Supercharger Performance and Engine Performance Parts

Posts Tagged ‘supercharger tuning’

In part 1 of this engine tuning guide , we explored the difficulties associate with altering the target air to fuel ratio on cars equipped with wide-band oxygen sensors and self learning ECU’s

In part 2 we are going to look at three products that offer different ways to solve this problem. All of these product work on the same premise which is:

1- Intercept the Oxygen sensor current or voltage signal (depending on the sensor type) going to the ECU

2- Monitor a set of control signals that tell the piggyback when and If the car goes into a performance state (such as wide open throttle, or a predetermined boost or rpm level)

3- Once car crosses over into this ‘enrichment region’, alter the oxygen sensor signal such that the On Board ECU thinks that the engine is running leaner than required (for example to enrichen up the mixture by 5%, make the ECU think that the current mixture is 5% leaner than the factory target)

4- Over time , the ECU will compensate either directly (through its own feedback control range which is typically +/-15% duty cycle) or through an external fuel controller or piggyback controller to now regulate fuel delivery at a new target air to fuel ratio that is set by our signal interceptor.

5- Check using an external wide-band oxygen sensor (which is separate from the sensor who’s signal is being altered to fool the ECU) that your actual air to fuel ratio is closer to the ideal required air to fuel ratio based on your boost level, compression ratio, rpm, octane level, and timing advance figures.

6- Check using an OBD scanner that your Short Term Fuel Trims (STFT) are now near 0% which means that the ECU is now happy with what it believes the fuel mixture to be and will not make any adjustments from where you are now…. which is … the perfect tune

The three products on the market (and as far as I know, the ONLY three piggy back controllers that work on this type of problem) are:

• The SplitSecond Enricher
• The URD AFR sensor calibrator
• The AEM F/IC O2 Skew function

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The Split Second Enricher:

Split second is an electronics design and engineering firm that has been in the tuning game for quite some time now. Since they are a US based engineering firm, they have a collection of ‘niche’ products that serve specific applications really well. The root of this collection of unique products comes from the fact that many people approach them to solve difficult tuning problems, which later on become prototypes, and later on become full production products. A good example are both the narrow-band and wide-band enrichers which have had great success and a community following with custom turbocharged BMW’s…

The split second enricher has the following features:

• Dual Channel Correction which is handy on Boxer 4, V configured engines where every engine bank has its own primary wide-band oxygen sensor.
• External voltage triggered which means you can start altering your oxygen sensor signals based on an external map sensor at a preset pressure level, an external rpm trigger at a certain rpm level, an external MAS sensor once the car goes above a certain flow level or any other combination of external voltages (a nitrous kit arming and activation trigger signal would be a great example).
• In addition to the external trigger option, the enricher has an Internal Pressure Sensor and a voltage adjustment setting that allows you to trigger enrichment based on a preset boost level using all the built in hardware which reduces the cost, installation complexity, and most importantly the probability of failure when having to buy and wire up a second pressure sensor for activation.
• Dual mode operation: Since the enricher is triggered by a certain voltage point (internal or external) the enricher’s functionality is fairly straight forward and basic where you toggle between only two preset air to fuel ratios namely 14.7:1 (stock) and the air to fuel ratio that you set using the adjustment knobs. This works well on lightly modified cars but may not be enough to smooth out boost transitions or part throttle hesitations on certain applications.
• In addition to having two wide-band channels, the enricher has a pair of inputs and outputs to alter the voltage of the downstream narrow-band oxygen sensors positioned after the catalytic converters. These additional adjustment channels can be used to adjust the narrow-band signal to prevent the factory ECU from triggering check engine lights for catalytic converter efficiency (since the ECU can no longer read the correct cat efficiency figures due to the altered primary AFR sensor’s signal under high load).

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The URD AFR sensor calibrator

Underdog racing and development URD has been in the business of modifying Toyota engines for a long time coming now. Their original focus was the 1mzfe engine and related supercharger kit upgrades building on the original TRD (Toyota Racing and Development) supercharger package with additional fuel, more boost, and a better tune. Since then URD has branched out into more platforms, with more fueling options, and more tuning controllers including the URD AFR sensor calibrator and they have a very strong following on in the Toyota SUV market.

The URD AFR sensor calibrator has the following features:

• The unit has a built in programmable enrichment table that can either be pre-programmed by URD for common setups and familiar applications, or connected to their software for a custom program that fits the demands of your engine combination.
• Having a programmable enrichment map rather than a dual setting target AFR (like the SplitSec Enricher); the URD Capable of smoothing out transition enrichment and fixing hesitation problems related to part throttle & part boost conditions as well as altering the target AFR at full throttle and full boost.
• The device comes with dual channel capability similar to the AFR calibrator which works on V configured engines with dual sensors… however it does not have the ability to alter the secondary sensor voltages to prevent possible Check engine lights (for catalytic efficiency error codes) and additional narrow-band sensor simulators or oxygen sensor spacers might be needed on the downstream sensor depending on the exact application.

