Headlamp Power

A decent MOT place will look at the beam pattern when testing and fail it if poor. Which makes me wonder how some modern cars will ever pass one.

I remember having a car fail on this when a bulb had 'broken' in some way internally, but still worked. The beam pattern was poor. A new bulb sorted it.

The MOT test looks for a dip beam "hot spot" offset to the left and below the center. It also requires the upper part of the beam pattern to be "dark". There may be varying interpretations of "dark" as there is a big bright blob of a "hot spot" nearby. Basically anything with a visible dip beam cut off pattern will pass.

The MOT beam pattern test also detects when a bulb is fitted incorrectly

- just thrown / wedged in instead of seated with the tangs in the slots.

Incorrectly fitted bulbs are a very common mot failure. The difficulty of access to the bulb is generally the cause. It is often quickest (and less painful/annoying) to take the headlamp out (or partially remove it, depending on the vehicle) fit the bulb and refit the headlamp unit.

To the extent that replacing a bulb may be two hours work! It's a ridiculous design feature.

I think my local independent employs a mechanic with specially small hands just for headlamp work ...

It's rather a nice touch on the Boxster. There is a tool provided which pops the entire headlight out. The tool fits via an access hole in the front boot. Making it easy to change a bulb even out on the road, as it were.

I wonder whether you're forgetting that a 12v 60w bulb produces a hell of a lot more visible light than a mains 60w bulb because its filament is short and fat rather than long and thin, making it much stronger mechanically so that it can be run at a much higher temperature.

When halogen technology is applied to domestic bulbs a 43W halogen bulb is the equivalent of a conventional incandescent 60W bulb.

But CFL and LED use a fraction of that. CFL is a discharge lamp like HID but the discharge is UV and needs a large area of phosphor to convert the UV to visible light. LED for domestic use can either be multiple LEDs to make white light or a UV LED that needs a phosphor.

Okay, you've forced me into some extra info here, which I had hoped to avoid. My principle concern is with the top speed of this car, which is over 170MPH. Given a German autobahn at 3am, I would not feel the least bit comfortable with regular, myopic 55/60W bulbs, for what should be blindingly obvious reasons to anyone with half a brain or more.

I'm not sure that anyone with more than half a brain would drive at

Dipped headlights are never going to be suitable for high speed, and if autobahns are anything like as busy as UK motorways, very rare you can use main beam. So a good rule is never go faster than the distance you can see.

To be fair, the last time I was in Germany, my taxi was travelling at

SteveW

...to be clear. and stop in.

and the stopping distamce of a car at 130 is around 60% of that of a car at 170, and there is the problem of whether the brakes can actually do a hard stop from such a speed, particularly with an older car.

Leds and/or Projector HID. If the beam is narrow to get range you need more lights to get a decent spread.

A cluster of high output bike LED lights would do quite well if you can use main beam, or devise some blanking plate for a dip beam. I had one that was better than a 1980's Cibie Z beam for motorcycle and far better than any set of car headlamps I've ever owned (including rectangular Cibie's I had on a rwd Celica 2.0XT). It was sold as 1200 Lm but I think I been sent a mislabeled 2400/3200 Lm one. The Led retaining ring unscrewed itself after a year and it blew the battery PCM. It lit the road in the link so well that the reflector posts on the bend (what bend?) were quite dazzling. It was very focused but had a bright halo that lit reflective signs quite brightly. The halo was so wide it was impossible to direct the beam usefully and not light road signs. Frankly it was brilliant but a menace to other road users.

https://www.google.co.uk/maps/@52.8429846,-1.6228616,3a,60y,331.39h,84.1t/data=!3m6!1e1!3m4!1sIrigRzuXbsdkxQKA1Xg0wA!2e0!7i13312!8i6656?hl=en I'm now on my 3rd one. The 2nd had a very poor beam, the center of the beam was dark with a bright ring of light and poor focus. The 3rd is reasonable focus with a bright center beam that can be directed to form a nice pool of light with 20 to 50 ft range, about 6 ft wide on the road and has a not too bright halo. None of them cost more than £20 and the last one was on amazon offer at £13.

Good point, Dave. So even *you* agree that I need more powerful headlamps. I've done a bit of research and have discovered that cinemas use a form of arc lighting for their projectors. I need to get me a couple of those bulbs and I'll be all set for safe night-driving at anything up to the top speed of the car.

... and that was along Unter den Linden I'd guess. ;)

HID are ARC lamps.

Oh. I'm obviously a bit out of date on this subject. :/

I doubt it these days. High powered lights for film etc are all now discharge types, not arcs. And that's what HID is (high Intensity Discharge)

LEDs may take over one day.