from sdsefi.com Tech/FAQ section

The first reason is that on most naturally aspirated engines operating on pump fuel, the <U>only</U> way to achieve tangible power gains is by increasing airflow through the engine. Chips cannot do this therefore they cannot make much difference in power output. Chip re-programmers can richen the mixture slightly at full throttle and advance the ignition timing slightly perhaps but this would be at the expense of lowering the factory safety factors for detonation and emissions. The absolute maximum gain in this instance would be on the order of 5% and could be as little as 0%. Most independent tests that I have seen on performance chips for naturally aspirated engines have indeed shown minimal or no gains in acceleration. Some were slower than the factory chip.

Chips for use in factory stock turbocharged applications can increase power substantially in some cases by raising the boost pressure. This again reduces the factory detonation limits and you risk engine damage. Without increasing fuel octane, you are asking for trouble especially if your engine does not have a knock sensor.

Finally, we have chip companies doing "custom" chips for modified engines. What does this involve? This is a technically sound modification only if your engine has the same mechanical mods as the motor on their dyno that the chip is being developed for. If your cams, heads, turbo, exhaust, intercooler, injectors, throttle body or fuel are different, the chip will not be correct for your engine. A chip made for an engine slightly different from yours will be slightly wrong under some conditions. In some cases, poor driveability and performance are the result.

The only way to get good results on a modified engine with different mods from the base engine is to take <U> your</U> vehicle to the tuners facility and get a <U>true custom chip burnt for your engine.</U> This must be done on a chassis dyno then tested on the road also for driveabilty faults which often don't show up on the dyno. This will cost more.

Here is some advice when buying a performance chip:

Before buying, do acceleration testing with a stopwatch, Vericom or at the strip.

Get the chip maker to guarantee the performance gain in writing and make him understand that you will return the chip to him if the chip does not work as claimed. If emission compliance is a concern, ask if their chip will pass the test and get it in writing.

Follow all of the instructions provided by the chip maker when installing it.

Stick to reputable companies. Some people in the chip industry really don't know what they are doing. Talk to some people first who have used a certain chip and see if they are satisfied.

Test your car to be sure that you got what you paid for. This is all good advice when buying any aftermarket devices such as ignition wires, ignition products, oil or fuel additives etc. which advertise a performance gain. If it doesn't do what it is advertised to do, you just got hosed and with some chips costing $500, this is something that you should not put up with.

If all of this doesn't sound too good to you, the alternative is a programmable engine management system. These allow you to tune your engine yourself. This can be good and bad. The same things apply as above. If you don't have a fairly thorough understanding of the system, engines and tuning plus a dose of patience, DON'T buy one of these. Understand that you will have to program all of the values to make the engine start, warm up, cruise, accelerate and run at full power. This can entail entering hundreds of points in most cases and you will require either a dyno or a long deserted road plus some indication of mixture strength to properly tune such a system. These systems are great for the knowledgeable person and a nightmare for the lay person.

Remember, both the chip that you buy or the chip in your programmable ECU must have the proper values entered for your engine to run properly. The main advantage of user programmable systems is that they can be quickly changed if a new mod is done or if not quite right whereas the factory type chip must be changed or sent back to be redone, sometimes, several times at great cost.

If you are contemplating a strictly race situation, don't bother with the factory ECU or chips at all. These were not designed for performance use and you will usually not get the kind of power required with factory hardware. This is when a programmable system is a must.

When considering buying a programmable system, here are a few tips:

Discuss your goals and needs with the tech people selling the system. Make sure that the system will do what you require it to do. Don't expect the impossible- you can't expect a 400hp, 4 cylinder street car to have factory driveability, fuel economy, emission compliance, a smooth idle or long life on pump fuel. If you do, you are a nut and no one will talk to you. There is a reason why there are no factory cars like this driving around your neighborhood.

Removing the factory system and installing a stand alone system can be a lot of work. What hardware, skill and tools will you require to install the system? Can you handle it or do you know someone who can? What factory options will you lose when removing the factory ECU?

If emission legality is a concern, find out if their system is legal and if it will likely pass in your area when properly programmed. Many systems are not legal for street use and many manufacturers will not guarantee emission compliance because they cannot control the programming.

Find out how easy the unit is to program and if you can handle it. If it is difficult to use, either don't buy it or find a place where you can go to have it properly tuned.

Make sure that the company has good, accessible tech support, you may need it.

You are responsible if you program the system too lean and melt your engine, don't blame the system maker. If the engine runs like crap, you are probably asking the system to do something that it was not designed for or have not programmed it correctly. This is your problem now.

Read, understand and follow the manufacturers instructions. LISTEN. It will save you a lot of time. Remember, that the people who design and build this stuff likely know a hell of a lot more than you do about it. If all of this discourages you, sell the present car and simply buy a faster one, you will probably be happier in the end.

R.F.