What is chipping?

[thegoth 5]

(Something I found whilst googling 4 history/gossip behind another recent thread regarding membership #s ;-) )

An old article, but the theory is still valid.

What's a chip? …

Just a more common and friendly term for an Eprom, one of many components held on the circuit board of the E.C.U. (computer) which controls your engine. When you re-chip your car, you are changing the values inside this eprom to make them a better match for your engines's requirements. The revised values are loaded into another chip, which then replace the original chip on your E.C.U.'s circuit board. The engine then uses these revised values each time the engine is started. In other words, you are having your engine tuned, except that in this case it is being tuned electronically rather than mechanically (i.e by tinkering around with distributor timing and carburettor needles).

These controlling values held within the chip are referred to as 'maps'; hence the process of re-chipping is also often referred to as 're-mapping' (more about mapping later).

The accepted understanding of the terms 're-chipping' and 're-mapping', is that former means buying an 'off the shelf' plug-in chip with an approximate set of revised contents, and that the latter implies a more custom and tailored approach with some hands-on rolling road mapping taking place. The truth is that it is a very grey area and that you need to ask the right questions. No-one would expect several hours of serious E.C.U re-mapping on a rolling road by a graduate electronics engineer for the accepted cost of a re-chip. This is in the realms of serious racers with big budgets. However, if you shop around you can find companies with the appropriate level of electronics expertise, who will include an element of custom re-mapping so that you get a much better result. No pre-programmed off-the-shelf chip can be exactly right for all cars. Remember the earlier comment about it only being engine tuning? You couldn't take two identical carburettor-controlled cars and make exactly the same set of needle and ignition timing changes to both and get the same result. No two cars are identical in their requirements in the first place.

So why re-chip at all? …

Primarily to make the engine's behavior more suitable for the car in question, more suitable for the way the car is driven, and more suitable for the country in which it is driven. The reason the standard chip does not always perform as well as it should is often blamed on the car manufacturers. In reality, it is the result of a compromise the manufacturers are forced into when they launch any new vehicle. Each new car launched has to undergo 'Type Approval' tests and part of this Type Approval is the 'Urban Driving Cycle' test. Based on a simulated trip around the city of Los Angeles, the Urban Driving Cycle test is remote from European driving conditions, to say the least. The resulting noxious gases are collected in a bag for testing. The car manufacturers have no option but to comply with this test, and to pass it is no mean achievement. The car is virtually de-tuned to meet these unusually stringent emissions requirements and as a result, it never performs as well as it's mechanically controlled counterpart. Hesitancy and flat spots become the norm. That's the bad news, but the good news is that a whole new industry has formed as a result, rechipping and re-mapping to render the car better and more responsive to drive. We've had almost twenty years of being able to re-chip our cars to eliminate the problems and produce extra power at the same time, without infringing our own emissions regulations or being accused of being un-environmentally friendly.

Changing devices ..

Chips first appeared as 28pin plug-in devices (as used inside the VW Digifant E.C.U). The next progression was a chip which was soldered (by conventional means) to the circuit board; after that came the 16-bit devices, with a few variants in-between. The post 1996 VR6 and 1.8 Turbo engines now have E.C.U's with the latest 16-bit, 44pin devices, which are 'surface-mounted' to the circuit board rather than being conventionally soldered. A whole new ball game this, requiring not only new de-soldering technology but also new mapping hardware and software to go with it. People often ask if these device changes have been made to deter re-chipping. In the absence of any other evidence it can be assumed that it is just normal progression. Nothing in the world of computer technology stands still.

What's a map then?……

In order to explain we need to start at the beginning. The most difficult concept to grasp for most people is that a chip is merely an electronic storage device. It contains values in a binary form, which the E.C.U's main processor (another device on the same circuit board) can understand and use to control the engine. Each value inside the chip is held in its own separate 'address' or position, and when a car is 're-chipped', all we are basically doing is finding those groups of addresses with values which control fuelling and those which control ignition. These groups are called maps, and we alter the contours of these maps to tune the car (don't lose sight of the fact that re-chipping is engine tuning!). To carry out this re-mapping process it necessary to have the right computer hardware and software, and of course the appropriate electronics qualifications in order to understand the procedures.

To access the chip values in a readable form, firstly the contents of the chip are 'dumped' into the appropriate computer programme. A huge list of addresses with values (and many empty addresses) appears on the monitor. The maps (the groups of filled addresses which actually perform some engine control function) are found, eventually, by running the car on the rolling road at the appropriate engine speed and load with the E.C.U connected to the computer, and the engine attached to an engine analyzer. Addresses are highlighted on the PC monitor as they are being used by the engine, and this way, the regularly accessed groups of numbers can be isolated and we can be sure it is a map of some kind. If the emissions increase when we raise some of the values, then we have found a fuelling map. If timing advances or retards when we make changes, then we have accessed an ignition map. Once both fuelling and timing maps have been located, the changes in value which improve performance are made. The revised fuelling map values are used by the E.C.U's main processor to control how much fuel should be propelled through the injectors at certain engine speeds and loads. The revised timing maps become the areas in the chip which affect ignition advance.

The numerical maps can also be plotted on screen as a contoured graph, i.e. the numerical values of a map plotted against engine speed and load.

Whilst all this is going on the car is still attached to the engine analyzer so that emissions can be monitored to remain well within statutory limits. After all, there's no point in gaining a couple of extra bhp at the expense of failing the M.O.T test. To accurately locate the maps being used at part-load, and full-load (foot flat to the floor), controlled simulated road conditions are absolutely essential. For this purpose a rolling road comes into its own, making it possible to run the car under load, i.e as it would normally be driven.

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AmD