Engine Performance Parts for supercharged performance
A brief guide that explains how to pick the least engine performance parts to improve the performance of your supercharged car.
A lot of times we find ourselves seeking a supercharged car, not only because it has good power from the factory, but also because we expect that a car that has forced induction from the factory is:
1- Better engineered or even over engineered with strengthened blocks, thicker rods, factory cast pistons, upgraded cooling capacity, additional engine oil and transmission oil coolers …etc.
2- Has factory revised engine performance parts, such as a longer duration higher lift camshaft, a factory ported cylinder head, an extrude honed intake or exhaust manifold, more robust ignition system…etc
3- More overall power potential, as manufacturers like to deliver cars that are easy to maintain and will last for a very long time, they usually ship the cars with very conservative boost settings, conservative air fuel ratios, and conservative timing figures to make sure that no matter what condition the car is used in (towing, sand duning, extreme heat, extreme cold ..etc) that under no possible extreme condition will the car lean out, over heat, or fail giving you a healthy margin of safety to work with to increase the car’s performance if you don’t live in an EXTREME climate. Which most of us don’t!
If you are interested in upgrading the performance of your supercharged car using engine performance parts, these are the modifications I would recommend:
1- Performance pulley:
A supercharger performance pulley is either a smaller supercharger snout pulley, or a larger crank pulley, or a kit that includes both. This may also be known as an ODPS (over drive pulley system) in case you need to google search for engine performance part manufacturers later.
The cheapest, most widely available and very effective upgrade for a supercharged car is the pulley upgrade. The pulley on the snout of your supercharger decides the mechanical gearing between your supercharger and your motor. Changing this gearing increases the maximum rpm that your supercharger will reach (which is a function of maximum engine rpm), and thus will increase the maximum amount of boost pressure that your engine will find available for it to create horsepower.
Typical supercharger systems will ship from the factory at a boost setting of 7 to 10psi, whereas the performance pulley will usually extend your supercharger’s working rpms to the maximum safe rpm bringing boost up between 13 and 15psi (depending on the exact setup of your vehicle).
Each psi of boost (from the same charger) is worth 4.5% of your factory horsepower so a jump from 7psi to 15psi can be an increase of 36% of your factory horsepower!
That is quite a horsepower gain for a part that typically costs 300-500 dollars and can be installed over the weekend with basic tools.
Depending on the exact vehicle, a performance pulley may require some supporting modifications. In some cases it may be even sold in ‘kit’ form. These kits will typically include some or all of the following:
1- One stage colder spark plugs, typically copper or iridium.
2- A flash tune for your ECU, a fuel pressure regulator upgrade, or a different MAS/Injector combination.
Again this depends on your exact car specifications, and are needed when the factory ECU is unable to compensate on its own for the increased airflow and performance. This is not the case with about 75% of the cars out there, but it may be with yours so I’m letting you know right now.
2- Performance exhaust system:
Unlike turbochargers, where it is fairly straight forward to find a larger turbocharger in the same family or series of turbochargers that you have on your car, and perform a turbo upgrade; superchargers are typically packaged into the intake manifold of the engine, and have a unique snout and pulley system to connect the supercharger to its drive belt.
What this means is that once you have increased your supercharger gearing using the pulley upgrade system we mentioned earlier that you have run out of ‘boost’ need to find a different way to increase the performance of your motor.
Boost or pressure ratio is a ratio of how much air the supercharger is moving at that rpm divided by the amount of air the engine would breath normally at that rpm
Pressure ratio = Supercharger flow (CFM) / Engine natural aspiration (CFM).
If you look at a supercharger compressor map you will see that at any given supercharger rpm and for every given boost pressure (or pressure ratio) there is a range of flow that the supercharger can positively achieve.
This leads us to a performance opportunity that goes as follows:
“If my supercharger boost is maxed out, and I cannot upgrade to a larger unit like I would a turbocharger, then the only way for me to make more power, is to flow more air (CFM) at the same boost level!”
Here is where upgrading the exhaust system comes in. A typical factory exhaust system with a poorly designed header, a close coupled cat, crush bent small radius piping, a second cat converter, and several mufflers and pre-mufflers can have 5 to 7 psi of back pressure in the exhaust manifold.
In other words, if the exhaust back pressure is 3 psi and the supercharger boost pressure is 15psi, then the total engine boost pressure is only 15-3 = 12psi.