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The AEM F/IC O2 Skew

AEM is Advanced Engine Management, and although their primary claim to fame was the advanced design of their intake systems and dry element air filter (which won the famous filter shootout for maximum flow AND maximum filtration of all the tested elements); they have recently diversified the company into offering a full arsenal of performance equipment including standalone engine management systems, water injection kits, gauges and more..

The AEM F/IC is a piggyback fuel and ignition controller with an expanded feature set that is almost as capable as a standalone engine management system and comes with an O2 skew feature that is our focus today

The O2 Skew feature has the following characteristics:

• The O2 skew has a 16 X 21 (iirc) programmable enrichment table that has different enrichment capabilities with respect to engine load and rpm. Engine load can be mapped to a map sensor, or a flow meter alternatively depending on what your engine primary metering sensor is.
• This programmable table allows for extreme fine tuning of the entire throttle and boost range of the fuel map, all the way from Idle up to full throttle and full boost.
• The O2 skew feature can operate both in current and voltage mode (just as the other two products mentioned here) and also has two channels of adjustment for V configured engines with two AFR sensors.
• In addition to these features, the F/IC has the ability to control your fuel injectors and ignition timing directly has an advantage over the previous two devices…
  • On lightly modified cars, using an enricher alone for minor corrections relies on the ECU to fine tune the fuel table which works well for minor corrections, however when the modifications are extensive and the corrections are large, an additional fuel controller is required to deliver the right duty cycle to the injectors to compensate for the OEM tune being so different from the target tune and the AEM F/IC has the built in capability to do this.
  • Lying permanently to your ECU using the enricher will eventually reprogram your long term fuel trims (LTFT) to match what the ECU thinks is going on with your motor. If you reset your engine or ECU these trims will disappear and the car will have to relearn your tune from scratch. Since the AEM FIC zeroes out all your fuel trims and relies on your AEM FIC fuel map to deliver the correct fueling (rather than the trims in your factory ECU) then resetting the ECU has no affect on the stability of your tune, no matter how big the corrections.
  • You can not only prevent your ECU from going into limp mode or cutting power, but you can further maximize your tune to take full advantage of your modifications with the proper fueling and timing.
• Finally, as far as I know, the FIC does not have the ability to alter secondary O2 channels and an external O2 simulator, voltage drop resistor (500 ohms to 1k ohms depending on the sensor current), or oxygen sensor spacer may be required to correct the richer signal being read by the post-cat sensors to prevent the ECU from throwing catalytic efficiency check engine lights.

Watch this video of the process being performed on the AEM F/IC

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In conclusion:

All three of these devices are capable of making the modification experience a better and more refined experience on ULEV (ultra low emissions vehicles) and vehicles adhering to more stringent emissions requirements using wide-band primary oxygen sensors.

The choice of which device to go with will vary with the severity of the problem you have from minor corrections at WOT from a basic intake & exhaust install to a major retune for a ground up custom turbocharged application that has a completely differently shaped power curve.

Finally, if you are interested in more details on how to maximize the performance of your engine including what air to fuel ratios to target for your specific buildup, how to tune your timing curve to match the volumetric efficiency of your engine, and how to maximize both the response, power and longevity of your setup … be sure to checkout The Tuner Mastermind

Technorati Tags: Engine Tuning Guide, supercharger tuning, Wideband

If you’ve bought a car (or even a motorcycle) in the last 5 years, then chances are that your vehicle is equipped with an LSU4.2 wideband oxygen sensor. This wideband oxygen sensor, unlike old narrowband sensors of late, is able to tell the ECU exactly how much unburnt fuel is running through your exhaust system. Which allows the ECU tighter control over the exact amount of fuel injected into the cylinders both for better economy and for reduced emissions.

A must have guide for anyone embarking on tuning their own car

Technorati Tags: Engine Tuning Guide, supercharger tuning, Wideband

Staying with this theme of ’superchargers can have great top end’; I’ve geared this post for supercharger tuning for top end pull.

Let’s say for example you owned a 4G69 2.4 liter Lancer Ralliart. The Ralliart is a 2.4 Liter stroker motor with a massive 100mm stroke. In stock trim the car produces 168hp @ 6000 rpms and a respectable 167 ft-lbs of torque @ 4100 rpms.

The engine is a proven package which is related to the 4G63 legendary motor and the combination of this performance head with the healthy 10.5:1 Compression ratio makes the engine very responsive to modifications.

RPW (Racing Performance Works – Australia) has taken it upon themselves to boost the naturally aspirated performance of the 4G69 with a street and race header and a 3 stages of performance camshafts. The race header is what we’re interested in here due to it’s four into one design which is great for a singular increase in volumetric efficiency (and thus a nice power boost) closer to redline. The header also comes generously sized with 1.75″ primaries and a 2.5″ collector outlet, which will be needed when power output is greatly increased due to the supercharger application.

On RPW’s dyno the combination of their race-design 4-1 header, with their stage 2 camshaft, tuned cam gears, a press-bent 2.5″ exhaust system, a phenolic resin intake manifold spacer, and a computer flash increased the wheel horsepower delivered by the car from 151hp at 5750 rpm to 170hp @ 6000 rpms while holding over 165 wheel horsepower all the way to 6500 rpms.

