Archive for turbocharger solutions

Hyundai debuts two new Sonata variants at New York

At the ongoing New York Auto Show, Korean’s rising giant Hyundai debuted two new variants of new Sonata YF – the Sonata 2.0T and Sonata Hybrid. To be sold in the US market as 2011 models, both cars feature the latest all-aluminium Theta-II engine mated with the company’s newly-developed maintenance-free 6-speed automatic transmission.

First, let’s start with the Sonata 2.0T. It gets the 2.0-litre, 86mm × 86mm (bore × stroke) Theta-II engine enhanced with twin-scroll turbocharging and Gasoline Direct Injection. We are familiar with such trickery with the Germans, of course – Mercedes calls it Charged Gasoline Injection (CGI), whilst the VW Group calls it Turbocharged Fuel Stratified Injection (TFSI).

Hyundai Sonata 2.0T

But can we seriously contemplate comparing Hyundai’s products with the Germans? Yes, we can. Merc’s 1.8-litre CGI has thus far been tuned to as high as 204hp and 310Nm, while VW’s famous 2.0-litre TFSI engine produces 267hp and 350Nm, and this is for the Golf R no less. The Sonata 2.0T is rated to produce, drumroll please, 274hp @ 6,000rpm and 365Nm @ 1,800 – 4,500rpm.

Although it should be noted that the German examples utilize single-scroll blowers, how many of us predicted seeing a Sonata with more grunt than a Mercedes C-Class or VW Golf GTI? Even BMW’s much vaunted 2.0-litre N47 turbodiesel has no answer to this, being hopelessly outgunned at a modest 177hp and 350Nm. Fuel economy is also impressive, with Hyundai estimating 10.7 litres/100km for city driving and 6.9 litres/100km for the highway run.

2.0-litre, 274hp, 365Nm

Sending power to the Sonata 2.0T’s front wheels is Hyundai’s in-house developed 6-speed torque converter auto gearbox, which is designed to be maintenance free for at least 300,000km, or as long as the vehicle’s life under normal use. A manual overriding feature is included for the 2.0T, which can be activated by using either the gear lever or paddle-shifters.

Joining the 2.0T in American showrooms later this year is the Sonata Hybrid, which mates the 2.4-litre naturally aspirated Theta-II GDI engine with a 30kW (40hp) electric motor. Unlike most hybrids which feature CVTs, the Sonata Hybrid utilizes the same 6-speed auto as the 2.0T, but with its torque converter replaced by an electric motor and a high-efficiency oil pump. The whole system is lined up in what Hyundai calls the Hybrid Blue Drive architecture.

Hyundai Sonata Hybrid

Running on the Atkinson combustion cycle, the 2.4-litre engine produces 169hp @ 6,000rpm and 212Nm @ 4,500rpm. The electric motor is rated at 40hp, and has 204Nm @ 0 – 1,400rpm. This endows the Sonata Hybrid with a combined output of 209hp @ 6,000rpm and combined torque of 264Nm. Arranged in full parallel architecture, the Hybrid Blue Drive system can run either on all-electric mode or parallel drive mode.

Power from Hyundai’s proprietary Hybrid Blue Drive system

The Sonata’s hybrid system stores its electrical charge in a 270V lithium polymer rechargeable battery (5.3Ah / 270V). Utilizing a polymer gel in place of liquid as the electrolyte, it is said to possess the advantage of allowing for lighter and more compact packaging being about 20% smaller than a lithium-ion battery pack. Hyundai further claims that this battery heats up less readily than nickel-metal hydride or lithium-ion batteries, being maitainence free for at least 10 years or 240,000km in all weather conditions.


Tuesday, January 26th, 2010


The Continental Automotive Group has recently announced a collaboration with the Schaeffler Group for the series production of a new generation of petrol engine turbochargers. Developed by the Engine Systems Business Unit of Continental’s Powertrain Division, the new charger is set to commence production in 2011, with plans to reach an annual production capacity of 2 million units by 2014. It is designed to allow for fully automated assembly, which Continental claims to offer advantages in terms of production quality and cost.


“This collaboration is the result of Continental’s successful search for a strong partner to complete the final development phase and put the turbocharger into series production. It means we will be profiting from Schaeffler’s extensive mechanical expertise”, explained Dr. Peter Gutzmer, head of the aforementioned Engine Systems Business Unit.

