Turbochargers 101

Turbochargers 101

How a Turbocharger Works

The word turbocharger is actually an abbreviation of the word turbo-supercharger. Yes, a turbocharger is from the same family as a supercharger – it’s all about “forced induction” (FI), or forcing much more air into the engine to allow for a bigger, controlled and designed explosion in the cylinders resulting is much more power output. A turbocharger is designed to increase the amount of compressed air into an engine. Think of it like this, a turbocharger is, more or less, like a mouth blowing huge amounts of compressed air onto a fire to get a flame going.

Typically, both a turbocharger and supercharger will pump around eight pounds per square inch (8psi) of compressed air into the engine, for the base kits that are provided by aftermarket manufacturers. This is around twice normal atmospheric air pressure which is 14.7psi. This means, you can generally accept to increase performance of an engine, via turbocharging, or supercharging, by around 40% or a little less (there are efficiency losses during the process).  These kits can put out far more power and boost pressure when modified to do so, with the appropriate supporting engine modifications in place.  See our article about this HERE!

Unlike a supercharger which uses ‘engine drive’ to power its turbine, a turbocharger uses exhaust gases to spin its turbine which can spin at speeds of up to 200,000rpm – the more exhaust gases you pump into the turbine, the faster it will spin.  This is why custom exhaust manifolds are built to maximize exhaust pressure.  The pressurised and compressed air is then forced into the cylinders of the engine which, along with more fuel being injected at the same time, produced more power because of the bigger explosion that results.

If you’ve driven an older turbocharged car you have likely felt something called ‘lag’, basically this describes the time it takes for the turbocharger to be spinning fast enough to forcing air into the engine.  The feeling of pressing the throttle and then nothing, nothing, nothing, and then EVERYTHING – all the power in the world comes on. Older turbochargers tended to be larger, which took a lot longer to spin up to efficiency.  Today’s systems are smaller and have reduced friction because and start spinning up sooner, so there is far less lag than the previous generations of these implementations.  Going too small has its drawbacks too, Go too small with the turbocharger can cause problems too as it’s spinning faster than the engine can reasonably apply and manage the increase in air and fuel requirements.  More power is common these, as manufacturers are producing twin-turbo charged vehicles with smaller engines.  Getting big V8 power out of 4 and 6 cylinder engines, with less weight and par better fuel economy to boot!

Of course, the automotive aftermarket has exploited the use of turbochargers, and especially twin-turbocharger setups, to get more than 2X the normal power out of an engine.  It’s not uncommon to see a 200hp engine produce more than 400hp with a twin turbocharger setup.  You can imagine the power that be made with a modern V8 at 400HP…

Stay tuned as we explore Superchargers in more detail soon!

When do I need engine modifications for Forced Induction?

When do I need engine modifications for Forced Induction?

Engine Modifications and When to do them!

Whenever we are customizing a car that will employ some type of power adder, major upgrades or modifications will become necessary to safely handle the increase in power. What mods and how much will depend on the engine and the application and how much additional power the modifications are expected to make. An engine that’s going into a drag car or some other type of race car may not rack up a lot of miles in a season but the miles it runs will be hard miles at full throttle under heavy load. Street engines, on the other hand, spend most of their time running under relatively light loads and only occasionally are called upon to produce maximum power. They are expected to last tens of thousands of miles without any major problems. So it can be argued that engine durability is just as important for both types of power adder applications, while one of the applications will arguably require far more detailed maintenance and possible rebuilding of certain components on a more frequent basis.

The upgrades that are necessary to handle power adders will depend on the engine and the power level the engine is built to produce and how much power the end game is being designed for. For a typical street application, changes to the stock pistons, rods and crankshaft are usually unnecessary unless a ­customer wants to make insane levels of power. Most stock block V8s can safely handle 150 to 200 extra horsepower on the street without encountering any major problems.

When an engine’s power output exceeds about 600 hp with a small block, or 800 hp with a big block, upgrades start to become mandatory with power adders.  Again, it depends on how the car will ultimately be driven.  A few examples follow.

Let’s take a newer Mustang for example.  The new S550 platform has the ability to handle almost 2X the power without any significant engine modifications taking place.  That means the 2015+ V8 Mustang can reach almost 800 Wheel Horsepower (WHP) with the addition of a supercharger or turbo setup without much of an issue at all.  If the car is being daily driven and spends only a few days at the track, then you will likely not need very much, or any, engine fortifying at all.  However, when breaching that 600-650WHP level, some drivetrain modifications will be needed, as the stock driveshaft and rear axles cannot handle that power for very long before they will break and leave you stranded and embarrassed.

The key to deciding on which modifications to make comes with some consulting time.  We need to fully understand how the car will be used and how you drive it in racing situations.  Some drag racers drop the hammer when the RPM’s are above 4000 when coming off the line, other’s maybe 6000RPM, and some just roll into power from about 2000RPM.  The higher levels create a huge amount of stress on drivetrain components, and they will break.  A stronger 1-piece driveshaft is a must and higher performance axles shafts should also be installed.  It also wouldn’t hurt to change the clutch.  Above 600WHP, the factory clutch will not last or grab and basically burn itself out pretty quickly.  If the car is being treated harshly – severe duty driving, possibly a change to the oil pump gears and timing chain gear should also be done.  Again, this requires a deeper conversation to make a reliable recommendation.  These motors can respectively handle 1000WHP+ with drivetrain modifications and the right fuel system, though longevity and reliability will catch up without a solid forged bottom end upgrade.

