Intercooler tubing is something that a lot of people seem to take for granted. They figure that if it connects from the turbo compressor housing to intercooler, then to the throttle body, that things are fine and dandy. These same people believe that intercooler tubing is intercooler tubing. WRONG. IC tubes from the factory are usually designed with package and cost restraints in mind. This often leads to unnecessary bends, flexible materials that expand under boost, and small tubing diameters. Don’t think for a moment that Nissan or Mitsubishi gave you the absolute best designed intercooler tubing just because your car is a GT-R or an EVO. Remember that we’re still talking about Nissans and Mitsubishis here. These are the same companies that manufactured the super lame B210 and the equally lame Tredia.
Some mass produced bolt-on intercooler kits also typically have compromised IC tube designs. Some popular brand Japanese IC or IC tube kits are often manufactured in China so often times fitment sucks ass too. Forget about the made in China Ebay shit from the bullshit copy companies (xs power, ss autochrome, etc.) – there was no designing. IC tubes designed by inexperienced fabricators also often suffer from tight radii, small tube diameters, and poor routing. Let’s not even talk about the ghetto dudes that go to Home Depot to buy their hoses. Always use high quality, multi-ply, silicone hoses.
The best IC tubes I see are typically on high end race cars or made by experienced fabricators and experienced tuning shops. It’s all about large, smooth radius bends, proper tubing diameters, good routing, and quality materials. Proper design is everything with intercooler tubes. On some twin turbo Skyline GT-Rs, we’ve gained as much as 60whp by fabricating proper IC tubes.
Some Q&A’s:
Q: “How can a hard pipe upgrade spool faster and make more horsepower if the tubes are larger in diameter?”
A: Smoother bends and larger diameters = less pressure drop. The turbo compressor can fill the engine faster with less pressure drop.
Q: “How can a hard pipe upgrade make more horsepower if it’s the same turbo and nothing else was changed?”
A: Since a lot of factory applications have flexible hoses, crazy bends, small diameters, and of course more pressure drop, the compressor has to work harder. This means that the compressor wheel has to turn more RPM to fill the engine. Since the turbo must turn more RPM, exhaust back pressure increases and the engine cannot take as much ignition advance. For example, by installing the XS hard pipe system on an EVO 8/9, your tuner can actually run additional ignition advance which generates more horsepower (see dynosheet below). On an application like the EVO where the stock turbo is already being run near the limit, properly designed rigid IC tubes can be extremely beneficial.
Q: “How can Greddy sell a $500 front mount intercooler kit for my S13?”
A: Make it in China, use a cheap ass 45 lb. made in China refrigerant heat exchanger core, and not give a shit about how it fits. Your IC tubes will rub away on everything in a year. While you’re at it, make sure you increase the spring rates in the front of your car because of that additional 45 lbs.
Q: “By going to a front mount kit on my STi, I will loose low end turbo response because the intercooler tubing will be much longer. Is this true?”
A: Don’t believe everything you read on the forums. What the hell does a dental implant salesman or a thug kid know about intercoolers? What another Sparklett’s guy forum member told him? My point is that speculation from an average guy is absolutely MEANINGLESS; especially when there are good, hard numbers that prove otherwise. Anyhow, in the case of the STi, the factory top mounted intercooler is such a piece of shit that there is actually more pressure drop and turbo lag than a properly designed front mounted intercooler system. The top mounted factory IC is a mass produced, low cost piece with too much fin density attempting to maximize cooling ability with poor packaging (What did you expect from the company that made the Brat?). The last time I checked, heat rises and that can’t be good for an intercooler sitting dead smack on top of an engine and turbocharger. When’s the last time you saw a factory Subaru WRC car use a top mount? NEVER. Before your thug kid buddy starts mouthing off about a top mount IC cooling from the hood scoop, WRC cars move a lot faster than your street car the last time I checked and WRC intercoolers are in the FRONT. Stop the subscribing to that stupid idea that top mounted intercoolers are equivalent or better than front mounted intercoolers. I can’t help you if you’re stupid or ignorant though.
Proper tubing diameters with smooth flowing bends.
EVO 9: Faster spool (120rpm) and 26whp @ 7500rpm.
Absolutely no increase in turbo lag on an STi.