The scope of collaboration between the two parties are being revealed as such: Continental shall be responsible for integrating the turbocharger into the vehicle manufacturers’ engine systems, and for application development, product engineering, purchasing, sales and quality, whereas Schaeffler will provide support in the final development phase and will assume full responsibility for industrialization.

Revealed details of the turbocharger specify a 38mm-diameter turbine designed to spin at speeds up to 240,000 rpm. Such specification levels calls for a high level of fit and finish of the various moving parts, and Continental has expressed its confidence in that the Schaeffler Group’s possess sufficient technical prowess to meet these demands.


Schaeffler’s site at Lahr, Germany, shall serve as the ‘Centre of Excellence’ for the process development and the transfer of know-how to other production sites. The Schaeffler Group’s mechanical engineering department will be tasked to design the assembly line and production facilities. Additionally, Continental also plans to further leverage on the Schaeffler Group’s massive worldwide presence to ensure speedy response to orders.

With European manufacturers increasingly favouring forced induction over large displacement, Continental’s development of this new turbocharger certainly couldn’t be timelier. According to Dr. Gutzmer “turbocharging gasoline engines is becoming ever more important since it is the only way to achieve the downsizing of engines that is essential to the reduction of fuel consumption.”


Continental’s maiden attempt at developing a turbo was completed in a record time of three years, with work being spread out between the company’s two sites at Grünstadt in Rhineland-Palatinate and Regensburg in Bavaria. The turbo is designed for assembly along a fully automated single axis production line, a setup which Continental claims to simultaneously deliver lower defect rates, cost benefits and increased volume. It is also further claimed to be vastly scalable and easily adaptable for various engine

Compressor Flow Maps and Calculations

There seems to be a lot of confusion about which turbocharger to choose for which application.  These are some notes and calculations for the MR2 Turbo and which maps I thinkare best for this 2.0 liter engine.  If anything is wrong here, please let me know, and I will make the corrections.

The Compressor

The turbocharger compressors that I will be comparing are the TD06 20G compressor from Mitsubishi that comes with a couple of the Greddy kits, the T04E-46, T04E-50, and the T04E-60 trim compressor wheels from Garrett.  This method and formulas was taken from A. Graham Bell’s excellent book, ‘Forced Induction Performance Tuning’.
First we need to calculate the engine air flow rate (CFM).  The formula for this is:

CFM = L x RPM x VE x Pr

Where L = engine capacity in liters
RPM = maximum engine speed (we’ll adjust this later)
VE = engine volumetric efficiency.  From A. Graham Bell’s book Forced Induction Performance Tuning some good values for VE are:
Stock 2-valve = 85%
Stock 4-valve = 90%
Street modified = 93%
Competition = 105%
Pr = pressure ratio

To calculate the pressure ratio you need to know what boost pressure you want to run and then plug that into the following formula:

Pr = 14.7 + Boost

So – let’s plug in some numbers and then apply them to the compressor maps.  Say we want to run 18psi of boost.  The pressure ratio comes out to be (14.7 + 18) / 14.7 = 2.22
Now lets calculate airflow.  I think it’s best to calculate airflow at at least two different RPM points.  For our example, let’s say we want to have full boost by half of max RPM.  Redline on the MR2 is 7200RPM.  So we’ll calculate airflow for 3600RPM and 7200RPM, and then see which map works out best for these values.  We’ll choose 90% for volumetric efficiency (VE).
For 7200RPM:
CFM = (2.0 x 7200 x 90 x 2.22) / 5660 = 508.32 or 35.6lb/min.  To convert this value to lb/min take CFM and divide by 14.27.
For 3600RPM:
CFM = (2.0 x 3600 x 90 x 2.22) / 5660 = 254.1 or 17.8 lb/min.  As a side note, since half the RPM will result in half the airflow, 254.1 is indeed half of 508.32

Check out the new CFM calculator. It will generate a table with varying RPM given boost, volumetric efficicency, max engine RPM, and engine size.

Now we can look at some compressor maps and see where these points fall.  Let’s take a look at the TD06 – 20g compressor map first.