This bolt on affair is a good starter for our top-end screamer as we have gained around 20hp and extended peak power by 750 rpms on the top end through the use of these modifications. With the most conservative estimates the engine will no be producing 188 hp @ 6000 rpms.

Enter the boost:

The ripp mods SDS EFI supercharger kit for the Lancer is built around a vortech V-5 G-trim supercharger head unit which delivers a peak boost and peak efficiency in the higher RPM ranges. The kit in stage 2 trim delivers over 8 psi to the 4G69 which in conjunction with our previous modifications can deliver over 290 crank horsepower at 6000 to 6500 rpms.

This combination of parts is all geared towards top end power (the four into one header, the stage 2 camshafts, and the centrifugal supercharger) and so the result is an engine that gains only 34 horsepower at 2500 rpms but gains over 120 horsepower at 6500 rpms (on what was originally a 168 horsepower motor).

For more information please visit:

Ripp mods
RPW

Technorati Tags: 4G69, Lancer, Mitsubishi, Ripp, RPW, supercharger tuning, Vortech

We are excited to release the third in our series of How-To videos on using the horsepowercalculator.

In this edition:

Calculating the right dimensions for your exhaust system and more specifically for a Y-Pipe exhaust.

The application today is a 5.7 litre chevrolet Camaro supercharged to 530 hp.

Technorati Tags: Calculator, Camaro, Chevrolet, exhaust, LS1, Supercharger, supercharger tuning

I am inspired by GM-Australia. They have taken the Vauxhaull (Pontiac GTO) family car and turned into a car for the automotive enthusiast family. The latest edition of the Vauxhall is dubbed the Vauxhall VXR8 Bathurst S, and packs alot of bite. 

The Vauxhall VXR8 Bathurst  S starts off with a factory 6.2 liter V8 producing 431 hp and builds on that with the addition of an Eaton M122 supercharger. The charger forces 8 pounds of boost into the massive V8 giving out over 560 hp in its most basic form and 527 ft-lbs of torque!

The engine modifications on this car include:

• A large capacity intercooler
• High-flow fuel injectors
• A separate cold air intake
• Walkinshaw-developed ECU map

Also availabe as an option is a bi-model exhaust system worth another 10hp at the current boost and power level. The exhaust can be switched by the user between a tame ’street’ performance and sound level, and a more aggressive ‘optimum‘ setting. 

Considering the tame nature of the LS3’s idle and the very modest boost level. A camshaft swap, an increase in boost could produce more power on this engine, however, it is very unfortunate that the Eaton M122 at it full swing can only breathe aboud 575hp worth of air leaving the current setup pretty ‘maxed out’ as is. However, there still remains the option for a ported blower (al la stiegemeier) as this blower is similar to the M122 fitted to the GT-500.

Therefore a new camshaft for the LS3, a ported M122, and a smaller charger pulley could easily push this Vauxhaull over the 630 hp mark! 

Find more information here:

Car magazine’s review of the Vauxhall VXR8 Bathurst S

Stiegemeier blower services

Walkinshaw performance

Technorati Tags: Eaton M122, Stiegemeier, supercharger tuning, v8, VXR-8, Walkinshaw

Building on the potent GT-500 plant, there are many possible ways of creating more horsepower, from basic bolt ons, to upgraded superchargers, to oversized motors… This is a great article by MM&FF showing three different power stages that are possible for your GT-500:

Stage 1:     JLT cold-air intake Single-blade throttle body Supercharger and crank overdrive pulleys Bassani axle-back race exhaust Everything else was left completely stock. Result 580 rear wheel horse power (rwhp). Stage 2: (In addition to the existing stage 1 upgrades) eaton TVS supercharger Afco heat exchanger. 2.6″ supercharger pulley 720 cc/min injectors Kenne Belle boost-a-pump Result 720 rwhp. Stage 3: 0.020″ overbore 9:1 compression ratio ford GT Supercar camshafts 3.4L whipple supercharger Result 800+ rwhp.

The 3.4L Whipple Supercharger crowns the power hungry 5.4L                             If this is what I think it is, you can see here a racer 'secret' modification. The four bolts in the center of the supercharger pulley break up the pulley into an inner sleeve and an outer ring, which allows for a quick change of supercharger gearing to change from low boost to high boost pulleys for race days, and then swap back easily back to a low boost pulley at the end of the race day. Very neat.

Find the complete article here:
Muscle Mustangs and Fast Fords

Technorati Tags: Eaton TVS, GT-500, supercharger performance, supercharger tuning, Whipple Supercharger

What modifications do I need when adding a supercharger to a truck? What modifications do you need when adding a supercharger to any car for that matter?

When adding a supercharger to your car there isn’t that much that changes with the basics of how the car works. The main difference between a supercharged car and a normal car is the elevated power output, which comes from literally cramming more air into the engine than what it would have breathing on its own under atmospheric pressure. There are a lot of myths out there about needing to upgrade EVERYTHING when supercharging or turbo charging or even using nitrous injection on a car. That’s simply not true, this is not a fire sale J.