If we’re talking about a Challenger with the 5.7 engine, you are maxed at the real horsepower it can make to begin with.  The heads on this car cannot breathe enough to handle more than about 550WHP reliably, without being modified to do so, although we have built a few that are at about 600WHP.  At this level, it is strongly advised to change driveshaft and axles as well, and likely the clutch.  Anything planned for above 550WHP should get at least a forged bottom end done with the heads being re-worked as well, among others items.  If the car is a Hellcat, much more can be had, as that engine will breathe and handle far more power.  The drivetrain components can also handle more power and don’t really need to be changed until you breach around 900WHP as well.

If you want to talk about the Camaro, it’s not much different either.  The Ford engine will breathe better than all of them and handle more power adder horsepower in the end with less modifications, which is why they are so popular to build.  It takes larger engines and more build work to make the Camaro and Challenger make the same power as the Ford.  That doesn’t mean we want everyone doing 5.0 swaps, but it is something to think about and remember when buying one of the other cars when considering your build and budget.

What are the differences between Turbo’s and Superchargers?

What are the differences between Turbo’s and Superchargers?

Forced Induction Differences

A turbocharger uses hot exhaust gases to spin its ­turbine wheel, at speeds that will vary based on the exhaust pressure, that is connected by a short shaft to an impeller wheel inside the compressor housing. The impeller sucks air into the turbo housing, compresses it and pushes it into the engine to create boost pressure. As it is compressed, the air gets hot, so the air exiting the turbo is usually routed through an air-to-air or air-to-water heat exchanger called an “intercooler.”

Boost pressure is controlled by a “waste gate” that opens to vent pressure once a certain level of boost has been achieved.

Turbo kits are available for many popular ­applications and greatly simplify installation issues by providing all of the hardware and plumbing that is needed to fit a particular vehicle, including higher flow fuel injectors, a higher flow fuel pump in some cases and a special tuner tool for recalibrating the ECM.

Supercharging, by comparison, typically provides more instant throttle response depending on the type of supercharger that is used. A supercharger is a belt-driven blower so it is somewhat less efficient than a turbo because it takes power from the engine to drive the blower. A turbo gets its drive energy for free from the exhaust but also creates a small amount of power-reducing backpressure that has to be overcome before it develops boost and starts to make power, otherwise termed at turbo lag.

A “positive displacement” supercharger (also called a “Roots” style blower) — like that on the ZR1 Corvette, GT 500 Shelby Mustangs, Roush Mustangs and many street rods — has counter-rotating lobed rotors that force air into the engine. The boost pressure developed depends on engine speed and the underdrive ratio of the pulley on the supercharger.

By comparison, a “centrifugal” supercharger does not have counter-rotating rotors, but uses a compressor design similar to the impeller wheel on a turbocharger. Boost builds with rpm more like a turbo, but throttle response is better because of the belt-drive setup.

Supercharger kits are available for many popular street engines and typically offer a boost in performance of 150 to 200 or more horsepower — which most stock blocks can handle. But additional modifications become necessary to maintain engine reliability with higher levels of boost, as well as safety precautions such as enhanced brake systems.

More about engine and other vehicle systems modifications coming in future posts of this series.  So stay tuned for more to come!

What is Forced Induction

What is Forced Induction

FORCED INDUCTION EXPLAINED

The ­displacement and efficiency of a naturally aspirated ­engine limit how ­much power it can make. The engine can only inhale so much air because the atmospheric force is only 14.7 lbs. per square inch, at sea level mind you.  Atmospheric pressure decreases with elevation. Air density also decreases with temperature because hot air is thinner than cold air.  On top of all of this, most stock naturally aspirated engines can only achieve a peak efficiency ­of 75% to 85%.

Small block or big block Chevy, Ford or Chrysler engines are ­usually ­limited to two valves per cylinder and fixed valve timing, but if you’re working on a late-model engine, multiple valves per cylinder and variable valve timing can help improve breathing ­efficiency, and do so at extreme levels compared to just 10-15 years ago.

Common ways to improve airflow on naturally aspirated engines

• Installing a higher lift, longer duration camshaft.

• Modifying the stock heads or replacing them with aftermarket performance heads that have larger valves and better ports.

• Installing an intake manifold with taller and longer runners to help ram more air into the cylinders.

• Installing a larger throttle body or carburetor (or multiple carburetors) that can flow more CFM (cubic feet per minute).

• Adding an air scoop or cold air intake ­system to help route more and cooler denser air into the engine.

• Improving exhaust scavenging with headers and crossover pipes that help improve air flow out of the cylinders.

With such improvements, it is possible to boost an engine’s volumetric efficiency into the 90% range or even higher. But achieving 100% or higher volumetric efficiency (especially at higher rpms) usually requires some type of forced ­induction system such as a turbocharger or ­supercharger…and we call this Forced Induction.

Forced Induction

A forced induction system overcomes the limitations of atmospheric pressure by pushing more air into the cylinders. Consequently, the engine’s power output becomes a function of how much boost it gets. What’s more, dialing up the boost pressure overcomes a lot of deficiencies in the induction system and cylinder heads that would otherwise limit air flow and the engine’s volumetric efficiency.

After all, it is much easier to push air into an engine with a turbo or blower than to suck it in with intake vacuum alone.

Even with a relatively moderate amount of boost like 6 to 8 psi, a forced induction system can easily increase the power output of a typical street engine 150 or more horsepower.

Turn up the boost pressure to 14 to 16 psi and you can usually double the power output of most engines. Crank it up even more and you’re off to the races.

We’ll address the the differences of the various air induction systems and technologies in the rest of the series, so stay tuned!