We need to plot our two points on this map:

From these two points (where the above red lines intersect), this compressor looks like a great fit.  According to the compressor map it can make 18psi by 3600RPM, and at 7200RPM it is in the 76% efficiency ‘island’.  The higher the efficiency island the lower the outlet temperature of the compressed air, and hence the more power you can make.  This map also includes compressor RPM as denoted by the numbers on the graph 55000rpm, 75000rpm and so on.  At 7200 engine RPM, and making 18psi of boost, the compressor RPM is between 105,000 and 120,000RPM.  This means that the compressor is capable of supplying this type of spool up, but only when matched with a correct sized turbine for your application.  See ‘The Turbine Side‘ below.

There is yet another item we can determine from the compressor map.  We want to make sure that the turbocharger selected will not operate to the left of the ‘surge line’.  The above graph does not specify a surge line, but it is to the left of any point within the largest island on the graph.  Check out the T04E-46 and 50 trim maps below, they include a surge line on the graph.  A good approximate method for checking to be sure we are away from the surge line, is to plot one more point on the compressor map.  This is 20% airflow at a pressure ratio of 1.0.  Then connect that point with the 3600RPM point.

20% airflow, in our example is 101.6CFM or 7.12lb/min.  Plotting this point and connecting the dots:

Great!  The line plotted from 20% max airflow to our 3600RPM point falls to the right of the surge line.  If this line fell to the left at any point, this compressor would not be a good choice.  If the turbocharger operates to the left of the surge line, the compressor will be unstable, and will eventually damage the compressor.  From this, the TD06-20G compressor is a wonderful fit for the MR2 turbo.  Now that we have these numbers, we can plot them on other compressor maps.

For the T04E-46 trim compressor map, we need the values in lb/min.
At 7200 RPM we have 35.6lb/min.
At 3600RPM we have 17.8lb/min.
20% max airflow is 7.12lb/min.

Plotting our points results in:

Here at 18psi of boost and 7200RPM we are at about 73% efficiency.  This turbo will also make 18psi by 3600RPM, and we are very safe from surge.  Looking at this map, it is clear that this compressor is smaller than the TD06-20G and will spool faster.  Just for fun, we can see where on this plot we will be at 25psi of boost.
Pr = (14.7 + 25) / 14.7 = 2.70
CFM = (2 x 7200RPM x 90 x 2.70) / 5660 =  618 or 43.3lb/min.
Valid intersections are denoted by arrows.  Plotting this point for the T04E-46

Whoops! – Off the graph.  So we know that this compressor and the MR2′s 2.0 liter engine cannot run 25psi at 7200RPM.  Doing the same for the TD06-20g compressor:

This compressor can produce 25psi with the 2.0 liter engine at an efficiency of  73%.  Looks like 25psi, at 7200RPM is about all this compressor will do.  Keep in mind, that more boost can be made at lower RPMs, but it will start to drop off as the RPMs rise.  The TD06-20g should be able to hold 25psi to redline, but can certainly make more boost at lower RPMs.

Having fun?  I sure am.  How about the T04E-50 trim compressor (my favorite).

Looks like we cannot make 18psi by 3600RPM with this compressor, so it is going to have slightly more lag than the above two compressors.  At 7200RPM, we are just out of the 78% efficiency island, and with room to spare for more boost.  So how do we make sure that we are not to the left of the surge line?  If you draw a line from 20% airflow (7.12lb/min) to the 3600RPM point (17.8lb/min), the line is to the right of the surge line right up until the intersection.  The method for determining if you are to the right of the surge line is an approximate one, and suffice it to say, will not work if the compressor doesn’t make full boost by half of redline as the method prescribes.  That said, given this compressors record, it does not operate in surge with the 2.0 liter MR2 engine.  An explanation of this is beyond the scope here.  Surge usually can be noticed by a pop or backfire out of the compressor inlet.
Plotting 25psi:

This compressor has room to spare, even at 25psi of boost and 7200RPM it is on the 76% island!  So how far can we go?  We’ll try 29psi of boost.
Pr = (14.7 + 29) / 14.7 = 2.97
CFM at 7200RPM = (2.0 x 7200 x 90 x 3.08) / 5600 = 680.6CFM or 47.6lb/min

Just makes it!  Again, keep in mind that more boost can be made at lower RPMs, but it will just start to drop off to about 29psi as the RPMs rise.

