Now we don't want to be feeding our engine some really hot air do we? One of the most effective mods that can be done to a turbocharger setup is the addition of an intercooler. There are two types of intercoolers, air-air and air-water. Air-air intercoolers rely on the ambient air to decrease the temperature of the pressurized air from the turbo, much like how your radiator cools the engine coolant. On the other hand, an air-water intercooler uses water to cool the intake air. A simple air-water intercooler could be an air-air intercooler with a jacket welded over the fins. What happens is a high-flow pump pumps water over the fins of the intercooler, thus cooling the air, then moves the water out to an external radiator, which then cools the water and it gets pumped back into the intercooler. An air-water setup isn't hard to make if you can weld aluminum, but I can't, so I went with an air-air setup. Some of the advantages of an air-air intercooler is that it requires much less maintenance than the air-water setup because you don't have to worry about coolant leaks out of the system or into the intake pipe, or pump or coolant line failures. My setup consists of an aluminum Saab 900 intercooler, some aluminum piping that came with my Volvo turbo kit, some piping that came with the Saab intercooler, and 2 2'' mandrel U bends from JC Whitney. My Miata has both power steering and air conditioning, so running the intercooler piping ain't gonna be easy, and the pipe lengths are going to be fairly long. I ended up going with an under-the-radiator piping setup as it seemed to be the most effective with my conditions with the least amount of bends. The couplers you see are 2'' ID flexible exhaust hose from my local boating supply store. At about 5$/ft, and each foot makes 3-4 couplers, this is a steal, and much better than those fancy, expensive silicone couplers. I'm not sure what the exact material is, but it's mildly flexible and reinforced with a twine mesh, so there should be any problems with these not withstanding the heat and elements. Being a huge fan of the DIY nature, I came across this article in the tech section of the website on making your own fiberglass reinforced silicone couplers. All of the credit goes to their forum member wret for this idea. I decided to try it out and make the reducer couplers on my own since they are expensive and would take about a week to order and get in the mail. The throttle body inlet is 2.5'' while the intercooler piping is 2'', so I needed a custom coupler there. The Mass Airflow Meter is 2.75'' and needed to mate up with my 2'' piping, so I also need a custom coupler there. I also needed a sharp 90 degree elbow coupler coming off of the 2.25'' intercooler inlet so that the pipes didn't hang too low. All in all, these couplers were not too hard to make, they don't look necessarily all that pretty, but beauty is in the eye of the beholder, and these things work great!
Here's my first setup. I was running a straight crossover tube welded from 2'' stainless steel mandrel U bends. There's nothing too sophisticated here, it was only a temporary design that I used for about a week until I got the intercooler situation figured out. You can see the custom couplers for the throttle body and MAF meter.
This is the initial fitment of the intercooler in the front of the car. The bumper was left on because I simply could not take it off. The plastic undertray needed to be removed to get to this area, then it just took some muscle to stick it up in the nose in front of the A/C condensor. It sits at a decent level in the nose, with almost all of the fins in direct sight of the opening. On the right side of the intercooler you can see how I used some 1'' angle aluminum to make a bracket to hold it up. The two pegs on the ic just slip right in. On the left side of the ic I put a large hose clamp around the upper tube (the outlet) and made a bracket that slid under the clamp and bolted up on the crossmember in front of the radiator.
The turbo's compressor outlet has a 90 degree silicone elbow that was supplied with the kit clamped to it. Connected to the other end of the coupler is a tapered, 90 degree aluminum pipe that was also supplied with the Volvo kit. These pipes and couplers are just slightly larger than 2'' in diameter, so a reducer (which was also supplied with the kit!) was put on the other end of this pipe to connect to my 2'' mandrel bent pipe. This pipe turns down in right in front of the thermostat housing, and clearance between the pullies/belts and the piping CAN be a problem if you don't be careful. After the turn down I used one of my cheap boating couplers to connect the sharp 90 degree pipe that was supplied with the Saab intercooler. The way this pipe curves is perfect for keeping it away from the belts, but just to be safe, I put some zip-ties there to hold it near the strut bar so it doesn't inadvertently bounce back and tear up a belt or two. The positioning was perfect after some minor adjustments by rotating the pipes. All I needed for the rest of the ic inlet piping was a straight pipe to connect to my custom coupler, then the ic inlet piping is complete! I had to make a custom coupler because it need a sharp 90 degree angle to go just slightly under the radiator. I don't want the pipes banging the ground when I gotta go over speed bumps!
Here are a couple shots of the piping going under the radiator. Notice the decent ground clearance, but also keep in mind that my car isn't dropped yet, so I'm not sure how big of a problem that will pose later on. Also note that I covered the custom coupler in duct tape just for extra preventive measures against the elements and sharp rocks...ghetto :)
Now it's time to do the ic -> throttle body piping. I used the factory ic coupler which reduces the ic's 2.25'' outlet to a nice 2'' to connect my piping. I had already made a 2.5'' to 2'' reducer for the throttle body, so it was just a matter of getting the piping to fit into that. I also needed to weld on a bung to connect the idle air controller sensor. I went to the Home Depot plumbing department to find the right size pipe that the factor IAC hose would fit over, and simply cut it down to size, drilled a hole in the ic piping, and welded it on. So from the ic outlet I made a 90 degree elbow to connect to a coupler under the radiator that'll then go to another 90 degree elbow that will go straight up in front of the throttle body. Keep in mind that couplers are great because they'll allow for the fine tuning of the position of the piping plus they'll take stress off of the piping when the engine etc. rocks.
So now that the piping is complete, it's time to turn up the boost a few psi! You can see the pics of the ic piping before and after it was painted. It just looks hideous without the uniform color! My original intent was to use this candy apple red paint, but without thinking I tried to paint the bare pipes and it just didn't show up. If you wanna use a paint like that, you gotta put down a white base coat, and then lay on the good stuff. I ended up just using black primer since I had 2 cans of it. A couple coats on each pipe and it was good to go! It's not perfect, but it looks MUCH better.
And here's the piping for the MAF along with the custom reducer I made. Nothing spectacular here, just a setup similar to the Greddy kit's placement. Hopefully my TSIs will bring in enough air to keep that thing from breathing that hot turbo air.