The first thing you have to work out is what type of Scalextric car you have is the car a Digital Plug Ready (DPR) car,F1 car or does the car need one of the chips that require soldering either the F1 chip or the saloon car chip.
The digital plug ready cars are very simple and can easily be fitted in less than 60 seconds. DPR cars have a small trap door behind the guide blade with a single screw to hold the door securely. Simply unscrew the door and you will find a small white in colour plug fitted to the door. Remove this plug and discard the trap door then fit the white plug to the digital chip C8515. Then replace the chip in the hole in the chassis and tighten the screw. Then your car is ready to race on your digital track. The process is exactly the same for the F1 cars that are DPR but with this conversion you will require digital chip C8516. You will find the process a little harder as on the F1 cars there is very little room to place the chip but with a little pressure the chip will go in to place correctly and then with the tightening of the screw will ensure that the chip is flush with the level of the chassis.

The second car conversion it is more technical and will require soldering and possibly some modelling techniques. As with the DPR cars the Scalextric F1 chip C7005 are smaller due to the area contained under the body of the car is very small, thus the chip has to be far smaller compared to the Saloon chip. F1 chips can be used on some car where space is at a premium like Rally cars and some other single seater cars. For years Scalextric have been adding the chip mounts to the inside of the chassis of their cars and also a small hole for fitting the LED behind the guide blade with small screw mounts to make this process easier.
To start with you will need to remove the body of your car and then you will be able to see which chip you will need with the space available. Once you have decided on the chip first look at the routing of wires for when fitting the chip you will need the wires to follow the current path for the best fit for the chip. This should prevent any distorting of the guide due to poor wire mapping inside the car. Then you will need to remove the wires from the motor this is best done with a soldering iron by melting the existing solder while gently pulling the wires and then the wires will come free. The next stage is to remove the wires completely from the car from the guide. Simply slip the metal plates off the guide and at this point the wires can be removed.

We find the next stage is best to fit the digital chip to the mounts on the chassis. The mounts will look like two plastic spikes and on the chip there will be two groves where the chip fits to the mount. Some cars it can be a very tight fit so be careful not to damage the chip in the process. Once the chip is securely in place, look for the hole behind the guide. There is a possibility that there will be mounts for screwing the LED detector in place but do not worry if there is not, just make sure the hole is big enough for let the led through the hole and glue in place with strong glue such as super glue. Only glue around the edges so not to get any glue on the part of the led that will be visible to the bottom of the car as this can affect the detection of the car on the track.
The final stage will be fitting the wires to the guide and motor. The guide wires have metal contact for fitting to most modern guides. These contact just slip on to the guide from the side then replace the guide braid disc and this part is complete. Pay attention to make sure that the wires are running as they were when you removed the old wires. If done correctly the guide should be facing straight. If the guide is pointing either way try to route the wires so to rectify any deviation from the correct position. Now for the final use of the soldering iron, attach the motor wires to the motor, only lightly solder the wires to ensure that you have then to the correct points, as it is very simple to wire then the wrong way round and send you car backwards round the track. So at this point test the car to see if everything is running correctly. If all ok solder the wires completely and then attach the body back to the car an you are ready to go race on your digital track. If the car runs backwards
un-attach the wires as covered earlier and swap their positions and then solder.
Now you have completed you first digital conversion to your Scalextric car using either C7005 or C7006 digital conversion chip.

Overall the process is very easy and will just require a little patience and a steady hand. So if you find you dream Scalextric car and it is not DPR then do not worry you can get it racing around your Scalextric digital track with a little work. Also it is possible to convert other makes of cars to digital but we advise to seek help from various forums for the correct advice for each make of car as they all vary.