How about that 60 trim Garrett compressor.

Clearly there is more lag with this compressor, but it is over 78% efficient at 7200RPM and 18psi of boost!  Again, surge is a consideration, and from word of mouth from those using this compressor, it doesn’t seem to exhibit surge problems.  That said, I have not tried it myself.

Makes 25psi at 7200RPM – still at 75% efficiency.  
Here is an interesting one, this compressor, despite being larger, cannot make the 29psi that the 50 trim can.  The graph doesn’t even extend to a pressure ratio of 3.0.  At boost levels of around 18-25psi, however, it is extremely efficient and hence will make more power at those boost levels.

Great resource for compressor maps.

The Turbine Side

The compressor is only half the story for turbochargers – the other half is the turbine side.  Important numbers to consider are the A/R ratio on the turbine side, and the exducer bore diameter.  Exducer bore can be seen in the following figure.

Some general numbers for exducer bore are:
200HP – exducer bore between 41mm and 51mm
300HP – exducer bore between 52mm and 60mm.
400HP – exducer bore between 61mm and 70mm
500HP – exducer bore between 67mm and 78mm

A/R is the real important dimension for judging a turbines potential.  It is determined by dividing the area of the turbine nozzle A by the radius R from the center of the turbine axle to the center of the housing throat.

There doesn’t seem to be a very good way to find out what A/R is best for your particular application.  Usually one must resort to other’s experience. A small A/R turbine housing will make more boost at lower engine RPM at the expense of reduced maximum power at high RPMs because of exhaust restriction.  Consequently a larger A/R will take longer to spool, but make more power at high RPMs.  For example (these are for example only!), a 0.63A/R may make 12psi of boost by 2500RPM, a 0.82A/R may make the same 12psi by 3500RPM, and a 1.06A/R may take as high as 5000RPM.
The above two diagrams were pulled from ‘Forced Induction Performance Tuning’.

Some Comments/Opinions

Since this is the internet and I can write whatever I want….

I’ve noticed that many turbo kits have been released to the aftermarket recently.  This is really great stuff.  However sometimes claims are made about turbochargers and kits put together using a compressors that no one knows about, and for which no maps are available.  If you come across a kit that has wonderful claims about power production, but is using a compressor that you have not heard about and do not have a map for, ask them for the compressor map.  Do the calculations yourself and plot them on the map before plunking down your cash.  It seems that some compressors are used just because somebody told someone else that it was a really great fit.  It’s not that hard to find out, if you have the map.  If the map is not available, or the map sent to you looks suspect, I would forget about it.  Keep in mind that if the company/vendor/whomever building the kit doesn’t have the map, how could they determine that it was a good fit for your application!


Turbochargers Explained

The turbocharger is a most excellent device that I love dearly.  It is a form of supercharger that forces additional air, under pressure, into the engine so that additional fuel can be added to create more engine power.  Whereas a supercharger is driven off of the engine crank, typically with a drive belt, the turbocharger has a ‘turbine’ section.  The turbine sits in the exhaust path very close to the head, and hence very close to the combustion chambers.  It is driven by the hot exhaust gases.  One would think that it would be the flow of high pressure air that spins the turbine, but it is also the significant amount of heat that drives the turbine.  If you were to measure the temperature of the exhaust gas before and after the turbocharger, you would see a significant temperature drop.  This heat would otherwise be wasted out the exhaust pipe, but on a turbo engine, it is more fully utilized to create more engine power.  It is for this reason, that turbochargers really came into use during the first gas crisis in the 1970′s.

A turbocharger is actually a mechanically simple device – there is only one moving part, and four connections.  The turbine is directly attached to the compressor via a shared shaft, and rides on an oil bearing.  Both the turbine and compressor sides of the turbo have an inlet and outlet.  The turbocharger assembly is bolted to the exhaust manifold or cast with the exhaust manifold as one piece.  This is the turbine inlet, connected to the exhaust manifold so that hot exhaust gases will be forced through it.  The compressor inlet is connected to a fresh air supply through an air filter.  The compressor outlet, where the nice high pressure air is produced is connected to either the engine intake, or an intercooler.  The intercooler is simply a heat exchanger(radiator) to cool the high pressure air before it enters the engine.  Cooler air is more dense, and hence contains more oxygen allowing more fuel to be introduced creating a bigger bang and more horsepower.  The cooler charge can also reduce the chance of detonation (which is bad, and the bane of my existence).  The outlet of the turbine section is connected to the exhaust pipe through what is called a down pipe.


