What bulb types are suitable for conversion
Unlike other HID outfits, we don’t say that all bulbs are equally suitable. In fact some are more suitable than others, and twin filament bulbs are of questionable suitability at all.
In general, single filament bulbs, such as H1, H3, H7, H11 etc are appropriate to convert to HID. Dipped or Low beams that operate behind a projector work remarkably well when converted to HID, similarly Main or High beams that operate in front of a reflector work particularly well.
To illustrate the different between projector and reflector lights, the image below is of a typical modern headlight unit. The light on the left is a projector dipped beam light, with the distinctive hemispherical glass lens in front of the lamp. On the right side of the headlight unit is the high beam lamp, which is a reflector lamp. There is no glass lens in front of the lamp, just a large open reflective surface.
Note that points raised here apply to all HID bulbs / conversions. Most other sellers wont tell you of potential risks and pitfalls, but we prefer telling it straight.
H7 Bulbs – the most common bulb
H7 halogen bulbs have a black tip, a tip that shields some of the light from going directly forwards from the bulb. As HID conversion H7s do not have this black light shield, marginally more glare can be expected from a H7 conversions in reflector lamps, that operate without a bulb shield. Fortunately most H7 halogen low (dipped) beam lights do not operate directly, but instead operate behind a projector lens or behind a bulb shield, as per the two images below: In these cases, increased glare is unlikely to be an issue.
This is not relevant for H7 high beam lights, but is worth bearing in mind for H7 reflector low beams, that operate in the absence of a bulb shield.
H1 and H3 bulbs
The older style H1 and H3 bulbs are good candidates to HID-ify. H1 HID units are normally a straight swap with no issues for the H1 halogen bulb. In a few cases, I have heard of H1 conversions needing to file down slightly the HID base slightly to get a perfect fit, but I stress this is in rare cases only. The main issue to be aware of in fitting H3 HID fitments is that H3 bulbs typically exists in spot lights or driving lights. If those driving lights are small then you need to be aware of space constraints both behind the HID bulb and in front of it. While the light source is in the same place as the halogen bulb, the H3 HID unit is longer overall and very small spot lights may not fit the H3 HID bulb. Also make sure there is sufficient space behind the bulb to fit the HID connections. Some H3 spot / fog lights may require minor modification to fit the H3 HID units. Also note that the H3 halogen bulb features a “transverse” filament, running across the axis of the bulb. This is not possible to duplicate with the HID conversion, and so a H3 HID may have a very slightly different beam pattern than the halogen it replaces. This is only minor and only affects the H3 fitment.
We feel the H1 and H3 halogen bulbs are good candidates to upgrade to HID.
What about H4 and 9007 bulbs?
H4 and 9007 bulbs are a bulb designers compromise that found their way on to vehicles in the economising days of the 1980s. The H4 and 9007 bulbs attempt to have a low beam and high beam in the same lamp.
Modern cars, performance cars and prestige cars are all equipped with separate low beam and high beams. This is because the direction and pattern of light required for each is very different. Quality modern headlight design not only gives cars a separate low beam lamp and high beam lamp within the headlight unit, but recognises that the low beam is more effective with a projector lamp and the high beam with a reflector lamp (see headlight unit pictured above). Trying to shoehorn a high beam and low beam into the same lamp was always going to be a poor compromise, even with the H4 halogen bulbs designed for it.
The H4 bulb looks like this:
It has two filaments, at (a) different lengths from the base and (b) offset, so that they are at different axes. Neither filament is on the central axis of the bulb and the low beam filament features a large shield to prevent light travelling in one direction.
There are no really adequate HID conversion solutions to this compromised design.
The first two pictures below look at two versions of HID conversion firms attempts to make a H4 HID conversion:
In the first picture, the idea of two light sources is considered too difficult and the light produces a shielded low beam HID light only. This is clearly not a suitable replacement for a halogen H4 bulb.
The second type that are quite common from sellers of questionable integrity has a low beam HID burner (down the central axis of the bulb) and a standard halogen bulb for high beam offset to the side. Neither the HID low beam nor the halogen high beam light sources are in the correct place. The light will not produce appropriate beam pattern in either high or low beam, and HID is only available in the low beam. Another poor compromise.
The third type of H4 conversion on the left above is called a “telescopic” H4 HID. The telescopic H4 HID has a number of points on which it suffers. Firstly, the critical issue of light source placement. The real H4 halogen bulb has two offset light sources, on different axes and at different lengths from the base of the bulb. The telescopic H4 or 9007 burners have either the burner or the shield on a telescopic motor which slides either the burner or shield up and down along the axis of the bulb to replicate low and high beam. The HID burner is located on the central axis of the bulb and as such BOTH the low and high beam light sources are in the incorrect place. Further, the small telescopic motor in the base of the unit is prone to break down on cheaper units.
Finally above right, we have the dual burner, dual ballast H4 / 9007 conversion. Unfortunately even with this set up, the light sources are NOT quite in the correct positions. We have tested this type of H4 burner to see if it is worthy of selling but have been unable to get a satisfactory beam pattern. We feel strongly that any HID conversion that fails to duplicate the original design performance of the respective halogen bulb is not suitable to be called a replacement. The idea of conversion is to boost lighting performance within the same parameters of the original design.
There is no such things as a perfect H4 HID conversion. In all cases, the beam patterns distort and are not faithful to the original. It is not possible to perfectly duplicate the H4 halogen light source with a HID unit, despite the best (and worst) claims in the market. How close you get to the original beam pattern depends on how much you spend on the H4 unit. The cheap ones are abysmal, the more expensive ones are merely satisfactory.
STOP PRESS: We have just started doing single H4 kits (specifically for bikes) as we have found a high quality unit that is as close as we have seen to worthy of replicating a halogen H4 bulb’s beam patterns. It does this by having the telescopic bulb at an angle to the axis of the bulb, thus getting much closer to the correct positions of the high and low beam light sources. It is available in 35 watt or 50 watt HID. If you are prepared to accept the limitations of any H4 conversion kit, then this is as good as we reckon it gets for H4 – its the best beam pattern replication we have found. It is considerably better than the dozens of others I have tried both in terms of reliability of the telescopic solenoid and in terms of light source placement. (note almost all other telescopic solenoid H4s on the market still run a telescopic unit operating along the axis of the bulb. This will give you poor beam replication)
A single 35 watt H4 with an Ultra-35 ballast to do high and low beam is now available for £99, plus £6 p&p … in 6000K only.
A single 50 watt H4 with an Ultra-50 ballast to do high and low beam is now available for £129, plus £6 p&p … in 6000K only.