loonyrobert3

wat is better and faster a turbocharger or a supercharger?
thanks
robert

007

definitely the turbo... but its more expensive and requires extensive modification. Do a search this has been discussed in depth before.

lexlyf

As stated before, this has been a long debated topic, with a multitude of useful information being put on display. In a nutshell, turbo or S/C, they are basically 2 different methods of forced induction & both have their trade offs. What you should really ask yourself is how much rear wheel horsepower are you looking for & which manufacturer's products are you intending to use as a base of comparison?

After selecting the above, then question what after effects are you willing or not willing to put up with? For example are you intending to set up your GS so that you can install & forget or do you want the ability to "adjust" your boost (or psi) settings from the cockpit? How do you feel about the possible and unavoidable whine of a S/C from underneath your "Lexus" hood? After a hard run, do you want to be able to just turn off the motor or can you allow for a proper "cool down" prior to keying off? Can you be patient enough to wait for your car to warn up to normal operating temp before entering boost? Do you care abour tapping your oil pan for possible oil supply and return lines? How is the car being used?........as a heavy street performer, drag duty, autocross, just for your personal leisure?

I could go on and on, but as you can see there are a lot of items that need to be addressed prior to selecting your form of forced induction. Having assisted on the front lines of R&D and personally installing both Supercharging and turbo setups on GS300s/400s/430s, IS300s,etc., I will tell you that as far as power is concerned you can make it either way, then again I am only specifically reffereing to SRT performance products.


I hope that this helps and was in no way an attempt to confuse or complicate matters.

Marken Smith, aka “Lexlyf”
Marketing Director
SWIFT RACING TECHNOLOGIES "
Performance without Compromise"

’92 SC300- “My Daily Lex Beater”- Plans to F/I again later this year
’98 GS300- The original “SWIFTLY!!!”
Watch for it this summer by SRT YOU HAVE BEEN PUT ON NOTICE!!!

fireballs gs400

still interested in the headlight? Also you all have any sc kits left over? any other speed parts that have been used, interested in a s/c. just had some good fortune come my way (for once!) could be interested...can there be some conviencing that i should buy from you instead of rmm?

benzz'sIS

lexlyf, will turbo stress more on the engine when the car is driven more on local city streets where you always stop and go? Is supercharger a more reliable setup for local city driven car? What i meant is that i seldom go highway cos i live near places. Thanks.

kodai

Here is some detail on this topic:

What Is A Turbo charger?
A turbo charger is basically a device that uses exhaust gasses produced by the engine to blow air back into the engine. The additional air is supplemented with fuel by the ECU (engine control unit). This causes the engine to produce much more power since it is being supplied with more air and fuel than it possibly could without it. A naturally aspirated engine (non-turbo, standard engine), or "N/A" engine, has to "suck" air through the intake manifolds, throttle body, air filter, etc. With this setup, the most air pressure that can enter the combustion chamber of the engine is a bit less than the current atmospheric pressure. With the turbo, air is being blown into the chamber with positive pressure so that much more air and fuel can enter. A typical turbo charged engine will generate 7 to 10 psi of maximum positive pressure, or "boost". The turbo charger, or "turbo", is mounted directly to the exhaust manifold, where exhaust gasses pass over a turbine impeller that is attached to a short shaft. On the other side of this shaft is a compressor turbine, which pulls outside air in through the air filter and blows it into the intake manifold. So basically, the energy from the expelled exhaust gasses, which would normally be wasted on a N/A engine, is being used to pump air back into the engine.
The shaft is supported by a bearing housing that is lubricated and cooled by an oil line from the engine. Since engine exhaust has such high temperatures, the exhaust side of the turbo can reach thousands of degrees F. This is why it is so critical that the engine oil be changed religiously (every 3,000 miles), because old oil can burn and leave deposits in oil lines and housings, called "coke". Coking can be virtually eliminated by using a synthetic oil and changing it frequently (every 6,000 miles). Some turbos feature an additional passage for a coolant line, to keep the bearing housing cool. This did little to keep temperatures down while running, but it had a huge effect after the engine was shut off. Without the coolant passage, the oil would drain when the engine was shut off and the turbo bearing housing would reach incredibly high temperatures from the heat transferring out of the exhaust manifold. This took its toll on the life of the bearings. The presence of the water keeps the housing cool.