What is true are four things:

1-      Head Gasket

A multi layer steel headgasket

Supercharging, turbo charging, nitrous injecting, or even increasing the compression ratio on the motor ultimately increases peak cylinder pressures inside the cylinder. By having more air and fuel in the cylinder we have more effective compression pressure inside the cylinder (whether this pressure is from a higher compression ratio, a hotter mixture, a compressed mixture, or a combination of these factors).

The typical scenario here is that a late teens early twenties takes his 13 year old car that has 160,000 miles on it and adds a basic supercharger or turbocharger kit without proper tuning. The car runs lean on its first couple of runs (and a lean mixture creates more combustion pressure than a rich mixture) and eventually the engine’s designed fail point gives way. In every engine there is a weak point that will give out first, and this weak point is typically the head gasket. On the first couple of days of boosting, the head gasket will probably blow, the engine will sound different, we’ll find oil floating in the coolant and coolant and oil floating out of the exhaust, the engine will lose its power and the person will say that the supercharger ‘blew up’ his motor. If you’ve previously overheated your car and driven it like that for a while (or a previous owner had overheated the car because of a coolant leak, a radiator failure, a stuck closed thermostat, a broken water pump or any of a multitude of very common cooling problems) then it is very likely that eventually the you will lose your head-gasket under normal operation. Thus it is even more understandable if it does so the first time the engine is supercharged.

4 to 6 hours of labor and a couple of hundred dollars later (mostly in labor) and the car is back on the road running perfectly.

So if you have an old car that you want to supercharger or turbocharger, make sure that your engine cylinder head is still torque down to manufacturer specifications giving you a good seal on your head gasket.

2-      Tuning:

An EGT pyrometer gauge is a good way to listen to the health of the combustion inside your cylinder

I kind of hinted at this earlier, the other aspect of supercharging or turbo charging a car is the tune. A lean tune or over-advanced timing will cause higher cylinder pressures and more heat. The car will make GREAT power because the combustion is leaning out and rather than being a controlled and safe combustion, it’s becoming more of an uncontrolled explosion that wants to melt pistons or break ring lands. Now the fuel system on a typical car is not that complex but the turbo kit that you buy as a complete package does not upgrade the entire system. One of the main fore sights is installing a turbo kit on a car with an old and clogged fuel filter or an old and weak fuel pump, all the while not having a fuel pressure gauge, a wideband air fuel ratio gauge or an exhaust gas temperature gauge to be able to track whether or not your install was successful. Tuning includes a number of things including air to fuel ratio tuning, camshaft timing adjustment and ignition timing adjustment, as well as the most ignored skill (yet the most useful) in any tuner which is diagnosis and troubleshooting. Anyone can tell you to theoretically put these parts together to make a ‘good’ kit, but only a true tuner will be able to take the car with all of its history and figure out why it isn’t making optimum power and bring it back to health.

The second supporting procedure you can do when you supercharge your car is to check your power on the dyno. If the power figures are low, or if the tune is too aggressive then a simple trip to the dyno and a hookup of an OBD scanner during the run can tell you within 10 minutes weather you are running safe, or whether you need to make some adjustments.

3-      Heat management:

An oil cooler will help keep your oil cooler and more viscous

As much as we like to talk about engine efficiency and mileage, the truth is that internal combustion engines are only about 30 to 40% efficient. That means that almost two thirds of the energy potentially contained in the air/fuel mixture is lost as ‘heat’ where only 30 to 40% is transferred down to the wheels as power or acceleration. So starting with a 100hp car (that releases 200hp worth of heat) and increasing its power level by 100% using a supercharger at 15psi for example, leaves us with a car that new puts down 200hp worth of power and emits 400hp worth of heat.

This heat has to be properly managed… one of the things that we do for in cylinder heating is use colder spark plugs to prevent the spark plug from becoming a hot ignition point inside the cylinder even when there is no spark. Other things we might need are a larger capacity radiator or an added/larger engine oil cooler. If the coolant temperature rises and the oil temperature eventually rises, then the oil will start to lose its thickness and viscosity. Now, fully synthetic oil is designed to be more resilient to higher oil temperatures, but eventually if you continue to cook your oil by heating it over its desired operating temperatures then it will no longer become useful as a lubricant, engine wear and friction will increase, and ultimately you will lose power from the added friction.

The thing to note here is that cars make a variable amount of power depending on what rpm, boost pressure, throttle opening, and load conditions you drive it. If you drive your car very sparingly and then do the occasional drag race then the engine has plenty of time to settle down and cool down. If on the other hand you are always asking your engine to produce its maximum amount of power then that heat will start to accumulate in the under-rated factory radiator and oil cooler (that were not designed for an extra 200hp worth of heat) and eventually you may run into problems.