Turbochargers were first used in aircraft engines in the 1930s.  The turbos in these engines were primarily designed so that the aircrafts could fly at higher altitudes.  The higher you go in the atmosphere the lower the air pressure.  On a normally aspirated engine, when the intake valves open, the best you can hope for is that the pressure inside the combustion chamber will equal the pressure of the outside air.  It never does since the intake valves are only open for a very short time.  This is called volumetric efficiency.  Turbochargers can significantly increase this by forcing air into the engine when the intake valves are open.  This allowed the World War II planes to fly higher.  Cool planes like the B-17 flying fortress used turbo engines.

GM was the first manufacturer to use turbochargers in automobile engines.  Go GM!  This was in the 1962 ‘Y-Body Oldsmobile Cutlass’ and the legendary Chevrolet Corvair shown below.

This car was revolutionary.  It was mid engined!  Really!  Is utilized a flat six (boxer, 180 degree opposed cylinders) turbocharged engine.  You can see the turbocharger in the picture below at the top back of the engine.  It’s hard to miss with the giant red ‘Turbocharged – 150HP’ sticker on it.

It wasn’t without fault, but it was only 1962.  The engine used what is called a draw through carburetor.  You can see above the inlet to the carburetor is the thing with the sticker on it.  Air came in, was mixed with fuel in the carburetor, and then sucked into the turbocharger (fuel and air together!), compressed and pushed into the combustion chambers.  Yeah, pretty insane.  It’s gets better.  There was absolutely no control system in place to adjust the speed of the turbocharger, it was simply sized to not be able to produce enough boost to blow the engine.  This caused a lot of reliability problems with the turbo.  In addition, with fuel constantly blasting away at the compressor wheel (which can spin in the well over 60,000RPM), it would start to erode, go out of balance, and shake itself to pieces.  These pieces of metal would find their way into the combustion chamber destroying the engine.  Ouch!

Porsche to the Rescue

Thank goodness for those Germans.  In 1972 (10 years later) they released the very first Porsche 911 Turbo, and the first production car to feature a wastegate.  The world was forever changed for the better!

1972 911 Turbo

The wastegate was key to controlling the speed of the turbocharger.  Remember how the turbocharger sits in the exhaust and is driven by the exhaust gases?  The wastegate is simply a valve that can open to bypass exhaust gases around the turbine to slow the turbcharger down so that it doesn’t produce too much boost or exceed the design limits of the bearings in the turbocharger (also referred to as overspeed).  In modern day turbochargers the wastegate is typically internal to the assembly.

The wastegate actuator is the golden cylinder with the rod attached.  When air pressure is applied to the cylinder from the turbocharger’s compressor outlet, the rod moves and opens the wastegate.  The rod opens the two valves in the turbo assembly below, which shows the turbine, or hot side, of the turbocharger.

This allows the hot exhaust gases to go through those two openings and out the exhaust instead of forcing the exhaust gases through the turbine.  Mechanically this was great.  Boost pressure from the turbocharger caused the cylinder in the actuator to move and open the wastegate, lowering boost pressure.  When the boost pressure dropped, the actuator would start to close the wastegate forcing more exhaust gas through the turbine, increasing boost.  It was a closed loop, 100% mechanical solution.  I love those.  Later, engine computers took control (very tight control) of the wastegate so that boost could be adjusted under all operating conditions.  I love that even more.

The 911 turbo’s engine was not without fault either, even though it was made by Porsche!  The materials used in the turbocharger were heavy, and this gave rise to the now dreaded turbo lag.  This is the time that it takes the turbine to spin up so that the compressor can make useful boost pressure.  What happened with the 911, rear drive, rear engine sports car was you were coming around a turn, off the gas.  Then in mid corner you start to come back on the gas.  The engine doesn’t produce much power because there is no boost pressure available yet.  The driver then asks for more power by jamming his right foot to the floor.  Suddenly the turbine picks up speed very fast, producing lots of boost pressure.  With the additional air, the carburetor mixes in lots more fuel, and a huge amount of engine power is suddenly available to the rear wheels.  This causes them to spin (especially those balloon tires of the 70s!), and being mid corner causes the car to oversteer (fish tail) and spin out, crash, burn, death, mayhem, mass hysteria, dogs and cats sleeping together etc..