When the engine has been idling or at low speed for a while, the turbo is not spinning or is spinning very slowly because there is very little exhaust leaving the engine. When the throttle is opened, the engine produces more exhaust, which spins the turbo faster. A faster spinning turbo means more air and fuel is being blown into the engine, therefore even more exhaust is being produced, which makes the turbo spin even faster and so on. This cycle is known as turbo "spool-up", which feels like a sudden surge in engine power and appears on your boost gauge as a sudden increase in pressure. The time before the surge, when the turbo is spooling up but the engine doesn't have much power yet, is called turbo lag. A large turbo charger can produce more air flow and pressure, but will have more lag because of its increased size. A small turbo charger will have a smaller amount of lag, but will not be able to move as much air. This is explained in more detail is the sections below.

A turbo is made of a exhaust and compressor housings:

The Turbine Housings
The exhaust and compressor housings on turbo chargers use a "scroll" design. For example, the exhaust housing's scroll is where the exhaust gasses enter the housing and are directed at the turbine. It's basically a smooth, tubular chamber that surrounds the turbine with a slot all the way around that acts as a nozzle to direct the exhaust gasses at the turbine. It's called a scroll because it slowly gets smaller in diameter as a goes around the turbine. This pressurizes the gasses, forcing them out of the slot/nozzle at a fast rate. In turbo-terms, the scroll is measured by the cross-sectional area of the scroll's "tube" (A) and the distance from the center of the "tube" to the turbine shaft (R). The values by themselves are not meaningful to the user and for the most part, R does not change much for different housings, but by dividing R into A, you get the A/R ratio. So, the A/R ratio of the exhaust housing refers to the size and shape of the scroll that is cast into the housing. It basically determines how restrictive the housing will be, versus how quickly the turbine will spin up. A lower A/R ratio (smaller scroll area, A) results in a more restrictive housing. This restriction speeds up the exhaust gasses and increases the amount that the gasses will expand. It's the speed and expansion of the gasses that causes the turbine to spin. So with a low A/R ratio, the turbine will spin up quicker, but as engine output and rpms increase, the restriction of the housing begins to build up too much back pressure on the engine, which reduces performance. A good rule of thumb for when there is too much back pressure is when the pressure in the exhaust manifold is more the half of the pressure in the cylinder. So basically, a larger A/R ratio will improve your engine's top end, while losing some mid range power and increasing turbo lag. A smaller A/R ratio will help the bottom and mid-range, but may effect the top end.
On the compressor side, the housing also features a scroll design, but it has the opposite function. The air leaving the compressor turbine has a lot of speed, but not much pressure. The scroll on the compressor housing starts small and gets larger as it approaches the compressor outlet. This collects the air and builds up air pressure. So, the compressor housing is designed to convert the speed-energy of the air coming off of the compressor turbine into pressure-energy, which is much more useful to an engine.

kodai

What is a supercharger ?

A supercharger is essentially an air pump, it allows a small engine to take in a similar volume of air (and fuel) as a larger engine. The only reason a large engine makes more power is that it converts a larger volume of air and fuel into energy.

A supercharged small engine achieves the same, but only when required, when under load or full throttle, not during normal driving or cruising.

How does a supercharger improve power output ?

The principal requirement to produce power in the internal combustion engine is a precise mixture of clean air and fuel. An engine's horsepower and torque output is directly proportional to the rate at which this mixture enters the combustion chamber. In other words, the density (or weight ) of the charge produces power, regardless of pressure, -an engine responds to density.

Therefore the more mixture that can be crammed into the cylinders, the greater the potential horsepower output will be.

What is an internal compression supercharger ?

There are essentially two types of supercharger, external compression and internal compression.

External compression superchargers (Roots type, Eaton etc.) are just an air pump and actual compression of the charge takes place as it is pumped into the cylinders and then backs up in the inlet manifold.

Internal compression superchargers (Autorotor - using the Lysholm principle) actually compress the charge within the supercharger. This internal compression ratio is the reason the Autorotor supercharger has the highest thermal efficiency of any fixed displacement supercharger in production in the world today.

These units give four primary advantages over all other style superchargers: lowered discharge temperatures higher volumetric efficiency, reduced drive power requirement and greater low rpm boost.

A cooler intake charge equates to a more dense charge = more power.

What difference does Internal Compression make ?

Quite a lot. There are two important parameters which determine how good a compressor (blower) is. One is Volumetric Efficiency , the other is Adiabatic (or overall) Efficiency. The twin screw supercharger is extremely efficient in both areas.

