Admittedly I have been quiet on the posting front, this is due to my carrying out large work on the car and the time constraints that this offers. Rather than a big list of non descript modifications I will drill down through them as I go along.
Starting with a Hybrid Turbo. Sounds kind of sexy doesn't it? But what does it actually mean?
Air entering the engine first passes through an exhaust driven compressor. Compressed air results in a larger quantity of air being forced into the engine, creating more power.
The energy used to drive the turbo compressor is extracted from waste exhaust gasses. As exhaust gasses leave the engine they are directed through a wheel placed in the exhaust flow. The gasses drive the turbine wheel around, which is directly connected via a shaft, to the compressor wheel.
Increased exhaust gas drives the turbine wheel faster, this provides the engine more air, producing more power. A limit is met once a pre-determined boost pressure is achieved. At this point the exhaust gas is redirected away from the turbine wheel, thus slowing it down and limiting the maximum boost pressure. This redirection valve is known as the wastegate.
This extraction of energy, from exhaust gas, to improve engine efficiency is the device known as the turbocharger.
Turbochargers are usually seen as power enhancements on performance cars, but today, turbochargers are becoming more regularly used to provide greater torque on small capacity engines. The advantages of using a turbo engine include improved fuel efficiency and reduced exhaust emissions.
The standard Skyline R33 GTS-25T comes with a ceramic turbo as standard and at max strength can deliver .8 bar (14.5 psi = 1 bar) of boost to the engine. Anything over that and it will have trouble.
Hybrid turbos only become necessary when significant performance improvement is required, normally on a modified engine. Most hybrid turbochargers will look identical to standard units from the outside. The changes occur inside, by using steel components, different aerodynamic configurations, both in the compressor and turbine housings.
Most turbocharged engines respond well to increased boost pressure, but only if the engine is modified to capitalise on the change. The same can be said of turbochargers. A hybrid turbo on a standard engine may offer a small benefit, but will be more effective on a modified engine.
Another way in which a hybrid turbocharger can improve an engine’s performance is by improving response, or reducing turbo lag.
Boost pressure will be able to be increased to 1.2 or 1.3 bar safely, any more than that would require a thicker head gasket to be fitted to handle the pressure build up.
The turbo unit I am fitting comes with a twin port Stainless steel turbo elbow (see picture) which replaces the standard cast iron combined turbo elbow. This should help reduce the affects of negative feedback pressure on the turbo vanes by separating the turbo and wastegate exhaust gasses, improving flow, speeding turbo spooling and reducing turbo lag.
Did you know?
The air entering a turbo's compressor impeller can be travelling at a speed close to mach 1.
A turbo will accelerate from 20,000 revs per minute to over 150,000 revs per minute in less that one second.
At average engine revs, a medium size turbo will swallow 130 cubic feet of air per minute, equivalent to the interior volume of a transit van.
The "hot end" turbine blades in a turbo, are made from a high nickel content alloy, as used in jet aircraft engines. A blade will travel in the region of 820 mph at average engine speed, and the exhaust gas entering it will be supersonic.
For more information on Hybrid's or general turbo enquires visit the Turbo Technics web site