One of the main problems with the standard Impreza, is that the headlights are extremely poor for the levels of performance offered by the car. Traditionally, owners wishing to increase the output of their headlamps would fit higher wattage bulbs (illegal in the UK!). Unfortunately, in some sort of cost/weight saving frenzy, Subaru seem to have equipped the Impreza with plastic reflectors and the absolute minimum thickness of wiring necessary to drive the standard headlights. There have been numerous cases reported of the wiring getting very hot, and in some cases reflectors and wiring melting with higher wattage bulbs fitted. Some owners have been running the higher wattage bulbs without problem for several years. Fit these types of bulbs at your own risk!
Another option are high performance "Xenon" bulbs, which claim to offer 30% brighter light, for the same power. A growing number of owners are fitting these type of bulbs, including myself, and they do make a noticeable difference. The light produced is noticeably brighter (whiter), especially off-beam, when you can pick up a lot more detail at the edge of the road. As long as you are not expecting them to turn darkness into daylight, then they are a worthwhile improvement. These Xenon bulbs are available from a number of sources, including IWOC member Andrew Batters who runs his own garage business, and sells them mail order at a discount. PIAA have also introduced a range of high-efficiency bulbs, with e.g. the 80w bulb producing equivalent light to a 130w conventional bulbs. These are very expensive though!
At the same time as fitting the higher performance bulbs, it would be prudent to check the headlamp alignment. The most accurate method is to have them calibrated using the correct equipment at any MOT testing station, or as part of your routine servicing. If this is inconvenient, then the following advice from Andrew Batters can be used as a rough guide.
The MOT "beam setter" is basically a box with a collecting lens at the front and a screen at the back with various markings onto which the headlight dipped beam is projected. It represents a scaled down version of the image projected onto plain screen 10 metres away from the light. The latter is still used for checking motorcycle beam aim.
The standing area for the vehicle and its relationship with the "beam setter", for the MOT, has to be accurate to within +/- 2mm laterally and when checking the beam aim, the equipment is set along the longitudinal axis of the vehicle each time. I'm telling you all this is so that you will realise the importance of getting things as accurate as possible.
We will assume that the left - right alignment is OK (mine was) so the vertical checking goes as follows:-
You will need a very flat area for the car to stand on and also your checking "screen" whether it be a wall, garage door or a sheet of something light coloured, it doesn't matter. The important thing is that it is in the same level plane as the vehicle and perpendicular.
In the centre of the headlight lens there is a dimple, this it the datum for setting the beam, mark a horizontal line on your wall, door etc. at exactly the same height as the dimple.
With somebody sitting in the driver's seat and the headlights on dipped beam and the internal level switch at zero you will see the horizontal portion of the beam with a 15° kick up to the near side.
The beam is measured as a percentage below the horizontal, a measurement of 10mm is 1 percent at a distance of the screen from the lamp of 1 metre (1000mm), so is 2cm at 2 metres.
On the headlamp casing there is a figure of 1.3 percent 13mm at 1 metre and this is optimum for the vehicle, but for me this is too low. The upper limit for the MOT is 0.5 (5mm) below and the lower is 2.0 (20mm) below. I have set mine at the top limit and is just a touch on the high side, but the control inside drops it to wherever is best, I use it a lot when driving as conditions change.
When using YOUR screen the accuracy will be better at greater distances than 1 metre, three metres the errors will be one third, the problem is that the further you go away from the light the probability of the vehicle standing area being out of true with your screen increases. If it is not right there are two adjusting wheels at the back of each lamp, one is up down, the other is left right. Can't remember from memory, which are which, fiddle and see.
Driving Lamp Conversion
If you are serious about fast night time driving in your Impreza ( and this can be the safest time to drive fast, if you're sure there are no cyclists, unlit skips or bambis in the road) then you should invest in one of several driving lamp conversions available.
The first option is a PIAA driving lamp conversion offered by Prodrive via your local Subaru dealer. This replaces the two fog lamps fitted as standard, with two PIAA (flamethrower!) driving lamps. Like all the Prodrive equipment, quality is top notch, but with a price to match. We've heard of some different fittings schemes: make sure your dealer wires them up to come on with main beam.
Another very popular driving lamp conversion is the kit provided by ScoobySport. Consisting of two Cibie Oscar Plus driving lamps, with 130w bulbs, mounting brackets, wiring, connectors, relay and full fitting instructions. Fitting can take less than 1 hour, but if it's your first time under the Scooby's bonnet you should allow two or three hours to make a professional job. Alternatively, a Subaru dealers or car electrics shop might do it for you.
There have been nothing but good reports from the growing number of owners who have fitted this kit. "Bugger me. Daylight!" were the words one owner uttered the first time he switched on his new driving lights. Total light output is the same as that of the Prodrive PIAA conversion. Some dealers have commented that the fitting is neater than that of the Prodrive kit, a glowing commendation indeed.
In Australia, MRT again offer a high quality driving lamp conversion. Full details are available on their web site.
Demon Tweeks sell the Morette twin-headlight kit with Cibie optics. With standard bulbs you'd have 2x55w on dipped and 4x60w on main beam. The standard wiring isn't affected, which means you need to rewire to allow higher-wattage bulbs. The kit is bordered in black ABS so you need to get the plastic painted to match. It gives the car a very agressive nose - some love it, some hate it. With these and a driving lights conversion you'd be well equipped for night stages
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