This is the trade off with standard turbochargers.  You can make them very small and light and they will produce boost pressure at very low engine RPMs, however at high engine speeds (RPMs) the can’t keep up and boost pressure drops.  In addition the small size restricts the exhaust flow reducing top end power.  The other option is to make the turbo larger, where you can achieve excellent top end power, but reduce the amount of low end torque the engine can produce.

Present Day Technology

Today turbochargers are again entering the automobile scene because of fuel costs.  It’s a wonderful thing though.  Turbochargers are great!  New, very light weight materials are being used, and much much smaller turbochargers are being developed to not only eliminate turbo lag, but make engines produce huge amounts of torque at ludicrously low engine speeds.  Combining turbochargers with other technology such as variable valve timing and lift, variable size intake manifolds, and direct fuel injection, engines are being produced that are an absolute delight!

Variable geometry turbochargers are now being used on some current cars.  They were first used by Chrysler in 1989 on the Shleby CSX-VNT model, but since then not used until the 2007 Porsche 911 turbo, a whopping  18 years later!  History sort of repeating itself.

Variable geometry turbochargers adjust ‘vanes’ in the exhaust/turbine section of the turbo to not only control boost pressure (no wastegate required), but allow a best of both worlds scenario.  When these vanes are nearly closed, the exhaust is forced through them, and consequently the speed of the exhaust air is increased.  Similar to holding your thumb over the end of a garden hose.  This causes the turbine to pick up speed rapidly, greatly enhancing low end torque.  At high engine speeds, the vanes open up, causing less of an exhaust restriction enabling excellent top end power.

Here the vanes are in their nearly closed position.  This would be used at low engine speed to quickly speed up the turbine at the expense of more exhaust restriction.  Also notice that the vanes cause the exhaust flow to ‘hit’ the turbine at 90 degrees, further speeding up the turbine.


At high engine speed the vanes open up and allow much more exhaust flow through the turbine, enhancing top end power.


When the Dodge ShelbyCSX-VNT (what a mouthful!) came out it really was a revolutionary engine setup.  It produced 178HP from the 2.2 liter four cylinder engine, but 210 ft-lbs of torque at an unheard of 2100RPM thanks to the hot VGT turbocharger.  Production of this car was limited to just 500 units.  At mentioned above, it wasn’t until 2007 when Porsche announced the new 911 turbo that the world would see VGT turbos in use again in production gasoline engined cars.  The engine in the 911 is a twin VGT turbocharged 3.6 liter flat six cylinder engine with 480HP and an insane 502ft-lbs of torque at only 1950RPM.  Incredible!

Turbocharger Lag

This text hopes to describe what exactly turbocharger lag is, why it is getting such a bad reputation, and why that bad reputation is usually unfounded.

Turbocharger lag is, for practical purposes, the time it takes the turbocharger to spin up and make useable boost pressure after you plant your right foot.  The turbocharger is driven by hot exhaust gases passing through the turbine side of the turbocharger assembly.  Before the turbo can make positive boost pressure, that is pressure above atmospheric pressure, there must be enough exhaust energy to spin the turbine.  The only way there can be a substantial amount of hot, high velocity exhaust gases passing through the turbine, is if the engine is under a significant load.  Once that occurs boost pressure is created, more fuel can be injected, and hence more hot exhaust gases produced to spin the turbo even faster.  What a wonderful cycle!

