Best Performance Chip to Buy?

[Bravo]

I have recently purchased a 1994 325i and have been told that an aftermarket chip is a great way to get some more ponies. Does anone have one? what brand? and how does it work?

Thanks,

Dean
1994 325i
1966 911 Coupe

[Dave at Pelican Parts]

I can't tell you which is "best" (best is always a tricky concept anyway), but I can give you some idea of how they work...

Your car has an Engine Management System which controls quite a few things on the engine. It controls the amount of fuel that goes in, and when the spark occurs. It also controls the VANOS system, which means it can change when the valves open and close to some extent. (If your car is "drive-by-wire"--not sure--then it even controls how much air goes into the engine!)

Since the computer controls all of these things, you can change any or all of them by changing the computer chip. So you can richen the air-fuel mixture a little, which will give you a tiny bit of power. You can fiddle when the cams advance and retard, which can let you trade low-end torque for high-end power. You can provide more spark advance. And you can raise the rev-limiter on the motor.

When carmakers design and build cars, they have to design so that what they build works correctly in 99+% of all the motors they make. But motors vary due to machining tolerances and other factors. So a chip-maker can tweak things to work for some lesser percentage of motors than the factory, and optimize things for those motors.

The chip-maker can also compromise other things. Often you will need to use higher-grade gasoline after the modification than before. This is mostly to accomodate more advanced spark timing, which is probably the single largest contributor to the extra power you get from a chip.

A chip-maker can also optimize his setup for a non-stock motor. If, for instance, there are a very common set of aftermarket modifications (I/H/E, for exampe) then the chip-maker can set up his chip so that it works best for a car set up that way. That will also let him get a few more ponies over the stock chip, which is designed to work best with the stock parts.

Frankly, these days the automakers really haven't left a whole lot of power on the table. Most gains from computer chips are relatively small, unless "other things" have been done. One major exception to this is turbocharged cars, where the EMS often controls the wastegate. Tell it to stay closed for longer, and you'll get more boost--which means a whole bunch more power...

Anyway, I hope this gives you a general idea of how the chips work.

--DD

[Bravo]

Wow! that was a ton of really good info. I printed it out and will read it a couple fo times to internalize it-- thanks

Dean

[Wayne 962]

Where are you located? Some of the chips (while maintaining legality in 50 states) can advance the timing so much that the car detonates. This particularly true with bad west-coast gas. Chips are good because they tailor your car for your needs - not the general needs that the chip was designed for at the factory. Here's some more info:

Motronic (DME) (1984-89) - The Motronic system (also called the Digital Motor Electronics or DME) is hands down the best overall fuel injection system that you can use when you consider price and performance. Ignition timing and fuel delivery are all controlled by a digital map that is recorded in a removable chip within the main fuel injection (DME) computer. The computer takes input from a variety of sensors that are located on the engine – cylinder head temperature, altitude (ambient air pressure), crank angle, throttle position, exhaust gas oxygen (mixture), ambient air temperature, and mass air flow. The DME chip is programmed from the factory with certain performance characteristics (mostly conservative) so that the engine will react well under a host of varying conditions. Major changes to the engine (including the addition of different camshafts) require an updated chip map to take full advantage of these modifications. Failure to update the Motronic system may actually result in a decrease in performance, as the original system is finely tuned to supply the correct timing and fuel injection values for a stock engine configuration.

However, each system is matched directly a specific engine configuration. Because of the proprietary nature of the Motronic system, there isn’t a whole lot of changes that you can perform without updating the DME chip. Major changes to the engine (different camshafts, increased displacement) will not work well with the stock Motronic system because the computer chip is designed to deliver the proper amount of fuel and spark only for a stock engine. To gain the maximum benefit from engine modifications, you need to either upgrade your DME chip, or install a programmable aftermarket engine management system (discussed in the next section).

If you are running a stock engine with the stock Motronic injection, the best upgrade you can perform is the installation of an aftermarket DME chip. As stated previously, the factory programmed the original chip to compensate for a wide variety of driving characteristics. These days, you can find chips that will elevate the rev-limiter, advance your timing, and generally run the engine with less conservatism than the factory chip. The only downside to running a more aggressive chip is that sometimes the timing curves are a bit too advanced and may cause detonation on low-octane pump gas (as it is here in California). It’s best to find a chip manufacturer that offers a few different levels of performance, and will guarantee that you will be happy with the system.

Hope this helps,

Wayne

[umnitza]

Jim Conforti

[Wayne 962]

What about Jim?

-Wayne