To sum things up, if you’re an aggressive drive and you’re looking to significantly boost the performance of your vehicle or plan to use it in severe conditions such as high load towing conditions, then it is advisable that you upgrade your radiator to a higher capacity better flowing radiator as well as install or upgrade your engine oil cooler. Other things you might see people do might include cooler thermostats and high pressure radiator caps and high flow water pumps. These are all geared towards helping the stock cooling system cope with an increased heat demand. For most of the rest of us that go on the occasional spirited drive, these modifications may not be necessary.

4-      Transmission:

Clutches are rated based on their torque holding capacity, the more torque you produce, the better the clutch you need.

When you are trying to put down all this increased power that you made with the addition of the supercharger on of the most common after problems realized is either clutch slip for manual transmissions or transmission slip for automatic transmissions.

If you have a manual transmission then typically an upgraded clutch and pressure plate combo may be necessary for supporting modifications. It may be a good idea to use synthetic fluid for your transmission oil as well as most manual transmissions don’t have any cooler associated with them.

If you have an automatic transmission, then you must know this: The ability of the automatic transmission to hold power is highly related to the viscosity of the transmission fluid, and the case of excessive heating of this fluid, then naturally the transmission will start to slip. To deal with this problem the typical first line of defense is switching to synthetic fluids that are better capable of dealing with the heat, as well as installing a transmission cooler to help cool down the fluid so that the transmission doesn’t slip.

The extent that these modifications are or are not required for your car will have a lot to do with the history of the car (is it well maintained or is it about time for something bad to happen such as an abused head gasket or a failing fuel injector). It also has a lot to do with whether the manufacturer is known for over-building their cars (such as companies like Mercedes or Toyota that typically design their cars with 15 years of service in mind) and whether or not some parts on your car (such as your motor, your fuel pump, your radiator and your transmission are shared with another car or platform that produces more horsepower than your car). It also has to do with the driving habits and ambient environment that you live in as we explained earlier. So these may or may not be required depending.

One good practical example of this ‘theory’ applied is the Underdog Racing and Development supercharger package for the 2005 to 2008 Toyota XRunner and Tacoma.

The V6 supercharger kit includes what you would expect in a well thought out supercharger system including:

§  Upgraded fuel injectors and a brand new fuel pump.

§  Customized ECU calibration software including air/ratio remapping and optimized ignition timing.

§  An adjustable cam gear for camshaft adjustment for optimum power delivery.

§  Cooler than stock iridium spark plugs

§  A cooler temperature thermostat that opens at 170*C

Furthermore, for their higher staged kits, that can be making over 400+ RWHP at 10PSI of boost, URD recommends:

Recommended vehicle upgrades for the increased power level:

• Install OEM Toyota engine oil cooler. This engine oil cooler is stock on some Tacomas with Toyota’s tow package. If your truck does not have an engine oil cooler, we recommend installing it to stabilize engine oil temperatures, especially in hot environments. Toyota part numbers are included in URD’s MKII installation manual.
• If your truck has an automatic transmission, URD recommends upgrading the transmission’s valve body so it will better withstand the additional power levels. Contact Import Performance Transmission for information regarding their auto transmission valve body upgrade.
• Grill Craft MX Series grill to improve airflow over the front mount intercooler.

Now considering that this is a truck supercharger application, then URD has operated under the assumption that the truck will be used for the purpose which it was designed, and that includes heavy lifting, towing, and rough terrain with adverse conditions, and so it makes sense that they have designed their kit to cover all the supporting modifications that I’ve mentioned above sans for the upgraded head gasket (which usually is not a problem that will appear on younger vehicle that has been well maintained).

For more information please visit:

Underdog Racing & Development (URD)

Technorati Tags: Intercooler, Rotrex, supercharger performance, supercharger tuning, URD, V6 Supercharger

I love limitless situations, the view of the open ocean, an endless twisty country road, and the limitless potential of

good engineering practices. One of the cars that I feel in love with a few years back is the BMW M3 CSL. The M3 badge tells you that this is a special car for a special driver, with increased horsepower, reduced weight, and ultimate driving balance that BMW is known for.

The CSL stands for Coupe Sports Lightweight, and is a racing heritage version of the M3 that takes street performance a couple of steps closer to being track prepared. The CSL of late incorporated a carbon fiber composite roof for reduced weight and a lower center of gravity, the trunk lid and trunk floor were also made of lightweight composites. The car had a retuned suspension, increased horsepower from a freer flowing exhaust system and an ECU recalibration, and came standard with 19” rims wrapped in ultimate grip Michelin pilot sport cups. To take delivery of the car you had to sign a waiver stating that you understand the track prepared nature of the car and that you understood that with its maximum grip setup and semi-slick tires, that it may not be brutally or candidly driven in adverse weather conditions. This is truly a car that demands respect in every way.

ESS tuning -- European Supercharger Systems – once again goes to show that proper engineering practices have limitless potential. ESS carries a kit specifically designed for the M3 CSL based on ASA’s TM1-20HD performance superchargers. The kit includes everything you need for a fully reliable supercharger upgrade including:       

                A properly sized front mount intercooler.

                6 Larger Bosch Fuel injectors

                A recalibrated ECU both for fuel demands as well as for optimum VANOS cam timing

                A revised positive crankcase breather system

The result is a powerful 530 horsepower at a measly 7 psi of boost on an already lightweight and engaging car.