So why am I saying that this nonsense about turbocharger lag is unfounded?  Well, in the old days of turbochargers, such as some of the first Porsche 911 turbos, large turbochargers (by today’s standards) were used.  These turbos contained heavier metals and hence took more energy to spin up.   So, when test drivers got on the gas there was a significant delay before (BAM!) loads of power was produced.  This was deemed undesirable and given the name turbo lag.  These engines also had poor low end torque, because the turbo would not spool up to create useable boost until higher RPMs were reached. When magazine articles were written about cars using turbochargers, lag was ‘driven home’ to the engine designers as a very bad thing.  So, back to the drawing board they went, and they came up with the idea of using much smaller turbochargers and eventually using much lighter materials to help eliminate lag.  In my opinion they succeeded greatly.  For whatever reason magazine editors, when they see that an engine is turbocharged, have to bring up lag as a negative issue, even if, in reality, it isn’t at all.

Here comes my rant.  A while back I read an article about the 2002 Audi S4.  This car comes with a wonderful 5 valve per cylinder twin turbocharged, intercooled, 2.7 liter V6 engine.  It produces 250HP at 5800RPM, and 256lb-ft at 1850RPM. Now that’s what I call low end torque!  That’s just off idle!  Audi accomplished this by using two small sized quick spooling turbochargers.  The down side in doing this is that top end power can suffer because of the smaller turbo placing a restriction on the exhaust.  In any case, the magazine article complained about turbo lag with this engine!  What turbo lag!?  It produces peak torque at 1850RPM!  So, for the next year (2003), Audi ditched the wonderful twin turbo V6 and used a 4.2 liter V8 engine.  This engine produces 340HP at 7200RPM, and 302lb-ft at 3500RPM.  The same magazine praised this engine for its low end torque.  While this engine is clearly more powerful, it cannot match the turbo engine for low end torque.  They’re just giving turbo engines a bad name!  Shame on them!

Unfortunately most car manufacturers that are using turbo engines are using very small turbochargers to get away from the ‘dreaded lag’.  As mentioned earlier, this leads to excellent low end torque, but limits top end horsepower.  Thankfully some are not giving in.  Mitsubishi’s Evo VIII MR uses a 2.0 liter engine with 280HP at 6500RPM and 295lb-ft at 3500RPM.  This is almost the same amount of torque as Audi’s 4.2 liter V8 and at the same RPM!  Hurray for turbos!  This engine is, however, highly criticized for its turbo lag.  While it does have some lag, it is very marginal.  In driving the car, boost pressure basically follows what your right foot does.  I would say that this engine has minimal lag, but noticeable at very low RPMs.  And there you have it – driving around in top gear at 30MPH wondering where the engine power is.  For goodness sakes downshift!  It is true that a turbo car must be driven differently than a normally aspirated car, but for the same size engine, you’ll never get the power out that you can with a forced induction engine – particularly turbo engines.  So does all this talk of turbo lag make any sense?  You could have a 2.0 liter engine with 150HP and 130lb-ft or you could have a turbo 2.0 liter with 280HP, and 295lb-ft, but then you must put up with turbo lag, and gosh, who wants that?

And then there is Honda.  Wow – what to say here!  They take a 2.0 liter engine, spin it to high heaven and get excellent power out of it.  Magazines, then criticize it because you have to rev it so high, but thank goodness it doesn’t have turbo lag!  So here are your choices:

  • Low power, low torque normally aspirated 2.0 liter engine.
  • High power, high revving, low torque 2.0 liter engine.
  • High power, high torque (at a relatively low RPM), 2.0 liter turbo engine.

I know where my vote is going!

In my opinion peak torque should be achieved at roughly half the maximum engine RPM.  So, for example, if redline is 6000RPM, peak torque should be around 3000RPM.  I feel this leads to a well performing fun to drive car.  Audi took it a little too far, in my opinion, with a peak torque at 1850RPM – and they still got hammered for turbo lag. You’ll never see a normally aspirated gasoline engine (within reason) with peak torque so low.

I was worried there for a little while with respect to turbo engines, but am very happy to see cars today such as the EVO VIII, STi, WRX, Volvo cars, Saab cars, and SRT-4 using turbocharged power plants.  Lag is over rated!

My turbo is leaking oil, is it time for a replacement?

A common complaint, my turbo is leaking oil. Time for a replacement right? Not always! A small amount of oil in the turbocharger is present from when the vehicle is brand new and is not always an issue with your turbocharger. We explain below:

Possible Cause: Engine Breather. 

