Headlights

Headlamps: H-4 vs. H-5

#1
There are several differences between the H-4 European and H-5 US headlamps. The greatest single difference, is that the H-4 headlamps are MUCH more expensive. They are worth the difference in money if the use of the car is largely in rural areas where municipal road illimination is one bulb every five hundred feet.

The H-4 Euro has a flat low beam that rises 15 degrees on the right side for side road illumination. the H-5, is merely a poorly focussed flat band of light that sort of lights up the road in front of the car. This is not a function of bulb type or of bulb wattage. It is a function of lens design.

The H-5 lamp throws a substantial amount of light down the road in the form of a big blob. While the H4 Euro lamps do the same thing, they have a more focussed beam of light extending directly in front of the car. Regardless of wattage, either lamps high beam is for most use adequate, although for rural driving the H4 beam is stronger and better.

For quite a long time in my sordid past, I sold driving lights to sports car clubs and individuals as a hobby. The European lamps are simply better because of the focussed patterns of the lenses.

I have European headlamps in my Audi 200. The American version of these lights are pitifully inadequate, but with the Euro lamps, which use both an H4 and an H3 bulb in two separate sections, on high beam, the lighting is "outfield class".

In my 928S4 (8" lamps), and my 911, I have the H5 bulbs with US specification lenses. High beam is ok on both of these cars, the 928 aided, no doubt, by the rectangular driving lamp that comes on automatically with high beam. however, I live in rural coastal Maine, and it gets to be seriously dark here. Right now, the deer are starting the fall rut, and there are apt to be deer everywhere. Neither of these H5 systems provide enough light for serious night driving, and soon I will replace the 928 lights....then later on, the 911's. The Euro lamps have a vastly superior high beam spread and depth.

However, if I lived in a more civilized part of the world, I would save the money, as the H5 systems are good enough as they are. With higher wattage bulbs, they would suffice for most folks and most locations.

Roger Woodbury


#2
For USA spec Porsche 928s , the H4 Euro is a 7" direct replacement for the old round sealed beam. The H4 bulb itself is about 2 in. (3.6 cm) and plugs into the housing. A sizable rubber seal is used to keep water out of the headlamp housing. On the US spec 928s a plastic/chrome ring is used as a spacer to fill the gap between the glass and the frame. The H4 beam pattern provides a very sharp cutoff in the low beam setting with a flair up to the right. For this reason, precise alignment is needed to keep from blinding on coming drivers. European cars were mandated with inside alignment control so if the trunk (boot) was loaded down the driver could easily further dip the alignment. Having driven in Europe, I feel this pattern is superior to the more "blurred" DOT approved pattern.

For Porsche, the H5 is the newer style 8" headlamp used on the S4. There is no chrome spacer needed, the headlamp glass fills out the entire headlamp housing. The bulbs (9004) are also separate from the glass, are longer than H4s, and have an integrated "O" ring so no rubber seal is needed. H5 bulbs are used on most of the new American cars today.

Rich
'93 GTS
'83S