Find more information about the kit here:

ESS tuning

Simpson Motorsports

Technorati Tags: ASA, ESS, Performance superchargers, supercharger performance, supercharger tuning

Camshaft tuning is an essencial part of supercharger tuning. Camshafts orchestrate the valve opening and closing events in the engine and decide whether what comes out of our motor is beautiful high power music, or a mess of dysphonics.

The use of the proper supercharger optimized cam shaft can go a long way towards supercharger tuning and give considerable power gains for the money invested.

To understand camshaft timing and camshaft selection we have to understand first:

Relativity:

Changing when the valves open or close (intake or exhaust) changes the the valve timing with respect to:

• The piston position inside the cylinder. Depending on where the pistons is in the stroke, and where we are in the combustion cycle, then opening the valves will exploit the pressure difference between the cylinder and the intake and exhaust manifolds.For example it would make sense that the ideal time to open the intake valve is when there is peak vacuum inside the cylinder so that when the valve opens, the maximum amount of fresh air can be ingested. Similarly, it makes sense not to open the exhaust valve until peak cylinder pressures have been achieved inside the combustion chamber and the combustion is complete and all the power is extracted.

 

•  The high and low pressure pulses created by the design and runner lengths of the intake and exhaust manifolds.It would make sense to open the intake valve just as the reflected pressure waves in the intake manifold reach the intake valve as a high pressure portion of the wave, thus opening the valve at this high pressure point gives a ‘ram air’ effect through volumetric effeciency resonance tuning increasing air ingestion which increases power.Similarly on the exhaust side, it makes sense to open the exhaust valve, just as the reflected low pressure (vacuum) portion of the exhaust wave (reflected back from the collector) reaches the back of the exhuast valve. At this point in time there is both peak pressure inside the cylinder, and vacuum in the exhaust which creates a higher pressure differencial and a faster evacuating exhaust gas.

 

• With respect to the ignition timing event, for example a shorter duration or advanced exhaust cam, opens the exhaust valve sooner with respect to when the mixture was originally ignited, this means that although by advancing the exhaust cam we may have matched our header design and opened the valve with the lowest possible exhaust back pressure for best effeciency, at the same time, we have reduced the amount of time that the mixture is combusted and possibly opened the valve before reaching our peak cylinder pressures and thrown away some horsepower.

 

• The intake valves with respect to the exhaust valves: and this is usually described in terms of lobe seperation angles (the offset in degrees between the center of the exhaust cam and between the center of the intake cam), or in terms of how many degrees of overlap (the number of degrees that both intake and exhaust valves are open at the same time). 

Since the combustion inside the cylinder occurs at a much higher pressure than atmospheric pressure, and since exhaust valves are usually smaller than intake valves (for this same high pressure reason) then exhaust gas velocity is much higher than intake gas velocity. So, in some engines it is beneficial to open the intake valve earlier than usual during the last part of the exhaust stroke, this is called overlap. During overlap – at the very end of the exhaust stroke – the amount of pressure left in the cylinder is low so it is possible to breathe in new air under atmospheric pressure, at the same time, the high velocity of the exhaust gasses exiting help draw in even more fresh air from the intake side in an effect much like ’syphoning’ where the fluid (in our case air) flows as a continuous stream drawing in new intake air after the old exhaust gas leaves. 

The other part of phenomenon that relates to timing intake vavles with respect to exhaust valves is the duration of time where both valves are absolutely closed, which is your power stroke. This is the part of the combustion cycle where the mixture can be compressed and combusted. If either (or both) intake or exhaust valves are open you will not be able to neither compress nor combust the mixture, and the absolute duration of time (in degrees of rotation) that your mixture is combusted and allowed to reach peak cylinder pressures is affected by camshaft selection and cam timing. One thing to note is that the valve angle has alot to do with exhaust scavanging, obviously you will get maximum scavanging if the exhaust and intake valves had ‘line of sight’ i.e. if the valves were seperated  by an angle of 180*. If so, the exhaust air can directly pull in new air. Conversely, you would have the least possible scavanging if you had valves that were at a narrow angle (zero degrees at the extreme) between each other, so that the air would essencially have to make a U turn to come in through the intake and get pulled out the exhaust.

So different motors respond differently to overlap depending on the exhaust back pressure and the valve angle.

Duration:

Cam duration is the number of degrees of the entire 360* rotation that the intake or exhaust valve is open. The longer the duration, the more air you can get into the motor, the more overlap you have (which helps more with higher rpm power performance), the shorter your power stroke is (which reduces your combustion duration and your peak cylinder pressures reducing low rpm fuel effeciencly and clean idle….etc

Increased duration (with it’s increased overlap and scavanging) also gives the opportunity for exhaust gasses to get to the intake, or intake gasses to leak to the exhaust, and so are more sensitive to proper timing events otherwise we can get some negative effects from being ‘overcammed’

Lift:

Lift is how far or how deep the valve opens into the cylinder. The more lift you have, the less the valve is a restriction to incoming air because it is farther away from the direct path of entering or exiting air. Adding lift in general adds power to all rpms, depending on how well the camshaft (and valve train) can accelerate the valve to a higher lift number in a short duration. It’s like a ramp, the shorter the duration and higher the lift, the steeper the ramp. So what happens here is that if your valve train isn’t light enough and well controlled (Through proper valve springs or hydraulic lifting and damping) to operate that rapidly then lift will give you improved performance at lower rpms (where there is alot of time to move the valve to peak lift) but reduced performance at higher rpms, where there are more rounds per minute and so less time per round, and thus less time to go up the steep ramp and push the valve out to full extension.

