Here's why:
Reduced Power and Efficiency:Turbochargers heat the intake air as they compress it. Without an inter cooler, this hot air, which is less dense, enters the engine, leading to lower oxygen content and reduced combustion efficiency. This results in a noticeable decrease in power output.
Increased Risk of Detonation:Hotter intake air also increases the risk of engine knock (detonation), which can damage the engine.Higher Emissions:Reduced combustion efficiency due to hot intake air can also lead to higher emissions.Reduced Engine Longevity:The increased heat and potential for detonation can put extra stress on the engine, potentially shortening its lifespan.
In short, while you can run a turbo without an inter cooler, the performance and longevity of your engine will be negatively impacted.
If you are running low amounts of boost, like 5 to 6psi, it’s no big deal. The intake air charge will certainly get heated up but nothing too drastic and most likely within the realm of what the engine, fueling and ECU can handle.
If you are running lots of boost, like 15psi and up, you could be in for a lot of trouble. The more a turbo compresses the air, the more the air gets heated up. If this heated air isn’t cooled by an intercooler, you will be dumping it straight into the cylinders. The trouble you may run into is pre-ignition, or detonation. This occurs when the air/fuel mixture is so hot it combusts on its own WITHOUT the spark plug. This can be really bad since you can’t control when it happens. If the piston is on its way up and you get detonation, you now have a lot of force opposing the upward motion of the piston. Uh oh. This is how rods get bent, head gaskets blow out, piston heads get damaged, etc. The car can dump tons of fuel to try to keep the temps in check but that may not be sufficient. This is where compression ratio plays a role - high compression ratios decrease the amount of room in the cylinder head - increasing pressure, which can also increase heat, and be more prone to detonation.
So. Low boost turbo? You are fine. Depending on how hot your intake air charge is, there might be benefit to running a small inter cooler. High boost turbo? You really will want an inter cooler. Otherwise the car ECU will be doing all kinds of things to try to keep the heat down like pulling timing, dumping fuel, etc. All these things lead to reduced power, which defeats the purpose of running a hi boost turbo.
