03-06-2011, 02:57 AM
I thought I would take a minute to revisit the subject of chips and such. At risk of great personal peril, I felt it was long overdue that some of this stuff be explained for those who don't really understand how much of it works. I have no intention of getting into a discussion of which chip is best, or who is right or wrong, or even attempting to point anybody in any direction. There are just way too many variables, and what is the right chip for one guy, is not necessarily the right one for the next.
Chips have long been a discussion for car enthusiasts. The topic of tuning for power dates back to the days of hot rods and big holleys. With the onset of computer tuning, it has gotten even more common to hear people talking about this. It is fascinating stuff, and done right can really wake a car up and provide performance that the factory left on the table. Done wrong it can really make mess of things. The consumer needs to do their homework on the product, the company, the process, and the results, before deciding to proceed. But that's no different than buying a microwave oven.
Basically a chip does 2 things. It tells the computer what to do to the fuel mixture and the ignition timing. It does this based on readings taken from a number of sensors in the car (such as coolant temp, oil temp, airflow from the MAF, throttle position, O2 level, and rpm). The computer is constantly taking measurements, nowadays many times a second, and making continual adjustments.
Fuel mixture has always been a way to gain more power. Timing advance is too. Each can be wonderful things, if used judiciously. Abused they can cause premature wear failure of some components, and can even kill an engine. This is not something to be experimented with without the proper training, skills and tools.
Feeling fuelish?
In the old days with carburetors and such, you would change jets and fatten up your mixture to the mid to upper 12s. This would make the most power. The down sides were a loss of fuel economy, (but with gas at 69 cents a gallon, who cared?) and some decrease in engine life due to ring and bearing wear from the extra fuel in the oil.
But things have changed. The average car now runs at 14.7:1 most of the time. This provides for the best fuel economy and cleanest running condition.
Cars with Catalytic Converters cannot run as rich as the cars of yesteryear. Doing so will foul O2 sensors and also prematurely cause the Converter to fail. Also, it increases CO emissions, which will cause it to fail inspections, and is really bad for the environment. One of the reasons that engines last so long now is that they run leaner. There is less fuel in the oil, and so there is less breakdown of the lubrication.
Lamda sensors (O2 sensors) are delicate devices, and are easily upset. A rich or lean mixture will cause them to fail.
A lambda sensor's normal life span is 30,000 to 50,000 miles, but the sensor may fail prematurely if it becomes clogged with carbon, or is contaminated by lead from leaded petrol or silicone from an antifreeze leak or from silicone sealer. As the sensor ages, it becomes sluggish. Eventually it produces an unchanging signal or no signal at all. When this happens, the Check Engine Light may come on, and the engine may experience drivability problems caused by an overly rich fuel condition. Poor fuel economy, elevated CO and HC emissions, poor idle, and/or hesitation during acceleration are typical complaints.
If the lambda sensor continually reads high (rich), it will cause the engine computer to lean out the fuel mixture in an attempt to compensate for the rich reading. This can cause lean misfire, hesitation, stumbling, poor idle and high hydrocarbon emissions (from misfiring).
If the lambda sensor continually reads low (lean), it will cause the engine computer to enrich the fuel mixture. Injector pulse width will increase causing fuel consumption and carbon monoxide emissions to go up. Constant rich fuel mixture can also cause the catalytic converter to overheat and it may be damaged.
If the lambda sensor's output is sluggish and does not change (low cross counts & long transition times), the engine computer will not be able to maintain a properly balanced fuel mixture. The engine may run too rich or too lean, depending on the operating conditions. This, in turn, may cause drivability problems such as misfiring, surging, poor idle, and high emissions.
If a heated sensor has a faulty heating circuit or element, the sensor can cool off at idle causing the system to go into open loop. This usually results in a fixed, rich fuel mixture that will increase emissions.
In summary, while you can gain more power by fattening things up, you do so at the peril of lessening engine life. A little isn't a bad thing, but too much and you cross a line that you may not want to cross. A rule of thumb is that on a normally aspirated street car with a Catalytic Converter you do not want to dip below about 13.5:1 for any kind of sustained period (more than a few seconds). On a race car you can get down into the 12s for a bit without worrying so much, because you don't have a Catalytic Converter, and you will likely be tearing the motor down every year anyway. On a boosted car, more fuel will need to be added to keep temperatures down, and prevent detonation, but only on boost, and really only at higher rpms.
Timing is everything
Ignition advance is a much trickier subject. A little advance is a good thing. A little more can be even better. Too much and you can expect to have lots of little metal bits to take to the recycler.
Today's engine management systems are much more sophisticated than the ones many of us grew up with. We used to mange ignition timing with a centrifugal distributor that had weights and springs to provide controlled advance curves. As the engine revved higher, the distributor spun faster, and the springs would stretch, allowing the timing to be advanced. The weights helped control the springs.