In essence we are making our charger work harder to maintain a psi level, and at that level it is not flowing the maximum amount of CFM that it can flow, because the entire system is choked off at the exhaust side.
Upgrading the complete exhaust system will relieve the engine and supercharger of some 3 to 5 psi of exhaust back pressure which will result in a 14% to 22% power increase. This system would include a well designed header or high flow manifold, a single high flow catalytic converter, a properly chosen pre-muffler resonator, and a single high flow exhaust muffler, all connected using adequate sized mandrel bent piping Having the least number of best producing and high flowing parts in the system will give minimal backpressure allowing the engine to breathe better.
With this, you will make more horse power and at the same time you will see your boost pressure drop somewhat here’s why:
Pressure ratio = Supercharger flow (CFM) / Engine natural aspiration (CFM).
New pressure ratio = Supercharger flow2 / Engine natural aspiration 2.
There is a doubly effect going on here:
1- As the exhaust system is more free flowing, the engine is able to breathe more air now and produce more horsepower (even if there were no supercharger boosting it).
2- This increase in natural aspiration (which is our denominator) makes the new pressure ratio lower because the supercharger is having to work less hard to move the same CFM, and it can’t increase the boost because it is mechanically locked to its gearing relative to the engine RPM.
3- The decrease in boost pressure, moves the supercharger to a higher efficiency point on its compressor map where it can produce even more CFM of flow at the new lower boost pressure, and with less effort, giving us cooler denser air into the engine.
4- The increase in supercharger flow (our numerator) means that the resultant boost pressure increases a bit, but usually is not as high as it was before.
From this sequence of events you can see how upgrading the exhaust system on a supercharged car (and similarly on a turbocharged car) has a double improvement effect on horsepower so long as the supercharger or turbocharger CFM (not boost pressure) portion of the compressor map has not already been maxed out.
Kamikaze headers are designed with 0.25" larger primaries, shorter primaries, and a 2.5" outlet collector for supercharged hondas.
One thing to keep in mind is that headers for supercharged engines would be different in design from a header for the same engine without a supercharger. So if you own a corvette for example, and install a supercharger package, then headers designed for a normally aspirated corvette will not be optimal for your car. Supercharged cars usually perform better with headers with shorter and larger primary tubes. Furthermore, since the supercharged car produces more horsepower (typically 50 to 100% more) then the collector outlet, and exhaust system should also be upsized to match the engine’s exhaust flow demands.
The combination of the two modifications mentioned here can be installed in a 3 day long weekend and can result in an overall gain of 58% horsepower over your stock power figure.
As I said earlier, there may be some supporting modifications needed depending on the exact setup of your car’s ECU and fuel system, however, if I wanted to invest in 20% of the modifications that would give me 80% of the gains, this is where I would put my money FIRST, then comes everything else. Actually, I am more of a high power / low boost junkie than a high power / high boost junkie, and so in that sense I personally would do these modifications the other way around. First I would upgrade my complete exhaust system, making the engine smoother and more efficient, and extending my power rpm range up higher closer to redline and I’d see if that much power increase was satisfactory for me. If not, then I’d go ahead and increase the boost pressure on an already efficient system.
The reason people go for the pulley upgrade first is that it is cheaper to do, and gives higher power gains so therefore it is a bigger bang for your buck quite literally. But I prefer things the other way around.
Related posts:
- Engine Performance Parts for your Range Rover
- Engine perfrmance parts simplified Part 2 engine efficiency
- Engine Performance Parts for your Cayman S
- Engine Performance Parts Simplified Part 3 Boost
- Engine Performance Parts to improve supercharger performance…
Categories: Aftermarket Supercharger Performance, Supercharger Power Parts
supercharger for Audi S5 4.24 litre V8
by alan platt on Oct 5, 2009 at 1:08 pm
http://www.europeancarweb.com/features/epcp_0809_mtm_gt_s5_supercharged/index.html
http://www.mtm-online.de/en/Audi/S5/4-2-l-260-kW-354hp-quattro?FZID=S5257q
MTM offers a kit including :
Performance Exhaust
Supercharger conversion
Remapped to speed…
501 hp!
0-60 4.4 seconds
186mph top speed
by admin on Oct 5, 2009 at 5:01 pm
Thanks for the info, very interesting!
by ben on Nov 17, 2009 at 6:19 am