The high thermodynamic performance is due to internal compression of the charge combined with very fine clearances rotor to rotor and casing to rotors.

The effect of this internal compression is to increase the density and therefore the weight of charge per revolution and consequently reducing the temperature rise usually encountered for a given weight of inlet charge.

Internal Compression - What difference does it make in real terms ?

The cooler more dense charge can have the same psi as a less dense charge. An internal compression supercharger making 6 psi boost is going to make more power than an external compression supercharger making seemingly the same 6 psi boost. Altho' the pressure is the same the more dense charge produces more power. Some sources suggest this equates to 1 - 2 psi more boost when compared to external compression superchargers for the same fuel requirement.

The twin-screw supercharger has the inherent ability to produce impressive boost pressures at low engine RPM's. No other supercharger can match the Autorotor in this respect.

What is boost ?

A normally aspirated engine relies on atmospheric pressure (at sea level = 14.7 psi. [pounds per square inch] or 1 bar) to push the inlet charge into the negative pressure (vacuum) area within the cylinders. Boost is the amount of additional pressure created by the supercharger. So if the supercharger makes 6 psi boost the inlet charge is atmospheric pressure plus 6 psi for a total of 20.7psi.

Bear in mind most engines struggle to achieve 70% volumetric efficiency.

With supercharging, when the boost gauge shows 0 the engine is achieving 100%. The difference in driveability must be experienced.

kodai

Sorry one more point,

Turbo's produce power from mid to high end, and Superchargers produce power from low to mid range.
Turbos are not better then Superchargers and same goes the other way as well. It all come down to what you are looking for out of your vehicle for performance.


Sorry to be long winded.......I run into this question every day...Hope it helps...

Leonardo

I'm verry happy with my Toyomoto turbo kit

JBrady

Actually, most aftermarket street superchargers are the centrifugal variety. This type of SC is basically a turbocharger style compressor that is driven off the crankshaft by a pulley and belt system. These types of compressors are dynamic and need considerable speed before producing boost in the engine. The normal boost threshold (the point of first making positive pressure in the manifold) is around 3000rpm. The boost rises to redline at which point maximum boost is seen. Anywhere below redline boost is below maximum. These types of SC are fairly reliable but typically need rebuilding at around 25k miles of use. Some are more durable, some much less.

Most street turbochargers are sized to begin making boost between 2000 and 2500rpm. Turbos control boost with a wastegate and therefore can reach maximum boost fairly quickly and hold it until redline. Because of this (and other efficiency advantages) most turbocharged street cars make more low end, mid range and top end power for a given amount of boost than a SC car.

Now, if you compare a turbocharger to a positive displacement SC like a roots type or lysolm (screw) compressor... the quoted statement is partially correct. These type SC make boost right off idle and hold more or less their maximum boost across the RPM range. Still, turbochargers are more efficient, make more power and are more reliable than superchargers. They are also more expensive to design, build and install.

Turbochargers (on a typical correctly engineered comparison) place more stress on the cooling system than a SC due to the higher pressure between the exhaust valve and the turbine housing. SC place more stress on the front crankshaft bearing and seal area especially on higher boost applications requiring a tight belt.

LexCiting

I have had both a supercharger, and turbos installed on my GS4, and I must say I like the turbos better. Here are some of my personal pros/cons:

Supercharger:
Pros
- More of a linear power boost. The power seems to keep building, and building
- Less modifications to the engine. You can basically disconnect the SC, and keep on going if there ever was a problem. With a turbo, it is too complex to do. (Oil lines, Turbo positions, etc) IMHO
- Less worries. Basically, you have to worry more about external heat with the turbos, than with the SC. That means heat shielding, exhaust wrap, and coolant additives.

Cons
- Less power potential
- Noise. The SC is ALWAYS on. Mine sounded like a jet fighter when I turned the car on.
- Wear and Tear. Some SCs are notorious for breaking. Think about it, it is alway running.

Turbos:
Pros
- More power potential. Just adjust the boost controller, and you have more power.
- More efficient. Turbos use the exhaust to spin, SCs are parasitic
- Reliable. Turbos last longer than SCs without have to adjust the unit.

Cons
- Once you turbo, it is hard to go back to stock compared to a SC. Too complex.
- Problem Potential. You have more to worry about with turbos, as I said before. Including Boost spikes.
- Emissions. Need I say more?

Just my .05