Today we have computers controlling variable valve timing, variable intake runner lengths, and all sorts of maps to deal with just about every situation. This has opened up a whole new world for tuners. However, it has brought with it a whole new set of problems.
Determining optimal ignition timing is a very complicated combination factors. It takes a lot of time to see how things react, and to determine what effects it has on things like combustion temperatures. The more advance you add, the more heat is generated, due to the earlier combustion. Things may seem just fine on a nice cold winter day, but this can easily result in burning things out if other factors come into play (like a hot day). It's not necessarily just about maximum power. It takes a lot of testing under a wide range of conditions to tune the timing maps for the intended use. The timing curves you would set for a race car would likely create a lot of problems in street use.
What does this all mean to the guy who just wants to buy a chip?
Auto manufacturers spends countless hundreds of thousands of dollars tuning just one car. The conditions are carefully controlled and monitored, and each and every scenario is anticipated. Aftermarket tuners can't do that. Often they don't even bother to tune for part throttle conditions, and only tune full throttle. It is extremely rare that they bother to work on cold start, hot start, or extended climate conditions. They don't generally consider different fuels, or even do any oil or metals testing to see what their tuning has done. This is not to say they are evil, or even irresponsible. It is a very real limitation to what they can do, given time and resource available, and the justifiability of the expense due to the market. Most of these vendors are pretty responsible. Obviously you need to be wary of the internet vendors, but generally the companies making chips in bulk have done enough testing to at least determine that within a nominal range of conditions that their products are predictable.
Really it all comes down to compromise. As with anything, tuning for power is a tradeoff, varying in degree based on how much you want. It's not just limited to chips. If you only drive a couple thousand miles a year, it probably doesn't matter much what you do. If you don't care about fuel economy, it helps open things up. If you don't have to undergo emissions testing, you have less to worry about there too (apart from the obvious environmental karma). If you have a daily driver, and expect to maintain the lifespan of the engine, you need to be a bit more conservative in your choices. A chip for a race car can ruin a street engine. A chip for a street car will not do as well on the track.
In making your choice, ask questions. Find out what the intended use is. Be specific in describing what you want to do. Find out what the vendor did to provide what you want, given how you would use the car. There are some good vendors out there, and some not so good. There are countless discussions, with widely varying opinions, and sorting through that can be daunting, but in the end, it will all come down to you asking questions, and a bit of faith.
Always remember though, never modify an engine in poor condition.
Chips have long been a discussion for car enthusiasts. The topic of tuning for power dates back to the days of hot rods and big holleys. With the onset of computer tuning, it has gotten even more common to hear people talking about this. It is fascinating stuff, and done right can really wake a car up and provide performance that the factory left on the table. Done wrong it can really make mess of things. The consumer needs to do their homework on the product, the company, the process, and the results, before deciding to proceed. But that's no different than buying a microwave oven.
Basically a chip does 2 things. It tells the computer what to do to the fuel mixture and the ignition timing. It does this based on readings taken from a number of sensors in the car (such as coolant temp, oil temp, airflow from the MAF, throttle position, O2 level, and rpm). The computer is constantly taking measurements, nowadays many times a second, and making continual adjustments.
Fuel mixture has always been a way to gain more power. Timing advance is too. Each can be wonderful things, if used judiciously. Abused they can cause premature wear failure of some components, and can even kill an engine. This is not something to be experimented with without the proper training, skills and tools.
Feeling fuelish?
In the old days with carburetors and such, you would change jets and fatten up your mixture to the mid to upper 12s. This would make the most power. The down sides were a loss of fuel economy, (but with gas at 69 cents a gallon, who cared?) and some decrease in engine life due to ring and bearing wear from the extra fuel in the oil.
But things have changed. The average car now runs at 14.7:1 most of the time. This provides for the best fuel economy and cleanest running condition.
Cars with Catalytic Converters cannot run as rich as the cars of yesteryear. Doing so will foul O2 sensors and also prematurely cause the Converter to fail. Also, it increases CO emissions, which will cause it to fail inspections, and is really bad for the environment. One of the reasons that engines last so long now is that they run leaner. There is less fuel in the oil, and so there is less breakdown of the lubrication.
Lamda sensors (O2 sensors) are delicate devices, and are easily upset. A rich or lean mixture will cause them to fail.
A lambda sensor's normal life span is 30,000 to 50,000 miles, but the sensor may fail prematurely if it becomes clogged with carbon, or is contaminated by lead from leaded petrol or silicone from an antifreeze leak or from silicone sealer. As the sensor ages, it becomes sluggish. Eventually it produces an unchanging signal or no signal at all. When this happens, the Check Engine Light may come on, and the engine may experience drivability problems caused by an overly rich fuel condition. Poor fuel economy, elevated CO and HC emissions, poor idle, and/or hesitation during acceleration are typical complaints.
