Car Tuning,Car Finance,Auto Loans

Archive for November, 2008

The Basics

Many Import Performance Tuners start out simply by finding the right information. If that’s what you’re looking for, you’re in the right place.

Most imports are simply classified as being built overseas, however in the industry I work in, imports are defined as not only foreign vehicles, but also the sport compact vehicles of American manufacturers, such as the Dodge SRT4’s, Chevy Cobalt and Pontiac Solstice.

Tuning for most people is trying to squeeze every available bit of horsepower from a vehicle, and for some of the less informed, this also means sacrifice engine longevity and reliability (what good is an extra 5whp when it breaks 45k miles sooner).

Import tuning is no different then the hot rod building of the old days. Small lightweight cars with big power plants stuffed into them. Getting the power/weight ratio as high as possible and still maintain reliability.

Import tuning’s most basic adjustment hasn’t changed. Fuel pressure. Simply increasing or decreasing fuel pressure at the rail has a dramatic effect on air/fuel ratios, as well as Short term and Long term fuel trims.

Modifying your fuel system to support modifications is extremely important. Most items like a S-AFC or a e-manage simply modify sensor values going into the computer to increase or decrease fuel injector duty. While this works in practice, if you’re adding 10% across the board to richen a car up, leaving that at 0 and simply increasing fuel pressure is a much safer way to do things, and lets the computer work how it was originally intended.

But back to the fuel pressure. As the most basic and fundamental import tuning point on the car, it is important to get this right before any other adjustments are made. Reearch tells us how Fuel injector flow is based off of a fixed pressure value of a standard viscosity fluid. Most companies rate them differently, but the most used rating for the aftermarket is 43psi, while some vehicle builders test them much higher. The reason this is crucial is because the fuel pressure behind the fuel injector itself will raise it’s basic output. A 450cc injector supplied at 37psi at the rail is putting out far less fuel then a 450cc injector supplied at 55psi at the rail.

After doing a few runs with your car, look at your complete air/fuel value for the extent of your test. If you’ve changed anything to increase the volumetric efficiency of the motor, the motor will be leaner (Air/fuel ratio is higher then before) then when you began. If there is a noticeable need overall in the ratio, then simple fuel pressure adjustments can fix that. At cruising speeds, the air/fuel should always be 14.7:1, an all-motor car under full load should be about 13.5:1, and a forced induction car under full load should aim for 11.2-11.9:1. The higher the number, the leaner (less fuel) the car is. To richen the car to make the the ideal points, increase fuel pressure, and if you need to lean the car out to lower the air/fuel ratio, decrease fuel pressure.

Some cars will not show a change, but need further tuning via the short term and long term fuel trims. Most vehicles these days will let these values go +/- 25%, but ideally the fuel pressure should be adjusted so that they are all +/- 5% so that the maps are open to the car if they’re needed.

Run the car a few more times with an obd-2 datalogger on board. Look at the fuel trim values, and see where they are resting. If the vehicle is adding a lot of fuel trim (increasing the numbers) then adding a few more psi of fuel pressure (generally 1-2psi and recheck) can greatly reduce that number. Likewise, if you see it pulling fuel trim, decreasing the fuel pressure will off-set this. This is very important to allow the vehicle it’s full range in making adjustments for varying conditions, such as weather, temperature and altitude.

In further articles on Car Performance I will dive further into piggy back systems, standalones, MAF and MAP sensors and where everything falls into place.

When you are purchasing parts and putting together a turbo system, the blow off valve is a fairly important part of the system. Not only does it release all the excess pressure built up in the intercooler piping after the intake manifold closes, but a turbo BOV also creates a unique BOV sound, which can make your car sound like it’s quality tuned and unique. The HKS Super SQV (SSQV) turbo blow off valve is a BOV every turbo tuner should consider purchasing, as this specific BOV has many benefits to its unique construction.

In 1994, HKS released the first blow off valve, the SSQV BOV, containing the “pull” valve design, which was unlike the usual “push” valved blow off valves turbo tuners have always used. The “push” blow off valves have been the traditional type of turbo BOV used and they allow pressure to build up until the valve spring cannot hold anymore pressure, or the valve reaches its threshold, and then pushes the excess pressure out of the valve.

HKS created a design with the “pull” valve system, found on the HKS SSQV BOV, which uses and alters the pressure to pull open a dual valve system. The primary valve is the smaller valve, which opens up during smaller pressure conditions. When heavier pressure conditions are encountered, the SSQV BOV will open the larger, secondary valve, which allows all the excess pressure out during heavier and faster driving conditions.

Having the pull valve system allows the HKS SSQV BOV to prevent leaking, even when the car is idling or under extreme conditions. This system also allows a cleaner, more solid BOV sound, as it releases all the pressure with a fresh tuned sound, once the valve is pulled open.

Engine Tuning (ECU Modifications)

The ECU (also known as the Engine Control Unit) is basically the brain of your vehicle. It controls amongst many other things all the ignition timing and fueling settings and would have been setup by the manufacturer in the factory with economy, reliability and drivability being the main priority.

By re-programming it (better known as remapping), the settings can be altered to produce more power from the engine it controls.

Chip Upgrades and Remapping

Modern uprated ECU chips, from the many reputable aftermarket tuning companies can improve the drivability and torque curve all the way through the revs. It should not effect the fuel economy or reliability in a major way and due to the way they are setup, but they are pre-programmed and are therefore wont give the optimum gain.

One of the main issues with the standard chip, is that the parameters and settings it controls are designed to be used on all of the engines that a manufacturer produces, and therefore has to have built in safety margins in mind, as all engines, even if of the same design, will be slightly different.

With after market performance chips this problem is not cured, as yet again, these chips, designed more for performance than fuel economy, are intended to fit in any ECU of any particular model. Again, they are not designed specifically for the one particular engine in your car and therefore must cater for the slight differences between the different engines.

On a positive note, one of the best things about chips is the ability to raise the rev limiter to a more powerful level. On some cars the rev limiter has been set to come in quite low in the rev range, e.g. : 6000 revs/min, so by raising this to a slightly higher, yet not dangerous, level, e.g. : 7200 revs/min, then more power can be reached and performance will therefore be increased.

It is widely recognised that the only way you can get the absolute optimum performance from any engine is to have the ECU completely remapped for that particular engine.

ECU Replacements

To obtain the optimum performance from your cars engine it would really need to be on a rolling road and have the ignition and fueling setup perfectly to match the other components of the engine, but as the standard systems are not programmable, a new system must be installed to store the new settings.

There are 3 options here.

Firstly is the ECU chipping method as described above, however these are usually not remappable, although remappable chips are available which will do the job.

Secondly there are piggy-back units which are basically plugged in line in order to override some of the settings of the standard ECU. However, because the complete original ECU system is still in place, there may be some controls, such as the rev limit, that will be fixed at the manufacturers setting.

Lastly, and the most effective solution, is to install a complete new programmable ECU, which once fitted, will offer complete control over the engine and all the settings that control it.

On modified cars, ECU remapping can give excellent results, making the car more driveable and refined, while maximising the benefits from all the other modifications, giving the absolute optimum performance for the specification available.