Lift is good, but usually people don’t try to radically increase lift on their aftermarket cams because of a few considerations:

1. Make sure that at this new lift, that there is still enough clearance between the valve (at full extension) and the cylinder (at top dead center) to prevent any catastrophic mechanical failure.
2. Upgrade to lighter valve train, with stiffer springs or dual valve springs to have more control over the valve with this steeper cam profile. 
3. It does add power but it doesn’t shift the power curve up or down as radically as chaning cam duration does, and so in most aftermarket applications we really want a cam to give us peak power at a certain rpm range and so we care much more about the best duration (and some added lift).

I know this is a somewhat complex topic, but I need to make sure we’re speaking the same language before we go into how this relates to superchargers. Before you decide which camshaft to use (or how to adjust the timing on your stock cams) you have to look at one very important thing:

Your exhaust system and exhaust back pressure:

If you have a stock log type exhaust manifold, with a close coupled cat, with a dual cat exhaust system, small exhaust tubing, and a couple of restrictive mufflers on your car then it is possible at peak power to have upto 10psi of back pressure. 

If this is the case, my first recommendation would be to upgrade to a high flow, low pressure exhaust system because of the potential power gains; however, I do know that some of our readers have cars that they are setting up for their parents or for dual use where their partner or the laws in their location …etc are really strict when it comes to any added exhaust noise or any aftermarket exhaust. In this case, where exhaust upgrades are not an option, then you must select your camshafts, and tune your cam timing to where you have ABSOLUTLEY the minimum possible amount of overlap. If you have significant overlap, then the more you rise above about 4500 rpms the more your supercharger will suffer and the more power you will waste. If the supercharger is geared to 7psi of boost for example, then during overlap, the cylinder sees 7psi of boost on the intake side, and 10psi of back pressure on the exhaust side, the net result is that air will flow from the high pressure zone (the exhaust) to the lower pressure zone (the intake) and so your cylinder will start to fill with exhaust gases. As the rotation continues, the exhaust valve will close and overlap will end, and the intake valve will stay open for the remainder of the intake stroke (for the rest of the duration of your intake cam), and the rest of the cylinder will fill with fresh air. 

What happens here is that we get a cylinder that filled for 30* of overlap with exhaust air, and then filled for another 210* (of the original 240* of duration for a typical street cam) with fresh air. The result is a cylinder that is only 85% filled with fresh air or an engine that is literally 15% smaller in displacement! On the other hand, if our supercharger is geared for 18psi for example, then during overlap we will have 18psi on the intake side and our exhaust back pressure of 10psi on the exhaust side, the net result of this overlap is that our supercharger is effectively only producing 8psi worth of differencial pressure between the intake and the cylinder and so we are only going to get a power boost of 8psi during overlap. So, during those 30* of overlap the supercharger is only effectively porducing 8psi of boost, and after that once the exhaust valve closes, the supercharger will be able to go back to operating at full boost for the other 210*. The net result is something like 16psi of boost so 2psi (or about 12%) of our power was wasted.

Illustration of the 4 strokes , cam duration, and cam timing

Supercharger tuning through cam selection and cam timing

Intake cam:

Because of the negative effects of overlap on a supercharger car’s performance, and especially in the case of high exhaust back pressure as is the case with most factory supercharged cars, we find that the optimal cam duration for the intake cam is typically 30-40* of duration less than a normally aspirated camshaft for the same peak power RPM. The decision to reduce the intake cam duration rather than split the duration reduction between the intake and exhaust cams, is that the intake cam will flow air under pressurized conditions (due to the addition of the supercharger and the increase in intake manifold pressure) and so at a reduced intake cam duration the engine will still be able to get it’s full share of intake air. At the same time, the high rpm effeciency improvement from the reduction of overlap will also boost power production with a more conservative cam. Finally, if we would like to get more flow from the intake cam, there is still the option of using a higher lift camshaft (with a steeper profile due to the decreased duration) with supporting valvetrain modifications to make sure valve float doesn’t occur at higher rpms.

Intake cam timing:

The cam timing for the intake cam would ideally be retarded which would move the intake cam opening event farther away from the exhaust valve closing event so as to reduce or eliminate overlap, and as a side effect the power stroke duration will increase by retarding the intake cam which can also compensate for the lost power from the duration reduction.