If the lambda sensor continually reads high (rich), it will cause the engine computer to lean out the fuel mixture in an attempt to compensate for the rich reading. This can cause lean misfire, hesitation, stumbling, poor idle and high hydrocarbon emissions (from misfiring).
If the lambda sensor continually reads low (lean), it will cause the engine computer to enrich the fuel mixture. Injector pulse width will increase causing fuel consumption and carbon monoxide emissions to go up. Constant rich fuel mixture can also cause the catalytic converter to overheat and it may be damaged.
If the lambda sensor's output is sluggish and does not change (low cross counts & long transition times), the engine computer will not be able to maintain a properly balanced fuel mixture. The engine may run too rich or too lean, depending on the operating conditions. This, in turn, may cause drivability problems such as misfiring, surging, poor idle, and high emissions.
If a heated sensor has a faulty heating circuit or element, the sensor can cool off at idle causing the system to go into open loop. This usually results in a fixed, rich fuel mixture that will increase emissions.
In summary, while you can gain more power by fattening things up, you do so at the peril of lessening engine life. A little isn't a bad thing, but too much and you cross a line that you may not want to cross. A rule of thumb is that on a normally aspirated street car with a Catalytic Converter you do not want to dip below about 13.5:1 for any kind of sustained period (more than a few seconds). On a race car you can get down into the 12s for a bit without worrying so much, because you don't have a Catalytic Converter, and you will likely be tearing the motor down every year anyway. On a boosted car, more fuel will need to be added to keep temperatures down, and prevent detonation, but only on boost, and really only at higher rpms.
Timing is everything
Ignition advance is a much trickier subject. A little advance is a good thing. A little more can be even better. Too much and you can expect to have lots of little metal bits to take to the recycler.
Today's engine management systems are much more sophisticated than the ones many of us grew up with. We used to mange ignition timing with a centrifugal distributor that had weights and springs to provide controlled advance curves. As the engine revved higher, the distributor spun faster, and the springs would stretch, allowing the timing to be advanced. The weights helped control the springs.
Today we have computers controlling variable valve timing, variable intake runner lengths, and all sorts of maps to deal with just about every situation. This has opened up a whole new world for tuners. However, it has brought with it a whole new set of problems.
Determining optimal ignition timing is a very complicated combination factors. It takes a lot of time to see how things react, and to determine what effects it has on things like combustion temperatures. The more advance you add, the more heat is generated, due to the earlier combustion. Things may seem just fine on a nice cold winter day, but this can easily result in burning things out if other factors come into play (like a hot day). It's not necessarily just about maximum power. It takes a lot of testing under a wide range of conditions to tune the timing maps for the intended use. The timing curves you would set for a race car would likely create a lot of problems in street use.
What does this all mean to the guy who just wants to buy a chip?
Auto manufacturers spends countless hundreds of thousands of dollars tuning just one car. The conditions are carefully controlled and monitored, and each and every scenario is anticipated. Aftermarket tuners can't do that. Often they don't even bother to tune for part throttle conditions, and only tune full throttle. It is extremely rare that they bother to work on cold start, hot start, or extended climate conditions. They don't generally consider different fuels, or even do any oil or metals testing to see what their tuning has done. This is not to say they are evil, or even irresponsible. It is a very real limitation to what they can do, given time and resource available, and the justifiability of the expense due to the market. Most of these vendors are pretty responsible. Obviously you need to be wary of the internet vendors, but generally the companies making chips in bulk have done enough testing to at least determine that within a nominal range of conditions that their products are predictable.
Really it all comes down to compromise. As with anything, tuning for power is a tradeoff, varying in degree based on how much you want. It's not just limited to chips. If you only drive a couple thousand miles a year, it probably doesn't matter much what you do. If you don't care about fuel economy, it helps open things up. If you don't have to undergo emissions testing, you have less to worry about there too (apart from the obvious environmental karma). If you have a daily driver, and expect to maintain the lifespan of the engine, you need to be a bit more conservative in your choices. A chip for a race car can ruin a street engine. A chip for a street car will not do as well on the track.
In making your choice, ask questions. Find out what the intended use is. Be specific in describing what you want to do. Find out what the vendor did to provide what you want, given how you would use the car. There are some good vendors out there, and some not so good. There are countless discussions, with widely varying opinions, and sorting through that can be daunting, but in the end, it will all come down to you asking questions, and a bit of faith.
Always remember though, never modify an engine in poor condition.
94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com
"It isn't nearly as expensive to do it right as it is to do it wrong."