The turbocharger pulls an oil vapour from the crank case ventilator into the air intake tube between the air cleaner and the turbocharger.  When this vapour cools and/or when it goes through the turbocharger the oil content is  seperated and reduced back to a liquid which leaves a small amount of oil residue on the compressor side (cold side) of the turbocharger.

My turbo is leaking oil

It is the same concept as a boiling kettle. When the steam vapour cools it is reduced to water.

This is what is happening with your oil vapour and as a result you are seeing oil residue on your turbocharger. This small amount of oil residue is present right from the time that the vehicle is brand new. It is usually not noticed until the vehicle becomes older and the rubber connections and hoses become a little bit harder, the oil then begins to weep around the connections.

But it looks like a lot of oil! 

It is often only a tablespoon of oil but because of the nature of oil it can look like a lot.
If the turbo was genuinely faulty and was using as much oil as it appears this would be evident on the dip stick. If your vehicle is not using excessive amounts of oil then it is most likely that there is no cause for concern with your turbocharger.

If you are still unsure as to whether your turbo might be faulty you can contact us here and we would be happy to go through it with you.

How Do I know if My Turbo has Failed?


Unlike a baby, a turbocharger does not require much special attention and inspection is limited to a few periodic checks. If an engine is not operating properly the following should be inspected prior to assuming that the turbocharger is at fault:

  • Fluid Levels
  • Any air an exhaust restrictions
  • Split pressure hoses or leaking gaskets (eg. manifold to turbo, EGR)
  • Sensors such as Air Mass Sensor or Turbo Boost Sensor
  • Fuel system (eg. Worn Fuel pump)

Many times, fully functioning turbochargers are replaced due to misdiagnosis.

Well then …..What are the signs that my turbocharger might not be operating correctly?

Lack of Acceleration

Turbo lag is natural. It is the spool up time required from when you put your foot down on the accelerator and when the boost pressure comes up to give you the power. As the blades slow in rotation the compression will lessen and therefore result in low performance. Should your turbocharger be showing signs of these symptoms it should be inspected immediately as the turbo can restrict airflow to the cylinders in your engine.

Lack of Performance/Power

Turbo boost gauges can indicate your boost pressure. If a decrease in boost pressure occurs, it may be a problem with your turbocharger or could still be an issue on engine. When turbo boost pressure is reduced airflow through the turbocharger is then restricted. Reduced air pressure could be a result of:

  • Turbocharger shaft, compressor wheel or vanes are damaged
  • The wastegate bypass port is stuck open
  • The vacuum actuator is either faulty or there is an issue with vacuum supply to the actuator (if the turbo is variable geometry).
  • Possible Manifold leak

If the vehicle has an ECU with an electronically controlled fuel injection system, check for possible fault codes using a scan diagnostic tool and/or air flow parameters to ensure lack of boost isn’t an on engine issue (eg. problems with the Air Mass Sensor)

Blue Smoke

Blue smoke generally means the engine is burning excessive oil. If your turbocharger fails oil can enter the air intake and cylinders and therefore change the exhaust colour and smell. Oil passing on the turbine end of the turbo is a result of either ring wear or wear to the ring groove and seating area.

PLEASE NOTE: A small amount of oil showing in the compressor cover (intake) of a turbocharger is common and is not cause for alarm as it is pulled out of the engine through the engine breather pipe as a vapour. The vapour is redirected through the turbocharger and once cooled turns back to oil.

So …… What can I do I do if my vehicle is showing these signs? 

If you are experiencing any of the above problems with your vehicle a few quick checks on vehicle can help determine if the turbocharger is at fault or if the problem lies somewhere else on the vehicle.

  • Check over the first three points mentioned above with regards to filters/air restrictions, fluid levels and hose/gasket leaks.
  • Remove the air inlet piping connecting to the turbo where possible and grab hold of the shaft. Up and down movement of the shaft when the turbocharger is mounted to the exhaust manifold  is acceptable to a certain degree, due to the bearings floating in a film of oil which centralises oil pressure. There should be no axial play (otherwise known as end float). End float is the end to end movement of the shaft from front housing to back housing. If there is end float in the turbocharger the turbo will need to be removed for overhaul or replacement. If there is no excessive play in the turbocharger (or you are unsure) it is best to call our turbo repair shop.


Turbocharger Parts Explained

Turbocharger Parts Explained