Exhaust cam: 

The exhaust cam duration and lift for a supercharged version of the motor should be similar to a nitrous camshaft, in the sense that the exhaust cams on nitrous specific builds have:

1- Very healthy cam duration & very healthy cam lift to allow a severely elevated amount of exhaust gases to be able to effeciently exit the motor when the nitrous is activated and the horsepower (and thus the exhaust gasses) have both doubled in quantity.

2- As little or no overlap if possible, as any overlap would mean that nitrous would be sprayed from the intake side and out the exhaust, which is wasteful of our limited supply of nitrous. Similarly the more overlap we have, the harder the supercharger will have to work because of what we explained earlier about either exhaust reversion into the intake, or the supercharger pressurizing the exhaust.

Exhaust cam timing:

Advancing the exhaust cam both opens and closes the exhaust valves sooner. Opening the exhaust valve sooner slightly reduces the power stroke, but at the same time it reduces overlap and makes better use of our supercharger. Typically an an advanced exhaust cam combined with retarded intake cam will provide the best results on a supercharged car, especially with a restrictive exhaust.

If we had a high flow exhaust system installed, then it may not be beneficial to advance the exhaust cam, a high flow exaust system that is optimized for our engine’s power requirements can clear the combustion chamber of all it’s gasses very effeciently. Having a high duration exhaust cam, a low back pressure exhaust system and a no overlap what so ever camshaft means that we are giving the exhaust gas plenty of time to exit they cylinder, the intake valve still hasn’t opened (because the we have decide to retard it, or use a conservative cam with less duration) and so the supercharger is not pushing any new fresh air in yet, now the cylinder is void and so some of the exhaust gas can revert back into the cylinder, then the exhaust valve will close, and then the intake valve will open only to find the cylinder already partially filled with exhaust gases.

This isn’t a problem with a restrictive exhaust because a restrictive exhaust will take some time to clear the cylinder at a lower velocity, however with a higher flow exhaust system we must be careful not to dial out ALL of the overlap in the cam timing, or to overcam the exhaust cam (using too much duration). 

So exhaust cam timing can be advanced or retarded, depending on the exhaust modifications and the intake cam selection and thus must be dynotuned. 

It’s important to note that with all of these changes in cam selection , overlap, power stroke duration, and cam timing, that the power stroke duration is effected and if it is effectively shortened then we may need to retune the car’s timing advance on the dyno (for increased advance) to regain losses in duration of the power stroke (again this against popular thinking of never to advance timing on forced induction cars, if we have a shortened power stroke, or an application with signficant overlap then it may be necessary to do so).

So we see here that the end result here a lop-sided camshaft with a conservative duration, high lift cam on the intake side, and a normal duration, high lift cam on the exhaust with minimal lobe seperation angle and minimal (but not necessarily no) overlap.

The exception to the rule:

Sometimes people take a car that starts off with a 9000 rpm redline, has an 11.5:1 compression ratio, and a 280* duration camshaft, and an aggressive naturally aspirated-esque timing curve and decide to supercharge it for more power. One suck example is kleemann’s kompressor for the SLK55 AMG (which already makes 400 hp in normally aspirated form from an 11:1 compression ratio motor). In this type of application, if you use a more conservative cam, and dial out all the overlap, and increase the power stroke, in combination with an already high 11:1 compression ratio and a healthy amount of boost pressure (7psi or above) you will end up with a motor that produces extremely high peak cylinder pressures and those intense pressures and heat may easily start off a chain reaction of pre-ignition and detonation and you will find that no matter how much you retard the timing that the setup will end up both powerless and still not that safe.

In this case, I would consider RPM and compression my primary power adder, and my supercharger as my secondary power adder (that is unless I decided to change that and went ahead and lowered the compression ratio of the motor). In this case it is ok to sacrifice some supercahrger high rpm effeciency for preventing high-load & low-rpm detonation. Furthermore, to overcome the overlap inherent in this kind of high rpm normally aspirated powerplant it would be very advisable to use a centrifugal supercahrger that is capable of producing more boost and flow with increased rpm rather than a  roots type charger that will easily run out of boost and flow capacity (CFM) when facing an aggressive camshaft ‘leaking’ boost away.

Here is a great example of how cam tuning can affect supercharged power:

The car is a 1.8 liter honda motor equipped with:

• Supercharger optimized big pirmaries and short runners Kamakazi header
• A greddy 2.5″ SP2 catback exhaust system.
• An LHT ported “S” supercharger inlet tube
• An LHT ported intake manifold ( Non intercooled)
• A Carbon fibre intake
• A Jackson racing eaton M62 supercharger geared for 7.5-8 psi.

B18c5 with JRSC tuned

The black line is the baseline run with all of these modifications before tuning.

The blue line is the power acheived after a full tine (camshaft timing redone for reduced overlap, ignition timing re-optimized, and air fuel ratio optimized for peak power).

The red line is the same as previous but running open-header with no exhaust system. Obviously this last run shows that the 2.5″ exhaust is more than adequate for the 250hp power figure.

You can see on this graph that by reducing overlap and properly tuning the car the power peak not only increased by 25 horsepower, but more importantly shifted up by 1000 RPM’s due to increased supercharger high rpm effeciency from reduced overlap.

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