Turbo engines are amazing for big power, but modify them badly and it will end in tears. This article will help you to do it right…We bet most of you would love to own a turbo car or have owned one, but we’re sure a lot of you aren’t much confident on what to do to make them faster. And it’s not surprising, as it’s so complicated!
And to teach you everything in exact detail would take an age, but that’s why here are the turbo tuning basics.
Tuning turbo engines in a nutshell:
One downside of air going into the turbo is it’s heated up to three times the heat it was when it entered the turbo in the first place. The hotter the air is, the less dense it is. Being less dense results in lower proportion of oxygen content, meaning less power. Another downside of hot air is that it increases the chances of detonation, and that’s absolutely bad for engine life.
Boost is the key to every engine’s power, but will also be the key to its destruction if you’re not careful. Upping the boost means more air is forced into the engine, and if combined with extra fuel to match you will get loads more power and torque. There is no such thing as too much boost, just too much for YOUR engine. Most turbo cars run about 7-10psi boost as standard and with some simple fuelling improvements the performance becomes improved hugely and safely for very little extra cash.
Fitting a different turbo can give you more power. Some replacement turbos could be the same size as your current one, but are simply stronger and more capable of running boost pressure without failing. The most common uprated turbos are those with larger compressor and exhaust housing.
On some vehicles fitting a proper sized intercooler is a nigh-on impossible job, so water injection is used for cooling the inlet charge. It works by injecting a great mist of water into your inlet pipe when on boost. The evaporating water absorbs the heat from the pressurized air, bringing the temperature down to a safe level.
Besides being good power booster, Nitrous, on a turbo engine it has two other uses as well. It is mega cold, far more than an intercooler and water injection could be, so when injected it cools the boost pressure hugely, increasing power far more than it would on a non-turbo engine. It’s also great for spooling big turbos up. Injecting nitrous at low rpm will bring it on boost far faster.
It’s an unsilenced exhaust that is separate from the main exhaust system and is fed via external wastegate/s. The downside is the jet like noise it can produce while an advantage is that the less gas will be going down your main exhaust system.
Getting the fuelling right is so important on a turbocharged car. With proper fueling you can make a difference between a quick car, and a quick car that blows up/melts. Make sure it is sorted because just turning up the boost with no appropriate adjustments to fuelling is bound to end in disaster.
If you are considering buying an imported car, be sure to get it to a good rolling road to make sure the fuelling is safe. High octane fuel is the friend of turbo cars, as it’s much more resistant to detonation, allowing cars to run higher boost safely.
You’ve got to be careful of the positioning of your air filter. As important as position though, is it being unrestrictive. If it’s sucking in really hot air it can lose you power, so keep it away from hot engine parts. A good filter setup can give good gains and can speed up the time the car takes to come on boost.
Pre-ignition / detonation
Det is the main killer for modified turbo engines, and is what destroys pistons and blows headgaskets. The main cause of det is when there is not enough fuel for the boost the car was running, or too much ignition advance.
The theory behind dump valves is that by opening a valve to let excess air escape, they stop the turbo from stalling as the throttle is closed. The more boost you run, the more effective a dump valve will become. The turbo can continue spinning so only then it will be able to boost quicker and faster. When the throttle is reapplied, throttle response is improved.
The wastegate is a valve that vents the exhaust gas from the manifold to the exhaust without passing through the turbo first. By allowing some exhaust gas straight into the exhaust it regulates the boost and prevents the turbo from spinning too fast.
Head gaskets are probably the most common thing to fail on turbo cars. They are intentionally made to be the weakest link in an engine, so should anything goes wrong they will blow before anything more expensive does. Cylinder pressure makes head gaskets blow. If it’s too high, it blows, but there are ways of reducing the chance of this happening.
Any significant changes to the engine need modifications to the management to get maximum power, reliability and drivability from your engine.
If you fit a huge bore exhaust to a non-turbo engine it can often lose you low down power and torque, but fit it on a turbo car, and it is the bigger the better! Ideally you want zero backpressure in the turbo car’s exhaust, hence a large bore exhaust from the turbo back will maximise your power and response.
The compression ratio is how much the fuel/air mix is squeezed by the piston before it is ignited. Once you start running big boost you will need to drop the compression to keep the cylinder pressures at a sensible level. The common myth about low compression engines being laggy is wrong; compression ratio has little relevance to what rpm the boost comes in.
The moment when you need stronger internals depends on the car, but forged pistons are the main upgrade on turbo engines, as they can handle much higher temps and are more resistant to detonation.
Headwork and aftermarket cams are nowhere near as important as on non-turbo engines as for the turbos force air in under pressure so the head port size and valves opening lift/duration isn’t as big an issue. Unlike some mods on turbo cars which have no downsides, head and cam work often loses low down power, so don’t rush into them until you are sure you need them.