb from the BOV protruding inside the hose disturbs the flow of air inside, though. See the Blow Off Valves page for more information.

If you decide to go with another intercooler, or wish to install the stock Turbo II intercooler behind the front facia, then you will have to follow the procdure outlined in the Relocating Your Intercooler section.

To achieve the higher boost levels of the Turbo II using stock boost control (no bleeds, etc.), you will need to install the Turbo II ECU that is compatable with your year. The 1986 and 1987 logic modules are compatible with each other. The 1988 and 1989 SMECs are also compatible with each other. I don't know about later years. If you install the Turbo II SMEC on a 1988 or later engine, then you will have to install your own air charge temperature sensor, since these Turbo I engines did not have one. You can drill and tap a hole in your intake manifold or you can install it into the upper radiator hose somehow. Either way, you will have to run wires to the appropriate pins on the SMEC. It is easiest to remove the sensor and harness from another engine equppied with one.

The Pull-Through Setup

Intercooling a pre-1988 Turbo I engine is significantly more complicated. Which ever way you choose to do it, you will need to remove the head from your engine to work on the manifolds.

The least complicated way to do this is to install the Turbo II or blow-through Turbo I intake manifold and throttle body on the engine. If you do this, you will also have to either replace the exhaust manifold and turbo with Turbo II or blow-through Turbo I units, or you will need to do some grinding on the exhaust and intake manifolds so that they clear each other. It really isn't that difficult of you have a grinder.

Here is a link to a web page that details this:

Spraying Your Intercooler With Water

Another trick to increase intercooler efficiency is to setup your own intercooler sprayer. The idea here is to spary a mist of water in front of the intercooler. When the water evaporates from the surface of the intercooler, it generates a cooling effect. You can do this by using a windshield washer tank and pump as the water source and a spray nozzle or two from a spray bottle (Windex or whatever) as your sprayer. Keep in mind that the spray pattern with change significantly when your are driving because of the air rapidly passing by. The best way to adjust your spray pattern is to dry the intercooler, turn the pump on and off while driving, then immediately stop and look at what part of the intercooler is wet. Adjust accordingly.

You can control your sprayer manually with a switch on your dash, or you can rig it to a pressure switch that is connected to your intake manifold. When boost reaches a certain pressure, the pump will turn on. Or, you can do a combo of the two so that it automatically turns on only when you really want it to.

While this idea is not all that practical for the daily driver (unless you are a serious street racer), it works great for drag racing if your track will allow it. Some tracks won't let you spray anything while going down the track, but if you have your sprayer setup right, all the water should evaporate and they would never notice.

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This page is maintained by Russell W. Knize and was last updated 01/21/99. Comments? Questions? Email minimopar@myrealbox.com.